-mm merge plans for 2.6.23

-mm merge plans for 2.6.23

[Andrew Morton]

When replying, please rewrite the subject suitably and try to Cc: the
appropriate developer(s).



add-lzo1x-algorithm-to-the-kernel.patch
make-common-helpers-for-seq_files-that-work-with-list_head-s.patch
lots-of-architectures-enable-arbitary-speed-tty-support.patch

 Merge

serial-assert-dtr-for-serial-console-devices.patch

 Don't know.  I worry about Russell's concern (see the changelog)

git-acpi-s390-struct-bin_attribute-changes.patch
cpuidle-add-rating-to-the-governors-and-pick-the-one-with-highest-rating-by-default-fix.patch
exit-acpi-processor-module-gracefully-if-acpi-is-disabled.patch
fix-empty-macros-in-acpi.patch
drivers-acpi-sbsc-remove-dead-code.patch
acpi-enable-c3-power-state-on-dell-inspiron-8200.patch
drivers-acpi-pci_linkc-lower-printk-severity.patch

 Sent to lenb

working-3d-dri-intel-agpko-resume-for-i815-chip.patch

 Sent to davej

cifs-use-simple_prepare_write-to-zero-page-data.patch
cifs-zero_user_page-conversion.patch

 Sent to sfrench

bugfix-cpufreq-in-combination-with-performance-governor.patch
restore-previously-used-governor-on-a-hot-replugged-cpu.patch

 Sent to davej

kcopyd-use-mutex-instead-of-semaphore.patch

 Sent to agk

powerpc-promc-remove-undef-printk.patch
8xx-mpc885ads-pcmcia-support.patch
dts-kill-hardcoded-phandles.patch
ppc-remove-dead-code-for-preventing-pread-and-pwrite-calls.patch
viotape-use-designated-initializers-for-fops-member.patch
make-drivers-char-hvc_consoleckhvcd-static.patch
powerpc-enable-arbitary-speed-tty-ioctls-and-split.patch
powerpc-tlb_32c-build-fix.patch
sky-cpu-and-nexus-code-style-improvement.patch
sky-cpu-and-nexus-include-ioh.patch
sky-cpu-and-nexus-check-for-platform_get_resource-ret.patch
sky-cpu-and-nexus-check-for-create_proc_entry-ret-code.patch
sky-cpu-use-c99-style-for-struct-init.patch

 Sent to paulus

revert-gregkh-driver-block-device.patch
driver-core-check-return-code-of-sysfs_create_link.patch
driver-core-coding-style-cleanup.patch
pm-do-not-use-saved_state-from-struct-dev_pm_info-on-arm.patch
nozomi-remove-termios-checks-from-various-old-char-serial-drivers.patch

 Sent to greg

git-dvb-saa7134-tvaudio-fix.patch
dvb_en_50221-convert-to-kthread-api.patch

 Sent to mchehab

hdaps-switch-to-using-input-polldev.patch
applesmc-switch-to-using-input-polldev.patch
applesmc-add-temperature-sensors-set-for-macbook.patch
ams-switch-to-using-input-polldev.patch

 Sent to mhoffman

sn-correct-rom-resource-length-for-bios-copy.patch

 Sent to Tony

make-input-layer-use-seq_list_xxx-helpers.patch
touchscreen-fujitsu-touchscreen-driver.patch
serio_raw_read-warning-fix.patch
tsdev-fix-broken-usecto-millisecs-conversion.patch

 Sent to Dmitry

use-posix-bre-in-headers-install-target.patch
modpost-white-list-pattern-adjustment.patch
strip-config_-automatically-in-kernel-configuration-search.patch
fix-the-warning-when-running-make-tags.patch
kconfig-reset-generated-values-only-if-kconfig-and-config-agree.patch

 Sent to Sam

led_colour_show-warning-fix.patch

 Sent to rpurdie

libata-config_pm=n-compile-fix.patch
pata_acpi-restore-driver.patch
libata-core-convert-to-use-cancel_rearming_delayed_work.patch
libata-implement-ata_wait_after_reset.patch
sata_promise-sata-hotplug-support.patch
libata-add-irq_flags-to-struct-pata_platform_info-fix.patch
ata-add-the-sw-ncq-support-to-sata_nv-for-mcp51-mcp55-mcp61.patch
sata_nv-allow-changing-queue-depth.patch
pata_hpt3x3-major-reworking-and-testing.patch
iomap-sort-out-the-broken-address-reporting-caused-by-the-iomap-layer.patch
ata-use-iomap_name.patch

 Sent to jgarzik

libata-check-for-an-support.patch
scsi-expose-an-to-user-space.patch
libata-expose-an-to-user-space.patch
scsi-save-disk-in-scsi_device.patch
libata-send-event-when-an-received.patch

 Am sitting on these due to confusion regarding the status of the ata-ahci
 patches.

ata-ahci-alpm-store-interrupt-value.patch
ata-ahci-alpm-expose-power-management-policy-option-to-users.patch
ata-ahci-alpm-enable-link-power-management-for-ata-drivers.patch
ata-ahci-alpm-enable-aggressive-link-power-management-for-ahci-controllers.patch

 These appear to need some work.

libata-add-human-readable-error-value-decoding.patch
libata-fix-hopefully-all-the-remaining-problems-with.patch
testing-patch-for-ali-pata-fixes-hopefully-for-the-problems-with-atapi-dma.patch
pata_ali-more-work.patch

 Dead/dying/abandoned ata things.  Might drop.

mips-make-resources-for-ds1742-static-__initdata.patch

 Sent to Ralf.

tty-add-the-new-ioctls-and-definitionto-the-mips.patch

 Awaiting merge of
 lots-of-architectures-enable-arbitary-speed-tty-support.patch

mmc-at91_mci-typo.patch

 Sent to drzeus

mtd-onenand-build-fix.patch
nommu-present-backing-device-capabilities-for-mtd.patch
nommu-add-support-for-direct-mapping-through-mtdconcat.patch
nommu-make-it-possible-for-romfs-to-use-mtd-devices.patch
romfs-printk-format-warnings.patch
mtd-add-module-license-to-mtdbdi.patch

 Sent to dvmw2

8139too-force-media-setting-fix.patch
blackfin-on-chip-ethernet-mac-controller-driver.patch
atari_pamsnetc-old-declaration-ritchie-style-fix.patch
sundance-phy-address-form-0-only-for-device-id-0x0200.patch
use-is_power_of_2-in-cxgb3-cxgb3_mainc.patch
use-is_power_of_2-in-myri10ge-myri10gec.patch
3csoho100-tx-needs-extra_preamble.patch

 Sent to jgarzik

3x59x-fix-pci-resource-management.patch
update-smc91x-driver-with-arm-versatile-board-info.patch
drivers-net-ns83820c-add-paramter-to-disable-auto.patch

 netdev patches which are stuck in limbo land.

make-atm-driver-use-seq_list_xxx-helpers.patch
make-some-network-related-proc-files-use-seq_list_xxx.patch
wrong-timeout-value-in-sk_wait_data-v2-fix.patch
use-mutex-instead-of-semaphore-in-vlsi-82c147-irda-controller-driver.patch
bonding-bond_mainc-make-2-functions-static.patch
net-make-struct-dccp_li_cachep-static.patch
net-ipv4-netfilter-ip_tablesc-lower-printk-severity.patch
rpc-remove-makefile-reference-to-obsolete-rxrpc-config.patch

 Sent to davem (mostly merged now, I think)

bluetooth-remove-the-redundant-non-seekable-llseek-method.patch
rfcomm-hangup-ttys-before-releasing-rfcomm_dev.patch

 Sent to Marcel

git-ioat-vs-git-md-accel.patch
ioat-warning-fix.patch
fix-i-oat-for-kexec.patch

 I don't seem to be able to get rid of these.  Chris Leech appears to have
 vanished.

auth_gss-unregister-gss_domain-when-unloading-module.patch

 Sent to Trond and Bruce, needs work.

pa-risc-use-page-allocator-instead-of-slab-allocator.patch

 Sent to Kyle

pcmcia-delete-obsolete-pcmcia_ioctl-feature.patch
use-menuconfig-objects-pcmcia.patch

 Am a bit stuck with the pcmcia patches.  Dominik has disappeared.

pcmcia-pccard-deadlock-fix.patch

 I think this isn't a good patch.  Am holding onto it as a reminder that
 pcmcia deadlocks.

dont-optimise-away-baud-rate-changes-when-bother-is-used.patch
serial-add-support-for-ite-887x-chips.patch
serial_txx9-fix-modem-control-line-handling.patch
serial_txx9-cleanup-includes.patch

 Serial stuff.  Will run these past rmk and Alan and will merge them if they
 survive.

revert-gregkh-pci-pci_bridge-device.patch
fix-gregkh-pci-pci-syscallc-switch-to-refcounting-api.patch
pci-x-pci-express-read-control-interfaces-fix.patch
remove-pci_dac_dma_-apis.patch
round_up-macro-cleanup-in-drivers-pci.patch
pcie-remove-spin_lock_unlocked.patch
add-pci_try_set_mwi.patch
cpci_hotplug-convert-to-use-the-kthread-api.patch
pci_set_power_state-check-for-pm-capabilities-earlier.patch

 Sent to Greg

s390-rename-cpu_idle-to-s390_cpu_idle.patch

 Sent to Martin.

restore-acpi-change-for-scsi.patch
git-scsi-misc-vs-greg-sysfs-stuff.patch
aacraid-rename-check_reset.patch
scsi-dont-build-scsi_dma_mapunmap-for-has_dma.patch
drivers-scsi-small-cleanups.patch
sym53c8xx_2-claims-cpqarray-device.patch
drivers-scsi-wd33c93c-cleanups.patch
make-seagate_st0x_detect-static.patch
pci-error-recovery-symbios-scsi-base-support.patch
pci-error-recovery-symbios-scsi-first-failure.patch
drivers-scsi-pcmcia-nsp_csc-remove-kernel-24-code.patch
drivers-message-i2o-devicec-remove-redundant-gfp_atomic-from-kmalloc.patch
drivers-scsi-aic7xxx_oldc-remove-redundant-gfp_atomic-from-kmalloc.patch
use-menuconfig-objects-ii-scsi.patch
remove-dead-references-to-module_parm-macro.patch
ppa-coding-police-and-printk-levels.patch
remove-the-dead-cyberstormiii_scsi-option.patch
config_scsi_fd_8xx-no-longer-exists.patch
use-mutex-instead-of-semaphore-in-megaraid-mailbox-driver.patch

 Sent to James.

scsi-lpfc-lpfc_initc-remove-unused-variable.patch

 Will add to the James queue once add-pci_try_set_mwi.patch is merged.

use-menuconfig-objects-block-layer.patch
use-menuconfig-objects-ib-block.patch
use-menuconfig-objects-ii-block-devices.patch
block-device-elevator-use-list_for_each_entry-instead-of-list_for_each.patch
update-documentation-block-barriertxt.patch

 Sent to Jens.

videopix-frame-grabber-fix-unreleased-lock-in-vfc_debug.patch

 Sent to davem

fix-gregkh-usb-usb-ehci-cpufreq-fix.patch
fix-gregkh-usb-usb-use-menuconfig-objects.patch
make-usb-autosuspend-timer-1-sec-jiffy-aligned.patch
drivers-block-ubc-use-list_for_each_entry.patch
ftdi_sio-fix-something.patch
usb-make-the-usb_device-numa_node-to-get-assigned-from.patch
mos7840c-turn-this-into-a-serial-driver.patch
pl2303-remove-bogus-checks-and-fix-speed-support-to-use.patch
visor-and-whiteheat-remove-bogus-termios-change-checks.patch
mos7720-remove-bogus-no-termios-change-check.patch
io_-remove-bogus-termios-no-change-checks.patch
usb-remove-makefile-reference-to-obsolete-ohci_at91.patch

 Sent to Greg.

use-list_for_each_entry-for-iteration-in-prism-54-driver.patch

 Sent to linville

revert-x86_64-mm-verify-cpu-rename.patch
add-kstrndup-fix.patch
xen-build-fix.patch
fix-x86_64-numa-fake-apicid_to_node-mapping-for-fake-numa-2.patch
fix-x86_64-mm-xen-xen-smp-guest-support.patch
more-fix-x86_64-mm-xen-xen-smp-guest-support.patch
fix-x86_64-mm-sched-clock-share.patch
fix-x86_64-mm-xen-add-xen-virtual-block-device-driver.patch
fix-x86_64-mm-add-common-orderly_poweroff.patch
fix-x86_64-mm-xen-xen-event-channels.patch
arch-i386-xen-mmuc-must-include-linux-schedh.patch
tidy-up-usermode-helper-waiting-a-bit-fix.patch
update-x86_64-mm-xen-use-iret-directly-where-possible.patch
i386-add-support-for-picopower-irq-router.patch
make-arch-i386-kernel-setupcremapped_pgdat_init-static.patch
arch-i386-kernel-i8253c-should-include-asm-timerh.patch
make-arch-i386-kernel-io_apicctimer_irq_works-static-again.patch
quicklist-support-for-x86_64.patch
x86_64-extract-helper-function-from-e820_register_active_regions.patch
x86_64-fix-e820_hole_size-based-on-address-ranges.patch
x86_64-acpi-disable-srat-when-numa-emulation-succeeds.patch
x86_64-slit-fake-pxm-to-node-mapping-for-fake-numa-2.patch
x86_64-numa-fake-apicid_to_node-mapping-for-fake-numa-2.patch
x86-use-elfnoteh-to-generate-vsyscall-notes-fix.patch
mmconfig-x86_64-i386-insert-unclaimed-mmconfig-resources.patch
x86_64-fix-smp_call_function_single-return-value.patch
x86_64-o_excl-on-dev-mcelog.patch
x86_64-support-poll-on-dev-mcelog.patch
x86_64-mcelog-tolerant-level-cleanup.patch
x86_64-mce-poll-at-idle_start-and-printk-fix.patch
i386-fix-machine-rebooting.patch
x86-fix-section-mismatch-warnings-in-mtrr.patch
x86_64-ratelimit-segfault-reporting-rate.patch
x86_64-pm_trace-support.patch
make-alt-sysrq-p-display-the-debug-register-contents.patch
i386-flush_tlb_kernel_range-add-reference-to-the-arguments.patch
round_jiffies-for-i386-and-x86-64-non-critical-corrected-mce-polling.patch
pci-disable-decode-of-io-memory-during-bar-sizing.patch
mmconfig-validate-against-acpi-motherboard-resources.patch
x86_64-irq-check-remote-irr-bit-before-migrating-level-triggered-irq-v3.patch
i386-remove-support-for-the-rise-cpu.patch
x86-64-calgary-generalize-calgary_increase_split_completion_timeout.patch
x86-64-calgary-update-copyright-notice.patch
x86-64-calgary-introduce-handle_quirks-for-various-chipset-quirks.patch
x86-64-calgary-introduce-chipset-specific-ops.patch
x86-64-calgary-abstract-how-we-find-the-iommu_table-for-a-device.patch
x86-64-calgary-introduce-calioc2-support.patch
x86-64-calgary-add-chip_ops-and-a-quirk-function-for-calioc2.patch
x86-64-calgary-implement-calioc2-tce-cache-flush-sequence.patch
x86-64-calgary-make-dump_error_regs-a-chip-op.patch
x86-64-calgary-grab-plssr-too-when-a-dma-error-occurs.patch
x86-64-calgary-reserve-tces-with-the-same-address-as-mem-regions.patch
x86-64-calgary-cleanup-of-unneeded-macros.patch
x86-64-calgary-tabify-and-trim-trailing-whitespace.patch
x86-64-calgary-only-reserve-the-first-1mb-of-io-space-for-calioc2.patch
x86-64-calgary-tidy-up-debug-printks.patch
i386-make-arch-i386-mm-pgtablecpgd_cdtor-static.patch
i386-fix-section-mismatch-warning-in-intel_cacheinfo.patch
i386-do-not-restore-reserved-memory-after-hibernation.patch
paravirt-helper-to-disable-all-io-space-fix.patch
dmi_match-patch-in-rebootc-for-sff-dell-optiplex-745-fixes-hang.patch
i386-hpet-check-if-the-counter-works.patch
i386-trim-memory-not-covered-by-wb-mtrrs.patch
kprobes-x86_64-fix-for-mark-ro-data.patch
kprobes-i386-fix-for-mark-ro-data.patch
divorce-config_x86_pae-from-config_highmem64g.patch
remove-unneeded-test-of-task-in-dump_trace.patch
i386-move-the-kernel-to-16mb-for-numa-q.patch
i386-show-unhandled-signals.patch
i386-minor-nx-handling-adjustment.patch
x86-smp-alt-once-option-is-only-useful-with-hotplug_cpu.patch
x86-64-remove-unused-variable-maxcpus.patch
move-functions-declarations-to-header-file.patch
x86_64-during-vm-oom-condition.patch
i386-during-vm-oom-condition.patch
x86-64-disable-the-gart-in-shutdown.patch
x86_84-move-iommu-declaration-from-proto-to-iommuh.patch
i386-uaccessh-replace-hard-coded-constant-with-appropriate-macro-from-kernelh.patch
i386-add-cpu_relax-to-cmos_lock.patch
x86_64-flush_tlb_kernel_range-warning-fix.patch
x86_64-add-ioapic-nmi-support.patch
x86_64-change-_map_single-to-static-in-pci_gartc-etc.patch
x86_64-geode-hw-random-number-generator-depend-on-x86_3.patch
x86_64-fix-wrong-comment-regarding-set_fixmap.patch
arch-x86_64-kernel-processc-lower-printk-severity.patch
nohz-fix-nohz-x86-dyntick-idle-handling.patch
acpi-move-timer-broadcast-and-pmtimer-access-before-c3-arbiter-shutdown.patch
clockevents-fix-typo-in-acpi_pmc.patch
timekeeping-fixup-shadow-variable-argument.patch
timerc-cleanup-recently-introduced-whitespace-damage.patch
clockevents-remove-prototypes-of-removed-functions.patch
clockevents-fix-resume-logic.patch
clockevents-fix-device-replacement.patch
tick-management-spread-timer-interrupt.patch
highres-improve-debug-output.patch
hrtimer-speedup-hrtimer_enqueue.patch
pcspkr-use-the-global-pit-lock.patch
ntp-move-the-cmos-update-code-into-ntpc.patch
i386-pit-stop-only-when-in-periodic-or-oneshot-mode.patch
i386-remove-volatile-in-apicc.patch
i386-hpet-assumes-boot-cpu-is-0.patch
i386-move-pit-function-declarations-and-constants-to-correct-header-file.patch
x86_64-untangle-asm-hpeth-from-asm-timexh.patch
x86_64-use-generic-cmos-update.patch
x86_64-remove-dead-code-and-other-janitor-work-in-tscc.patch
x86_64-fix-apic-typo.patch
x86_64-convert-to-cleckevents.patch
acpi-remove-the-useless-ifdef-code.patch
x86_64-hpet-restore-vread.patch
x86_64-restore-restore-nohpet-cmdline.patch
x86_64-block-irq-balancing-for-timer.patch
x86_64-prep-idle-loop-for-dynticks.patch
x86_64-enable-high-resolution-timers-and-dynticks.patch
x86_64-dynticks-disable-hpet_id_legsup-hpets.patch
xen-fix-x86-config-dependencies.patch
x86_64-get-mp_bus_to_node-as-early.patch
xen-suppress-abs-symbol-warnings-for-unused-reloc-pointers.patch
xen-cant-support-numa-yet.patch
x86-fix-iounmaps-use-of-vm_structs-size-field.patch
arch-x86_64-kernel-aperturec-lower-printk-severity.patch
arch-x86_64-kernel-e820c-lower-printk-severity.patch
ich-force-hpet-make-generic-time-capable-of-switching-broadcast-timer.patch
ich-force-hpet-restructure-hpet-generic-clock-code.patch
ich-force-hpet-ich7-or-later-quirk-to-force-detect-enable.patch
ich-force-hpet-late-initialization-of-hpet-after-quirk.patch
ich-force-hpet-ich5-quirk-to-force-detect-enable.patch
ich-force-hpet-ich5-fix-a-bug-with-suspend-resume.patch
ich-force-hpet-add-ich7_0-pciid-to-quirk-list.patch
geode-basic-infrastructure-support-for-amd-geode-class.patch
geode-mfgpt-support-for-geode-class-machines.patch
geode-mfgpt-clock-event-device-support.patch
i386-x86_64-insert-hpet-firmware-resource-after-pci-enumeration-has-completed.patch
i386-ioapic-remove-old-irq-balancing-debug-cruft.patch
i386-deactivate-the-test-for-the-dead-config_debug_page_type.patch

 Sent to Andi

fix-xfs_ioc_fsgeometry_v1-in-compat-mode.patch
fix-xfs_ioc__to_handle-and-xfs_ioc_openreadlink_by_handle-in-compat-mode.patch
fix-xfs_ioc_fsbulkstat_single-and-xfs_ioc_fsinumbers-in-compat-mode.patch

 Sent to Tim & David.

xtensa-enable-arbitary-tty-speed-setting-ioctls.patch

 Sent to czankel

kgdb-warning-fix.patch
kgdb-kconfig-fix.patch
kgdb-use-new-style-interrupt-flags.patch
kgdb-section-fix.patch
kgdb_skipexception-warning-fix.patch
kgdb-ia64-fixes.patch
kgdb-bust-on-ia64.patch
kgdb-build-fix-2.patch

 Sent to Jason

pci-x-pci-express-read-control-interfaces-myrinet.patch
pci-x-pci-express-read-control-interfaces-mthca.patch
pci-x-pci-express-read-control-interfaces-e1000.patch
pci-x-pci-express-read-control-interfaces-qla2xxx.patch

 Will send these to maintainers once
 gregkh-pci-pci-add-pci-x-pci-express-read-control-interfaces.patch gets
 merged.

gen_estimator-fix-locking-and-timer-related-bugs.patch
netpoll-fix-a-leak-n-bug-in-netpoll_cleanup.patch

 I think these might be defunct.  Will let the net guys sort that out.

vmscan-give-referenced-active-and-unmapped-pages-a-second-trip-around-the-lru.patch

 This is scary.  Will sit and admire it until it has been demonstrated
 to be a net gain.

console-more-buf-for-index-parsing.patch
console-console-handover-to-preferred-console.patch

 Merge

x86-initial-fixmap-support.patch
serial-convert-early_uart-to-earlycon-for-8250.patch
change-zonelist-order-zonelist-order-selection-logic.patch
hugetlb-remove-unnecessary-nid-initialization.patch
mm-use-div_round_up-in-mm-memoryc.patch
make-proc-slabinfo-use-seq_list_xxx-helpers.patch
mm-alloc_large_system_hash-can-free-some-memory-for.patch
remove-the-deprecated-kmem_cache_t-typedef-from-slabh.patch
slob-rework-freelist-handling.patch
slob-remove-bigblock-tracking.patch
slob-improved-alignment-handling.patch
vmscan-fix-comments-related-to-shrink_list.patch

 mm stuff: will merge.

mm-fix-fault-vs-invalidate-race-for-linear-mappings.patch
mm-merge-populate-and-nopage-into-fault-fixes-nonlinear.patch
mm-merge-nopfn-into-fault.patch
convert-hugetlbfs-to-use-vm_ops-fault.patch
mm-remove-legacy-cruft.patch
mm-debug-check-for-the-fault-vs-invalidate-race.patch
mm-fix-clear_page_dirty_for_io-vs-fault-race.patch
invalidate_mapping_pages-add-cond_resched.patch
ocfs2-release-page-lock-before-calling-page_mkwrite.patch
document-page_mkwrite-locking.patch

 The fault-vs-invalidate race fix.  I have belatedly learned that these need
 more work, so their state is uncertain.

slub-support-slub_debug-on-by-default.patch
numa-mempolicy-dynamic-interleave-map-for-system-init.patch
oom-stop-allocating-user-memory-if-tif_memdie-is-set.patch
numa-mempolicy-trivial-debug-fixes.patch
mm-fix-improper-init-type-section-references.patch
page-table-handling-cleanup.patch
kill-vmalloc_earlyreserve.patch
mm-more-__meminit-annotations.patch
mm-slabc-start_cpu_timer-should-be-__cpuinit.patch
madvise_need_mmap_write-usage.patch
slob-initial-numa-support.patch
mm-page_allocc-lower-printk-severity.patch
mm-avoid-tlb-gather-restarts.patch
mm-remove-ptep_establish.patch
mm-remove-ptep_test_and_clear_dirty-and-ptep_clear_flush_dirty.patch

 mm misc: will merge.

mm-revert-kernel_ds-buffered-write-optimisation.patch
revert-81b0c8713385ce1b1b9058e916edcf9561ad76d6.patch
revert-6527c2bdf1f833cc18e8f42bd97973d583e4aa83.patch
mm-clean-up-buffered-write-code.patch
mm-debug-write-deadlocks.patch
mm-trim-more-holes.patch
mm-buffered-write-cleanup.patch
mm-write-iovec-cleanup.patch
mm-fix-pagecache-write-deadlocks.patch
mm-buffered-write-iterator.patch
fs-fix-data-loss-on-error.patch
fs-introduce-write_begin-write_end-and-perform_write-aops.patch
mm-restore-kernel_ds-optimisations.patch
implement-simple-fs-aops.patch
block_dev-convert-to-new-aops.patch
ext2-convert-to-new-aops.patch
ext3-convert-to-new-aops.patch
ext3-convert-to-new-aops-fix.patch
ext4-convert-to-new-aops.patch
ext4-convert-to-new-aops-fix.patch
xfs-convert-to-new-aops.patch
gfs2-convert-to-new-aops.patch
fs-new-cont-helpers.patch
fat-convert-to-new-aops.patch
#adfs-convert-to-new-aops.patch
hfs-convert-to-new-aops.patch
hfsplus-convert-to-new-aops.patch
hpfs-convert-to-new-aops.patch
bfs-convert-to-new-aops.patch
qnx4-convert-to-new-aops.patch
reiserfs-use-generic-write.patch
reiserfs-convert-to-new-aops.patch
reiserfs-use-generic_cont_expand_simple.patch
with-reiserfs-no-longer-using-the-weird-generic_cont_expand-remove-it-completely.patch
nfs-convert-to-new-aops.patch
smb-convert-to-new-aops.patch
fuse-convert-to-new-aops.patch
hostfs-convert-to-new-aops.patch
jffs2-convert-to-new-aops.patch
ufs-convert-to-new-aops.patch
udf-convert-to-new-aops.patch
sysv-convert-to-new-aops.patch
minix-convert-to-new-aops.patch
jfs-convert-to-new-aops.patch
fs-adfs-convert-to-new-aops.patch
fs-affs-convert-to-new-aops.patch
ocfs2-convert-to-new-aops.patch

 pagefault-in-write deadlock fixes.  Will hold for 2.6.24.

fix-read-truncate-race.patch
make-sure-readv-stops-reading-when-it-hits-end-of-file.patch
fs-remove-some-aop_truncated_page.patch
remove-alloc_zeroed_user_highpage.patch

 Will merge if they're mergeable.

add-a-bitmap-that-is-used-to-track-flags-affecting-a-block-of-pages.patch
add-__gfp_movable-for-callers-to-flag-allocations-from-high-memory-that-may-be-migrated.patch
split-the-free-lists-for-movable-and-unmovable-allocations.patch
choose-pages-from-the-per-cpu-list-based-on-migration-type.patch
add-a-configure-option-to-group-pages-by-mobility.patch
drain-per-cpu-lists-when-high-order-allocations-fail.patch
move-free-pages-between-lists-on-steal.patch
group-short-lived-and-reclaimable-kernel-allocations.patch
group-high-order-atomic-allocations.patch
do-not-group-pages-by-mobility-type-on-low-memory-systems.patch
bias-the-placement-of-kernel-pages-at-lower-pfns.patch
be-more-agressive-about-stealing-when-migrate_reclaimable-allocations-fallback.patch
fix-corruption-of-memmap-on-ia64-sparsemem-when-mem_section-is-not-a-power-of-2.patch
bias-the-location-of-pages-freed-for-min_free_kbytes-in-the-same-max_order_nr_pages-blocks.patch
remove-page_group_by_mobility.patch
dont-group-high-order-atomic-allocations.patch
fix-calculation-in-move_freepages_block-for-counting-pages.patch
breakout-page_order-to-internalh-to-avoid-special-knowledge-of-the-buddy-allocator.patch
do-not-depend-on-max_order-when-grouping-pages-by-mobility.patch
print-out-statistics-in-relation-to-fragmentation-avoidance-to-proc-pagetypeinfo.patch

 Mel's page allocator work.  Might merge this, but I'm still not hearing
 sufficiently convincing noises from a sufficient number of people over this.

create-the-zone_movable-zone.patch
allow-huge-page-allocations-to-use-gfp_high_movable.patch
handle-kernelcore=-generic.patch

 Mel's moveable-zone work.  In a similar situation.  We need to stop whatever
 we're doing and get down and work out what we're going to do with all this
 stuff.

maps2-uninline-some-functions-in-the-page-walker.patch
maps2-eliminate-the-pmd_walker-struct-in-the-page-walker.patch
maps2-remove-vma-from-args-in-the-page-walker.patch
maps2-propagate-errors-from-callback-in-page-walker.patch
maps2-add-callbacks-for-each-level-to-page-walker.patch
maps2-move-the-page-walker-code-to-lib.patch
maps2-simplify-interdependence-of-proc-pid-maps-and-smaps.patch
maps2-move-clear_refs-code-to-task_mmuc.patch
maps2-regroup-task_mmu-by-interface.patch
maps2-make-proc-pid-smaps-optional-under-config_embedded.patch
maps2-make-proc-pid-clear_refs-option-under-config_embedded.patch
maps2-add-proc-pid-pagemap-interface.patch
maps2-add-proc-kpagemap-interface.patch

 The advanced process-memory-inspection interfaces.

 These weren't quite ready for 2.6.22 and nothing has changed in the past
 month or two.  Not looking like 2.6.23 material either.

lumpy-reclaim-v4.patch
have-kswapd-keep-a-minimum-order-free-other-than-order-0.patch
only-check-absolute-watermarks-for-alloc_high-and-alloc_harder-allocations.patch

 Lumpy reclaim.  In a similar situation to Mel's patches.  Stuck due to
 general lack or interest and effort.

mm-clean-up-and-kernelify-shrinker-registration.patch
mm-clean-up-and-kernelify-shrinker-registration-vs-git-nfs.patch

 Merge.

split-mmap.patch
only-allow-nonlinear-vmas-for-ram-backed-filesystems.patch
mm-document-fault_data-and-flags.patch
slub-mm-only-make-slub-the-default-slab-allocator.patch

 Merge.

slub-exploit-page-mobility-to-increase-allocation-order.patch
slub-reduce-antifrag-max-order.patch

 These are slub changes which are dependent on Mel's stuff, and I have a note
 here that there were reports of page allocation failures with these.  What's
 up with that?


 Maybe I should just drop the 100-odd marginal-looking MM patches?  We're
 simply not showing compelling reasons for merging them and quite a lot of them
 are stuck in a 90% complete state.


slub-change-error-reporting-format-to-follow-lockdep-loosely.patch
slub-use-list_for_each_entry-for-loops-over-all-slabs.patch
slub-slab-validation-move-tracking-information-alloc-outside-of.patch
slub-ensure-that-the-object-per-slabs-stays-low-for-high-orders.patch
slub-debug-fix-initial-object-debug-state-of-numa-bootstrap-objects.patch
slab-allocators-consolidate-code-for-krealloc-in-mm-utilc.patch
slab-allocators-consistent-zero_size_ptr-support-and-null-result-semantics.patch
slab-allocators-support-__gfp_zero-in-all-allocators.patch
slub-add-some-more-inlines-and-ifdef-config_slub_debug.patch
slub-extract-dma_kmalloc_cache-from-get_cache.patch
slub-do-proper-locking-during-dma-slab-creation.patch
slub-faster-more-efficient-slab-determination-for-__kmalloc.patch
slub-simplify-dma-index-size-calculation.patch
mm-slubc-make-code-static.patch
slub-style-fix-up-the-loop-to-disable-small-slabs.patch
slub-do-not-use-length-parameter-in-slab_alloc.patch
slab-allocators-cleanup-zeroing-allocations.patch
slab-allocators-replace-explicit-zeroing-with-__gfp_zero.patch
slub-do-not-allocate-object-bit-array-on-stack.patch
slub-move-sysfs-operations-outside-of-slub_lock.patch
slub-fix-config_slub_debug-use-for-config_numa.patch

 Slub stuff.  Will merge whatever's mergeable after the above droppage and
 stalls.

add-vm_bug_on-in-case-someone-uses-page_mapping-on-a-slab-page.patch
mm-make-needlessly-global-hugetlb_no_page-static.patch

 Merge

fs-introduce-some-page-buffer-invariants.patch
nfs-invariant-fix.patch
fs-introduce-some-page-buffer-invariants-obnoxiousness.patch

 Re-review, maybe merge.

memory-unplug-v7-migration-by-kernel.patch
memory-unplug-v7-isolate_lru_page-fix.patch
memory-unplug-v7-memory-hotplug-cleanup.patch
memory-unplug-v7-page-isolation.patch
memory-unplug-v7-page-offline.patch
memory-unplug-v7-ia64-interface.patch

 These are new, and are dependent on Mel's stuff.  Not for 2.6.23.

freezer-make-kernel-threads-nonfreezable-by-default.patch

 Merge, subject to re-review.

implement-file-posix-capabilities.patch
implement-file-posix-capabilities-fix.patch
file-capabilities-introduce-cap_setfcap.patch
file-capabilities-get_file_caps-cleanups.patch
file-caps-update-selinux-xattr-hooks.patch

 file-caps seems to be stuck.  There has been some movement lately, might
 merge it subject to suiable acks from suitable parties.

frv-connect-up-new-syscalls.patch
frv-be-self-consistent-and-use-config_gdb_console-everywhere.patch
frv-remove-some-dead-code.patch

 Merge

blackfin-enable-arbitary-speed-serial-setting.patch

 Will send to Bryan when
 lots-of-architectures-enable-arbitary-speed-tty-support.patch is merged

nommu-stub-expand_stack-for-nommu-case.patch
m68knommu-use-trhead_size-instead-of-hard-constant.patch
m68knommu-remove-cruft-from-setup-code.patch
m68knommu-remove-old-cache-management-cruft-from-mm-code.patch

 Merge

h8300-enable-arbitary-speed-tty-port-setup.patch
h8300-zimage-support-update.patch

 Merge

alpha-fix-trivial-section-mismatch-warnings.patch
fix-alpha-isa-support.patch

 Merge

arm26-enable-arbitary-speed-tty-ioctls-and-split.patch
arm26-remove-broken-and-unused-macro.patch

 Will send to Ian

freezer-run-show_state-when-freezing-times-out.patch
pm-do-not-require-dev-spew-to-get-pm_debug.patch
swsusp-remove-incorrect-code-from-userc.patch
swsusp-remove-code-duplication-between-diskc-and-userc.patch
swsusp-introduce-restore-platform-operations.patch
swsusp-fix-hibernation-code-ordering.patch
hibernation-prepare-to-enter-the-low-power-state.patch
freezer-avoid-freezing-kernel-threads-prematurely.patch
freezer-use-__set_current_state-in-refrigerator.patch
freezer-return-int-from-freeze_processes.patch
freezer-remove-redundant-check-in-try_to_freeze_tasks.patch
pm-introduce-hibernation-and-suspend-notifiers.patch
pm-disable-usermode-helper-before-hibernation-and-suspend.patch
pm-prevent-frozen-user-mode-helpers-from-failing-the-freezing-of-tasks-rev-2.patch
pm-reduce-code-duplication-between-mainc-and-userc-updated.patch
acpi-do-not-prepare-for-hibernation-in-acpi_shutdown.patch
pm-introduce-pm_power_off_prepare.patch
pm-optional-beeping-during-resume-from-suspend-to-ram.patch
pm-integrate-beeping-flag-with-existing-acpi_sleep-flags.patch

 Merge

m32r-enable-arbitary-speed-tty-rate-setting.patch

 Merge

etrax-enable-arbitary-speed-setting-on-tty-ports.patch
cris-replace-old-style-member-inits-with-designated-inits.patch

 Merge

uml-fix-request-sector-update.patch
uml-use-get_free_pages-to-allocate-kernel-stacks.patch
add-generic-exit-time-stack-depth-checking-to-config_debug_stack_usage.patch
uml-debug_shirq-fixes.patch
uml-xterm-driver-tidying.patch
uml-pty-channel-tidying.patch
uml-handle-errors-on-opening-host-side-of-consoles.patch
uml-sigio-support-cleanup.patch
uml-simplify-helper-stack-handling.patch
uml-eliminate-kernel-allocator-wrappers.patch

 Merge

v850-enable-arbitary-speed-tty-ioctls.patch

 Merge

deprecate-smbfs-in-favour-of-cifs.patch

 Send to sfrench

cpuset-remove-sched-domain-hooks-from-cpusets.patch

 Stuck.

clone-flag-clone_parent_tidptr-leaves-invalid-results-in-memory.patch

 ebiederm no likee.  Stuck.

cache-pipe-buf-page-address-for-non-highmem-arch.patch

 Ugly, will probably drop.

fix-rmmod-read-write-races-in-proc-entries.patch

 Merge

more-scheduled-oss-driver-removal.patch
doc-kernel-parameters-use-x86-32-tag-instead-of-ia-32.patch
introduce-write_trylock_irqsave.patch
use-write_trylock_irqsave-in-ptrace_attach.patch
use-menuconfig-objects-ii-auxdisplay.patch
use-menuconfig-objects-ii-edac.patch
use-menuconfig-objects-ii-ipmi.patch
use-menuconfig-objects-ii-misc-strange-dev.patch
use-menuconfig-objects-ii-module-menu.patch
use-menuconfig-objects-ii-oprofile.patch
use-menuconfig-objects-ii-telephony.patch
use-menuconfig-objects-ii-tpm.patch
use-menuconfig-objects-connector.patch
use-menuconfig-objects-crypto-hw.patch
use-menuconfig-objects-i2o.patch
use-menuconfig-objects-parport.patch
use-menuconfig-objects-pnp.patch
use-menuconfig-objects-w1.patch
fix-jvc-cdrom-drive-lockup.patch
use-no_pci_devices-in-pci-searchc.patch
introduce-boot-based-time.patch
use-boot-based-time-for-process-start-time-and-boot-time.patch
use-boot-based-time-for-uptime-in-proc.patch
udf-check-for-allocated-memory-for-data-of-new-inodes.patch
add-argv_split-fix.patch
add-common-orderly_poweroff-fix.patch
prevent-an-o_ndelay-writer-from-blocking-when-a-tty-write-is-blocked-by.patch
udf-check-for-allocated-memory-for-inode-data-v2.patch
fix-stop_machine_run-problem-with-naughty-real-time-process.patch
cpu-hotplug-fix-ksoftirqd-termination-on-cpu-hotplug-with-naughty-realtime-process.patch
use-mutexes-instead-of-semaphores-in-i2o-driver.patch
fuse-warning-fix.patch
vxfs-warning-fixes.patch
percpu_counters-use-cpu-notifiers.patch
percpu_counters-use-for_each_online_cpu.patch
make-afs-use-seq_list_xxx-helpers.patch
make-crypto-api-use-seq_list_xxx-helpers.patch
make-proc-misc-use-seq_list_xxx-helpers.patch
make-proc-modules-use-seq_list_xxx-helpers.patch
make-proc-tty-drivers-use-seq_list_xxx-helpers.patch
make-proc-self-mountstats-use-seq_list_xxx-helpers.patch
make-nfs-client-use-seq_list_xxx-helpers.patch
fat-gcc-43-warning-fix.patch
remove-unnecessary-includes-of-spinlockh-under-include-linux.patch
drivers-block-z2ram-remove-true-false-defines.patch
fix-compiler-warnings-in-acornc.patch
update-zilog-timeout.patch
edd-switch-to-pci_get-based-api.patch
fix-up-codingstyle-in-isofs.patch
define-config_bounce-to-avoid-useless-inclusion-of-bounce-buffer.patch
mpu401-warning-fixes.patch
introduce-config_virt_to_bus.patch
pie-randomization.patch
remove-unused-tif_notify_resume-flag.patch
rocketc-fix-unchecked-mutex_lock_interruptible.patch
only-send-sigxfsz-when-exceeding-rlimits.patch
procfs-directory-entry-cleanup.patch
8xx-fix-whitespace-and-indentation.patch
vdso-print-fatal-signals.patch
rtc-ratelimit-lost-interrupts-message.patch
reduce-cpusetc-write_lock_irq-to-read_lock.patch
char-n_hdlc-allow-restartsys-retval-of-tty-write.patch
afs-implement-file-locking.patch
tty_io-use-kzalloc.patch
remove-clockevents_releaserequest_device.patch
kconfig-no-strange-misc-devices.patch
afs-drop-explicit-extern.patch
remove-useless-tolower-in-isofs.patch
char-mxser_new-fix-sparse-warning.patch
char-tty_ioctl-use-wait_event_interruptible_timeout.patch
char-tty_ioctl-little-whitespace-cleanup.patch
char-genrtc-use-wait_event_interruptible.patch
char-n_r3964-use-wait_event_interruptible.patch
char-ip2-use-msleep-for-sleeping.patch
proc-environ-wrong-placing-of-ptrace_may_attach-check.patch
udf-coding-style-conversion-lindent.patch
ext2-fix-a-comment-when-ext2_release_file-is-called.patch
mutex_unlock-later-in-seq_lseek.patch
zs-move-to-the-serial-subsystem.patch
fs-block_devc-use-list_for_each_entry.patch
fault-injection-add-min-order-parameter-to-fail_page_alloc.patch
fault-injection-fix-example-scripts-in-documentation.patch
add-printktime-option-deprecate-time.patch
fs-clarify-dummy-member-in-struct.patch
dma-mapping-prevent-dma-dependent-code-from-linking-on.patch
remove-odd-and-misleading-comments-from-uioh.patch
add-a-flag-to-indicate-deferrable-timers-in-proc-timer_stats.patch
buffer-kill-old-incorrect-comment.patch
introduce-o_cloexec-take-2.patch
o_cloexec-for-scm_rights.patch
init-wait-for-asynchronously-scanned-block-devices.patch
atmel_serial-fix-break-handling.patch
documentation-proc-pid-stat-files.patch
seq_file-more-atomicity-in-traverse.patch
lib-add-idr_for_each.patch
lib-add-idr_remove_all.patch
remove-capabilityh-from-mmh.patch
kernel-utf-8-handling.patch
remove-sonypi_camera_command.patch
drop-an-empty-isicomh-from-being-exported-to-user-space.patch
ext3-ext4-orphan-list-check-on-destroy_inode.patch
ext3-ext4-orphan-list-corruption-due-bad-inode.patch
remove-apparently-useless-commented-apm_get_battery_status.patch
taskstats-add-context-switch-counters.patch
sony-laptop-use-null-for-pointer.patch
undeprecate-raw-driver.patch
hfsplus-change-kmalloc-memset-to-kzalloc.patch
submitchecklist-update-fix-spelling-error.patch
add-support-for-xilinx-systemace-compactflash-interface.patch
fix-typo-in-prefetchh.patch
zsc-drain-the-transmission-line.patch
hugetlbfs-use-lib-parser-fix-docs.patch
report-that-kernel-is-tainted-if-there-were-an-oops-before.patch
intel-rng-undo-mess-made-by-an-80-column-extremist.patch
improve-behaviour-of-spurious-irq-detect.patch
audit-add-tty-input-auditing.patch
remove-config_uts_ns-and-config_ipc_ns.patch

 Merge, subject to re-review.

user-namespace-add-the-framework.patch

 I still think the magical root-user thing in here is odd and perhaps poorly
 thought-out.

user-namespace-add-unshare.patch
revert-vanishing-ioctl-handler-debugging.patch
binfmt_elf-warning-fix.patch
document-the-fact-that-rcu-callbacks-can-run-in-parallel.patch
cobalt-remove-all-references-to-cobalt-nvram.patch
allow-softlockup-to-be-runtime-disabled.patch
dirty_writeback_centisecs_handler-cleanup.patch
mm-fix-create_new_namespaces-return-value.patch
add-a-kmem_cache-for-nsproxy-objects.patch
ptrace_peekdata-consolidation.patch
ptrace_pokedata-consolidation.patch
adjust-nosmp-handling.patch
ext3-fix-deadlock-in-ext3_remount-and-orphan-list-handling.patch
ext4-fix-deadlock-in-ext4_remount-and-orphan-list-handling.patch
remove-unused-lock_cpu_hotplug_interruptible-definition.patch
kerneldoc-fix-in-audit_core_dumps.patch
introduce-compat_u64-and-compat_s64-types.patch
diskquota-32bit-quota-tools-on-64bit-architectures.patch
remove-final-two-references-to-__obsolete_setup-macro.patch
update-procfs-guide-doc-of-read_func.patch
ext3-remove-extra-is_rdonly-check.patch
namespace-ensure-clone_flags-are-always-stored-in-an-unsigned-long.patch
doc-oops-tracing-add-code-decode-info.patch
drop-obsolete-sys_ioctl-export.patch
is_power_of_2-ext3-superc.patch
is_power_of_2-jbd.patch

 Merge, subject to re-review

sys_time-speedup.patch

 Am skeptical about this one.

cdrom-replace-hard-coded-constants-by-kernelh-macro.patch
update-description-in-documentation-filesystems-vfstxt-typo-fixed.patch
futex-tidy-up-the-code-v2.patch
add-documentation-sysctl-ctl_unnumberedtxt.patch
sysctlc-add-text-telling-people-to-use-ctl_unnumbered.patch
# drivers-pmc-msp71xx-gpio-char-driver.patch: david-b panned it
drivers-pmc-msp71xx-gpio-char-driver.patch
mistaken-ext4_inode_bitmap-for-ext4_block_bitmap.patch
hfs-refactor-ascii-to-unicode-conversion-routine.patch
hfs-add-custom-dentry-hash-and-comparison-operations.patch
sprint_symbol-cleanup.patch

 Merge, svbject to re-review.

hwrng-add-type-categories.patch

 This generated a flamewar.  Wil probably drop.

fs-namespacec-should-include-internalh.patch
proper-prototype-for-proc_nr_files.patch
replace-obscure-constructs-in-fs-block_devc.patch
bd_claim_by_disk-fix-warning.patch
fs-reiserfs-cleanups.patch
adb_probe_task-remove-unneeded-flush_signals-call.patch
kcdrwd-remove-unneeded-flush_signals-call.patch
nbdcsock_xmit-cleanup-signal-related-code.patch
move-seccomp-from-proc-to-a-prctl.patch
make-seccomp-zerocost-in-schedule.patch
is_power_of_2-kernel-kfifoc.patch
parport_pc-it887x-fix.patch
is_power_of_2-ufs-superc.patch
codingstyle-add-information-about-trailing-whitespace.patch
codingstyle-add-information-about-editor-modelines.patch
uninline-check_signature.patch
add-werror-implicit-function-declaration.patch
generic-bug-use-show_regs-instead-of-dump_stack.patch
udf-fix-function-name-from-udf_crc16-to-udf_crc.patch
dma-make-dma-pool-to-use-kmalloc_node.patch
unregister_chrdev-ignore-the-return-value.patch
unregister_chrdev-return-void.patch
unregister_blkdev-do-warn_on-on-failure.patch
unregister_blkdev-delete-redundant-messages-in-callers.patch
unregister_blkdev-delete-redundant-message.patch
unregister_blkdev-return-void.patch
add-missing-files-and-dirs-to-00-index-in-documentation.patch
remove-the-last-few-umsdos-leftovers.patch
update-documentation-filesystems-vfstxt-second-part.patch
rename-cancel_rearming_delayed_work-to-cancel_delayed_work_sync.patch
make-cancel_xxx_work_sync-return-a-boolean.patch
ext3-fix-error-handling-in-ext3_create_journal.patch
ext4-fix-error-handling-in-ext4_create_journal.patch
modules-remove-modlist_lock.patch
amiserial-remove-incorrect-no-termios-change-check.patch
genericserial-remove-bogus-optimisation-check-and-dead-code-paths.patch
synclink-remove-bogus-no-change-termios-optimisation.patch
68360serial-remove-broken-optimisation.patch
serial-remove-termios-checks-from-various-old-char-serial.patch
docs-static-initialization-of-spinlocks-is-ok.patch
kernel-printkc-document-possible-deadlock-against-scheduler.patch
remove-mm-backing-devccongestion_wait_interruptible.patch
gitignore-update.patch
isapnp-remove-pointless-check-of-type-against-0-in-isapnp_read_tag.patch
fix-trivial-typos-in-anon_inodesc-comments.patch
vsprintfc-optimizing-part-1-easy-and-obvious-stuff.patch
vsprintfc-optimizing-part-2-base-10-conversion-speedup-v2.patch
drivers-char-ipmi-ipmi_poweroffc-lower-printk-severity.patch
drivers-char-ipmi-ipmi_si_intfc-lower-printk-severity.patch
drivers-block-rdc-lower-printk-severity.patch
ext2-statfs-speed-up.patch
ext3-statfs-speed-up.patch
ext4-statfs-speed-up.patch
permit-mempool_freenull.patch
nls-remove-obsolete-makefile-entries.patch
compat32-ignore-the-loop_clr_fd-ioctl.patch
ia64-arbitary-speed-tty-ioctl-support.patch

 Merge, subject to re-review.

writeback-fix-time-ordering-of-the-per-superblock-dirty-inode-lists.patch
writeback-fix-time-ordering-of-the-per-superblock-dirty-inode-lists-2.patch
writeback-fix-time-ordering-of-the-per-superblock-dirty-inode-lists-3.patch
writeback-fix-time-ordering-of-the-per-superblock-dirty-inode-lists-4.patch
writeback-fix-comment-use-helper-function.patch
writeback-fix-time-ordering-of-the-per-superblock-dirty-inode-lists-5.patch
writeback-fix-time-ordering-of-the-per-superblock-dirty-inode-lists-6.patch
writeback-fix-time-ordering-of-the-per-superblock-dirty-inode-lists-7.patch

 I guess these should be merged.  There are still bugs in there which I think
 Ken Chen has fixed, but I haven't got onto that yet.

introduce-i_sync.patch
introduce-i_sync-fix.patch

 Merge, I guess.

ibmasm-whitespace-cleanup.patch
ibmasm-dont-use-extern-in-function-declarations.patch
ibmasm-miscellaneous-fixes.patch
ibmasm-must-depend-on-config_input.patch

 Merge.

sync_sb_inodes-propagate-errors.patch

 Needs work.

spi-controller-drivers-check-for-unsupported-modes.patch
spi-add-3wire-mode-flag.patch
crc7-support.patch
spidev-compiler-warning-gone.patch
spi_lm70llp-parport-adapter-driver.patch
spi_mpc83xxc-underclocking-hotfix.patch
atmel_spi-minor-updates.patch
s3c24xx-spi-controllers-both-select-bitbang.patch
spi-tle620x-power-switch-driver.patch
spi-master-driver-for-xilinx-virtex.patch
spi_mpc83xxc-support-qe-enabled-83xx-cpus-like-mpc832x.patch
spi-omap2_mcspi-driver.patch
spi_txx9-controller-driver.patch

 Merge

move-page-writeback-acounting-out-of-macros.patch
ext2-balloc-use-io_error-label.patch

 Might merge.

ext2-reservations.patch

 Still needs decent testing.

use-mutex-instead-of-semaphore-in-capi-20-driver.patch
mismatching-declarations-of-revision-strings-in-hisax.patch
make-isdn-capi-use-seq_list_xxx-helpers.patch
update-isdn-tree-to-use-pci_get_device.patch
sane-irq-initialization-in-sedlbauer-hisax.patch
use-menuconfig-objects-isdn-config_isdn.patch
use-menuconfig-objects-isdn-config_isdn_drv_gigaset.patch
use-menuconfig-objects-isdn-config_isdn_capi.patch
use-menuconfig-objects-isdn-config_capi_avm.patch
use-menuconfig-objects-isdn-config_capi_eicon.patch
isdn-capi-warning-fixes.patch
i4l-leak-in-eicon-idifuncc.patch

 Merge

use-menuconfig-objects-isdn-config_isdn_i4l.patch

 tilman didn't like it - might drop

i2o_cfg_passthru-cleanup.patch
wrong-memory-access-in-i2o_block_device_lock.patch
i2o-message-leak-in-i2o_msg_post_wait_mem.patch
i2o-proc-reading-oops.patch
i2o-debug-output-cleanup.patch

 Merge

knfsd-exportfs-add-exportfsh-header.patch
knfsd-exportfs-remove-iget-abuse.patch
knfsd-exportfs-add-procedural-interface-for-nfsd.patch
knfsd-exportfs-remove-call-macro.patch
knfsd-exportfs-untangle-isdir-logic-in-find_exported_dentry.patch
knfsd-exportfs-move-acceptable-check-into-find_acceptable_alias.patch
knfsd-exportfs-add-find_disconnected_root-helper.patch
knfsd-exportfs-split-out-reconnecting-a-dentry-from-find_exported_dentry.patch
nfsd-warning-fix.patch
knfsd-lockd-nfsd4-use-same-grace-period-for-lockd-and-nfsd4.patch
knfsd-nfsd4-fix-nfsv4-filehandle-size-units-confusion.patch
knfsd-nfsd4-silence-a-compiler-warning-in-acl-code.patch
knfsd-nfsd4-fix-enc_stateid_sz-for-nfsd-callbacks.patch
knfsd-nfsd4-fix-handling-of-acl-errrors.patch
knfsd-nfsd-remove-unused-header-interfaceh.patch
knfsd-nfsd4-vary-maximum-delegation-limit-based-on-ram-size.patch
knfsd-nfsd4-dont-delegate-files-that-have-had-conflicts.patch

 Merge

couple-fixes-to-fs-ecryptfs-inodec.patch
ecryptfs-move-ecryptfs-docs-into-documentation-filesystems.patch

 Merge

rtc-ds1307-cleanups.patch
rtc-rs5c372-becomes-a-new-style-i2c-driver.patch
thecus-n2100-register-rtc-rs5c372-i2c-device.patch
rtc-make-example-code-jump-to-done-instead-of-return-when-ioctl-not-supported.patch
rtc-dev-return-enotty-in-ioctl-if-irq_set_freq-is-not-implemented-by-driver.patch
driver-for-the-atmel-on-chip-rtc-on-at32ap700x-devices.patch
rtc_class-is-no-longer-considered-experimental.patch
rtc-kconfig-tweax.patch
rtc-add-rtc-m41t80-driver-take-2.patch
rtc-watchdog-support-for-rtc-m41t80-driver-take-2.patch
rtc-add-support-for-the-st-m48t59-rtc.patch
rtc-add-support-for-the-st-m48t59-rtc-vs-git-acpi.patch
rtc-driver-for-ds1216-chips.patch
rtc-driver-for-ds1216-chips-fix.patch
rtc-ds1307-oscillator-restart-for-ds1337383940.patch

 Merge.

revoke-special-mmap-handling.patch
revoke-special-mmap-handling-vs-fault-vs-invalidate.patch
revoke-core-code.patch
revoke-support-for-ext2-and-ext3.patch
revoke-add-documentation.patch
revoke-wire-up-i386-system-calls.patch
fs-introduce-write_begin-write_end-and-perform_write-aops-revoke.patch
revoke-vs-git-block.patch

 Don't know.  Need to ping suitable developers over this work.

lguest-export-symbols-for-lguest-as-a-module.patch
lguest-the-guest-code.patch
lguest-the-host-code.patch
lguest-the-host-code-lguest-vs-clockevents-fix-resume-logic.patch
lguest-the-asm-offsets.patch
lguest-the-makefile-and-kconfig.patch
lguest-the-console-driver.patch
lguest-the-net-driver.patch
lguest-the-block-driver.patch
lguest-the-documentation-example-launcher.patch

 Merge

oss-trident-massive-whitespace-removal.patch
oss-trident-fix-locking-around-write_voice_regs.patch
oss-trident-replace-deprecated-pci_find_device-with-pci_get_device.patch
remove-options-depending-on-oss_obsolete.patch

 Merge

unprivileged-mounts-add-user-mounts-to-the-kernel.patch
unprivileged-mounts-allow-unprivileged-umount.patch
unprivileged-mounts-account-user-mounts.patch
unprivileged-mounts-propagate-error-values-from-clone_mnt.patch
unprivileged-mounts-allow-unprivileged-bind-mounts.patch
unprivileged-mounts-put-declaration-of-put_filesystem-in-fsh.patch
unprivileged-mounts-allow-unprivileged-mounts.patch
unprivileged-mounts-allow-unprivileged-fuse-mounts.patch
unprivileged-mounts-propagation-inherit-owner-from-parent.patch
unprivileged-mounts-add-no-submounts-flag.patch

 Don't know.  Need to ping suitable developers over this work.
 
char-cyclades-add-firmware-loading.patch
char-cyclades-fix-sparse-warning.patch
char-isicom-cleanup-locking.patch
char-isicom-del_timer-at-exit.patch
char-isicom-proper-variables-types.patch
char-moxa-eliminate-busy-waiting.patch
char-specialix-remove-busy-waiting.patch
char-riscom8-eliminate-busy-loop.patch
char-vt-use-kzalloc.patch
char-vt-use-array_size.patch
char-kconfig-mxser_new-remove-experimental-comment.patch
char-stallion-remove-user-class-report-request.patch
char-istallion-initlocking-fixes-try-2.patch
stallion-remove-unneeded-lock_kernel.patch

 Merge

fbcon-smart-blitter-usage-for-scrolling.patch
nvidiafb-adjust-flags-to-take-advantage-of-new-scroll-method.patch
fbcon-cursor-blink-control.patch
fbcon-use-struct-device-instead-of-struct-class_device.patch
fbdev-move-arch-specific-bits-to-their-respective.patch
fbdev-detect-primary-display-device.patch
fbcon-allow-fbcon-to-use-the-primary-display-driver.patch
radeonfb-add-support-for-radeon-xpress-200m-rs485.patch
nvidiafb-add-proper-support-for-geforce-7600-chipset.patch
pm2fb-white-spaces-clean-up.patch
fbcon-set_con2fb_map-fixes.patch
fbcon-revise-primary-device-selection.patch
fbdev-fbcon-console-unregistration-from-unregister_framebuffer.patch
vt-add-comment-for-unbind_con_driver.patch
68328fb-the-pseudo_palette-is-only-16-elements-long.patch
controlfb-the-pseudo_palette-is-only-16-elements-long.patch
cyblafb-fix-pseudo_palette-array-overrun-in-setcolreg.patch
epson1355fb-color-setting-fixes.patch
fm2fb-the-pseudo_palette-is-only-16-elements-long.patch
gbefb-the-pseudo_palette-is-only-16-elements-long.patch
macfb-fix-pseudo_palette-size-and-overrun.patch
offb-the-pseudo_palette-is-only-16-elements-long.patch
platinumfb-the-pseudo_palette-is-only-16-elements.patch
pvr2fb-fix-pseudo_palette-array-overrun-and-typecast.patch
q40fb-the-pseudo_palette-is-only-16-elements-long.patch
sgivwfb-the-pseudo_palette-is-only-16-elements-long.patch
tgafb-actually-allocate-memory-for-the-pseudo_palette.patch
tridentfb-fix-pseudo_palette-array-overrun-in-setcolreg.patch
tx3912fb-fix-improper-assignment-of-info-pseudo_palette.patch
atyfb-the-pseudo_palette-is-only-16-elements-long.patch
radeonfb-the-pseudo_palette-is-only-16-elements-long.patch
i810fb-the-pseudo_palette-is-only-16-elements-long.patch
intelfb-the-pseudo_palette-is-only-16-elements-long.patch
sisfb-fix-pseudo_palette-array-size-and-overrun.patch
matroxfb-color-setting-fixes.patch
pm3fb-fillrect-acceleration.patch
pm3fb-possible-cleanups.patch
vt8623fbc-make-code-static.patch
matroxfb-color-setting-fixes-fix.patch
fb-epson1355fb-kill-off-dead-sh-support.patch
fix-the-graphic-corruption-issue-on-ia64-machines.patch

 Merge

omap-add-ti-omap-framebuffer-driver.patch
omap-add-ti-omap1610-accelerator-entry.patch
omap-add-ti-omap1-internal-lcd-controller.patch
omap-add-ti-omap2-internal-display-controller-support.patch
omap-add-ti-omap1-external-lcd-controller-support-sossi.patch
omap-add-ti-omap2-external-lcd-controller-support-rfbi.patch
omap-add-external-epson-hwa742-lcd-controller-support.patch
omap-add-external-epson-blizzard-lcd-controller-support.patch
omap-lcd-panel-support-for-the-ti-omap-h4-board.patch
omap-lcd-panel-support-for-the-ti-omap-h3-board.patch
omap-lcd-panel-support-for-the-palm-tungsten-e.patch
omap-lcd-panel-support-for-palm-tungstent.patch
omap-lcd-panel-support-for-the-palm-zire71.patch
omap-lcd-panel-support-for-the-ti-omap1610-innovator-board.patch
omap-lcd-panel-support-for-the-ti-omap1510-innovator-board.patch
omap-lcd-panel-support-for-the-ti-omap-osk-board.patch
omap-lcd-panel-support-for-the-siemens-sx1-mobile-phone.patch

 Merge

use-menuconfig-objects-ii-md.patch
md-improve-message-about-invalid-superblock-during-autodetect.patch
md-improve-the-is_mddev_idle-test-fix.patch
md-check-that-internal-bitmap-does-not-overlap-other-data.patch
md-change-bitmap_unplug-and-others-to-void-functions.patch

 Merge

raid5-add-the-stripe_queue-object-for-tracking-raid.patch
raid5-use-stripe_queues-to-prioritize-the-most.patch

 Ping Neil

readahead-introduce-pg_readahead.patch
readahead-add-look-ahead-support-to-__do_page_cache_readahead.patch
readahead-min_ra_pages-max_ra_pages-macros.patch
readahead-data-structure-and-routines.patch
readahead-on-demand-readahead-logic.patch
readahead-convert-filemap-invocations.patch
readahead-convert-splice-invocations.patch
readahead-convert-ext3-ext4-invocations.patch
readahead-remove-the-old-algorithm.patch
readahead-move-synchronous-readahead-call-out-of-splice-loop.patch
readahead-pass-real-splice-size.patch
mm-share-pg_readahead-and-pg_reclaim.patch
readahead-split-ondemand-readahead-interface-into-two-functions.patch
readahead-sanify-file_ra_state-names.patch

 Merge

fallocate-implementation-on-i86-x86_64-and-powerpc.patch
fallocate-on-s390.patch
fallocate-on-ia64.patch
fallocate-on-ia64-fix.patch

 Merge.

jprobes-make-struct-jprobeentry-a-void.patch
jprobes-remove-jprobe_entry.patch
jprobes-make-jprobes-a-little-safer-for-users.patch

 Merge.

intel-iommu-dmar-detection-and-parsing-logic.patch
intel-iommu-pci-generic-helper-function.patch
intel-iommu-clflush_cache_range-now-takes-size-param.patch
intel-iommu-iova-allocation-and-management-routines.patch
intel-iommu-intel-iommu-driver.patch
intel-iommu-avoid-memory-allocation-failures-in-dma-map-api-calls.patch
intel-iommu-intel-iommu-cmdline-option-forcedac.patch
intel-iommu-dmar-fault-handling-support.patch
intel-iommu-iommu-gfx-workaround.patch
intel-iommu-iommu-floppy-workaround.patch

 Don't know.  I don't think there were any great objections, but I don't
 think much benefit has been demonstrated?

define-new-percpu-interface-for-shared-data-version-4.patch
use-the-new-percpu-interface-for-shared-data-version-4.patch

 Merge

arch-personality-independent-stack-top.patch
audit-rework-execve-audit.patch
mm-variable-length-argument-support.patch

 Merge.

ext4-zero_user_page-conversion.patch
ext4-remove-extra-is_rdonly-check.patch
is_power_of_2-ext4-superc.patch

 Send to tytso

fs-introduce-vfs_path_lookup.patch
sunrpc-use-vfs_path_lookup.patch
nfsctl-use-vfs_path_lookup.patch
fs-mark-link_path_walk-static.patch
fs-remove-path_walk-export.patch

 Merge, after poking suitable maintainers

kernel-doc-add-tools-doc-in-makefile.patch
kernel-doc-fix-unnamed-struct-union-warning.patch
kernel-doc-strip-c99-comments.patch
kernel-doc-fix-leading-dot-in-man-mode-output.patch

 Merge

coredump-masking-bound-suid_dumpable-sysctl.patch
coredump-masking-reimplementation-of-dumpable-using-two-flags.patch
coredump-masking-add-an-interface-for-core-dump-filter.patch
coredump-masking-elf-enable-core-dump-filtering.patch
coredump-masking-elf-fdpic-remove-an-unused-argument.patch
coredump-masking-elf-fdpic-enable-core-dump-filtering.patch
coredump-masking-documentation-for-proc-pid-coredump_filter.patch

 Merge

kernel-relayc-make-functions-static.patch

 Merge

configfsdlm-separate-out-__configfs_attr-into-configfsh.patch
configfsdlmocfs2-convert-subsystem-semaphore-to-mutex.patch
configfsdlm-rename-config_group_find_obj-and-state-semantics-clearly.patch

 Merge, subject to Joel acks

use-data_data-in-cris.patch
add-missing-data_data-in-powerpc.patch
use-data_data-in-xtensa.patch

 Merge

drivers-edac-add-edac_mc_find-api.patch
drivers-edac-core-make-functions-static.patch
drivers-edac-add-rddr2-memory-types.patch
drivers-edac-split-out-functions-to-unique-files.patch
drivers-edac-add-edac_device-class.patch
drivers-edac-mc-sysfs-add-missing-mem-types.patch
drivers-edac-change-from-semaphore-to-mutex-operation.patch
drivers-edac-new-intel-5000-mc-driver.patch
drivers-edac-new-intel-5000-mc-driver-fix.patch
drivers-edac-coreh-fix-scrubdefs.patch
drivers-edac-new-i82443bxgz-mc-driver.patch
drivers-edac-new-i82443bxgz-mc-driver-broken.patch
drivers-edac-add-new-nmi-rescan.patch
drivers-edac-mod-use-edac_coreh.patch
drivers-edac-add-dev_name-getter-function.patch
drivers-edac-new-inte-30x0-mc-driver.patch
drivers-edac-mod-mc-to-use-workq-instead-of-kthread.patch
drivers-edac-updated-pci-monitoring.patch
drivers-edac-mod-assert_error-check.patch
drivers-edac-mod-pci-poll-names.patch
drivers-edac-core-lindent-cleanup.patch
drivers-edac-edac_device-sysfs-cleanup.patch
drivers-edac-cleanup-workq-ifdefs.patch
drivers-edac-lindent-amd76x.patch
drivers-edac-lindent-i5000.patch
drivers-edac-lindent-e7xxx.patch
drivers-edac-lindent-i3000.patch
drivers-edac-lindent-i82860.patch
drivers-edac-lindent-i82875p.patch
drivers-edac-lindent-e752x.patch
drivers-edac-lindent-i82443bxgx.patch
drivers-edac-lindent-r82600.patch
drivers-edac-drivers-to-use-new-pci-operation.patch
drivers-edac-add-device-sysfs-attributes.patch
drivers-edac-device-output-clenaup.patch
drivers-edac-add-info-kconfig.patch
drivers-edac-update-maintainers-files-for-edac.patch
drivers-edac-cleanup-spaces-gotos-after-lindent-messup.patch
driver-edac-add-mips-and-ppc-visibility.patch
driver-edac-mod-race-fix-i82875p.patch
driver-edac-fix-ignored-return-i82875p.patch
include-linux-pci_id-h-add-amd-northbridge-defines.patch
driver-edac-i5000-define-typo.patch
driver-edac-remove-null-from-statics.patch
driver-edac-i5000-code-tidying.patch
driver-edac-edac_device-code-tidying.patch
driver-edac-mod-edac_align_ptr-function.patch
driver-edac-mod-edac_opt_state_to_string-function.patch
driver-edac-remove-file-edac_mc-h.patch

 Probably hold - there are sysfs issues and a large number of update patches
 in my inbox.  Might merge, undecided.

cpuset-zero-malloc-revert-the-old-cpuset-fix.patch
containersv10-basic-container-framework.patch
containersv10-basic-container-framework-fix.patch
containersv10-basic-container-framework-fix-2.patch
containersv10-basic-container-framework-fix-3.patch
containersv10-basic-container-framework-fix-for-bad-lock-balance-in-containers.patch
containersv10-example-cpu-accounting-subsystem.patch
containersv10-example-cpu-accounting-subsystem-fix.patch
containersv10-add-tasks-file-interface.patch
containersv10-add-tasks-file-interface-fix.patch
containersv10-add-tasks-file-interface-fix-2.patch
containersv10-add-fork-exit-hooks.patch
containersv10-add-fork-exit-hooks-fix.patch
containersv10-add-container_clone-interface.patch
containersv10-add-container_clone-interface-fix.patch
containersv10-add-procfs-interface.patch
containersv10-add-procfs-interface-fix.patch
containersv10-make-cpusets-a-client-of-containers.patch
containersv10-make-cpusets-a-client-of-containers-whitespace.patch
containersv10-share-css_group-arrays-between-tasks-with-same-container-memberships.patch
containersv10-share-css_group-arrays-between-tasks-with-same-container-memberships-fix.patch
containersv10-share-css_group-arrays-between-tasks-with-same-container-memberships-cpuset-zero-malloc-fix-for-new-containers.patch
containersv10-simple-debug-info-subsystem.patch
containersv10-simple-debug-info-subsystem-fix.patch
containersv10-simple-debug-info-subsystem-fix-2.patch
containersv10-support-for-automatic-userspace-release-agents.patch
containersv10-support-for-automatic-userspace-release-agents-whitespace.patch
add-containerstats-v3.patch
add-containerstats-v3-fix.patch
update-getdelays-to-become-containerstats-aware.patch
containers-implement-subsys-post_clone.patch
containers-implement-namespace-tracking-subsystem-v3.patch

 Container stuff.  Hold, I guess.  I was expecting updates from Paul.

fix-raw_spinlock_t-vs-lockdep.patch
lockdep-sanitise-config_prove_locking.patch
lockdep-reduce-the-ifdeffery.patch
lockstat-core-infrastructure.patch
lockstat-human-readability-tweaks.patch
lockstat-hook-into-spinlock_t-rwlock_t-rwsem-and-mutex.patch

 Merge

lockdep-various-fixes.patch
lockdep-fixup-sk_callback_lock-annotation.patch
lockstat-measure-lock-bouncing.patch
lockstat-better-class-name-representation.patch
lockdep-debugging-give-stacktrace-for-init_error.patch
stacktrace-fix-header-file-for-config_stacktrace.patch

 Merge

some-kmalloc-memset-kzalloc-tree-wide.patch

 Merge

reiser4-sb_sync_inodes.patch
reiser4-export-remove_from_page_cache.patch
reiser4-export-radix_tree_preload.patch
reiser4-export-find_get_pages.patch
make-copy_from_user_inatomic-not-zero-the-tail-on-i386-vs-reiser4.patch
reiser4.patch
mm-clean-up-and-kernelify-shrinker-registration-reiser4.patch
reiser4-fix-for-new-aops-patches.patch
git-block-vs-reiser4.patch

 Hold.

make-sure-nobodys-leaking-resources.patch
journal_add_journal_head-debug.patch
page-owner-tracking-leak-detector.patch
releasing-resources-with-children.patch
nr_blockdev_pages-in_interrupt-warning.patch
detect-atomic-counter-underflows.patch
device-suspend-debug.patch
#slab-cache-shrinker-statistics.patch
mm-debug-dump-pageframes-on-bad_page.patch
make-frame_pointer-default=y.patch
mutex-subsystem-synchro-test-module.patch
slab-leaks3-default-y.patch
profile-likely-unlikely-macros.patch
put_bh-debug.patch
acpi_format_exception-debug.patch
lockdep-show-held-locks-when-showing-a-stackdump.patch
add-debugging-aid-for-memory-initialisation-problems.patch
kmap_atomic-debugging.patch
shrink_slab-handle-bad-shrinkers.patch
keep-track-of-network-interface-renaming.patch
workaround-for-a-pci-restoring-bug.patch
prio_tree-debugging-patch.patch
check_dirty_inode_list.patch
alloc_pages-debug.patch
squash-ipc-warnings.patch
random-warning-squishes.patch
w1-build-fix.patch

 -mm only things.

intel iommu (Re: -mm merge plans for 2.6.23)

[Jan Engelhardt]

On Jul 10 2007 01:31, Andrew Morton wrote:

>intel-iommu-dmar-detection-and-parsing-logic.patch
>intel-iommu-pci-generic-helper-function.patch
>intel-iommu-clflush_cache_range-now-takes-size-param.patch
>intel-iommu-iova-allocation-and-management-routines.patch
>intel-iommu-intel-iommu-driver.patch
>intel-iommu-avoid-memory-allocation-failures-in-dma-map-api-calls.patch
>intel-iommu-intel-iommu-cmdline-option-forcedac.patch
>intel-iommu-dmar-fault-handling-support.patch
>intel-iommu-iommu-gfx-workaround.patch
>intel-iommu-iommu-floppy-workaround.patch

Here's some fix:


Signed-off-by: Jan Engelhardt <jengelh@gmx.de>

---
 arch/x86_64/Kconfig |   20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

Index: linux-2.6.22-rc6/arch/x86_64/Kconfig
===================================================================
--- linux-2.6.22-rc6.orig/arch/x86_64/Kconfig
+++ linux-2.6.22-rc6/arch/x86_64/Kconfig
@@ -753,11 +753,11 @@ config DMAR
 	depends on PCI_MSI && ACPI && EXPERIMENTAL
 	default y
 	help
-	  DMA remapping(DMAR) devices support enables independent address
-	  translations for Direct Memory Access(DMA) from Devices.
+	  DMA remapping (DMAR) devices support enables independent address
+	  translations for Direct Memory Access (DMA) from devices.
 	  These DMA remapping devices are reported via ACPI tables
-	  and includes pci device scope covered by these DMA
-	  remapping device.
+	  and include PCI device scope covered by these DMA
+	  remapping devices.
 
 config DMAR_GFX_WA
 	bool "Support for Graphics workaround"
@@ -765,9 +765,9 @@ config DMAR_GFX_WA
 	default y
 	help
 	 Current Graphics drivers tend to use physical address
-	 for DMA and avoid using DMA api's. Setting this config
+	 for DMA and avoid using DMA APIs. Setting this config
 	 option permits the IOMMU driver to set a unity map for
-	 all the OS visible memory. Hence the driver can continue
+	 all the OS-visible memory. Hence the driver can continue
 	 to use physical addresses for DMA.
 
 config DMAR_FLOPPY_WA
@@ -775,10 +775,10 @@ config DMAR_FLOPPY_WA
 	depends on DMAR
 	default y
 	help
-	 Floppy disk drivers are know to by pass dma api calls
-	 their by failing to work when IOMMU is enabled. This
-	 work around will setup a 1 to 1 mappings for the first
-	 16M to make floppy(isa device) work.
+	 Floppy disk drivers are know to bypass DMA API calls
+	 thereby failing to work when IOMMU is enabled. This
+	 workaround will setup a 1:1 mapping for the first
+	 16M to make floppy (an ISA device) work.
 
 source "drivers/pci/pcie/Kconfig"
 

Re: -mm merge plans for 2.6.23 -- sys_fallocate

[Heiko Carstens]

> fallocate-implementation-on-i86-x86_64-and-powerpc.patch

Still broken: arch/x86_64/ia32/ia32entry.S wants compat_sys_fallocate instead
of sys_fallocate. Also compat_sys_fallocate probably should be moved to
fs/compat.c.

> fallocate-on-s390.patch

We reserved a different syscall number than the one that is used right now
in the patch. Please drop this patch... Martin or I will wire up the syscall
as soon as the x86 variant is merged. Everything else just causes trouble and
confusion.

Re: cpuset-remove-sched-domain-hooks-from-cpusets

[Paul Jackson]

Andrew wrote:
> cpuset-remove-sched-domain-hooks-from-cpusets.patch
> 
>  Stuck.

Well ... a few hours ago I just finished the 'unrelated task' that kept
me from doing much cpuset work the last six months.

So, after a little bit of saved up vacation (SGI sabbatical - yippee!),
I should be able to dig into this, see what Dinikar and Cliff have been
up to here, and make some progress on this.  Cliff -- did I see some
work from you go by relating to cpusets and the sched domain hooks in
cpusets?

As before, Andrew, if you're getting bored holding this patch, it's ok
to drop it, even though I still figure you'll see it again, as part of
a patch set to improve this cpuset to sched domain interaction.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.925.600.0401

Re: -mm merge plans for 2.6.23 -- sys_fallocate

[Andrew Morton]

On Tue, 10 Jul 2007 11:07:37 +0200 Heiko Carstens <heiko.carstens@de.ibm.com> wrote:

> > fallocate-implementation-on-i86-x86_64-and-powerpc.patch
> 
> Still broken: arch/x86_64/ia32/ia32entry.S wants compat_sys_fallocate instead
> of sys_fallocate. Also compat_sys_fallocate probably should be moved to
> fs/compat.c.
> 
> > fallocate-on-s390.patch
> 
> We reserved a different syscall number than the one that is used right now
> in the patch. Please drop this patch... Martin or I will wire up the syscall
> as soon as the x86 variant is merged. Everything else just causes trouble and
> confusion.

OK, I dropped all the fallocate patches.

That means that a few other syscalls (or at least, revoke) get renumbered.

Re: -mm merge plans for 2.6.23

[Con Kolivas]

On Tuesday 10 July 2007 18:31, Andrew Morton wrote:
> When replying, please rewrite the subject suitably and try to Cc: the
> appropriate developer(s).

~swap prefetch

Nick's only remaining issue which I could remotely identify was to make it 
cpuset aware:
http://marc.info/?l=linux-mm&m=117875557014098&w=2
as discussed with Paul Jackson it was cpuset aware:
http://marc.info/?l=linux-mm&m=117895463120843&w=2

I fixed all bugs I could find and improved it as much as I could last kernel 
cycle.

Put me and the users out of our misery and merge it now or delete it forever 
please. And if the meaningless handwaving that I 100% expect as a response 
begins again, then that's fine. I'll take that as a no and you can dump it.

-- 
-ck

containers (was Re: -mm merge plans for 2.6.23)

[Srivatsa Vaddagiri]

On Tue, Jul 10, 2007 at 01:31:52AM -0700, Andrew Morton wrote:
> cpuset-zero-malloc-revert-the-old-cpuset-fix.patch
> containersv10-basic-container-framework.patch
> containersv10-basic-container-framework-fix.patch
> containersv10-basic-container-framework-fix-2.patch
> containersv10-basic-container-framework-fix-3.patch
> containersv10-basic-container-framework-fix-for-bad-lock-balance-in-containers.patch
> containersv10-example-cpu-accounting-subsystem.patch
> containersv10-example-cpu-accounting-subsystem-fix.patch
> containersv10-add-tasks-file-interface.patch
> containersv10-add-tasks-file-interface-fix.patch
> containersv10-add-tasks-file-interface-fix-2.patch
> containersv10-add-fork-exit-hooks.patch
> containersv10-add-fork-exit-hooks-fix.patch
> containersv10-add-container_clone-interface.patch
> containersv10-add-container_clone-interface-fix.patch
> containersv10-add-procfs-interface.patch
> containersv10-add-procfs-interface-fix.patch
> containersv10-make-cpusets-a-client-of-containers.patch
> containersv10-make-cpusets-a-client-of-containers-whitespace.patch
> containersv10-share-css_group-arrays-between-tasks-with-same-container-memberships.patch
> containersv10-share-css_group-arrays-between-tasks-with-same-container-memberships-fix.patch
> containersv10-share-css_group-arrays-between-tasks-with-same-container-memberships-cpuset-zero-malloc-fix-for-new-containers.patch
> containersv10-simple-debug-info-subsystem.patch
> containersv10-simple-debug-info-subsystem-fix.patch
> containersv10-simple-debug-info-subsystem-fix-2.patch
> containersv10-support-for-automatic-userspace-release-agents.patch
> containersv10-support-for-automatic-userspace-release-agents-whitespace.patch
> add-containerstats-v3.patch
> add-containerstats-v3-fix.patch
> update-getdelays-to-become-containerstats-aware.patch
> containers-implement-subsys-post_clone.patch
> containers-implement-namespace-tracking-subsystem-v3.patch
> 
>  Container stuff.  Hold, I guess.  I was expecting updates from Paul.

Paul,
	Are you working on a new version? I thought it was mostly ready
for mainline.

-- 
Regards,
vatsa

Re: containers (was Re: -mm merge plans for 2.6.23)

[Ingo Molnar]

* Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> wrote:

> On Tue, Jul 10, 2007 at 01:31:52AM -0700, Andrew Morton wrote:
> > cpuset-zero-malloc-revert-the-old-cpuset-fix.patch
> > containersv10-basic-container-framework.patch
> > containersv10-basic-container-framework-fix.patch
> > containersv10-basic-container-framework-fix-2.patch
> > containersv10-basic-container-framework-fix-3.patch
> > containersv10-basic-container-framework-fix-for-bad-lock-balance-in-containers.patch
> > containersv10-example-cpu-accounting-subsystem.patch
> > containersv10-example-cpu-accounting-subsystem-fix.patch
> > containersv10-add-tasks-file-interface.patch
> > containersv10-add-tasks-file-interface-fix.patch
> > containersv10-add-tasks-file-interface-fix-2.patch
> > containersv10-add-fork-exit-hooks.patch
> > containersv10-add-fork-exit-hooks-fix.patch
> > containersv10-add-container_clone-interface.patch
> > containersv10-add-container_clone-interface-fix.patch
> > containersv10-add-procfs-interface.patch
> > containersv10-add-procfs-interface-fix.patch
> > containersv10-make-cpusets-a-client-of-containers.patch
> > containersv10-make-cpusets-a-client-of-containers-whitespace.patch
> > containersv10-share-css_group-arrays-between-tasks-with-same-container-memberships.patch
> > containersv10-share-css_group-arrays-between-tasks-with-same-container-memberships-fix.patch
> > containersv10-share-css_group-arrays-between-tasks-with-same-container-memberships-cpuset-zero-malloc-fix-for-new-containers.patch
> > containersv10-simple-debug-info-subsystem.patch
> > containersv10-simple-debug-info-subsystem-fix.patch
> > containersv10-simple-debug-info-subsystem-fix-2.patch
> > containersv10-support-for-automatic-userspace-release-agents.patch
> > containersv10-support-for-automatic-userspace-release-agents-whitespace.patch
> > add-containerstats-v3.patch
> > add-containerstats-v3-fix.patch
> > update-getdelays-to-become-containerstats-aware.patch
> > containers-implement-subsys-post_clone.patch
> > containers-implement-namespace-tracking-subsystem-v3.patch
> > 
> >  Container stuff.  Hold, I guess.  I was expecting updates from Paul.
> 
> Paul,
> 	Are you working on a new version? I thought it was mostly ready
> for mainline.

in particular CONFIG_FAIR_GROUP_SCHED depends on these APIs. Once the 
APIs to configure are upstream, the group scheduler can be enabled too. 
(basically all the group scheduling bits are upstream now as part of 
CFS.)

	Ingo

fallocate-implementation-on-i86-x86_64-and-powerpc.patch (was: re: -mm merge plans for 2.6.23)

[Theodore Tso]

On Tue, Jul 10, 2007 at 01:31:52AM -0700, Andrew Morton wrote:
>  Merge
> 
> fallocate-implementation-on-i86-x86_64-and-powerpc.patch

Andrew,

Could you replace the comment/header section of
fallocate-implementation-on-i86-x86_64-and-powerpc.patch with the
following (attached below) ?  This is from the ext4 patches, where
Amit had cleaned up description, which will make for a cleaner and
easier to understand submission into the git tree.

I've reviewed the other fallocate patches, noting the request to drop
the s390 patches since Martin has said he will wire up it up after
this hits mainline, and the only other change that I've found between
what we have in the ext4 tree and -mm is that we have 

	fallocate-on-ia64.patch
and
	fallocate-on-ia64-fix.patch 

merged into a single patch.  It probably would be better to merge them
before sending it off to Linus, in the interests of cleanliness and
making the tree more git-bisect friendly.

Regards,

						- Ted


From: Amit Arora <aarora@in.ibm.com>

sys_fallocate() implementation on i386, x86_64 and powerpc

fallocate() is a new system call being proposed here which will allow
applications to preallocate space to any file(s) in a file system.
Each file system implementation that wants to use this feature will need
to support an inode operation called ->fallocate().
Applications can use this feature to avoid fragmentation to certain
level and thus get faster access speed. With preallocation, applications
also get a guarantee of space for particular file(s) - even if later the
the system becomes full.

Currently, glibc provides an interface called posix_fallocate() which
can be used for similar cause. Though this has the advantage of working
on all file systems, but it is quite slow (since it writes zeroes to
each block that has to be preallocated). Without a doubt, file systems
can do this more efficiently within the kernel, by implementing
the proposed fallocate() system call. It is expected that
posix_fallocate() will be modified to call this new system call first
and incase the kernel/filesystem does not implement it, it should fall
back to the current implementation of writing zeroes to the new blocks.
ToDos:
1. Implementation on other architectures (other than i386, x86_64,
ppc64 and s390(x)). David Chinner has already posted a patch for ia64.
2. A generic file system operation to handle fallocate
(generic_fallocate), for filesystems that do _not_ have the fallocate
inode operation implemented.
3. Changes to glibc,
   a) to support fallocate() system call
   b) to make posix_fallocate() and posix_fallocate64() call fallocate()


Signed-off-by: Amit Arora <aarora@in.ibm.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

clam

[Andy Whitcroft]

Andrew Morton wrote:

[...]
> lumpy-reclaim-v4.patch
> have-kswapd-keep-a-minimum-order-free-other-than-order-0.patch
> only-check-absolute-watermarks-for-alloc_high-and-alloc_harder-allocations.patch
> 
>  Lumpy reclaim.  In a similar situation to Mel's patches.  Stuck due to
>  general lack or interest and effort.

The lumpy reclaim patches originally came out of work to support Mel's
anti-fragmentation work.  As such I think they have become somewhat
attached to those patches.  Whilst lumpy is most effective where
placement controls are in place as offered by Mel's work, we see benefit
from reduction in the "blunderbuss" effect when we reclaim at higher
orders.  While placement control is pretty much required for the very
highest orders such as huge page size, lower order allocations are
benefited in terms of lower collateral damage.

There are now a few areas other than huge page allocations which can
benefit.  Stacks are still order 1.  Jumbo frames want higher order
contiguous pages for there incoming hardware buffers.  SLUB is showing
performance benefits from moving to a higher allocation order.  All of
these should benefit from more aggressive targeted reclaim, indeed I
have been surprised just how often my test workloads trigger lumpy at
order 1 to get new stacks.

Truly representative work loads are hard to generate for some of these.
 Though we have heard some encouraging noises from those who can
reproduce these problems.

[...]

-apw

Re: -mm merge plans for 2.6.23

[Serge E. Hallyn]

Quoting Andrew Morton (akpm@linux-foundation.org):
...
> implement-file-posix-capabilities.patch
> implement-file-posix-capabilities-fix.patch
> file-capabilities-introduce-cap_setfcap.patch
> file-capabilities-get_file_caps-cleanups.patch
> file-caps-update-selinux-xattr-hooks.patch
> 
>  file-caps seems to be stuck.  There has been some movement lately, might
>  merge it subject to suiable acks from suitable parties.

Andrew Morgan has requested a series of changes.  Since one of these
would involve a change in the on-disk format of file capabilities, I
guess these should (sigh) wait another cycle.

I will try to get that change out the door next, as soon as possible, so
that hopefully there are no more definite blocking requests.

thanks,
-serge

Re: -mm merge plans for 2.6.23

[Rafael J. Wysocki]

On Tuesday, 10 July 2007 10:31, Andrew Morton wrote:
[--snip--]
>
> freezer-make-kernel-threads-nonfreezable-by-default.patch
> 
>  Merge, subject to re-review.

Hmm, I'm not sure what that means.  Am I supposed to do anything about it?

Greetings,
Rafael


-- 
"Premature optimization is the root of all evil." - Donald Knuth

Re: -mm merge plans for 2.6.23 -- sys_fallocate

[Theodore Tso]

On Tue, Jul 10, 2007 at 02:22:13AM -0700, Andrew Morton wrote:
> On Tue, 10 Jul 2007 11:07:37 +0200 Heiko Carstens <heiko.carstens@de.ibm.com> wrote:
> > We reserved a different syscall number than the one that is used right now
> > in the patch. Please drop this patch... Martin or I will wire up the syscall
> > as soon as the x86 variant is merged. Everything else just causes trouble and
> > confusion.
> 
> OK, I dropped all the fallocate patches.

Andrew, I want to clarify who is going to push the fallocate patches.
I can either push them to Linus as part of the ext4 patch set, or we
can wait for you to push them.  I thought since you had them in -mm
and we were going to wait you to push them (and presume that this was
going to happen soon).

Alternatively I can push them directly to Linus along with other ext4
patches.  We can drop the s390 patch if Martin or Heiko wants to wire
it up themselves.

As far as I know there hasn't been any real contention on the actual
syscall patches, other than the numbering issues, so it seems that
pushing them to Linus sooner rather than later is the right thing to
do. 

I don't particularly care who pushes them, just as long as they get
pushed.  :-)  

So if you've dropped, shall I push them to Linus as part of the ext4
patches we've been planning on pushing?

Regards,

					- Ted

Re: -mm merge plans for 2.6.23 (pcmcia)

[Randy Dunlap]

On Tue, 10 Jul 2007 01:31:52 -0700 Andrew Morton wrote:

> 
> When replying, please rewrite the subject suitably and try to Cc: the
> appropriate developer(s).

...

> pcmcia-delete-obsolete-pcmcia_ioctl-feature.patch
> use-menuconfig-objects-pcmcia.patch
> 
>  Am a bit stuck with the pcmcia patches.  Dominik has disappeared.

The menuconfig patch looks fine.

I looked at the May-2007 discussion of ioctl removal.
I don't see that much has changed since then, so it's either be
brave/foolish/whatever and see what happens or just wait.
I'll gladly send a patch to update the removal date in
feature-removal-schedule.txt

---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***

Re: -mm merge plans for 2.6.23 - ioat/dma engine

[Kok, Auke]

Andrew Morton wrote:
> git-ioat-vs-git-md-accel.patch
> ioat-warning-fix.patch
> fix-i-oat-for-kexec.patch
> 
>  I don't seem to be able to get rid of these.  Chris Leech appears to have
>  vanished.

Chris is a moving target. Thankfully we have Shannon Nelson taking over Chris' 
duties. Shannon, can you take a look at these and see what needs to happen to it 
? Most likely these just need to be pushed to the right person.

Cheers,

Auke


PS: I think we should add an I/OAT / DMA engine section in the MAINTAINERS...

Re: fallocate-implementation-on-i86-x86_64-and-powerpc.patch (was: re: -mm merge plans for 2.6.23)

[Andrew Morton]

On Tue, 10 Jul 2007 07:52:51 -0400 Theodore Tso <tytso@mit.edu> wrote:

> On Tue, Jul 10, 2007 at 01:31:52AM -0700, Andrew Morton wrote:
> >  Merge
> > 
> > fallocate-implementation-on-i86-x86_64-and-powerpc.patch
> 
> Andrew,
> 
> Could you replace the comment/header section of
> fallocate-implementation-on-i86-x86_64-and-powerpc.patch with the
> following (attached below) ?  This is from the ext4 patches, where
> Amit had cleaned up description, which will make for a cleaner and
> easier to understand submission into the git tree.

There were issues with the x86 patch, the s390 patch was wrong and Tony
wants the the ia64 patch to use a different syscall number.

So I dropped everything.  Let's start again from scratch.  I'd suggest that
for now we go with just an i386/x86_64 implementation, let the arch
maintainers wire things up when that has settled down.

Re: -mm merge plans for 2.6.23 -- sys_fallocate

[Andrew Morton]

On Tue, 10 Jul 2007 11:45:03 -0400 Theodore Tso <tytso@mit.edu> wrote:

> On Tue, Jul 10, 2007 at 02:22:13AM -0700, Andrew Morton wrote:
> > On Tue, 10 Jul 2007 11:07:37 +0200 Heiko Carstens <heiko.carstens@de.ibm.com> wrote:
> > > We reserved a different syscall number than the one that is used right now
> > > in the patch. Please drop this patch... Martin or I will wire up the syscall
> > > as soon as the x86 variant is merged. Everything else just causes trouble and
> > > confusion.
> > 
> > OK, I dropped all the fallocate patches.
> 
> Andrew, I want to clarify who is going to push the fallocate patches.
> I can either push them to Linus as part of the ext4 patch set, or we
> can wait for you to push them.  I thought since you had them in -mm
> and we were going to wait you to push them (and presume that this was
> going to happen soon).

How about you send them?  The syscall numbers might need to be changed
based upon when/whether the revoke patches get merged.

> Alternatively I can push them directly to Linus along with other ext4
> patches.

I note that nobody really bothered reviewing all those ext4 patches.

Do you feel that they have been adequately reviewed?  I don't.  I guess I
know what I'll be doing today :(

>  We can drop the s390 patch if Martin or Heiko wants to wire
> it up themselves.

ia64 needs changing too.

Re: -mm merge plans for 2.6.23 (pcmcia)

[Andrew Morton]

On Tue, 10 Jul 2007 09:29:58 -0700 Randy Dunlap <randy.dunlap@oracle.com> wrote:

> On Tue, 10 Jul 2007 01:31:52 -0700 Andrew Morton wrote:
> 
> > 
> > When replying, please rewrite the subject suitably and try to Cc: the
> > appropriate developer(s).
> 
> ...
> 
> > pcmcia-delete-obsolete-pcmcia_ioctl-feature.patch
> > use-menuconfig-objects-pcmcia.patch
> > 
> >  Am a bit stuck with the pcmcia patches.  Dominik has disappeared.
> 
> The menuconfig patch looks fine.

Yeah, I'll merge that.

> I looked at the May-2007 discussion of ioctl removal.
> I don't see that much has changed since then, so it's either be
> brave/foolish/whatever and see what happens or just wait.
> I'll gladly send a patch to update the removal date in
> feature-removal-schedule.txt

I have a note here that the ioctl-removal patch needs Dominik
consideration.  I see no rush on it so I'll just sit on it.

ata and netdev (was Re: -mm merge plans for 2.6.23)

[Jeff Garzik]

(just to provide my indicator of status)

Andrew Morton wrote:
> libata-config_pm=n-compile-fix.patch

that's for a branch that you don't get via libata-dev#ALL, #mv-ahci-pata.


> pata_acpi-restore-driver.patch

see Alan's comments.  I've been ignoring pata_acpi for a while, because 
IMO it always needed work.


> libata-core-convert-to-use-cancel_rearming_delayed_work.patch

will merge


> libata-implement-ata_wait_after_reset.patch

I'm pretty much this is obsolete.  Tejun?


> sata_promise-sata-hotplug-support.patch

will merge


> libata-add-irq_flags-to-struct-pata_platform_info-fix.patch

are other pata_platform people happy with this?  I don't know embedded 
well enough to know if adding this struct member will break things.


> ata-add-the-sw-ncq-support-to-sata_nv-for-mcp51-mcp55-mcp61.patch
> sata_nv-allow-changing-queue-depth.patch

should be combined, really.  will merge eventually.  basic concept OK, 
but need to review in depth.

> pata_hpt3x3-major-reworking-and-testing.patch
> iomap-sort-out-the-broken-address-reporting-caused-by-the-iomap-layer.patch
> ata-use-iomap_name.patch

generally OK


> libata-check-for-an-support.patch
> scsi-expose-an-to-user-space.patch
> libata-expose-an-to-user-space.patch
> scsi-save-disk-in-scsi_device.patch
> libata-send-event-when-an-received.patch
> 
>  Am sitting on these due to confusion regarding the status of the ata-ahci
>  patches.

I will apply what I can, but it seems there are lifetime problems


> ata-ahci-alpm-store-interrupt-value.patch
> ata-ahci-alpm-expose-power-management-policy-option-to-users.patch
> ata-ahci-alpm-enable-link-power-management-for-ata-drivers.patch
> ata-ahci-alpm-enable-aggressive-link-power-management-for-ahci-controllers.patch
> 
>  These appear to need some work.

seemed mostly OK to me.  what comments did I miss?


> libata-add-human-readable-error-value-decoding.patch

still pondering; in my mbox queue

> libata-fix-hopefully-all-the-remaining-problems-with.patch
> testing-patch-for-ali-pata-fixes-hopefully-for-the-problems-with-atapi-dma.patch
> pata_ali-more-work.patch

No idea.  I would poke Alan.  Probably drop.


> 8139too-force-media-setting-fix.patch
> blackfin-on-chip-ethernet-mac-controller-driver.patch
> atari_pamsnetc-old-declaration-ritchie-style-fix.patch
> sundance-phy-address-form-0-only-for-device-id-0x0200.patch

Needs a bug fix, so that the newly modified loop doesn't scan the final 
phy id, then loop back around to scan the first again.


> 3x59x-fix-pci-resource-management.patch
> update-smc91x-driver-with-arm-versatile-board-info.patch
> drivers-net-ns83820c-add-paramter-to-disable-auto.patch
> 
>  netdev patches which are stuck in limbo land.

?  I don't think I've seen these.


> bonding-bond_mainc-make-2-functions-static.patch

FWIW bonding stuff should go to me, since it lives mostly in drivers/net


> x86-initial-fixmap-support.patch

Andi material?


> mm-revert-kernel_ds-buffered-write-optimisation.patch
> revert-81b0c8713385ce1b1b9058e916edcf9561ad76d6.patch
> revert-6527c2bdf1f833cc18e8f42bd97973d583e4aa83.patch
> mm-clean-up-buffered-write-code.patch
> mm-debug-write-deadlocks.patch
> mm-trim-more-holes.patch
> mm-buffered-write-cleanup.patch
> mm-write-iovec-cleanup.patch
> mm-fix-pagecache-write-deadlocks.patch
> mm-buffered-write-iterator.patch
> fs-fix-data-loss-on-error.patch
> mm-restore-kernel_ds-optimisations.patch
>  pagefault-in-write deadlock fixes.  Will hold for 2.6.24.

Any of the above worth 2.6.23?  Just wondering if they were useful 
cleanups / minor fixes prior to new aops patches?


> more-scheduled-oss-driver-removal.patch

ACK


> oss-trident-massive-whitespace-removal.patch
> oss-trident-fix-locking-around-write_voice_regs.patch
> oss-trident-replace-deprecated-pci_find_device-with-pci_get_device.patch
> remove-options-depending-on-oss_obsolete.patch
> 
>  Merge

what about just removing the OSS drivers in question?  :)


> intel-iommu-dmar-detection-and-parsing-logic.patch
> intel-iommu-pci-generic-helper-function.patch
> intel-iommu-clflush_cache_range-now-takes-size-param.patch
> intel-iommu-iova-allocation-and-management-routines.patch
> intel-iommu-intel-iommu-driver.patch
> intel-iommu-avoid-memory-allocation-failures-in-dma-map-api-calls.patch
> intel-iommu-intel-iommu-cmdline-option-forcedac.patch
> intel-iommu-dmar-fault-handling-support.patch
> intel-iommu-iommu-gfx-workaround.patch
> intel-iommu-iommu-floppy-workaround.patch
> 
>  Don't know.  I don't think there were any great objections, but I don't
>  think much benefit has been demonstrated?

Just the general march of progress on new hardware :)

I would like to see this support merged in /some/ form.  We've been 
telling Intel for years they were sillyheads for not bothering with an 
IOMMU.  Now that they have, we should give them a cookie and support 
good technology.

	Jeff

Re: fallocate-implementation-on-i86-x86_64-and-powerpc.patch

[Jeff Garzik]

Andrew Morton wrote:
> So I dropped everything.  Let's start again from scratch.  I'd suggest that
> for now we go with just an i386/x86_64 implementation, let the arch
> maintainers wire things up when that has settled down.


It's my observation that that plan usually works the best.  Arch 
maintainers come along and wire up batches of syscalls when they have a 
chance to glance at the ABI, and catch up with x86[-64].

	Jeff

ext2 reservations (Re: -mm merge plans for 2.6.23)

[Alexey Dobriyan]

> ext2-reservations.patch
> 
>  Still needs decent testing.

Was this oops silently fixed?
http://lkml.org/lkml/2007/3/2/138
2.6.21-rc2-mm1: EIP is at ext2_discard_reservation+0x1c/0x52

I still have that ext2 partition backed up.

Re: -mm merge plans for 2.6.23 -- sys_fallocate

[Heiko Carstens]

> Alternatively I can push them directly to Linus along with other ext4
> patches.  We can drop the s390 patch if Martin or Heiko wants to wire
> it up themselves.

Yes, please drop the s390 patch. In general it seems to be better if only
one architecture gets a syscall wired up initially and let other arches
follow later.

Just wondering if the x86_64 compat syscall gets ever fixed? I think
I mentioned already three or four times to Amit that it is broken.
Or is it that nobody cares? Dunno..

In addition there used to be a somewhat inofficial rule that new syscalls
have to come with a test program, so people can easily test if they wired
up the syscall correctly.

RE: -mm merge plans for 2.6.23 - ioat/dma engine

[Nelson, Shannon]

Kok, Auke wrote: 
>Andrew Morton wrote:
>> git-ioat-vs-git-md-accel.patch
>> ioat-warning-fix.patch
>> fix-i-oat-for-kexec.patch
>> 
>>  I don't seem to be able to get rid of these.  Chris Leech 
>appears to have
>>  vanished.
>
>Chris is a moving target. Thankfully we have Shannon Nelson 
>taking over Chris' 
>duties. Shannon, can you take a look at these and see what 
>needs to happen to it 
>? Most likely these just need to be pushed to the right person.

Auke: Thanks for the introduction :-).

Andrew: All three of these patches are reasonable and can be pushed on
up.  You can add my sign-off to all three:
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>

>
>Cheers,
>
>Auke
>
>
>PS: I think we should add an I/OAT / DMA engine section in the 
>MAINTAINERS...
>

I'll be posting a MAINTAINERS patch Real Soon Now with my name on
IOAT/DMA.

sln
======================================================================
Mr. Shannon Nelson                 LAN Access Division, Intel Corp.
Shannon.Nelson@intel.com                I don't speak for Intel
(503) 712-7659                    Parents can't afford to be squeamish.

Re: -mm merge plans for 2.6.23 -- sys_fallocate

[Mark Fasheh]

On Tue, Jul 10, 2007 at 11:45:03AM -0400, Theodore Tso wrote:
> On Tue, Jul 10, 2007 at 02:22:13AM -0700, Andrew Morton wrote:
> > On Tue, 10 Jul 2007 11:07:37 +0200 Heiko Carstens <heiko.carstens@de.ibm.com> wrote:
> > > We reserved a different syscall number than the one that is used right now
> > > in the patch. Please drop this patch... Martin or I will wire up the syscall
> > > as soon as the x86 variant is merged. Everything else just causes trouble and
> > > confusion.
> > 
> > OK, I dropped all the fallocate patches.
> 
> Andrew, I want to clarify who is going to push the fallocate patches.
> I can either push them to Linus as part of the ext4 patch set, or we
> can wait for you to push them.  I thought since you had them in -mm
> and we were going to wait you to push them (and presume that this was
> going to happen soon).
> 
> Alternatively I can push them directly to Linus along with other ext4
> patches.  We can drop the s390 patch if Martin or Heiko wants to wire
> it up themselves.
> 
> As far as I know there hasn't been any real contention on the actual
> syscall patches, other than the numbering issues, so it seems that
> pushing them to Linus sooner rather than later is the right thing to
> do. 

Where is the latest and greatest version of those patches? Is it still the
patch set distributed in 2.6.22-rc6-mm1? I'd mostly like to see the final
set of flags we're planning on supporting. But yeah, I second the "sooner
rather than later" :)
	--Mark

--
Mark Fasheh
Senior Software Developer, Oracle
mark.fasheh@oracle.com

Re: ata and netdev (was Re: -mm merge plans for 2.6.23)

[Andrew Morton]

On Tue, 10 Jul 2007 13:42:16 -0400
Jeff Garzik <jeff@garzik.org> wrote:

> 
> (just to provide my indicator of status)

Thanks.

> > libata-add-irq_flags-to-struct-pata_platform_info-fix.patch
> 
> are other pata_platform people happy with this?  I don't know embedded 
> well enough to know if adding this struct member will break things.

This is just a silly remove-unneeded-cast-of-void* cleanup.  I wrote this
as a fixup against
libata-add-irq_flags-to-struct-pata_platform_info.patch with the intention
of folding it into that base patch, but you went and merged the submitter's
original patch so this trivial fixup got stranded in -mm.  Feel free to give
it the piss-off-too-trivial treatment.

> > ata-ahci-alpm-store-interrupt-value.patch
> > ata-ahci-alpm-expose-power-management-policy-option-to-users.patch
> > ata-ahci-alpm-enable-link-power-management-for-ata-drivers.patch
> > ata-ahci-alpm-enable-aggressive-link-power-management-for-ahci-controllers.patch
> > 
> >  These appear to need some work.
> 
> seemed mostly OK to me.  what comments did I miss?

Oh, I thought these were the patches which affected scsi and which James
had issues with.  I guess I got confused.

> 
> > libata-add-human-readable-error-value-decoding.patch
> 
> still pondering; in my mbox queue
> 
> > libata-fix-hopefully-all-the-remaining-problems-with.patch
> > testing-patch-for-ali-pata-fixes-hopefully-for-the-problems-with-atapi-dma.patch
> > pata_ali-more-work.patch
> 
> No idea.  I would poke Alan.  Probably drop.
> 

Alan: poke.

> 
> > 8139too-force-media-setting-fix.patch
> > blackfin-on-chip-ethernet-mac-controller-driver.patch
> > atari_pamsnetc-old-declaration-ritchie-style-fix.patch
> > sundance-phy-address-form-0-only-for-device-id-0x0200.patch
> 
> Needs a bug fix, so that the newly modified loop doesn't scan the final 
> phy id, then loop back around to scan the first again.
> 
> 
> > 3x59x-fix-pci-resource-management.patch
> > update-smc91x-driver-with-arm-versatile-board-info.patch
> > drivers-net-ns83820c-add-paramter-to-disable-auto.patch
> > 
> >  netdev patches which are stuck in limbo land.
> 
> ?  I don't think I've seen these.
> 

3x59x-fix-pci-resource-management.patch: you wrote it ;) I have a comment
here:

- I don't remember the story with cardbus either.  Presumably once upon a
  time the cardbus layer was claiming IO regions on behalf of cardbus
  devices (?)

Need to think about that.

update-smc91x-driver-with-arm-versatile-board-info.patch:

See comment from rmk in changelog:
ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-rc6/2.6.22-rc6-mm1/broken-out/update-smc91x-driver-with-arm-versatile-board-info.patch

Deepak, can we move this along a bit please?

drivers-net-ns83820c-add-paramter-to-disable-auto.patch:

See comments in changelog: ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-rc6/2.6.22-rc6-mm1/broken-out/drivers-net-ns83820c-add-paramter-to-disable-auto.patch

Dan, Ben: is there any prospect of progress here?

> 
> > bonding-bond_mainc-make-2-functions-static.patch
> 
> FWIW bonding stuff should go to me, since it lives mostly in drivers/net
> 

Ah, noted.

> > x86-initial-fixmap-support.patch
> 
> Andi material?
> 

Spose so.  But it's buried in the middle of a series of four patches.

> 
> > mm-revert-kernel_ds-buffered-write-optimisation.patch
> > revert-81b0c8713385ce1b1b9058e916edcf9561ad76d6.patch
> > revert-6527c2bdf1f833cc18e8f42bd97973d583e4aa83.patch
> > mm-clean-up-buffered-write-code.patch
> > mm-debug-write-deadlocks.patch
> > mm-trim-more-holes.patch
> > mm-buffered-write-cleanup.patch
> > mm-write-iovec-cleanup.patch
> > mm-fix-pagecache-write-deadlocks.patch
> > mm-buffered-write-iterator.patch
> > fs-fix-data-loss-on-error.patch
> > mm-restore-kernel_ds-optimisations.patch
> >  pagefault-in-write deadlock fixes.  Will hold for 2.6.24.
> 
> Any of the above worth 2.6.23?  Just wondering if they were useful 
> cleanups / minor fixes prior to new aops patches?
> 

The first few patches will a) fix up our writev performance regression and
b) reintroduce the writev() deadlock which the writev()-regresion-adding
patch fixed.

So it's all a bit ugly.

> 
> > oss-trident-massive-whitespace-removal.patch
> > oss-trident-fix-locking-around-write_voice_regs.patch
> > oss-trident-replace-deprecated-pci_find_device-with-pci_get_device.patch
> > remove-options-depending-on-oss_obsolete.patch
> > 
> >  Merge
> 
> what about just removing the OSS drivers in question?  :)
> 

Hey, I only work here.

> 
> > intel-iommu-dmar-detection-and-parsing-logic.patch
> > intel-iommu-pci-generic-helper-function.patch
> > intel-iommu-clflush_cache_range-now-takes-size-param.patch
> > intel-iommu-iova-allocation-and-management-routines.patch
> > intel-iommu-intel-iommu-driver.patch
> > intel-iommu-avoid-memory-allocation-failures-in-dma-map-api-calls.patch
> > intel-iommu-intel-iommu-cmdline-option-forcedac.patch
> > intel-iommu-dmar-fault-handling-support.patch
> > intel-iommu-iommu-gfx-workaround.patch
> > intel-iommu-iommu-floppy-workaround.patch
> > 
> >  Don't know.  I don't think there were any great objections, but I don't
> >  think much benefit has been demonstrated?
> 
> Just the general march of progress on new hardware :)
> 
> I would like to see this support merged in /some/ form.  We've been 
> telling Intel for years they were sillyheads for not bothering with an 
> IOMMU.  Now that they have, we should give them a cookie and support 
> good technology.

OK, thanks.

Re: PCI probing changes

[Jesse Barnes]

On Tuesday, July 10, 2007 1:31:52 Andrew Morton wrote:
> pci-disable-decode-of-io-memory-during-bar-sizing.patch

This is a core PCI change, should probably go through Greg and/or 
linux-pci instead?  Or just send it to Linus directly, iirc everyone 
was ok with the change for 2.6.23.

Also, you can add a
Signed-off-by:  Jesse Barnes <jesse.barnes@intel.com>
to it.

Thanks,
Jesse

Re: containers (was Re: -mm merge plans for 2.6.23)

[Paul Menage]

On 7/10/07, Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> wrote:
> >
> >  Container stuff.  Hold, I guess.  I was expecting updates from Paul.
>
> Paul,
>         Are you working on a new version? I thought it was mostly ready
> for mainline.
>

There are definitely some big changes that I want to make internally
to the framework, but I guess they don't have to block pushing the
basic framework to mainline.

I've got a new patchset that's primarily got all the various -mm fix
patches rolled into the appropriate original patches, along with plus
some small tweaks

- changed the Kconfig files to avoid using "select"
- adding the subsystem name as a prefix for each control file to
enforce namespace scoping
- misc contributions from others

Short-term I also want to:

- rethink the linked list that runs through each task to its css_group
object, since that seemed to hurt performance a bit, but for now that
can probably be solved by just ripping it out and going back to
scanning the tasklist to enumerate tasks in a container.

- extend the options parsing, so we can have more than just a list of
subsystems. Probably changing the existing -o<subsys1>,<subsys2>,...
to be one of:
  -osubsys=<subsys1>:<subsys2>:...,<otheropt>=<otherval>
  -osubsys=<subsys1>,subsys=<subsys2>,subsys=...,<otheropt>=<otherval>
  (what's the preferred convention for fs mount options with multiple values?)

I'd not realised that anything else depending on containers was ready
for upstream merge, but if CFS group support is ready then merging a
subset of them is probably a good idea, since this is an application
that I can see a lot of people wanting to play with.

Andrew, how about we merge enough of the container framework to
support CFS? Bits we could leave out for now include container_clone()
support and the nsproxy subsystem, fork/exit callback hooks, and
possibly leave cpusets alone for now (which would also mean we could
skip the automatic release-agent stuff). I'm in Tokyo for the Linux
Foundation Japan symposium right now, but I should be able to get the
new patchset to you for Friday afternoon.

Paul

Re: -mm merge plans for 2.6.23 -- sys_fallocate

[Amit K. Arora]

On Tue, Jul 10, 2007 at 08:05:31PM +0200, Heiko Carstens wrote:
> > Alternatively I can push them directly to Linus along with other ext4
> > patches.  We can drop the s390 patch if Martin or Heiko wants to wire
> > it up themselves.
> 
> Yes, please drop the s390 patch. In general it seems to be better if only
> one architecture gets a syscall wired up initially and let other arches
> follow later.
> 
> Just wondering if the x86_64 compat syscall gets ever fixed? I think
> I mentioned already three or four times to Amit that it is broken.
> Or is it that nobody cares? Dunno..

Last time it was brought up was when TAKE5 of the patchset was posted
and I had planned to fix this in the TAKE6 - which didn't happen since
there was no final descision on the mode flags.
Anyhow, the x86_64 compat syscall has already been fixed in the ext4
patch queue.
I will repost all the patches rebased on 2.6.22 (as they are in the
ext4 patch queue), since these have already been dropped from -mm.
 
> In addition there used to be a somewhat inofficial rule that new syscalls
> have to come with a test program, so people can easily test if they wired
> up the syscall correctly.

Ok. Will work on a small testcase and post it soon.

--
Regards,
Amit Arora

Re: -mm merge plans for 2.6.23 -- sys_fallocate

[Andrew Morton]

On Tue, 10 Jul 2007 20:05:31 +0200
Heiko Carstens <heiko.carstens@de.ibm.com> wrote:

> > Alternatively I can push them directly to Linus along with other ext4
> > patches.  We can drop the s390 patch if Martin or Heiko wants to wire
> > it up themselves.
> 
> Yes, please drop the s390 patch. In general it seems to be better if only
> one architecture gets a syscall wired up initially and let other arches
> follow later.

Yep.

otoh, fallocate() was special, because we had so many problems working out
how to organise the args so that certain kooky architectures can implement
it.

> Just wondering if the x86_64 compat syscall gets ever fixed? I think
> I mentioned already three or four times to Amit that it is broken.
> Or is it that nobody cares? Dunno..
> 
> In addition there used to be a somewhat inofficial rule that new syscalls
> have to come with a test program, so people can easily test if they wired
> up the syscall correctly.

Yes please.  I normally just slam the whole .c file into the changelog.

I'd support an ununofficial rule that submitters of new syscalls also raise
a patch against LTP, come to that...

agp / cpufreq.

[Dave Jones]

On Tue, Jul 10, 2007 at 01:31:52AM -0700, Andrew Morton wrote:

 > working-3d-dri-intel-agpko-resume-for-i815-chip.patch
 > 
 >  Sent to davej

You managed to sneak this to me just hours before I handed
AGP maintainership to Dave Airlie.  FWIW, I think this needs
to redone in a much more generic manner before it goes mainline.

 > bugfix-cpufreq-in-combination-with-performance-governor.patch
 > restore-previously-used-governor-on-a-hot-replugged-cpu.patch
 > 
 >  Sent to davej

Will start merging the backlog once someone (ahem) pulls
the last lot of stuff.

	Dave

-- 
http://www.codemonkey.org.uk

Re: -mm merge plans for 2.6.23 - ioat/dma engine

[Andrew Morton]

On Tue, 10 Jul 2007 11:05:45 -0700
"Nelson, Shannon" <shannon.nelson@intel.com> wrote:

> Kok, Auke wrote: 
> >Andrew Morton wrote:
> >> git-ioat-vs-git-md-accel.patch
> >> ioat-warning-fix.patch
> >> fix-i-oat-for-kexec.patch
> >> 
> >>  I don't seem to be able to get rid of these.  Chris Leech 
> >appears to have
> >>  vanished.
> >
> >Chris is a moving target. Thankfully we have Shannon Nelson 
> >taking over Chris' 
> >duties. Shannon, can you take a look at these and see what 
> >needs to happen to it 
> >? Most likely these just need to be pushed to the right person.
> 
> Auke: Thanks for the introduction :-).

Hi, Shannon.

> Andrew: All three of these patches are reasonable and can be pushed on
> up.  You can add my sign-off to all three:
> Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>

OK, the way it works is that I send these patches at the git tree
maintainer, then the git tree maintainer merges them (this step is
unreliable) and then when I repull that git tree maintainer's tree I see
that they got merged so I drop them from -mm.  The git tree maintainer
decides when to send them to Linus.

I am presently pulling git://lost.foo-projects.org/~cleech/linux-2.6#master
into -mm.

Will you be taking over the IOAT git tree?  If so, please send me a
suitable git URL when it's ready.

The above tree has several changes in it from January (see
ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-rc6/2.6.22-rc6-mm1/broken-out/git-ioat.patch).
 Please take a look at those, work out what we should do with it all.

Re: containers (was Re: -mm merge plans for 2.6.23)

[Andrew Morton]

On Tue, 10 Jul 2007 11:34:38 -0700
"Paul Menage" <menage@google.com> wrote:

> Andrew, how about we merge enough of the container framework to
> support CFS? Bits we could leave out for now include container_clone()
> support and the nsproxy subsystem, fork/exit callback hooks, and
> possibly leave cpusets alone for now (which would also mean we could
> skip the automatic release-agent stuff). I'm in Tokyo for the Linux
> Foundation Japan symposium right now, but I should be able to get the
> new patchset to you for Friday afternoon.

mm..  Given that you propose leaving bits out for the 2.6.23 merge, and
that changes are still pending and that nothing will _use_ the framework in
2.6.23 I'd be inclined to err on the side of caution and hold it all back
from 2.6.23.

This has the advantage that the merge will happen after the kernel-summit
containers discussion which I suspect will be an important point in the
life of this project...

Re: ata and netdev (was Re: -mm merge plans for 2.6.23)

[James Bottomley]

On Tue, 2007-07-10 at 11:24 -0700, Andrew Morton wrote:
> > > ata-ahci-alpm-store-interrupt-value.patch
> > > ata-ahci-alpm-expose-power-management-policy-option-to-users.patch
> > > ata-ahci-alpm-enable-link-power-management-for-ata-drivers.patch
> > > ata-ahci-alpm-enable-aggressive-link-power-management-for-ahci-controllers.patch
> > > 
> > >  These appear to need some work.
> > 
> > seemed mostly OK to me.  what comments did I miss?
> 
> Oh, I thought these were the patches which affected scsi and which James
> had issues with.  I guess I got confused.

Well ... my concern was really how to make them more generic ... ahci
isn't the only controller that can do phy power management, and it also
seemed to me that the most generic entity for power management was the
transport rather than the SCSI mid-layer, but that debate is still
ongoing.

James

Re: PCI probing changes

[Andrew Morton]

On Tue, 10 Jul 2007 11:34:03 -0700
Jesse Barnes <jesse.barnes@intel.com> wrote:

> On Tuesday, July 10, 2007 1:31:52 Andrew Morton wrote:
> > pci-disable-decode-of-io-memory-during-bar-sizing.patch
> 
> This is a core PCI change, should probably go through Greg and/or 
> linux-pci instead?  Or just send it to Linus directly, iirc everyone 
> was ok with the change for 2.6.23.

Ah, thanks.  I moved it to the gregkh-pci queue.

> Also, you can add a
> Signed-off-by:  Jesse Barnes <jesse.barnes@intel.com>
> to it.

Updated, thanks.

Re: ata and netdev (was Re: -mm merge plans for 2.6.23)

[Jeff Garzik]

Andrew Morton wrote:
> On Tue, 10 Jul 2007 13:42:16 -0400
> Jeff Garzik <jeff@garzik.org> wrote:
> 
>> (just to provide my indicator of status)
> 
> Thanks.
> 
>>> libata-add-irq_flags-to-struct-pata_platform_info-fix.patch
>> are other pata_platform people happy with this?  I don't know embedded 
>> well enough to know if adding this struct member will break things.
> 
> This is just a silly remove-unneeded-cast-of-void* cleanup.  I wrote this
> as a fixup against
> libata-add-irq_flags-to-struct-pata_platform_info.patch with the intention
> of folding it into that base patch, but you went and merged the submitter's
> original patch so this trivial fixup got stranded in -mm.  Feel free to give
> it the piss-off-too-trivial treatment.

I'm sorry, I didn't look closely enough.  I was referring to the 
add-irq-flags patch itself, not your small fix.


>>> ata-ahci-alpm-store-interrupt-value.patch
>>> ata-ahci-alpm-expose-power-management-policy-option-to-users.patch
>>> ata-ahci-alpm-enable-link-power-management-for-ata-drivers.patch
>>> ata-ahci-alpm-enable-aggressive-link-power-management-for-ahci-controllers.patch
>>>
>>>  These appear to need some work.
>> seemed mostly OK to me.  what comments did I miss?
> 
> Oh, I thought these were the patches which affected scsi and which James
> had issues with.  I guess I got confused.

hrm.  ISTR James wanted some cleanups, Kristen did some cleanups, then 
looking at the cleanups decided they were needed / appropriate at this time.

Anyway, these are in my mbox queue and the libata portions (of which the 
code is the majority) seem OK.  Need to give them a final review.

	Jeff

Re: containers (was Re: -mm merge plans for 2.6.23)

[Paul Menage]

On 7/10/07, Andrew Morton <akpm@linux-foundation.org> wrote:
> > Andrew, how about we merge enough of the container framework to
> > support CFS? Bits we could leave out for now include container_clone()
> > support and the nsproxy subsystem, fork/exit callback hooks, and
> > possibly leave cpusets alone for now (which would also mean we could
> > skip the automatic release-agent stuff). I'm in Tokyo for the Linux
> > Foundation Japan symposium right now, but I should be able to get the
> > new patchset to you for Friday afternoon.
>
> mm..  Given that you propose leaving bits out for the 2.6.23 merge, and
> that changes are still pending and that nothing will _use_ the framework in
> 2.6.23

That's what I was originally thinking too, but since CFS has been
merged, CFS group scheduling would use it.

Paul

Re: fallocate-implementation-on-i86-x86_64-and-powerpc.patch (was: re: -mm merge plans for 2.6.23)

[Theodore Tso]

On Tue, Jul 10, 2007 at 10:15:58AM -0700, Andrew Morton wrote:
> So I dropped everything.  Let's start again from scratch.  I'd suggest that
> for now we go with just an i386/x86_64 implementation, let the arch
> maintainers wire things up when that has settled down.

Ok, so no objections if we push the i386/x86_64 implementation (only),
plus the ext4 support to Linus?

						- Ted

Re: fallocate-implementation-on-i86-x86_64-and-powerpc.patch (was: re: -mm merge plans for 2.6.23)

[Andrew Morton]

On Tue, 10 Jul 2007 15:07:35 -0400
Theodore Tso <tytso@mit.edu> wrote:

> On Tue, Jul 10, 2007 at 10:15:58AM -0700, Andrew Morton wrote:
> > So I dropped everything.  Let's start again from scratch.  I'd suggest that
> > for now we go with just an i386/x86_64 implementation, let the arch
> > maintainers wire things up when that has settled down.
> 
> Ok, so no objections if we push the i386/x86_64 implementation (only),
> plus the ext4 support to Linus?
> 

Sounds like a plan.

I haven't seriously looked at ext4 code in many months.  When I did I found
the changes to be quite incomprehensible, very, very poorly commented and
with quite a lot of odd-looking things about which I asked but got, iirc,
no useful reply.

Hopefully it got better.

Which patches are you proposing merging into 2.6.23?

Re: ata and netdev (was Re: -mm merge plans for 2.6.23)

[Sergei Shtylyov]

Hello.

Jeff Garzik wrote:

>> 3x59x-fix-pci-resource-management.patch

    Now that the fix for CONFIG_PCI=n has been merged, what's left is to test 
this on EISA (at least Andrew wanted it :-).

>>  netdev patches which are stuck in limbo land.

> ?  I don't think I've seen these.

    You should have, I was sending it to you.

WBR, Sergei

Re: -mm merge plans for 2.6.23

[Christoph Lameter]

On Tue, 10 Jul 2007, Andrew Morton wrote:

> slub-exploit-page-mobility-to-increase-allocation-order.patch
> slub-reduce-antifrag-max-order.patch
> 
>  These are slub changes which are dependent on Mel's stuff, and I have a note
>  here that there were reports of page allocation failures with these.  What's
>  up with that?

Those were fixed and all has been well since as far as I know.

>  Maybe I should just drop the 100-odd marginal-looking MM patches?  We're
>  simply not showing compelling reasons for merging them and quite a lot of them
>  are stuck in a 90% complete state.

As far as I can tell the antifrag patches are stable and are significantly 
enhancing various aspects of the VM and also make it more reliable. SLUB 
can use it to increase scalability. MM has been using order 3 allocs via 
SLUB for months now without a problem. Without the antifrag patches order 
1 allocs could cause OOMs.

It opens the door for functionality that we wanted for a long time such a 
memory unplug etc.

Re: -mm merge plans for 2.6.23 -- sys_fallocate

[Amit K. Arora]

On Tue, Jul 10, 2007 at 11:20:47AM -0700, Mark Fasheh wrote:
> On Tue, Jul 10, 2007 at 11:45:03AM -0400, Theodore Tso wrote:
> > On Tue, Jul 10, 2007 at 02:22:13AM -0700, Andrew Morton wrote:
> > > On Tue, 10 Jul 2007 11:07:37 +0200 Heiko Carstens <heiko.carstens@de.ibm.com> wrote:
> > > > We reserved a different syscall number than the one that is used right now
> > > > in the patch. Please drop this patch... Martin or I will wire up the syscall
> > > > as soon as the x86 variant is merged. Everything else just causes trouble and
> > > > confusion.
> > > 
> > > OK, I dropped all the fallocate patches.
> > 
> > Andrew, I want to clarify who is going to push the fallocate patches.
> > I can either push them to Linus as part of the ext4 patch set, or we
> > can wait for you to push them.  I thought since you had them in -mm
> > and we were going to wait you to push them (and presume that this was
> > going to happen soon).
> > 
> > Alternatively I can push them directly to Linus along with other ext4
> > patches.  We can drop the s390 patch if Martin or Heiko wants to wire
> > it up themselves.
> > 
> > As far as I know there hasn't been any real contention on the actual
> > syscall patches, other than the numbering issues, so it seems that
> > pushing them to Linus sooner rather than later is the right thing to
> > do. 
> 
> Where is the latest and greatest version of those patches? Is it still the
> patch set distributed in 2.6.22-rc6-mm1? I'd mostly like to see the final
> set of flags we're planning on supporting. But yeah, I second the "sooner
> rather than later" :)

I have posted the latest fallocate patches as part of TAKE6. These
patches are exactly same as how they currently look in the ext4 patch
queue being maintained by Ted.

--
Regards,
Amit Arora

Re: ata and netdev (was Re: -mm merge plans for 2.6.23)

[Sergei Shtylyov]

Hello.

Andrew Morton wrote:

> 3x59x-fix-pci-resource-management.patch: you wrote it ;) I have a comment

    No, I did, almost a year ago already. :-)

> here:

> - I don't remember the story with cardbus either.  Presumably once upon a
>   time the cardbus layer was claiming IO regions on behalf of cardbus
>   devices (?)

    IIRC, that's your own comment.

> Need to think about that.

WBR, Sergei

Re: ata and netdev (was Re: -mm merge plans for 2.6.23)

[Andrew Morton]

On Wed, 11 Jul 2007 00:31:23 +0400
Sergei Shtylyov <sshtylyov@ru.mvista.com> wrote:

> Hello.
> 
> Andrew Morton wrote:
> 
> > 3x59x-fix-pci-resource-management.patch: you wrote it ;) I have a comment
> 
>     No, I did, almost a year ago already. :-)

I thought that was odd.  I fixed the attribution.
 
> > here:
> 
> > - I don't remember the story with cardbus either.  Presumably once upon a
> >   time the cardbus layer was claiming IO regions on behalf of cardbus
> >   devices (?)
> 
>     IIRC, that's your own comment.

yup, that's what "I have a comment" meant ;)

The comment seems rather bogus actually.  Let's just merge it.

RE: -mm merge plans for 2.6.23 - ioat/dma engine

[Nelson, Shannon]

Andrew Morton [mailto:akpm@linux-foundation.org] 
> 
>I am presently pulling 
>git://lost.foo-projects.org/~cleech/linux-2.6#master
>into -mm.
>
>Will you be taking over the IOAT git tree?  If so, please send me a
>suitable git URL when it's ready.

I'll be getting there Real Soon Now.  The transition seems to be a
little rocky at the moment...

>The above tree has several changes in it from January (see
>ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2
>.6.22-rc6/2.6.22-rc6-mm1/broken-out/git-ioat.patch).
> Please take a look at those, work out what we should do with it all.

Will do.  Thanks for your patience.

sln
======================================================================
Mr. Shannon Nelson                 LAN Access Division, Intel Corp.
Shannon.Nelson@intel.com                I don't speak for Intel
(503) 712-7659                    Parents can't afford to be squeamish.

Re: fallocate-implementation-on-i86-x86_64-and-powerpc.patch

[Paul Mackerras]

Jeff Garzik writes:

> Andrew Morton wrote:
> > So I dropped everything.  Let's start again from scratch.  I'd suggest that
> > for now we go with just an i386/x86_64 implementation, let the arch
> > maintainers wire things up when that has settled down.
> 
> 
> It's my observation that that plan usually works the best.  Arch 

... except when the initial implementer picks an argument order which
doesn't work on some archs, as happened with sys_sync_file_range.
That is also the case with fallocate IIRC.

We did come up with an order that worked for everybody, but that
discussion seemed to get totally ignored by the ext4 developers.

Paul.

Re: fallocate-implementation-on-i86-x86_64-and-powerpc.patch

[Andrew Morton]

On Wed, 11 Jul 2007 09:27:40 +1000
Paul Mackerras <paulus@samba.org> wrote:

> We did come up with an order that worked for everybody, but that
> discussion seemed to get totally ignored by the ext4 developers.

It was a long discussion.

Can someone please remind us what the signature of the syscall
(and the compat handler) should be?

Re: fallocate-implementation-on-i86-x86_64-and-powerpc.patch

[Paul Mackerras]

Andrew Morton writes:

> On Wed, 11 Jul 2007 09:27:40 +1000
> Paul Mackerras <paulus@samba.org> wrote:
> 
> > We did come up with an order that worked for everybody, but that
> > discussion seemed to get totally ignored by the ext4 developers.
> 
> It was a long discussion.
> 
> Can someone please remind us what the signature of the syscall
> (and the compat handler) should be?

long sys_fallocate(loff_t offset, loff_t len, int fd, int mode)

should work for everybody.  The compat handler would be

long compat_sys_fallocate(u32 offset_hi, u32 offset_lo, u32 len_hi, u32 len_lo,
			  int fd, int mode)

for big-endian, or swap hi/lo for little-endian.  (Actually it would
be good to have an arch-dependent "stitch two args together" macro and
call them offset_0, offset_1 etc.)

Paul.

Re: [ck] Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Wed, 11 Jul 2007 11:02:56 +1000 "Matthew Hawkins" <darthmdh@gmail.com> wrote:

> We all know swap prefetch has been tested out the wazoo since Moses was a
> little boy, is compile-time and runtime selectable, and gives an important
> and quantifiable performance increase to desktop systems.

Always interested.  Please provide us more details on your usage and
testing of that code.  Amount of memory, workload, observed results,
etc?

>  Save a Redhat
> employee some time reinventing the wheel and just merge it.  This wheel
> already has dope 21" rims, homes ;-)

ooh, kernel bling.

Fwd: [ck] Re: -mm merge plans for 2.6.23

[André Goddard Rosa]

On 7/10/07, Andrew Morton <akpm@linux-foundation.org> wrote:
>  On Wed, 11 Jul 2007 11:02:56 +1000 "Matthew Hawkins" <darthmdh@gmail.com> wrote:
>
> > We all know swap prefetch has been tested out the wazoo since Moses was a
> > little boy, is compile-time and runtime selectable, and gives an important
> > and quantifiable performance increase to desktop systems.
>
> Always interested.  Please provide us more details on your usage and
> testing of that code.  Amount of memory, workload, observed results,
> etc?
>
>

It keeps my machine responsive after some time of inactivity,
i.e.  when I try to use firefox in the morning after leaving it running
overnight with multiple tabs open. I have 1Gb of memory in this machine.

With regards,
-- 
[]s,
André Goddard

Re: [ck] Re: -mm merge plans for 2.6.23

[Ira Snyder]

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On Tue, 10 Jul 2007 18:14:19 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Wed, 11 Jul 2007 11:02:56 +1000 "Matthew Hawkins" <darthmdh@gmail.com> wrote:
> 
> > We all know swap prefetch has been tested out the wazoo since Moses was a
> > little boy, is compile-time and runtime selectable, and gives an important
> > and quantifiable performance increase to desktop systems.
> 
> Always interested.  Please provide us more details on your usage and
> testing of that code.  Amount of memory, workload, observed results,
> etc?
> 

I often leave long compiles running overnight (I'm a gentoo user). I always have the desktop running, with quite a few applications open, usually firefox, amarok, sylpheed, and liferea at the minimum. I've recently tried using a "stock" gentoo kernel, without the swap prefetch patch, and in the morning when I get on the computer, it hits the disk pretty hard pulling my applications (especially firefox) in from swap. With swap prefetch, the system responds like I expect: quick. It doesn't hit the swap at all, at least that I can tell.

Swap prefetch definitely makes a difference for me: it makes my experience MUCH better.

My system is a Core Duo 1.83GHz laptop, with 1GB ram and a 5400 rpm disk. With the disk being so slow, the less I hit swap, the better.

I'll cast my vote to merge swap prefetch.

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Re: [ck] Re: -mm merge plans for 2.6.23

[Matthew Hawkins]

On 7/11/07, Andrew Morton <akpm@linux-foundation.org> wrote:
> On Wed, 11 Jul 2007 11:02:56 +1000 "Matthew Hawkins" <darthmdh@gmail.com> wrote:

> Always interested.  Please provide us more details on your usage and
> testing of that code.  Amount of memory, workload, observed results,
> etc?

My usual workstation has 1Gb of ram & 2Gb of swap (single partition -
though in the past with multiple drives I would spread swap around the
less-used disks & fiddle with the priority).  Its acting as server for
my home network too (so it has squid, cups, bind, dhcpd, apache, mysql
& postgresql) but for the most part I'll have Listen playing music
while I switch between Flock &/or Firefox, Thunderbird, and
xvncviewer.  On the odd occasion I'll fire up some game (gewled,
actioncube, critical mass).  Compiling these days has been mostly
limited to kernels, I've been building mostly -ck and -cfs - keeping
up-to-date and also doing some odd things (like patching the non-SD
-ck stuff on top of CFS).  Mainly just to get swap prefetch, but also
not to lose skills since I'm out of the daily coding routine now.

Anyhow with swap prefetch, applications that may have been sitting
there idle for a while become responsive in the single-digit seconds
rather than double-digit or worse.  The same goes for a morning wakeup
(ie after nightly cron jobs throw things out) and also after doing
basically anything that wants memory, like benchmarking the various
kernels I'm messing with or doing some local DB work or coding a
memory leak into a web application running under apache ;)

-- 
Matt

Re: [ck] Re: -mm merge plans for 2.6.23

[timotheus]

[-- Attachment #1: Type: text/plain, Size: 2484 bytes --]

Ira Snyder <kernel@irasnyder.com> writes:

>> Always interested.  Please provide us more details on your usage and
>> testing of that code.  Amount of memory, workload, observed results,
>> etc?
>> 
>
> I often leave long compiles running overnight (I'm a gentoo user). I
> always have the desktop running, with quite a few applications open,
> usually firefox, amarok, sylpheed, and liferea at the minimum. I've
> recently tried using a "stock" gentoo kernel, without the swap
> prefetch patch, and in the morning when I get on the computer, it hits
> the disk pretty hard pulling my applications (especially firefox) in
> from swap. With swap prefetch, the system responds like I expect:
> quick. It doesn't hit the swap at all, at least that I can tell.
>
> Swap prefetch definitely makes a difference for me: it makes my
> experience MUCH better.
>
> My system is a Core Duo 1.83GHz laptop, with 1GB ram and a 5400 rpm
> disk. With the disk being so slow, the less I hit swap, the better.
>
> I'll cast my vote to merge swap prefetch.

Very similar experiences. Other usage patterns that swap prefetch can
cause improvements with:

- Idling VMware session with large memory. Since VMware (server) can use
  mixed swap/RAM, the prefetch allows it swap back into RAM without
  having to make the application active in the foreground.

- Firefox, OO Office, long from-source compilations, all of the normal.

- My largest RAM capacity machine is a Core 2 Duo Laptop with 2 GB of
  RAM. It still benefits from the prefetch after running long
  compilations or backups.

- Also, I have an old Pentium 4 server (1.3 GHz, original RDRAM, ...)
  that uses the CK patches including swap prefetch. It has only 640 MB
  of RAM, and runs GBytes of data backup every night. The swap is split
  among multiple disks, and can easily fill .5 GBytes over
  night. Applications that run in a VNC session, web browsers, office
  programs, etc., all resume much faster with the prefetch. Even the
  intial ssh-login appears snappier; but I think that is just CK's fine
  work elsewhere. :)

I am curious how much of the benefit is due to prefetch, or due to CK
using `vm_mapped' rather than `vm_swappiness'. Swappiness always seemed
such an unbenificial hack to me...

(The past 6 months I've tried weeks/months of using various kernels,
-mm, -ck, vanilla, genpatches, combinations there of -- x86 and ppc.)

I vote for prefetch and `vm_mapped'.

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Re: [ck] Re: -mm merge plans for 2.6.23

[Grzegorz Kulewski]

On Tue, 10 Jul 2007, Andrew Morton wrote:
> On Wed, 11 Jul 2007 11:02:56 +1000 "Matthew Hawkins" <darthmdh@gmail.com> wrote:
>
>> We all know swap prefetch has been tested out the wazoo since Moses was a
>> little boy, is compile-time and runtime selectable, and gives an important
>> and quantifiable performance increase to desktop systems.
>
> Always interested.  Please provide us more details on your usage and
> testing of that code.  Amount of memory, workload, observed results,
> etc?

I am using swap prefetch in -ck kernels since it was introduced.

My machine: Athlon XP 2000MHz, 1GB DDR 266, fast SATA disk, different 
swap configurations but usually heaps of swap (2GB and/or 8GB).

My workload: desktop usage, KDE, software development, Firefox (HUGE 
memory hog), Eclipse and all that stuff (HUGE memory hog), sometimes other 
applications, sometimes some game such as Americas Army (that one will eat 
all your memory in any configuration), Konsole with heaps of tabs, usually 
some heavy compilations in the background.

Observed result (of not broken swap prefetch versions): after closing some 
memory hog (for example stopping playing game and starting to write some 
code or reloading Firefox after it leaked enough memory to nearly bring 
the system down) the disk will work for some time and after that 
everything works as expected, no heavy swap-in when switching between 
applications and so on, nearly no lags in desktop usage.

This is nearly unnoticable. Unless I have to run pure mainline. In that 
case I can notice that swap prefetch is off very quickly because after 
closing such memory hog and returning to some other application the system 
is slow for long time. Worse: after it starts to work reasonably and I try 
to switch to some other application or even try to use some dialog window 
or module of current application I have to wait, sometimes > 10s for it to 
swap back in (even if 70% of my RAM is free at that time, after memory hog 
is gone). It is painfull.

I observed similar results on my laptop (Athlon 64, 512MB RAM, slow ATA 
disk, similar workload but reduced because hardware is weak).

For me swap prefetch makes huge difference. The system lags a lot less in 
such circumstances.

Personaly I think swap prefetch is a hack. Maybe not very dirty and ugly 
but still a hack. But since:

* nobody proposed anything that can replace it and can be considered a 
no-hack,
* swap prefetch is rather well tested and shouldn't cause regressions (no 
known regressions as far as I know, the patch does not look very 
invasive, was reviewed several times, ...),
* Con said he won't make further -ck relases and won't port these patches 
to newer kernels,
* there are at least several people who see the difference,
* if somebody really hates it (s)he can turn it off

I think it could get merged, at least temporarily, before somebody can 
suggest some better or extended solution.

Personaly I would be very happy to see it in so people like me don't have 
to patch it in or (worse) port it (possibly causing bugs and filling 
additional bug reports and asking additional questions on these lists).

I even wonder if adding the opposite of swap prefetch too wouldn't be even 
better for many workloads. Something like: "when system and swap-disk is 
idle try to copy some pages to swap so when system needs memory swap-out 
could be much cheaper". I suspect patch like that can reduce startup times 
(and other operations) of great memory hogs because disk (the slowest 
device) will only have to read the application and won't have to swap-out 
half of the RAM at the same time.

I am happy to provide further info if needed.


Thanks,

Grzegorz Kulewski

Re: containers (was Re: -mm merge plans for 2.6.23)

[Srivatsa Vaddagiri]

On Tue, Jul 10, 2007 at 11:53:19AM -0700, Andrew Morton wrote:
> On Tue, 10 Jul 2007 11:34:38 -0700
> "Paul Menage" <menage@google.com> wrote:
> 
> > Andrew, how about we merge enough of the container framework to
> > support CFS? Bits we could leave out for now include container_clone()
> > support and the nsproxy subsystem, fork/exit callback hooks, and
> > possibly leave cpusets alone for now (which would also mean we could
> > skip the automatic release-agent stuff). I'm in Tokyo for the Linux
> > Foundation Japan symposium right now, but I should be able to get the
> > new patchset to you for Friday afternoon.
> 
> mm..  Given that you propose leaving bits out for the 2.6.23 merge, and
> that changes are still pending and that nothing will _use_ the framework in
> 2.6.23 [...]

Andrew,
	The cpu group scheduler is ready and waiting for the container patches 
in 2.6.23 :)

Here are some options with us:

	a. (As Paul says) merge enough of container patches to enable
	   its use with cfs group scheduler (and possibly cpusets?)

	b. Enable group scheduling bits in 2.6.23 using the user-id grouping 
	   mechanism (aka fair user scheduler). For 2.6.24, we could remove 
	   this interface and use Paul's container patches instead. Since this 
	   means change of API interface between 2.6.23 and 2.6.24, I don't 
	   prefer this option.

	c. Enable group scheduling bits only in -mm for now (2.6.23-mmX), using 
	   Paul's container patches. I can send you a short patch that hooks up 
	   cfs group scheduler with Paul's container infrastructure.

If a. is not possible, I would prefer c.

Let me know your thoughts ..

-- 
Regards,
vatsa

Re: [ck] Re: -mm merge plans for 2.6.23

[Nick Piggin]

Matthew Hawkins wrote:
> On 7/11/07, Andrew Morton <akpm@linux-foundation.org> wrote:

> Anyhow with swap prefetch, applications that may have been sitting
> there idle for a while become responsive in the single-digit seconds
> rather than double-digit or worse.  The same goes for a morning wakeup
> (ie after nightly cron jobs throw things out)

OK that's a good data point. It would be really good to be able to
do an analysis on your overnight IO patterns and the corresponding
memory reclaim behaviour and see why things are getting evicted.

Not that swap prefetching isn't a good solution for this situation,
but the fact that things are getting swapped out for you also means
that mapped files and possibly important pagecache and dentries are
being flushed out, which we might be able to avoid.

Thanks,
Nick

-- 
SUSE Labs, Novell Inc.

Re: containers (was Re: -mm merge plans for 2.6.23)

[Andrew Morton]

On Wed, 11 Jul 2007 10:25:16 +0530 Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> wrote:

> On Tue, Jul 10, 2007 at 11:53:19AM -0700, Andrew Morton wrote:
> > On Tue, 10 Jul 2007 11:34:38 -0700
> > "Paul Menage" <menage@google.com> wrote:
> > 
> > > Andrew, how about we merge enough of the container framework to
> > > support CFS? Bits we could leave out for now include container_clone()
> > > support and the nsproxy subsystem, fork/exit callback hooks, and
> > > possibly leave cpusets alone for now (which would also mean we could
> > > skip the automatic release-agent stuff). I'm in Tokyo for the Linux
> > > Foundation Japan symposium right now, but I should be able to get the
> > > new patchset to you for Friday afternoon.
> > 
> > mm..  Given that you propose leaving bits out for the 2.6.23 merge, and
> > that changes are still pending and that nothing will _use_ the framework in
> > 2.6.23 [...]
> 
> Andrew,
> 	The cpu group scheduler is ready and waiting for the container patches 
> in 2.6.23 :)
> 
> Here are some options with us:
> 
> 	a. (As Paul says) merge enough of container patches to enable
> 	   its use with cfs group scheduler (and possibly cpusets?)
> 
> 	b. Enable group scheduling bits in 2.6.23 using the user-id grouping 
> 	   mechanism (aka fair user scheduler). For 2.6.24, we could remove 
> 	   this interface and use Paul's container patches instead. Since this 
> 	   means change of API interface between 2.6.23 and 2.6.24, I don't 
> 	   prefer this option.
> 
> 	c. Enable group scheduling bits only in -mm for now (2.6.23-mmX), using 
> 	   Paul's container patches. I can send you a short patch that hooks up 
> 	   cfs group scheduler with Paul's container infrastructure.
> 
> If a. is not possible, I would prefer c.
> 
> Let me know your thoughts ..

I'm inclined to take the cautious route here - I don't think people will be
dying for the CFS thingy (which I didn't even know about?) in .23, and it's
rather a lot of infrastructure to add for a CPU scheduler configurator
gadget (what does it do, anyway?)

We have plenty of stuff for 2.6.23 already ;)

Is this liveable with??

Re: [ck] Re: -mm merge plans for 2.6.23

[Ray Lee]

On 7/10/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> Matthew Hawkins wrote:
> > On 7/11/07, Andrew Morton <akpm@linux-foundation.org> wrote:
>
> > Anyhow with swap prefetch, applications that may have been sitting
> > there idle for a while become responsive in the single-digit seconds
> > rather than double-digit or worse.  The same goes for a morning wakeup
> > (ie after nightly cron jobs throw things out)
>
> OK that's a good data point. It would be really good to be able to
> do an analysis on your overnight IO patterns and the corresponding
> memory reclaim behaviour and see why things are getting evicted.

Eviction can happen for multiple reasons, as I'm sure you're painfully
aware. It can happen because of poor balancing choices, or it can
happen because the system is just short of RAM for the workload. As
for the former, you're absolutely right, it would be good to know
where those come from and see if they can be addressed.

However, it's the latter that swap prefetch can help and no amount of
fiddling with the aging code can address.

As an honest question, what's it going to take here? If I were to
write something that watched the task stats at process exit (cool
feature, that), and recorded the IO wait time or some such, and showed
it was lower with a kernel with the prefetch, would *that* get us some
forward motion on this?

I mean, from my point of view, it's a simple mental proof to show that
if you're out of RAM for your working set, things that you'll
eventually need again will get kicked out, and prefetch will bring
those back in before normal access patterns would fault them back in
under today's behavior. That seems like an obvious win. Where's the
corresponding obvious loss that makes this a questionable addition to
the kernel?

Ray

Re: [ck] Re: -mm merge plans for 2.6.23

[Nick Piggin]

Ray Lee wrote:
> On 7/10/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> 
>> Matthew Hawkins wrote:
>> > On 7/11/07, Andrew Morton <akpm@linux-foundation.org> wrote:
>>
>> > Anyhow with swap prefetch, applications that may have been sitting
>> > there idle for a while become responsive in the single-digit seconds
>> > rather than double-digit or worse.  The same goes for a morning wakeup
>> > (ie after nightly cron jobs throw things out)
>>
>> OK that's a good data point. It would be really good to be able to
>> do an analysis on your overnight IO patterns and the corresponding
>> memory reclaim behaviour and see why things are getting evicted.
> 
> 
> Eviction can happen for multiple reasons, as I'm sure you're painfully
> aware. It can happen because of poor balancing choices, or it can

s/balancing/reclaim, yes. And for the nightly cron job case, this is
could quite possibly be the cause. At least updatedb should be fairly
easy to apply use-once heuristics for, so if they're not working then
we should hopefully be able to improve it.

-- 
SUSE Labs, Novell Inc.

Re: [ck] Re: -mm merge plans for 2.6.23

[Nick Piggin]

Ray Lee wrote:

> As an honest question, what's it going to take here? If I were to
> write something that watched the task stats at process exit (cool
> feature, that), and recorded the IO wait time or some such, and showed
> it was lower with a kernel with the prefetch, would *that* get us some
> forward motion on this?

Honest answer? Sure, why not. Numbers are good.

-- 
SUSE Labs, Novell Inc.

Re: containers (was Re: -mm merge plans for 2.6.23)

[Srivatsa Vaddagiri]

On Tue, Jul 10, 2007 at 10:29:42PM -0700, Andrew Morton wrote:
> I'm inclined to take the cautious route here - I don't think people will be
> dying for the CFS thingy (which I didn't even know about?) in .23, and it's
> rather a lot of infrastructure to add for a CPU scheduler configurator
> gadget (what does it do, anyway?)

Hmm ok, if you think the container patches is too early for 2.6.23, fine.
We should definitely target to have it in 2.6.24, by which time I am
thinking the memory rss controller will also be in a good shape.

> We have plenty of stuff for 2.6.23 already ;)
> 
> Is this liveable with??

Fine. I will request you to enable group cpu scheduling in
2.6.23-rcX-mmY atleast, so that it gets some amount of testing. The
essential group scheduling bits is already in Linus' tree now (as part
of cfs merge), so what you need in -mm is a slim patch to hook it with Paul's 
container infrastructure (which I trust will continue to be in -mm until it goes
mainline). I will send across that slim patch later (to be included in
2.6.23-rc1-mm1 perhaps).

-- 
Regards,
vatsa

Re: [ck] Re: -mm merge plans for 2.6.23

[Ray Lee]

On 7/10/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> >> OK that's a good data point. It would be really good to be able to
> >> do an analysis on your overnight IO patterns and the corresponding
> >> memory reclaim behaviour and see why things are getting evicted.
> >
> > Eviction can happen for multiple reasons, as I'm sure you're painfully
> > aware. It can happen because of poor balancing choices, or it can
>
> s/balancing/reclaim, yes. And for the nightly cron job case, this is
> could quite possibly be the cause. At least updatedb should be fairly
> easy to apply use-once heuristics for, so if they're not working then
> we should hopefully be able to improve it.

<nod> Sorry, I'm not so clear on the terminology, am I.

So, that's one part of it: one could argue that for that bit swap
prefetch is a bit of a band-aid over the issue. A useful band-aid,
that works today, isn't invasive, and can be ripped out at some future
time if the underlying issue is eventually solved by a proper use-once
aging mechanism, but nevertheless a band-aid.

The other part is when I've got evolution and a few other things open,
then I run gimp on a raw photo and do some work on it, quit out of
gimp, do a couple of things in a shell to upload the photo to my
server, then switch back to evolution. Hang, waiting on swap in. Well,
the kernel had some free time there to repopulate evolution's working
set, and swap prefetch would help that, while better (or perfect!)
heuristics in the reclaim *won't*.

That's the real issue here.

Re: [ck] Re: -mm merge plans for 2.6.23

[Nick Piggin]

Ray Lee wrote:
> On 7/10/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> 
>> >> OK that's a good data point. It would be really good to be able to
>> >> do an analysis on your overnight IO patterns and the corresponding
>> >> memory reclaim behaviour and see why things are getting evicted.
>> >
>> > Eviction can happen for multiple reasons, as I'm sure you're painfully
>> > aware. It can happen because of poor balancing choices, or it can
>>
>> s/balancing/reclaim, yes. And for the nightly cron job case, this is
>> could quite possibly be the cause. At least updatedb should be fairly
>> easy to apply use-once heuristics for, so if they're not working then
>> we should hopefully be able to improve it.
> 
> 
> <nod> Sorry, I'm not so clear on the terminology, am I.
> 
> So, that's one part of it: one could argue that for that bit swap
> prefetch is a bit of a band-aid over the issue. A useful band-aid,
> that works today, isn't invasive, and can be ripped out at some future
> time if the underlying issue is eventually solved by a proper use-once
> aging mechanism, but nevertheless a band-aid.

I think for some workloads it is probably a bandaid, and for others
the concept of prefetching likely to be used again data back in is
undeniably going to be a win for others.

A lot of postitive reports I have seen about this say that desktop
the next morning is more responsive. So I kind of want to know what's
happening here -- as far as I can tell, swap prefetching shouldn't
help a huge amount to recover from a simple updatedb alone --
although if other cron stuff happened that used a bit more memory
afterwards and pushing out some of updatedb's cache, perhaps that's
when swap prefetching finds its niche. I don't know.

However, I don't like the fact that there is _any_ swap happening
on 1GB desktops after a single updatedb run. Is something else
running that hogs a huge amount of memory? Maybe that explains it,
but I don't know. I do know that we probably don't do very good
use-once algorithms on the dentry and inode caches, so updatedb
might cause them to push swap out. We could test that by winding
the vfs reclaim right up.


> The other part is when I've got evolution and a few other things open,
> then I run gimp on a raw photo and do some work on it, quit out of
> gimp, do a couple of things in a shell to upload the photo to my
> server, then switch back to evolution. Hang, waiting on swap in. Well,
> the kernel had some free time there to repopulate evolution's working
> set, and swap prefetch would help that, while better (or perfect!)
> heuristics in the reclaim *won't*.
> 
> That's the real issue here.

Yeah that's an issue, and swap prefetching has the potential to
help there no doubt at all. How much is the saving? I don't think
it will be like an order of magnitude because unfortunately we
also get mapped pagecache being thrown out as well as swap, so
for example all your evolution mailbox, libraries, executable,
etc. is still going to have to be paged back in.

Regarding swap prefetching. I'm not going to argue for or against
it anymore because I have really stopped following where it is
up to, for now. If the code and the results meet the standard that
Andrew wants then I don't particularly mind if he merges it.

It would be nice if some of you guys would still report and test
problems with reclaim when prefetching is turned off -- I have
never encountered the morning after sluggishness (although I don't
doubt for a minute that it is a problem for some).

-- 
SUSE Labs, Novell Inc.

Re: swap prefetch (Re: -mm merge plans for 2.6.23)

[Ingo Molnar]

* Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> Regarding swap prefetching. I'm not going to argue for or against it 
> anymore because I have really stopped following where it is up to, for 
> now. If the code and the results meet the standard that Andrew wants 
> then I don't particularly mind if he merges it.

I have tested it and have read the code, and it looks fine to me. (i've 
reported my test results elsewhere already) We should include this in 
v2.6.23.

Acked-by: Ingo Molnar <mingo@elte.hu>

	Ingo

Re: containers (was Re: -mm merge plans for 2.6.23)

[Ingo Molnar]

* Andrew Morton <akpm@linux-foundation.org> wrote:

> > 	c. Enable group scheduling bits only in -mm for now (2.6.23-mmX), using
> > 	   Paul's container patches. I can send you a short patch that hooks up 
> > 	   cfs group scheduler with Paul's container infrastructure.
> > 
> > If a. is not possible, I would prefer c.
> > 
> > Let me know your thoughts ..
> 
> I'm inclined to take the cautious route here - I don't think people 
> will be dying for the CFS thingy (which I didn't even know about?) in 
> .23, and it's rather a lot of infrastructure to add for a CPU 
> scheduler configurator gadget (what does it do, anyway?)
> 
> We have plenty of stuff for 2.6.23 already ;)
> 
> Is this liveable with??

another option would be to trivially hook up CONFIG_FAIR_GROUP_SCHED 
with cpusets, and to offer CONFIG_FAIR_GROUP_SCHED in the Kconfig, 
dependent on CPUSETS and defaulting to off. That would give it a chance 
to be tested, benchmarked, etc.

	Ingo

Re: containers (was Re: -mm merge plans for 2.6.23)

[Paul Jackson]

Ingo wrote:
> another option would be to trivially hook up CONFIG_FAIR_GROUP_SCHED 
> with cpusets, ...

ah ... you triggered my procmail filter for 'cpuset' ... ;).

What would it mean to hook up CFS with cpusets?  I've a pretty
good idea what a cpuset is, but don't know what kind of purpose
you have in mind for such a hook.  Could you say a few words to
that?  Thanks.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.925.600.0401

Re: Re: -mm merge plans -- lumpy reclaim

[Andy Whitcroft]

[Seems a PEBKAC occured on the subject line, resending lest it become a
victim of "oh thats spam".]

Andy Whitcroft wrote:
> Andrew Morton wrote:
> 
> [...]
>> lumpy-reclaim-v4.patch
>> have-kswapd-keep-a-minimum-order-free-other-than-order-0.patch
>> only-check-absolute-watermarks-for-alloc_high-and-alloc_harder-allocations.patch
>>
>>  Lumpy reclaim.  In a similar situation to Mel's patches.  Stuck due to
>>  general lack or interest and effort.
> 
> The lumpy reclaim patches originally came out of work to support Mel's
> anti-fragmentation work.  As such I think they have become somewhat
> attached to those patches.  Whilst lumpy is most effective where
> placement controls are in place as offered by Mel's work, we see benefit
> from reduction in the "blunderbuss" effect when we reclaim at higher
> orders.  While placement control is pretty much required for the very
> highest orders such as huge page size, lower order allocations are
> benefited in terms of lower collateral damage.
> 
> There are now a few areas other than huge page allocations which can
> benefit.  Stacks are still order 1.  Jumbo frames want higher order
> contiguous pages for there incoming hardware buffers.  SLUB is showing
> performance benefits from moving to a higher allocation order.  All of
> these should benefit from more aggressive targeted reclaim, indeed I
> have been surprised just how often my test workloads trigger lumpy at
> order 1 to get new stacks.
> 
> Truly representative work loads are hard to generate for some of these.
>  Though we have heard some encouraging noises from those who can
> reproduce these problems.
> 
> [...]
> 
> -apw

testcases, was Re: -mm merge plans for 2.6.23 -- sys_fallocate

[Christoph Hellwig]

On Tue, Jul 10, 2007 at 11:41:19AM -0700, Andrew Morton wrote:
> I'd support an ununofficial rule that submitters of new syscalls also raise
> a patch against LTP, come to that...

s/ununofficial//, please.  And extend this to every new kernel interface
that's not bound to a specific piece of hardware.

Re: testcases, was Re: -mm merge plans for 2.6.23 -- sys_fallocate

[Nick Piggin]

Christoph Hellwig wrote:
> On Tue, Jul 10, 2007 at 11:41:19AM -0700, Andrew Morton wrote:
> 
>>I'd support an ununofficial rule that submitters of new syscalls also raise
>>a patch against LTP, come to that...
> 
> 
> s/ununofficial//, please.  And extend this to every new kernel interface
> that's not bound to a specific piece of hardware.

Agree, and cc manpages maintainer too? (preferably write most
of the manpage body as well, IMO).

-- 
SUSE Labs, Novell Inc.

Re: -mm merge plans for 2.6.23 -- sys_fallocate

[Andi Kleen]

> I'd support an ununofficial rule that submitters of new syscalls also raise
> a patch against LTP, come to that...

And a patch for the manpages. Definitely in favor. 

-Andi

Re: -mm merge plans for 2.6.23

[Mel Gorman]

On (10/07/07 13:09), Christoph Lameter didst pronounce:
> On Tue, 10 Jul 2007, Andrew Morton wrote:
> 
> > slub-exploit-page-mobility-to-increase-allocation-order.patch
> > slub-reduce-antifrag-max-order.patch
> > 
> >  These are slub changes which are dependent on Mel's stuff, and I have a note
> >  here that there were reports of page allocation failures with these.  What's
> >  up with that?
> 
> Those were fixed and all has been well since as far as I know.
> 

SLUB using high orders without page allocation failures do depend on
two very questionable patches that I brought to attention in my inital
merge mail. If grouping pages by mobility goes through, I'll be revisiting
that properly to make sure it can work without deadlocking ever under any
circumstances. Right now, it theoritically could livelock although I've
never been able to reproduce it.

The patches as they are will work for high-order allocations if you are
willing to wait and reclaim memory. The more stressful users need more
effort but it's already been shown that it can be made work with one
approach as the last few months in -mm have shown.

> >  Maybe I should just drop the 100-odd marginal-looking MM patches?  We're
> >  simply not showing compelling reasons for merging them and quite a lot of them
> >  are stuck in a 90% complete state.
> 
> As far as I can tell the antifrag patches are stable and are significantly 
> enhancing various aspects of the VM and also make it more reliable. SLUB 
> can use it to increase scalability. MM has been using order 3 allocs via 
> SLUB for months now without a problem. Without the antifrag patches order 
> 1 allocs could cause OOMs.
> 
> It opens the door for functionality that we wanted for a long time such a 
> memory unplug etc.

And I want to avoid a catch-22 here where the features that depend on
grouping pages by mobility have to exist before grouping pages by
mobility is pushed through.

I would like the patches to go through on the grounds that higher order
allocations can succeed. However, I am also happy to say that order-0
pages should be used as much as possible, that case should always be
made as fast as possible and the world must not end if a high-order
allocation fails.

-- 
-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

Re: containers (was Re: -mm merge plans for 2.6.23)

[Srivatsa Vaddagiri]

On Wed, Jul 11, 2007 at 02:23:52AM -0700, Paul Jackson wrote:
> Ingo wrote:
> > another option would be to trivially hook up CONFIG_FAIR_GROUP_SCHED 
> > with cpusets, ...
> 
> ah ... you triggered my procmail filter for 'cpuset' ... ;).

:-)

> What would it mean to hook up CFS with cpusets?

CFS is the new cpu scheduler in Linus's tree (http://lwn.net/Articles/241085/).
It has some group scheduling capabilities added i.e the core scheduler
now recognizes the concept of a task-group and providing fair cpu time 
to each task-group (in addition to providing fair time to each task in a
group).

The core scheduler however is not concerned with how task groups are formed
and/or how tasks migrate between groups. Thats where a patch like Paul Menage's 
container infrastructure comes in hand - to provide a user-interface for 
managing task-groups (create/delete task groups, migrate task from one
group to another etc). Whatever the chosen user-interface is, cpu
scheduler needs to know about such task-group creation/destruction,
migration of tasks across groups etc.

Unfortunately, the group-scheduler bits will be ready in 2.6.23 while
Paul Menage's container patches aren't ready for 2.6.23 yet.

So Ingo was proposing we use cpuset as that user interface to manage
task-groups. This will be only for 2.6.23. In 2.6.24, when hopefully Paul
Menage's container patches will be ready and will be merged, the group
cpu scheduler will stop using cpuset as that interface and use the
container infrastructure instead.

If you recall, I have attempted to use cpuset for such an interface in
the past (metered cpusets - see [1]). It brings in some semantic changes
for cpusets, most notably:

	- metered cpusets cannot have grand-children
	- all cpusets under a metered cpuset need to share the same set
	  of cpus.

Is it fine if I introduce these semantic changes, only for 2.6.23 and
only when CONFIG_FAIR_GROUP_SCHED is enabled? This will let the group
cpu scheduler to receive some amount of testing.

The other alternative is to hook up group scheduler with user-id's
(again only for 2.6.23).

> I've a pretty
> good idea what a cpuset is, but don't know what kind of purpose
> you have in mind for such a hook.  Could you say a few words to
> that?  Thanks.

Reference:

1. http://marc.info/?l=linux-kernel&m=115946525811848&w=2


-- 
Regards,
vatsa

Re: containers (was Re: -mm merge plans for 2.6.23)

[Ingo Molnar]

* Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> wrote:

> The other alternative is to hook up group scheduler with user-id's 
> (again only for 2.6.23).

could you just try this and send an as simple patch as possible? This is 
actually something that non-container people would be interested in as 
well. (btw., if this goes into 2.6.23 then we cannot possibly turn it 
off in 2.6.24, so it must be sane - but per UID task groups are 
certainly sane, the only question is how to configure the per-UID weight 
after bootup. [the default after-bootup should be something along the 
lines of 'same weight for all users, a bit more for root'.]) This would 
make it possible for users to test that thing. (it would also help 
X-heavy workloads.)

	Ingo

Re: testcases, was Re: -mm merge plans for 2.6.23 -- sys_fallocate

[Michael Kerrisk]

> Christoph Hellwig wrote:
> > On Tue, Jul 10, 2007 at 11:41:19AM -0700, Andrew Morton wrote:
> > 
> >>I'd support an ununofficial rule that submitters of new syscalls also
> >> raise a patch against LTP, come to that...
> > 
> > 
> > s/ununofficial//, please.  And extend this to every new kernel interface
> > that's not bound to a specific piece of hardware.
> 
> Agree, and cc manpages maintainer too? (preferably write most
> of the manpage body as well, IMO).

Yes, please.  Docs written by, or with input from, the implementer
provide one of the few ways for everyone else to spot differences
between implementation and intention.
-- 
Ist Ihr Browser Vista-kompatibel? Jetzt die neuesten 
Browser-Versionen downloaden: http://www.gmx.net/de/go/browser

Re: containers (was Re: -mm merge plans for 2.6.23)

[Paul Jackson]

Srivatsa wrote:
> So Ingo was proposing we use cpuset as that user interface to manage
> task-groups. This will be only for 2.6.23.

Good explanation - thanks.

In short, the proposal was to use the task partition defined by cpusets
to define CFS task-groups, until the real process containers are
available.

Or, I see in the next message, Ingo responding favorably to your
alternative, using task uid's to partition the tasks into CFS
task-groups.

Yeah, Ingo's preference for using uid's (or gid's ??) sounds right to
me - a sustainable API.

Wouldn't want to be adding a cpuset API for a single 2.6.N release.

... gid's -- why not?

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.925.600.0401

Re: containers (was Re: -mm merge plans for 2.6.23)

[Peter Zijlstra]

On Wed, 2007-07-11 at 04:10 -0700, Paul Jackson wrote:
> Srivatsa wrote:
> > So Ingo was proposing we use cpuset as that user interface to manage
> > task-groups. This will be only for 2.6.23.
> 
> Good explanation - thanks.
> 
> In short, the proposal was to use the task partition defined by cpusets
> to define CFS task-groups, until the real process containers are
> available.
> 
> Or, I see in the next message, Ingo responding favorably to your
> alternative, using task uid's to partition the tasks into CFS
> task-groups.
> 
> Yeah, Ingo's preference for using uid's (or gid's ??) sounds right to
> me - a sustainable API.
> 
> Wouldn't want to be adding a cpuset API for a single 2.6.N release.
> 
> .... gid's -- why not?


Or process or process groups, or all of the above :-)

One thing to think on though, we cannot have per process,uid,gid,pgrp
scheduling for one release only. So we'd have to manage interaction with
process containers. It might be that a simple weight multiplication
scheme is good enough:

  weight = uid_weight * pgrp_weight * container_weight

Of course, if we'd only have a single level group scheduler (as was
proposed IIRC) it'd have to create intersection sets (as there might be
non trivial overlaps) based on these various weights and schedule these
resulting sets instead of the initial groupings.

Re: containers (was Re: -mm merge plans for 2.6.23)

[Peter Zijlstra]

On Wed, 2007-07-11 at 13:24 +0200, Peter Zijlstra wrote:
> On Wed, 2007-07-11 at 04:10 -0700, Paul Jackson wrote:
> > Srivatsa wrote:
> > > So Ingo was proposing we use cpuset as that user interface to manage
> > > task-groups. This will be only for 2.6.23.
> > 
> > Good explanation - thanks.
> > 
> > In short, the proposal was to use the task partition defined by cpusets
> > to define CFS task-groups, until the real process containers are
> > available.
> > 
> > Or, I see in the next message, Ingo responding favorably to your
> > alternative, using task uid's to partition the tasks into CFS
> > task-groups.
> > 
> > Yeah, Ingo's preference for using uid's (or gid's ??) sounds right to
> > me - a sustainable API.
> > 
> > Wouldn't want to be adding a cpuset API for a single 2.6.N release.
> > 
> > .... gid's -- why not?
> 
> 
> Or process or process groups, or all of the above :-)
> 
> One thing to think on though, we cannot have per process,uid,gid,pgrp
> scheduling for one release only. So we'd have to manage interaction with
> process containers. It might be that a simple weight multiplication
> scheme is good enough:
> 
>   weight = uid_weight * pgrp_weight * container_weight
> 
> Of course, if we'd only have a single level group scheduler (as was
> proposed IIRC) it'd have to create intersection sets (as there might be
> non trivial overlaps) based on these various weights and schedule these
> resulting sets instead of the initial groupings.

Lets illustrate with some ASCII art:

so we have this dual level weight grouping (uid, container)

uid:          a a a a a b b b b b c c c c c
container:    A A A A A A A B B B B B B B B

set:          1 1 1 1 1 2 2 3 3 3 4 4 4 4 4 

resulting in schedule sets 1,2,3,4

so that (for instance) weight_2 = weight_b * weight_A

Re: -mm merge plans for 2.6.23

[Christoph Hellwig]

On Tue, Jul 10, 2007 at 01:31:52AM -0700, Andrew Morton wrote:
> romfs-printk-format-warnings.patch

NACK on this one.  This bloats romfs by almost half of it's previous
size to add mtd support to it.  Given that romfs is a compltely
trivial filesystem it's much better to have a separate filesystem
driver handling the format on mtd instead of adding all these
indirections.  In addition to that argument the switch on the
underlying subsystem is done horrible.  There's lots of ifdefs instead
of proper functions pointers, there's one file containing both block
and mtd code instead of seaparate files, etc.

And the get_unmapped_area method in a bare filesystem needs a _lot_
of explanation.

scsi, was Re: -mm merge plans for 2.6.23

[Christoph Hellwig]

> restore-acpi-change-for-scsi.patch
> git-scsi-misc-vs-greg-sysfs-stuff.patch
> aacraid-rename-check_reset.patch
> scsi-dont-build-scsi_dma_mapunmap-for-has_dma.patch
> drivers-scsi-small-cleanups.patch
> sym53c8xx_2-claims-cpqarray-device.patch
> drivers-scsi-wd33c93c-cleanups.patch
> make-seagate_st0x_detect-static.patch
> pci-error-recovery-symbios-scsi-base-support.patch
> pci-error-recovery-symbios-scsi-first-failure.patch
> drivers-scsi-pcmcia-nsp_csc-remove-kernel-24-code.patch
> drivers-message-i2o-devicec-remove-redundant-gfp_atomic-from-kmalloc.patch
> drivers-scsi-aic7xxx_oldc-remove-redundant-gfp_atomic-from-kmalloc.patch
> use-menuconfig-objects-ii-scsi.patch
> remove-dead-references-to-module_parm-macro.patch
> ppa-coding-police-and-printk-levels.patch
> remove-the-dead-cyberstormiii_scsi-option.patch
> config_scsi_fd_8xx-no-longer-exists.patch
> use-mutex-instead-of-semaphore-in-megaraid-mailbox-driver.patch
> 
>  Sent to James.

Care to drop the patches James NACKed every single time?

Re: -mm merge plans for 2.6.23

[David Woodhouse]

On Wed, 2007-07-11 at 13:35 +0200, Christoph Hellwig wrote:
> On Tue, Jul 10, 2007 at 01:31:52AM -0700, Andrew Morton wrote:
> > romfs-printk-format-warnings.patch
> 
> NACK on this one. 

The rest of it is nacked anyway, until we unify the point and
get_unmapped_area methods of the MTD API.

-- 
dwmw2

Re: buffered write patches, -mm merge plans for 2.6.23

[Christoph Hellwig]

>  pagefault-in-write deadlock fixes.  Will hold for 2.6.24.

Why that?  This stuff has been in forever and is needed at various
levels.  We need this in for anything to move forward on the buffered
write front.

Re: containers (was Re: -mm merge plans for 2.6.23)

[Srivatsa Vaddagiri]

[-- Attachment #1: Type: text/plain, Size: 2593 bytes --]

On Wed, Jul 11, 2007 at 12:19:58PM +0200, Ingo Molnar wrote:
> * Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> wrote:
> 
> > The other alternative is to hook up group scheduler with user-id's 
> > (again only for 2.6.23).
> 
> could you just try this and send an as simple patch as possible? This is 
> actually something that non-container people would be interested in as 
> well. 

Note that interfacing with container infrastructure doesn't preclude the
possibility of doing fair-user scheduling (that a normal university server or 
desktop user would want). All that is needed is a daemon which listens for uid 
change events from kernel (using process-event connector) and moves the task 
(whose uid is changing) to an appropriate container for that user.
Primitive source for such a daemon is attached.

> (btw., if this goes into 2.6.23 then we cannot possibly turn it off in 2.6.24,

The fact that we will have two interface for group scheduler in 2.6.24
is what worries me a bit (one user-id based and other container based).
We would need some mechanism for admin to choose only one interface (and
not both together, otherwise the group definitions may conflict), which
doesn't sound very clean to me.

Ideally I would have liked to hook onto only container infrastructure
and let user-space decide grouping policy (whether user-id based or
something else).

Hmm ..would it help if I maintain a patch outside the mainline which turns on 
fair-user scheduling in 2.6.23-rcX? Folks will have to apply that patch on
top of 2.6.23-rcX to use and test fair-user scheduling.

In 2.6.24, when container infrastructure goes in, people can get
fair-user scheduling off-the-shelf by simply starting the daemon attached
at bootup/initrd time.

Or would you rather prefer that I add user-id based interface
permanently and in 2.6.24 introduce a compile/run-time switch for admin
to select one of the two interfaces (user-id based or container-based)?

> so it must be sane - but per UID task groups are 
> certainly sane, the only question is how to configure the per-UID weight 
> after bootup.

Yeah ..the container based infrastructure allows for configuring such
things very easily using a fs-based interface. In the absence of that,
we either provide some /proc interface or settle for the non-configurable 
default that you mention below.

>  [the default after-bootup should be something along the 
> lines of 'same weight for all users, a bit more for root'.]) This would 
> make it possible for users to test that thing. (it would also help 
> X-heavy workloads.)


-- 
Regards,
vatsa

[-- Attachment #2: cpuctld.c --]
[-- Type: text/plain, Size: 7072 bytes --]

/*
 * cpuctl_group_changer.c
 *
 * Used to change the group of running tasks to the correct
 * uid container.
 *
 * Copyright IBM Corporation, 2007
 * Author: Dhaval Giani <dhaval@linux.vnet.ibm.com>
 * Derived from test_cn_proc.c by Matt Helsley
 * Original copyright notice follows
 *
 * Copyright (C) Matt Helsley, IBM Corp. 2005
 * Derived from fcctl.c by Guillaume Thouvenin
 * Original copyright notice follows:
 *
 * Copyright (C) 2005 BULL SA.
 * Written by Guillaume Thouvenin <guillaume.thouvenin@bull.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <string.h>

#include <sys/socket.h>
#include <sys/types.h>

#include <sys/stat.h>
#include <sys/param.h>

#include <linux/connector.h>
#include <linux/netlink.h>
#include "linux/cn_proc.h"

#include <errno.h>

#include <signal.h>
#include <setjmp.h>

#define SEND_MESSAGE_LEN (NLMSG_LENGTH(sizeof(struct cn_msg) + \
				       sizeof(enum proc_cn_mcast_op)))
#define RECV_MESSAGE_LEN (NLMSG_LENGTH(sizeof(struct cn_msg) + \
				       sizeof(struct proc_event)))

#define SEND_MESSAGE_SIZE    (NLMSG_SPACE(SEND_MESSAGE_LEN))
#define RECV_MESSAGE_SIZE    (NLMSG_SPACE(RECV_MESSAGE_LEN))

#define max(x,y) ((y)<(x)?(x):(y))
#define min(x,y) ((y)>(x)?(x):(y))

#define BUFF_SIZE (max(max(SEND_MESSAGE_SIZE, RECV_MESSAGE_SIZE), 1024))
#define MIN_RECV_SIZE (min(SEND_MESSAGE_SIZE, RECV_MESSAGE_SIZE))

#define PROC_CN_MCAST_LISTEN (1)
#define PROC_CN_MCAST_IGNORE (2)

/*
 * SIGINT causes the program to exit gracefully
 * this could happen any time after the LISTEN message has
 * been sent
 */
#define INTR_SIG SIGINT


sigjmp_buf g_jmp;
char cpuctl_fs_path[MAXPATHLEN];

void handle_intr (int signum)
{
	siglongjmp(g_jmp, signum);
}

static inline void itos(int i, char* str)
{
	sprintf(str, "%d", i);
}

int set_notify_release(int val)
{
	FILE *f;

	f = fopen("notify_on_release", "r+");
	fprintf(f, "%d\n", val);
	fclose(f);
	return 0;
}

int add_task_pid(int pid)
{
	FILE *f;

	f = fopen("tasks", "a");
	fprintf(f, "%d\n", pid);
	fclose(f);
	return 0;
}

int set_value(char* file, char *str)
{
	FILE *f;

	f=fopen(file, "w");
	fprintf(f, "%s", str);
	fclose(f);
	return 0;
}

int change_group(int pid, int uid)
{
	char str[100];
	int ret;

	ret = chdir(cpuctl_fs_path);
	itos(uid, str);
	ret = mkdir(str, 0777);
	if (ret == -1) {
		/*
		 * If the folder already exists, then it is alright. anything
		 * else should be killed
		 */
		if (errno != EEXIST) {
			perror("mkdir");
			return -1;
		}
	}
	ret = chdir(str);
	if (ret == -1) {
		/*Again, i am just quitting the program!*/
		perror("chdir");
		return -1;
	}
	/*If using cpusets set cpus and mems*
	 *
	 * set_value("cpus","0");
	 * set_value("mems","0");
	 */
	set_notify_release(1);
	add_task_pid(pid);
	return 0;
}

int handle_msg (struct cn_msg *cn_hdr)
{
	struct proc_event *ev;
	int ret;

	ev = (struct proc_event*)cn_hdr->data;

	switch(ev->what){
	case PROC_EVENT_UID:
		printf("UID Change happening\n");
		printf("UID = %d\tPID=%d\n", ev->event_data.id.e.euid,
						ev->event_data.id.process_pid);
		ret = change_group(ev->event_data.id.process_pid,
					ev->event_data.id.r.ruid);
		break;
	case PROC_EVENT_FORK:
	case PROC_EVENT_EXEC:
	case PROC_EVENT_EXIT:
	default:
		break;
	}
	return ret;
}
int main(int argc, char **argv)
{
	int sk_nl;
	int err;
	struct sockaddr_nl my_nla, kern_nla, from_nla;
	socklen_t from_nla_len;
	char buff[BUFF_SIZE];
	int rc = -1;
	struct nlmsghdr *nl_hdr;
	struct cn_msg *cn_hdr;
	enum proc_cn_mcast_op *mcop_msg;
	size_t recv_len = 0;
	FILE *f;

	if (argc == 1)
		strcpy(cpuctl_fs_path, "/dev/cpuctl");
	else
		strcpy(cpuctl_fs_path, argv[1]);
	chdir(cpuctl_fs_path);
	f = fopen("tasks", "r");
	if (f == NULL) {
		printf("Container not mounted at %s\n", cpuctl_fs_path);
		return -1;
	}
	fclose(f);
	f = fopen("notify_on_release", "r");
	if (f == NULL) {
		printf("Container not mounted at %s\n", cpuctl_fs_path);
		return -1;
	}
	fclose(f);
	if (getuid() != 0) {
		printf("Only root can start/stop the fork connector\n");
		return 0;
	}
	/*
	 * Create an endpoint for communication. Use the kernel user
	 * interface device (PF_NETLINK) which is a datagram oriented
	 * service (SOCK_DGRAM). The protocol used is the connector
	 * protocol (NETLINK_CONNECTOR)
	 */
	sk_nl = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_CONNECTOR);
	if (sk_nl == -1) {
		printf("socket sk_nl error");
		return rc;
	}
	my_nla.nl_family = AF_NETLINK;
	my_nla.nl_groups = CN_IDX_PROC;
	my_nla.nl_pid = getpid();

	kern_nla.nl_family = AF_NETLINK;
	kern_nla.nl_groups = CN_IDX_PROC;
	kern_nla.nl_pid = 1;

	err = bind(sk_nl, (struct sockaddr *)&my_nla, sizeof(my_nla));
	if (err == -1) {
		printf("binding sk_nl error");
		goto close_and_exit;
	}
	nl_hdr = (struct nlmsghdr *)buff;
	cn_hdr = (struct cn_msg *)NLMSG_DATA(nl_hdr);
	mcop_msg = (enum proc_cn_mcast_op*)&cn_hdr->data[0];
	printf("sending proc connector: PROC_CN_MCAST_LISTEN... ");
	memset(buff, 0, sizeof(buff));
	*mcop_msg = PROC_CN_MCAST_LISTEN;
	signal(INTR_SIG, handle_intr);
	/* fill the netlink header */
	nl_hdr->nlmsg_len = SEND_MESSAGE_LEN;
	nl_hdr->nlmsg_type = NLMSG_DONE;
	nl_hdr->nlmsg_flags = 0;
	nl_hdr->nlmsg_seq = 0;
	nl_hdr->nlmsg_pid = getpid();
	/* fill the connector header */
	cn_hdr->id.idx = CN_IDX_PROC;
	cn_hdr->id.val = CN_VAL_PROC;
	cn_hdr->seq = 0;
	cn_hdr->ack = 0;
	cn_hdr->len = sizeof(enum proc_cn_mcast_op);
	if (send(sk_nl, nl_hdr, nl_hdr->nlmsg_len, 0) != nl_hdr->nlmsg_len) {
		printf("failed to send proc connector mcast ctl op!\n");
		goto close_and_exit;
	}
	printf("sent\n");
	for(memset(buff, 0, sizeof(buff)), from_nla_len = sizeof(from_nla);
	  ; memset(buff, 0, sizeof(buff)), from_nla_len = sizeof(from_nla)) {
		struct nlmsghdr *nlh = (struct nlmsghdr*)buff;
		memcpy(&from_nla, &kern_nla, sizeof(from_nla));
		recv_len = recvfrom(sk_nl, buff, BUFF_SIZE, 0,
				(struct sockaddr*)&from_nla, &from_nla_len);
		if (recv_len < 1)
			continue;
		while (NLMSG_OK(nlh, recv_len)) {
			cn_hdr = NLMSG_DATA(nlh);
			if (nlh->nlmsg_type == NLMSG_NOOP)
				continue;
			if ((nlh->nlmsg_type == NLMSG_ERROR) ||
			    (nlh->nlmsg_type == NLMSG_OVERRUN))
				break;
			if(handle_msg(cn_hdr)<0) {
				goto close_and_exit;
			}
			if (nlh->nlmsg_type == NLMSG_DONE)
				break;
			nlh = NLMSG_NEXT(nlh, recv_len);
		}
	}
close_and_exit:
	close(sk_nl);
	exit(rc);

	return 0;
}

Re: containers (was Re: -mm merge plans for 2.6.23)

[Paul Jackson]

Srivatsa wrote:
> The fact that we will have two interface for group scheduler in 2.6.24
> is what worries me a bit (one user-id based and other container based).

Yeah.

One -could- take linear combinations, as Peter drew in his ascii art,
but would one -want- to do that?

I imagine some future time, when users of this wonder why the API is
more complicated than seems necessary, with two factors determining
task-groups where one seems sufficient, and the answer is "the other
factor, user-id's, is just there because we needed it as an interim
mechanism, and then had to keep it, to preserve ongoing compatibility.
That's not a very persuasive justification.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.925.600.0401

Re: -mm merge plans for 2.6.23

[Christoph Hellwig]

> mutex_unlock-later-in-seq_lseek.patch
> zs-move-to-the-serial-subsystem.patch
> fs-block_devc-use-list_for_each_entry.patch
>
> introduce-o_cloexec-take-2.patch
> o_cloexec-for-scm_rights.patch
>

Umm, Andrew - mixing new userspace interface, compltely rewritten
drivers and simple fixes in a simple misc category doesn't exactly
help reading this list :)

fallocate, Re: -mm merge plans for 2.6.23

[Christoph Hellwig]

> fallocate-implementation-on-i86-x86_64-and-powerpc.patch
> fallocate-on-s390.patch
> fallocate-on-ia64.patch
> fallocate-on-ia64-fix.patch
> 
>  Merge.

Hopefull this will be done during the 2.6.23 merge window, but right now
it's not (yet).

Re: containers (was Re: -mm merge plans for 2.6.23)

[Peter Zijlstra]

On Wed, 2007-07-11 at 04:42 -0700, Paul Jackson wrote:
> Srivatsa wrote:
> > The fact that we will have two interface for group scheduler in 2.6.24
> > is what worries me a bit (one user-id based and other container based).
> 
> Yeah.
> 
> One -could- take linear combinations, as Peter drew in his ascii art,
> but would one -want- to do that?

I'd very much like to have it, but that is just me. We could take a
weight of 0 to mean disabling of that grouping and default to that. That
way it would not complicate regular behaviour.

It could be implemented with a simple hashing scheme where
sched_group_hash(tsk) and sched_group_cmp(tsk, group->some_task) could
be used to identify a schedule group.

pseudo code:

u64 sched_group_hash(struct task_struct *tsk)
{
	u64 hash = 0;

	if (tsk->pid->weight)
		hash_add(&hash, tsk->pid);

	if (tsk->pgrp->weight)
		hash_add(&hash, tsk->pgrp);

	if (tsk->uid->weight)
		hash_add(&hash, tsk->uid);

	if (tsk->container->weight)
		hash_add(&hash, tsk->container);

	...

	return hash;
}

s64 sched_group_cmp(struct task_struct *t1, struct task_struct *t2)
{
	s64 cmp;

	if (t1->pid->weight || t2->pid->weight) {
		cmp = t1->pid->weight - t2->pid->weight;
		if (cmp)
			return cmp;
	}

	...

	return 0;
}

u64 sched_group_weight(struct task_struct *tsk)
{
	u64 weight = 1024; /* 1 fixed point 10 bits */

	if (tsk->pid->weight) {
		weight *= tsk->pid->weight;
		weight /= 1024;
	}

	....

	return weight;
}

lguest, Re: -mm merge plans for 2.6.23

[Christoph Hellwig]

> lguest-export-symbols-for-lguest-as-a-module.patch

__put_task_struct is one of those no way in hell should this be exported
things because we don't want modules messing with task lifetimes.

Fortunately I can't find anything actually using this in lguest, so
it looks the issue has been solved in the meantime.


I also have a rather bad feeling about exporting access_process_vm.
This is the proverbial sledge hammer for access to user vm addresses
and I'd rather keep it away from module programmers with "if all
you have is a hammer ..." in mind.

In lguest this is used by send_dma which from my short reading of the
code seems to be the central IPC mechanism.  The double copy here
doesn't look very efficient to me either.  Maybe some VM folks could
look into a better way to archive this that might be both more
efficient and not require the export.


> lguest-the-guest-code.patch
> lguest-the-host-code.patch
> lguest-the-host-code-lguest-vs-clockevents-fix-resume-logic.patch
> lguest-the-asm-offsets.patch
> lguest-the-makefile-and-kconfig.patch
> lguest-the-console-driver.patch
> lguest-the-net-driver.patch
> lguest-the-block-driver.patch
> lguest-the-documentation-example-launcher.patch

Just started to reading this (again) so no useful comment here, but it
would be nice if the code could follow CodingStyle and place the || and
&& at the end of the line in multiline conditionals instead of at the
beginning of the new one.

Re: [ck] Re: -mm merge plans for 2.6.23

[Kevin Winchester]

[-- Attachment #1: Type: text/plain, Size: 1411 bytes --]

On Tue, 10 Jul 2007 18:14:19 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Wed, 11 Jul 2007 11:02:56 +1000 "Matthew Hawkins" <darthmdh@gmail.com> wrote:
> 
> > We all know swap prefetch has been tested out the wazoo since Moses was a
> > little boy, is compile-time and runtime selectable, and gives an important
> > and quantifiable performance increase to desktop systems.
> 
> Always interested.  Please provide us more details on your usage and
> testing of that code.  Amount of memory, workload, observed results,
> etc?
> 

I only have 512 MB of memory on my Athlon64 desktop box, and I switch between -mm and mainline kernels regularly.  I have noticed that -mm is always much more responsive, especially first thing in the morning.  I believe this has been due to the new schedulers in -mm (because I notice an improvement in mainline now that CFS has been merged), as well as swap prefetch.  I haven't tested swap prefetch alone to know for sure, but it seems pretty likely.

My workload is compiling kernels, with sylpheed, pidgin and firefox[1] open, and sometimes MonoDevelop if I want to slow my system to a crawl.

I will be getting another 512 MB of RAM at Christmas time, but from the other reports, it seems that swap prefetch will still be useful.

[1] Is there a graphical browser for linux that doesn't suck huge amounts of RAM?

-- 
Kevin Winchester

[-- Attachment #2: Type: application/pgp-signature, Size: 189 bytes --]

Re: containers (was Re: -mm merge plans for 2.6.23)

[Srivatsa Vaddagiri]

On Wed, Jul 11, 2007 at 05:09:53PM +0530, Srivatsa Vaddagiri wrote:
> > (btw., if this goes into 2.6.23 then we cannot possibly turn it off in 2.6.24,
> 
> The fact that we will have two interface for group scheduler in 2.6.24
> is what worries me a bit (one user-id based and other container based).

I know breaking user-interface is a bad thing across releases. But in
this particular case, it's probably ok (since fair-group scheduling is a
brand new feature in Linux)?

If we have that option of breaking API between 2.6.23 and 2.6.24
for fair-group scheduler, then we are in a much more flexible position.

For 2.6.23, I can send a user-id based interface for fair-group
scheduler (with some /proc interface to tune group nice value).

For 2.6.24, this user-id interface will be removed and we will instead
switch to container based interface. Fair-user scheduling will continue
to work, its just that users will have to use a daemon (sources sent in
previous mail) to enable it on top of container-based interface.

Hmm..?

-- 
Regards,
vatsa

Re: [ck] Re: -mm merge plans for 2.6.23

[Jesper Juhl]

On 11/07/07, Kevin Winchester <kjwinchester@gmail.com> wrote:
[snip]
>
> [1] Is there a graphical browser for linux that doesn't suck huge amounts of RAM?
>

Dillo (http://www.dillo.org/) is really really tiny , a memory
footprint somewhere in the hundreds of K area IIRC.

links 2 (http://links.twibright.com/) has a graphical mode in addition
to the traditional text only mode (links -g) and the memory footprint
is really tiny.

-- 
Jesper Juhl <jesper.juhl@gmail.com>
Don't top-post  http://www.catb.org/~esr/jargon/html/T/top-post.html
Plain text mails only, please      http://www.expita.com/nomime.html

x86 status was Re: -mm merge plans for 2.6.23

[Andi Kleen]

Andrew Morton <akpm@linux-foundation.org> writes:

> revert-x86_64-mm-verify-cpu-rename.patch
> add-kstrndup-fix.patch
> xen-build-fix.patch
> fix-x86_64-numa-fake-apicid_to_node-mapping-for-fake-numa-2.patch
> fix-x86_64-mm-xen-xen-smp-guest-support.patch
> more-fix-x86_64-mm-xen-xen-smp-guest-support.patch

> fix-x86_64-mm-sched-clock-share.patch
> fix-x86_64-mm-xen-add-xen-virtual-block-device-driver.patch
> fix-x86_64-mm-add-common-orderly_poweroff.patch
> fix-x86_64-mm-xen-xen-event-channels.patch
> arch-i386-xen-mmuc-must-include-linux-schedh.patch
> tidy-up-usermode-helper-waiting-a-bit-fix.patch
> update-x86_64-mm-xen-use-iret-directly-where-possible.patch


Xen is probably going to be merged. I'm still not fully happy
about the review status of the drivers and xenbus, but there doesn't seem
to be much value in delaying it further.

I'll consolidate the fixes and fixes-to-fixes.


These all need re-review:

> i386-add-support-for-picopower-irq-router.patch
> make-arch-i386-kernel-setupcremapped_pgdat_init-static.patch
> arch-i386-kernel-i8253c-should-include-asm-timerh.patch
> make-arch-i386-kernel-io_apicctimer_irq_works-static-again.patch
> quicklist-support-for-x86_64.patch
> x86_64-extract-helper-function-from-e820_register_active_regions.patch
> x86_64-fix-e820_hole_size-based-on-address-ranges.patch
> x86_64-acpi-disable-srat-when-numa-emulation-succeeds.patch
> x86_64-slit-fake-pxm-to-node-mapping-for-fake-numa-2.patch
> x86_64-numa-fake-apicid_to_node-mapping-for-fake-numa-2.patch
> x86-use-elfnoteh-to-generate-vsyscall-notes-fix.patch
> mmconfig-x86_64-i386-insert-unclaimed-mmconfig-resources.patch
> x86_64-fix-smp_call_function_single-return-value.patch
> x86_64-o_excl-on-dev-mcelog.patch
> x86_64-support-poll-on-dev-mcelog.patch

It's still not clear to me this is any useful. The current code
can run a program on MCE which should be really fast enough
for machine check handling.

> i386-fix-machine-rebooting.patch
> x86-fix-section-mismatch-warnings-in-mtrr.patch
> x86_64-ratelimit-segfault-reporting-rate.patch

I think that one was bogus.

> x86_64-pm_trace-support.patch
> make-alt-sysrq-p-display-the-debug-register-contents.patch
> i386-flush_tlb_kernel_range-add-reference-to-the-arguments.patch
> round_jiffies-for-i386-and-x86-64-non-critical-corrected-mce-polling.patch
> pci-disable-decode-of-io-memory-during-bar-sizing.patch
> mmconfig-validate-against-acpi-motherboard-resources.patch
> x86_64-irq-check-remote-irr-bit-before-migrating-level-triggered-irq-v3.patch
> i386-remove-support-for-the-rise-cpu.patch

> i386-make-arch-i386-mm-pgtablecpgd_cdtor-static.patch
> i386-fix-section-mismatch-warning-in-intel_cacheinfo.patch
> i386-do-not-restore-reserved-memory-after-hibernation.patch
> paravirt-helper-to-disable-all-io-space-fix.patch
> dmi_match-patch-in-rebootc-for-sff-dell-optiplex-745-fixes-hang.patch
> i386-hpet-check-if-the-counter-works.patch
> i386-trim-memory-not-covered-by-wb-mtrrs.patch

Might need more testing? 

More review:

> kprobes-x86_64-fix-for-mark-ro-data.patch
> kprobes-i386-fix-for-mark-ro-data.patch
> divorce-config_x86_pae-from-config_highmem64g.patch
> remove-unneeded-test-of-task-in-dump_trace.patch
> i386-move-the-kernel-to-16mb-for-numa-q.patch
> i386-show-unhandled-signals.patch
> i386-minor-nx-handling-adjustment.patch
> x86-smp-alt-once-option-is-only-useful-with-hotplug_cpu.patch
> x86-64-remove-unused-variable-maxcpus.patch
> move-functions-declarations-to-header-file.patch
> x86_64-during-vm-oom-condition.patch
> i386-during-vm-oom-condition.patch
> x86-64-disable-the-gart-in-shutdown.patch
> x86_84-move-iommu-declaration-from-proto-to-iommuh.patch
> i386-uaccessh-replace-hard-coded-constant-with-appropriate-macro-from-kernelh.patch
> i386-add-cpu_relax-to-cmos_lock.patch
> x86_64-flush_tlb_kernel_range-warning-fix.patch
> x86_64-add-ioapic-nmi-support.patch
> x86_64-change-_map_single-to-static-in-pci_gartc-etc.patch
> x86_64-geode-hw-random-number-generator-depend-on-x86_3.patch
> x86_64-fix-wrong-comment-regarding-set_fixmap.patch
> arch-x86_64-kernel-processc-lower-printk-severity.patch
> nohz-fix-nohz-x86-dyntick-idle-handling.patch
> acpi-move-timer-broadcast-and-pmtimer-access-before-c3-arbiter-shutdown.patch
> clockevents-fix-typo-in-acpi_pmc.patch
> timekeeping-fixup-shadow-variable-argument.patch
> timerc-cleanup-recently-introduced-whitespace-damage.patch
> clockevents-remove-prototypes-of-removed-functions.patch
> clockevents-fix-resume-logic.patch
> clockevents-fix-device-replacement.patch
> tick-management-spread-timer-interrupt.patch
> highres-improve-debug-output.patch
> hrtimer-speedup-hrtimer_enqueue.patch
> pcspkr-use-the-global-pit-lock.patch
> ntp-move-the-cmos-update-code-into-ntpc.patch
> i386-pit-stop-only-when-in-periodic-or-oneshot-mode.patch
> i386-remove-volatile-in-apicc.patch
> i386-hpet-assumes-boot-cpu-is-0.patch
> i386-move-pit-function-declarations-and-constants-to-correct-header-file.patch
> x86_64-untangle-asm-hpeth-from-asm-timexh.patch
> x86_64-use-generic-cmos-update.patch
> x86_64-remove-dead-code-and-other-janitor-work-in-tscc.patch
> x86_64-fix-apic-typo.patch
> x86_64-convert-to-cleckevents.patch
> acpi-remove-the-useless-ifdef-code.patch
> x86_64-hpet-restore-vread.patch
> x86_64-restore-restore-nohpet-cmdline.patch
> x86_64-block-irq-balancing-for-timer.patch
> x86_64-prep-idle-loop-for-dynticks.patch
> x86_64-enable-high-resolution-timers-and-dynticks.patch
> x86_64-dynticks-disable-hpet_id_legsup-hpets.patch


I'm sceptical about the dynticks code. It just rips out the
x86-64 timing code completely, which needs a lot more review and testing.
Probably not .23

More review: 

> xen-fix-x86-config-dependencies.patch
> x86_64-get-mp_bus_to_node-as-early.patch
> xen-suppress-abs-symbol-warnings-for-unused-reloc-pointers.patch
> xen-cant-support-numa-yet.patch
> x86-fix-iounmaps-use-of-vm_structs-size-field.patch
> arch-x86_64-kernel-aperturec-lower-printk-severity.patch
> arch-x86_64-kernel-e820c-lower-printk-severity.patch
> ich-force-hpet-make-generic-time-capable-of-switching-broadcast-timer.patch
> ich-force-hpet-restructure-hpet-generic-clock-code.patch
> ich-force-hpet-ich7-or-later-quirk-to-force-detect-enable.patch
> ich-force-hpet-late-initialization-of-hpet-after-quirk.patch
> ich-force-hpet-ich5-quirk-to-force-detect-enable.patch
> ich-force-hpet-ich5-fix-a-bug-with-suspend-resume.patch
> ich-force-hpet-add-ich7_0-pciid-to-quirk-list.patch
> geode-basic-infrastructure-support-for-amd-geode-class.patch
> geode-mfgpt-support-for-geode-class-machines.patch
> geode-mfgpt-clock-event-device-support.patch
> i386-x86_64-insert-hpet-firmware-resource-after-pci-enumeration-has-completed.patch
> i386-ioapic-remove-old-irq-balancing-debug-cruft.patch
> i386-deactivate-the-test-for-the-dead-config_debug_page_type.patch

-Andi

Re: containers (was Re: -mm merge plans for 2.6.23)

[Srivatsa Vaddagiri]

On Wed, Jul 11, 2007 at 01:30:40PM +0200, Peter Zijlstra wrote:
> > One thing to think on though, we cannot have per process,uid,gid,pgrp
> > scheduling for one release only. So we'd have to manage interaction with
> > process containers. It might be that a simple weight multiplication
> > scheme is good enough:
> > 
> >   weight = uid_weight * pgrp_weight * container_weight

We would need something like this to flatten hierarchy, so that for
example it is possible to do fair-container scheduling +
fair-user/process scheduling inside a container using a hierarchy depth of 
just 1 (containers) that core scheduler understands. We discussed this a bit at
http://marc.info/?l=linux-kernel&m=118054481416140&w=2 and is very much
on my todo list to experiment with.

> > Of course, if we'd only have a single level group scheduler (as was
> > proposed IIRC) it'd have to create intersection sets (as there might be
> > non trivial overlaps) based on these various weights and schedule these
> > resulting sets instead of the initial groupings.
> 
> Lets illustrate with some ASCII art:
> 
> so we have this dual level weight grouping (uid, container)
> 
> uid:          a a a a a b b b b b c c c c c
> container:    A A A A A A A B B B B B B B B
> 
> set:          1 1 1 1 1 2 2 3 3 3 4 4 4 4 4 
> 
> resulting in schedule sets 1,2,3,4

Wouldn't it be simpler if admin created these sets as containers
directly? i.e:


uid:          a a a a a b b b b b c c c c c
container:    1 1 1 1 1 2 2 3 3 3 4 4 4 4 4

That way scheduler will not have to "guess" such intersecting schedulable
sets/groups. It seems much simpler to me this way.

Surely there is some policy which is driving some tasks of userid 
'b' to be in container A and some to be in B. It should be trivial
enough to hook onto that policy making script and create separate
containers like above.

> so that (for instance) weight_2 = weight_b * weight_A



-- 
Regards,
vatsa

Re: fallocate-implementation-on-i86-x86_64-and-powerpc.patch

[Theodore Tso]

On Wed, Jul 11, 2007 at 10:50:49AM +1000, Paul Mackerras wrote:
> > On Wed, 11 Jul 2007 09:27:40 +1000
> > Paul Mackerras <paulus@samba.org> wrote:
> > 
> > > We did come up with an order that worked for everybody, but that
> > > discussion seemed to get totally ignored by the ext4 developers.

Well, in the end it was a toss-up between

asmlinkage long sys_fallocate(int fd, int mode, loff_t offset, loff_t len)

and 

asmlinkage long sys_fallocate(loff_t offset, loff_t len, int fd, int mode)

There were a number of folks who preferred having int fd first, and I
*thought* Amit had gotten agreement from either Martin or Heiko that
it was ok to do this as an exception, even though it was extra work
for that arch.  But if not, we can try going back the second
alternative, or even the 6 32-bits args (off_high, off_low, len_high,
len_low) approach, but I think that drew even more fire. 

Basically, no one approach made everyone happy, and at the end of the
day sometimes you have to choose.  I thought we had settled this in
May with something that people could live with, but if we need to
reopen the discussion, better now than later.....

						- Ted

Re: lguest, Re: -mm merge plans for 2.6.23

[Randy Dunlap]

On Wed, 11 Jul 2007 14:23:24 +0200 Christoph Hellwig wrote:

...

> > lguest-the-guest-code.patch
> > lguest-the-host-code.patch
> > lguest-the-host-code-lguest-vs-clockevents-fix-resume-logic.patch
> > lguest-the-asm-offsets.patch
> > lguest-the-makefile-and-kconfig.patch
> > lguest-the-console-driver.patch
> > lguest-the-net-driver.patch
> > lguest-the-block-driver.patch
> > lguest-the-documentation-example-launcher.patch
> 
> Just started to reading this (again) so no useful comment here, but it
> would be nice if the code could follow CodingStyle and place the || and
> && at the end of the line in multiline conditionals instead of at the
> beginning of the new one.

I prefer them at the ends of lines also, but that's not in CodingStyle,
it's just how we do it most of the time (so "coding style", without
caps).

---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***

Re: -mm merge plans -- lumpy reclaim

[Andrew Morton]

On Wed, 11 Jul 2007 10:34:31 +0100 Andy Whitcroft <apw@shadowen.org> wrote:

> [Seems a PEBKAC occured on the subject line, resending lest it become a
> victim of "oh thats spam".]
> 
> Andy Whitcroft wrote:
> > Andrew Morton wrote:
> > 
> > [...]
> >> lumpy-reclaim-v4.patch
> >> have-kswapd-keep-a-minimum-order-free-other-than-order-0.patch
> >> only-check-absolute-watermarks-for-alloc_high-and-alloc_harder-allocations.patch
> >>
> >>  Lumpy reclaim.  In a similar situation to Mel's patches.  Stuck due to
> >>  general lack or interest and effort.
> > 
> > The lumpy reclaim patches originally came out of work to support Mel's
> > anti-fragmentation work.  As such I think they have become somewhat
> > attached to those patches.  Whilst lumpy is most effective where
> > placement controls are in place as offered by Mel's work, we see benefit
> > from reduction in the "blunderbuss" effect when we reclaim at higher
> > orders.  While placement control is pretty much required for the very
> > highest orders such as huge page size, lower order allocations are
> > benefited in terms of lower collateral damage.
> > 
> > There are now a few areas other than huge page allocations which can
> > benefit.  Stacks are still order 1.  Jumbo frames want higher order
> > contiguous pages for there incoming hardware buffers.  SLUB is showing
> > performance benefits from moving to a higher allocation order.  All of
> > these should benefit from more aggressive targeted reclaim, indeed I
> > have been surprised just how often my test workloads trigger lumpy at
> > order 1 to get new stacks.
> > 
> > Truly representative work loads are hard to generate for some of these.
> >  Though we have heard some encouraging noises from those who can
> > reproduce these problems.

I'd expect that the main application for lumpy-reclaim is in keeping a pool
of order-2 (say) pages in reserve for GFP_ATOMIC allocators.  ie: jumbo
frames.

At present this relies upon the wakeup_kswapd(..., order) mechanism.

How effective is this at solving the jumbo frame problem?

(And do we still have a jumbo frame problem?  Reports seems to have subsided)

Re: ata and netdev (was Re: -mm merge plans for 2.6.23)

[Dan Faerch]

Andrew Morton wrote:
> drivers-net-ns83820c-add-paramter-to-disable-auto.patch:
>
> See comments in changelog: ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-rc6/2.6.22-rc6-mm1/broken-out/drivers-net-ns83820c-add-paramter-to-disable-auto.patch
>
> Dan, Ben: is there any prospect of progress here?
Mmm.. Ben had 2 comments last year:

In regards to the ethtool stuff i coded:

> This part is good, although doing something for copper cards needs doing, 

I know very little about hardware and only own the fiber version of this 
card. Even if i tried to make code for the copper version, it would 
probably blow it up the phy and set the switches on fire ;).

And in regards to the '"disable_autoneg" module argument':

> This is the part I disagree with.  Are you sure it isn't a bug in the 
> link autonegotiation state machine for fibre cards?  It should be defaulting 
> to 1Gbit/full duplex if no autonegotiation is happening, and if it isn't 
> then that should be fixed instead of papering over things with a config 
> option.

This is pretty much Russian to me. 
I wouldnt know where to find the "link-autonegotiation-state-machine-for-fibre-cards" or know what to do with it anyway :).

The "disable_autoneg" is a convenient feature (for me and the other guy who made the same patch last year) and i consider it a harmless feature in every way.
It is simply an 'if'-statement, that skips the "start autoneg" function upon load.
We can simply remove the feature entirely if it is deemed undesirable.



So in conclusion:
- I vote "use the patch as-is", but im fine with it being changed. 
- If it needs support for copper, someone else has to code it.


Regards
- Dan

Re: containers (was Re: -mm merge plans for 2.6.23)

[Paul Jackson]

Peter wrote:
> I'd very much like to have it, but that is just me.

Why? [linear combinations of uid, container, pid, pgrp weighting]

You provide some implementation details and complications, but no
motivation that I noticed.

Well ... a little motivation ... "just me", which would go a long
way of your first name was Linus.  For the rest of us ... ;).

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.925.600.0401

Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Wed, 11 Jul 2007 12:39:42 +0100 David Woodhouse <dwmw2@infradead.org> wrote:

> On Wed, 2007-07-11 at 13:35 +0200, Christoph Hellwig wrote:
> > On Tue, Jul 10, 2007 at 01:31:52AM -0700, Andrew Morton wrote:
> > > romfs-printk-format-warnings.patch
> > 
> > NACK on this one. 
> 
> The rest of it is nacked anyway, until we unify the point and
> get_unmapped_area methods of the MTD API.
> 

Methinks you meant
nommu-make-it-possible-for-romfs-to-use-mtd-devices.patch, not
romfs-printk-format-warnings.patch.

I'll drop nommu-make-it-possible-for-romfs-to-use-mtd-devices.patch, thamks.

Re: scsi, was Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Wed, 11 Jul 2007 13:37:18 +0200 Christoph Hellwig <hch@lst.de> wrote:

> > restore-acpi-change-for-scsi.patch
> > git-scsi-misc-vs-greg-sysfs-stuff.patch
> > aacraid-rename-check_reset.patch
> > scsi-dont-build-scsi_dma_mapunmap-for-has_dma.patch
> > drivers-scsi-small-cleanups.patch
> > sym53c8xx_2-claims-cpqarray-device.patch
> > drivers-scsi-wd33c93c-cleanups.patch
> > make-seagate_st0x_detect-static.patch
> > pci-error-recovery-symbios-scsi-base-support.patch
> > pci-error-recovery-symbios-scsi-first-failure.patch
> > drivers-scsi-pcmcia-nsp_csc-remove-kernel-24-code.patch
> > drivers-message-i2o-devicec-remove-redundant-gfp_atomic-from-kmalloc.patch
> > drivers-scsi-aic7xxx_oldc-remove-redundant-gfp_atomic-from-kmalloc.patch
> > use-menuconfig-objects-ii-scsi.patch
> > remove-dead-references-to-module_parm-macro.patch
> > ppa-coding-police-and-printk-levels.patch
> > remove-the-dead-cyberstormiii_scsi-option.patch
> > config_scsi_fd_8xx-no-longer-exists.patch
> > use-mutex-instead-of-semaphore-in-megaraid-mailbox-driver.patch
> > 
> >  Sent to James.
> 
> Care to drop the patches James NACKed every single time?

I'm not aware of any which fit that description.

There may be a couple in there which fix real bugs in an unapproved way. 
But I keep such patches as a matter of policy, so people keep on getting
pestered about their bugs.

Re: buffered write patches, -mm merge plans for 2.6.23

[Andrew Morton]

On Wed, 11 Jul 2007 13:39:44 +0200 Christoph Hellwig <hch@lst.de> wrote:

> >  pagefault-in-write deadlock fixes.  Will hold for 2.6.24.
> 
> Why that?

At Nick's request.  More work is needed and the code hasn't had a lot of
testing/thought/exposure/review.

>  This stuff has been in forever and is needed at various
> levels.  We need this in for anything to move forward on the buffered
> write front.

Re: -mm merge plans for 2.6.23

[Randy Dunlap]

On Wed, 11 Jul 2007 10:21:03 -0700 Andrew Morton wrote:

> On Wed, 11 Jul 2007 12:39:42 +0100 David Woodhouse <dwmw2@infradead.org> wrote:
> 
> > On Wed, 2007-07-11 at 13:35 +0200, Christoph Hellwig wrote:
> > > On Tue, Jul 10, 2007 at 01:31:52AM -0700, Andrew Morton wrote:
> > > > romfs-printk-format-warnings.patch
> > > 
> > > NACK on this one. 
> > 
> > The rest of it is nacked anyway, until we unify the point and
> > get_unmapped_area methods of the MTD API.
> > 
> 
> Methinks you meant
> nommu-make-it-possible-for-romfs-to-use-mtd-devices.patch, not
> romfs-printk-format-warnings.patch.
> 
> I'll drop nommu-make-it-possible-for-romfs-to-use-mtd-devices.patch, thamks.

Thanks.  I was certainly getting confused.

---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***

Re: x86 status was Re: -mm merge plans for 2.6.23

[Jesse Barnes]

> > i386-trim-memory-not-covered-by-wb-mtrrs.patch
>
> Might need more testing?

For the mtrr trim patch at least, I think the coverage we've received 
in -mm is probably sufficient (the failure mode would be fairly 
obvious).  The only thing I'm nervous about is adding AMD support for 
the quirk, since I don't have any way of testing it.  We can easily add 
that later though, if a tester steps forward or we see demand for it 
(should just be an extra conditional in the trim code).

Thanks,
Jesse

Re: x86 status was Re: -mm merge plans for 2.6.23

[Ingo Molnar]

* Andi Kleen <andi@firstfloor.org> wrote:

> > clockevents-fix-typo-in-acpi_pmc.patch
> > timekeeping-fixup-shadow-variable-argument.patch
> > timerc-cleanup-recently-introduced-whitespace-damage.patch
> > clockevents-remove-prototypes-of-removed-functions.patch
> > clockevents-fix-resume-logic.patch
> > clockevents-fix-device-replacement.patch
> > tick-management-spread-timer-interrupt.patch
> > highres-improve-debug-output.patch
> > hrtimer-speedup-hrtimer_enqueue.patch
> > pcspkr-use-the-global-pit-lock.patch
> > ntp-move-the-cmos-update-code-into-ntpc.patch
> > i386-pit-stop-only-when-in-periodic-or-oneshot-mode.patch
> > i386-remove-volatile-in-apicc.patch
> > i386-hpet-assumes-boot-cpu-is-0.patch
> > i386-move-pit-function-declarations-and-constants-to-correct-header-file.patch
> > x86_64-untangle-asm-hpeth-from-asm-timexh.patch
> > x86_64-use-generic-cmos-update.patch
> > x86_64-remove-dead-code-and-other-janitor-work-in-tscc.patch
> > x86_64-fix-apic-typo.patch
> > x86_64-convert-to-cleckevents.patch
> > acpi-remove-the-useless-ifdef-code.patch
> > x86_64-hpet-restore-vread.patch
> > x86_64-restore-restore-nohpet-cmdline.patch
> > x86_64-block-irq-balancing-for-timer.patch
> > x86_64-prep-idle-loop-for-dynticks.patch
> > x86_64-enable-high-resolution-timers-and-dynticks.patch
> > x86_64-dynticks-disable-hpet_id_legsup-hpets.patch
> 
> I'm sceptical about the dynticks code. It just rips out the x86-64 
> timing code completely, which needs a lot more review and testing. 
> Probably not .23

What you just did here is a slap in the face to a lot of contributors 
who worked hard on this code :(

Let me tell you about the history of this project first. Arjan wrote the 
first version of it a year ago, and it was added to -rt and tested there 
by many people and went through many iterations and fixes. Chris Wright 
then created a x86_64 clockevents cleanup and dynticks enabling patchset 
from it this spring and sent it to lkml three and a half months ago, on 
March 31:

    http://lwn.net/Articles/229094/

Thomas, the high resolution timers and clockevents maintainer, 
immediately picked up Chris' splitup/splitout/cleanup work and fixed and 
extended it, and sent a first cut to lkml on May 6th:

    http://lwn.net/Articles/233226/

Thomas then sent an updated version of the x86_64 clockevents cleanup 
and dynticks code to lkml (on June 10th), for a second round of review:

    http://lwn.net/Articles/237687/

As Thomas stated it in his submission:

  " The patch set has been tested in the -hrt and -rt trees for quite a 
    while and the initial problems have been sorted out. Thanks to the 
    folks from the PowerTop project for testing and feedback. "

Then on June 16th Thomas sent the third series:

    http://lwn.net/Articles/238834/

(which too was in -rt and was tested there on numerous machines. It was 
also added to -mm.)

Then on June 23rd Thomas sent the fourth series of the x86_64 
clockevents and dynticks code:

    http://lwn.net/Articles/239620/

We finally have someone (Thomas) with core kernel clue who actually 
_cares_ about the x86 time code and does not see it as an ugly chore, 
one who collects the right patches and maintains the -hrt tree and 
co-maintains the -rt tree and interacts with other contributors. What he 
did was _hard_ to do but we are making really good progress:

   http://lkml.org/lkml/2007/7/5/242

   " All in all, personally I'm very happy to see Linux making such a 
     huge step forward with tickless and can't wait for this step to be 
     available in all distros and for all architectures... "

Yes, touching the time code is a pain because both the hardware and the 
kernel has skeletons hidden in the closet, but we are mapping them one 
by one, and we already fixed several kernel skeletons in the process. 
The code is in -mm and there is no open regression related to this queue 
of patches at the moment.

But what is curiously absent from all this positive and dynamic activity 
around these patches on lkml? There is not a single email from Andi 
Kleen, the official maintainer of the x86_64 tree directly reacting to 
this submission in any way, shape or form. Not a single email from you 
thanking Arjan, Chris and Thomas for this amount of cleanup to the 
architecture you are maintaining:

   31 files changed, 698 insertions(+), 1367 deletions(-)

Not a single email from you reviewing the patchset in any meaningful 
way. Not a single email from you to indicate that you even did so much 
as boot into this patchset.

What contribution do we have from you instead? A week before the .23 
merge window is closed, in the very last possible moment, we finally get 
your first reaction to this patchset, albeit in the form of three terse 
sentences:

  > I'm sceptical about the dynticks code. It just rips out the x86-64 
  > timing code completely, which needs a lot more review and testing. 
  > Probably not .23

In the past 3+ months there was not a single email from you indicating 
that you are "doubtful" about this submission, and that you think that 
it needs "lot more review and testing". You dont offer any alternative, 
you dont offer any feedback, no review, no testing, no support, just a 
simple rejection on lkml that prevents this project from going upstream.

Yes, maintainers have veto power and often have to make hard decisions,
but, and let me stress this properly:

   Only if they actually act as honest maintainers!

Altogether 197 emails on lkml discussed these patches, and you were 
Cc:-ed to every one of them. Over a dozen kernel developers reviewed it 
or reacted to the patchset in one way or another. And your only reaction 
to this is silence and a rejection claiming that it needs "lot more 
review"? I'm utterly speechless.

	Ingo

Re: -mm merge plans for 2.6.23

[Christoph Lameter]

On Wed, 11 Jul 2007, Mel Gorman wrote:

> I would like the patches to go through on the grounds that higher order
> allocations can succeed. However, I am also happy to say that order-0
> pages should be used as much as possible, that case should always be
> made as fast as possible and the world must not end if a high-order
> allocation fails.

SLUB can easily be made to not use higher order pages.

If the SLUB mobility patches are not merged then higher order page use 
can be explicitly enabled via passing the following to the kernel on boot

	slub_max_order=<desired max order>

If they are merged then the higher order page use can be disabled in case 
of trouble via

	slub_max_order=0

Re: lguest, Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Wed, 11 Jul 2007 14:23:24 +0200
Christoph Hellwig <hch@lst.de> wrote:

> > lguest-export-symbols-for-lguest-as-a-module.patch
> 
> __put_task_struct is one of those no way in hell should this be exported
> things because we don't want modules messing with task lifetimes.
> 
> Fortunately I can't find anything actually using this in lguest, so
> it looks the issue has been solved in the meantime.
> 

Ther are a couple of calls to put_task_struct() in there, and that needs
__put_task_struct() exported.

> 
> I also have a rather bad feeling about exporting access_process_vm.
> This is the proverbial sledge hammer for access to user vm addresses
> and I'd rather keep it away from module programmers with "if all
> you have is a hammer ..." in mind.

hm, well, access_process_vm() is a convenience wrapper around
get_user_pages(), whcih is exported.

> In lguest this is used by send_dma which from my short reading of the
> code seems to be the central IPC mechanism.  The double copy here
> doesn't look very efficient to me either.  Maybe some VM folks could
> look into a better way to archive this that might be both more
> efficient and not require the export.
> 
> 
> > lguest-the-guest-code.patch
> > lguest-the-host-code.patch
> > lguest-the-host-code-lguest-vs-clockevents-fix-resume-logic.patch
> > lguest-the-asm-offsets.patch
> > lguest-the-makefile-and-kconfig.patch
> > lguest-the-console-driver.patch
> > lguest-the-net-driver.patch
> > lguest-the-block-driver.patch
> > lguest-the-documentation-example-launcher.patch
> 
> Just started to reading this (again) so no useful comment here, but it
> would be nice if the code could follow CodingStyle and place the || and
> && at the end of the line in multiline conditionals instead of at the
> beginning of the new one.

Re: x86 status was Re: -mm merge plans for 2.6.23

[Jeremy Fitzhardinge]

Andi Kleen wrote:
> More review: 
>
>   
>> xen-fix-x86-config-dependencies.patch
>> xen-suppress-abs-symbol-warnings-for-unused-reloc-pointers.patch
>> xen-cant-support-numa-yet.patch
>>     

The first and third of these are just simple Kconfig updates, and the 
middle one just updates the list of symbols which shouldn't be warned 
about in CONFIG_RELOCATABLE's absolute symbol check.  They're completely 
harmless but may prevent someone from generating an unbuildable .config.

>> x86-fix-iounmaps-use-of-vm_structs-size-field.patch
>>     

This appears to fix a real bug; the only question is whether x86-64 
needs the same treatment.  I'm not sure if the original bug reporter 
(dave young) has confirmed it fixed his problem.

    J

Re: -mm merge plans -- lumpy reclaim

[Andy Whitcroft]

Andrew Morton wrote:

>>>> lumpy-reclaim-v4.patch
>>>> have-kswapd-keep-a-minimum-order-free-other-than-order-0.patch
>>>> only-check-absolute-watermarks-for-alloc_high-and-alloc_harder-allocations.patch
>>>>
>>>>  Lumpy reclaim.  In a similar situation to Mel's patches.  Stuck due to
>>>>  general lack or interest and effort.
>>> The lumpy reclaim patches originally came out of work to support Mel's
>>> anti-fragmentation work.  As such I think they have become somewhat
>>> attached to those patches.  Whilst lumpy is most effective where
>>> placement controls are in place as offered by Mel's work, we see benefit
>>> from reduction in the "blunderbuss" effect when we reclaim at higher
>>> orders.  While placement control is pretty much required for the very
>>> highest orders such as huge page size, lower order allocations are
>>> benefited in terms of lower collateral damage.
>>>
>>> There are now a few areas other than huge page allocations which can
>>> benefit.  Stacks are still order 1.  Jumbo frames want higher order
>>> contiguous pages for there incoming hardware buffers.  SLUB is showing
>>> performance benefits from moving to a higher allocation order.  All of
>>> these should benefit from more aggressive targeted reclaim, indeed I
>>> have been surprised just how often my test workloads trigger lumpy at
>>> order 1 to get new stacks.
>>>
>>> Truly representative work loads are hard to generate for some of these.
>>>  Though we have heard some encouraging noises from those who can
>>> reproduce these problems.
> 
> I'd expect that the main application for lumpy-reclaim is in keeping a pool
> of order-2 (say) pages in reserve for GFP_ATOMIC allocators.  ie: jumbo
> frames.
> 
> At present this relies upon the wakeup_kswapd(..., order) mechanism.
> 
> How effective is this at solving the jumbo frame problem?

The tie in between allocator and kswapd is essentially unchanged,
so if allocators are dropping below the watermarks at the specified
order, reclaim will be triggered at that order.  Reclaim continues
until we return above the high watermarks, at the order at which
we are reclaiming.

What lumpy brings is a greater targetting of effort to get the pages.
kswapd now uses the desired allocator order when applying reclaim.
This leads to pressure being applied to contigious areas at the
required order, and so a higher chance of that order becoming
available.  Traditional reclaim could end up applying pressure to
a number of pages, but not all pages in any area at the required
order, leading to a very low chance of success.  By targetting
areas at the required order we significantly increase the chances
of success for any given amount of reclaim.  As we will reclaim
until we have the desired number of free pages, we will have to
reclaim less to achieve this compared to random reclaim.

This certainly is appealing intuitivly, and our testing at higher
orders shows that the cost of each reclaimed page is lower and more
importantly the time to reclaim each page is reduced.  So for a
'continuing' consumer like an incoming packet stream, we should
have to do much less work and thus disrupt the system as a whole
much less to get its pages.

Where demand for atomic higher order pages is not heavy we would
expect kswapd to maintain free levels pages more readily and so
under higher demand.  Though it should be stressed without placement
control success rates drop off significantly at higher orders as
the probabality of reclaim succeeding on all pages in the area
tends to zero.

> (And do we still have a jumbo frame problem?  Reports seems to have
subsided)

It is not in the least bit clear if the problem is resolved or if the
reporters have simply gone quiet.

Overall the approach taken in lumpy reclaim seems to be a logical
extension of the regular reclaim algorithm, leading to more
efficient reclaim.

-apw

Re: fallocate-implementation-on-i86-x86_64-and-powerpc.patch

[Heiko Carstens]

On Wed, Jul 11, 2007 at 11:39:39AM -0400, Theodore Tso wrote:
> On Wed, Jul 11, 2007 at 10:50:49AM +1000, Paul Mackerras wrote:
> > > On Wed, 11 Jul 2007 09:27:40 +1000
> > > Paul Mackerras <paulus@samba.org> wrote:
> > > 
> > > > We did come up with an order that worked for everybody, but that
> > > > discussion seemed to get totally ignored by the ext4 developers.
> 
> Well, in the end it was a toss-up between
> 
> asmlinkage long sys_fallocate(int fd, int mode, loff_t offset, loff_t len)
> 
> and 
> 
> asmlinkage long sys_fallocate(loff_t offset, loff_t len, int fd, int mode)
> 
> There were a number of folks who preferred having int fd first, and I
> *thought* Amit had gotten agreement from either Martin or Heiko that
> it was ok to do this as an exception, even though it was extra work
> for that arch.  But if not, we can try going back the second
> alternative, or even the 6 32-bits args (off_high, off_low, len_high,
> len_low) approach, but I think that drew even more fire. 

The second approach would work for all architectures..  but some people
didn't like (no technical reason) not having fd as first argument.

Just go ahead with the current approach. s390 seems to be the only
architecture which suffers from this and I wouldn't like to start this
discussion again.

Re: containers (was Re: -mm merge plans for 2.6.23)

[Peter Zijlstra]

On Wed, 2007-07-11 at 10:03 -0700, Paul Jackson wrote:
> Peter wrote:
> > I'd very much like to have it, but that is just me.
> 
> Why? [linear combinations of uid, container, pid, pgrp weighting]

Good question, and I really have no other answer than that it seems
usefull and not impossible (or even hard) to implement :-/

I'm not even that interested in using it, it just seems like a nice
idea.

Re: containers (was Re: -mm merge plans for 2.6.23)

[Paul Menage]

On 7/10/07, Andrew Morton <akpm@linux-foundation.org> wrote:
>
> I'm inclined to take the cautious route here - I don't think people will be
> dying for the CFS thingy (which I didn't even know about?) in .23, and it's
> rather a lot of infrastructure to add for a CPU scheduler configurator

Selecting the relevant patches to give enough of the container
framework to support a CFS container subsystem (slightly
tweaked/updated versions of the base patch, procfs interface patch and
tasks file interface patch) is about 1600 lines in kernel/container.c
and another 200 in kernel/container.h, which is about 99% of the
non-documentation changes.

So not tiny, but it's not very intrusive on the rest of the kernel,
and would avoid having to introduce a temporary API based on uids.

Paul

Re: fallocate-implementation-on-i86-x86_64-and-powerpc.patch

[Martin Schwidefsky]

On Wed, 2007-07-11 at 20:47 +0200, Heiko Carstens wrote:
> > There were a number of folks who preferred having int fd first, and I
> > *thought* Amit had gotten agreement from either Martin or Heiko that
> > it was ok to do this as an exception, even though it was extra work
> > for that arch.  But if not, we can try going back the second
> > alternative, or even the 6 32-bits args (off_high, off_low, len_high,
> > len_low) approach, but I think that drew even more fire. 
> 
> The second approach would work for all architectures..  but some people
> didn't like (no technical reason) not having fd as first argument.

For s390 we would have liked the second approach with the two int's as
last arguments since it would avoid the wrapper in the kernel. It does
not avoid the wrapper in user space since the call uses 6 register on 31
bit. So the fallocate call need special treatement in glibc so I don't
mind that it needs another wrapper in the kernel.

> Just go ahead with the current approach. s390 seems to be the only
> architecture which suffers from this and I wouldn't like to start this
> discussion again.

Yes, don't worry about s390 for fallocate, the patch that had been in
-mm only had an incorrect system call number. The wrapper is fine.

-- 
blue skies,
  Martin.

"Reality continues to ruin my life." - Calvin.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Pavel Machek]

Hi!

> > That would just save reading the directories. Not sure
> > it helps that much. Much better would be actually if it didn't stat the 
> > individual files (and force their dentries/inodes in). I bet it does that to 
> > find out if they are directories or not. But in a modern system it could just 
> > check the type in the dirent on file systems that support 
> > that and not do a stat. Then you would get much less dentries/inodes.
>  
> FWIW, find(1) does *not* stat non-directories (and neither would this
> approach).  So it's just dentries for directories and you can't realistically
> skip those.  OK, you could - if you had banned cross-directory rename
> for directories and propagated "dirty since last look" towards root (note
> that it would be a boolean, not a timestamp).  Then we could skip unchanged
> subtrees completely...

Could we help it a little from kernel and set 'dirty since last look'
on directory renames?

I mean, this is not only updatedb. KDE startup is limited by this,
too. It would be nice to have effective 'what change in tree'
operation.
							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: x86 status was Re: -mm merge plans for 2.6.23

[Randy Dunlap]

On Wed, 11 Jul 2007 19:42:52 +0200 Ingo Molnar wrote:

> 
> * Andi Kleen <andi@firstfloor.org> wrote:
> 
> > > clockevents-fix-typo-in-acpi_pmc.patch
> > > timekeeping-fixup-shadow-variable-argument.patch
> > > timerc-cleanup-recently-introduced-whitespace-damage.patch
> > > clockevents-remove-prototypes-of-removed-functions.patch
> > > clockevents-fix-resume-logic.patch
> > > clockevents-fix-device-replacement.patch
> > > tick-management-spread-timer-interrupt.patch
> > > highres-improve-debug-output.patch
> > > hrtimer-speedup-hrtimer_enqueue.patch
> > > pcspkr-use-the-global-pit-lock.patch
> > > ntp-move-the-cmos-update-code-into-ntpc.patch
> > > i386-pit-stop-only-when-in-periodic-or-oneshot-mode.patch
> > > i386-remove-volatile-in-apicc.patch
> > > i386-hpet-assumes-boot-cpu-is-0.patch
> > > i386-move-pit-function-declarations-and-constants-to-correct-header-file.patch
> > > x86_64-untangle-asm-hpeth-from-asm-timexh.patch
> > > x86_64-use-generic-cmos-update.patch
> > > x86_64-remove-dead-code-and-other-janitor-work-in-tscc.patch
> > > x86_64-fix-apic-typo.patch
> > > x86_64-convert-to-cleckevents.patch
> > > acpi-remove-the-useless-ifdef-code.patch
> > > x86_64-hpet-restore-vread.patch
> > > x86_64-restore-restore-nohpet-cmdline.patch
> > > x86_64-block-irq-balancing-for-timer.patch
> > > x86_64-prep-idle-loop-for-dynticks.patch
> > > x86_64-enable-high-resolution-timers-and-dynticks.patch
> > > x86_64-dynticks-disable-hpet_id_legsup-hpets.patch
> > 
> > I'm sceptical about the dynticks code. It just rips out the x86-64 
> > timing code completely, which needs a lot more review and testing. 
> > Probably not .23
> 
> What you just did here is a slap in the face to a lot of contributors 
> who worked hard on this code :(
> 
> Let me tell you about the history of this project first.

... [lwn.net articles and other quotes snipped]

> But what is curiously absent from all this positive and dynamic activity 
> around these patches on lkml? There is not a single email from Andi 
> Kleen, the official maintainer of the x86_64 tree directly reacting to 
> this submission in any way, shape or form. Not a single email from you 
> thanking Arjan, Chris and Thomas for this amount of cleanup to the 
> architecture you are maintaining:
> 
>    31 files changed, 698 insertions(+), 1367 deletions(-)

Hm, I don't usually get thanks emails.  Do other people?

> Not a single email from you reviewing the patchset in any meaningful 
> way. Not a single email from you to indicate that you even did so much 
> as boot into this patchset.
> 
> What contribution do we have from you instead? A week before the .23 
> merge window is closed, in the very last possible moment, we finally get 
> your first reaction to this patchset, albeit in the form of three terse 
> sentences:
> 
>   > I'm sceptical about the dynticks code. It just rips out the x86-64 
>   > timing code completely, which needs a lot more review and testing. 
>   > Probably not .23
> 
> In the past 3+ months there was not a single email from you indicating 
> that you are "doubtful" about this submission, and that you think that 
> it needs "lot more review and testing". You dont offer any alternative, 
> you dont offer any feedback, no review, no testing, no support, just a 
> simple rejection on lkml that prevents this project from going upstream.
> 
> Yes, maintainers have veto power and often have to make hard decisions,
> but, and let me stress this properly:
> 
>    Only if they actually act as honest maintainers!
> 
> Altogether 197 emails on lkml discussed these patches, and you were 
> Cc:-ed to every one of them. Over a dozen kernel developers reviewed it 
> or reacted to the patchset in one way or another. And your only reaction 
> to this is silence and a rejection claiming that it needs "lot more 
> review"? I'm utterly speechless.

I can understand being disappointed, but not quite as upset as you
appear to be.

so have you (Ingo) reviewed the ext4 patches?  or reiser4 patches?
or lumpy reclaim?  or anti-fragmentation?

I certainly haven't.  I can barely keep up with reading about 1/2
of lkml emails.  And in my non-scientific method, I think that we
are suffering from both (a) more patch submittals and (b) fewer
qualified reviewers (per kernel KLOC) than we had 3-5 years ago.

I don't see how you can expect Andrew to review these or any other
specific patchset.  Do you have some suggestions on how to clone
Andrew?

---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***

Re: x86 status was Re: -mm merge plans for 2.6.23

[Andi Kleen]

Well I spent a lot of time making the x86-64 timing code work
well on a variety of machines; working around a wide variety
of hardware and platform bugs. I obviously don't agree on your description
of its maintenance state. 

> What contribution do we have from you instead? A week before the .23 

I told him my objections privately earlier. Basically i would
like to see an actually debuggable step-by-step change, not a rip everything 
out.

If that isn't possible it needs very careful review which just hasn't
happened yet. But I'm not convinced even step by step is not possible
here.

I thought it was clear that rip everything out is rarely a good idea
in Linux land?  That's really not something I should need to harp on 
repeatedly.

-Andi

Re: x86 status was Re: -mm merge plans for 2.6.23

[Thomas Gleixner]

Randy,

On Wed, 2007-07-11 at 14:02 -0700, Randy Dunlap wrote: 
> I certainly haven't.  I can barely keep up with reading about 1/2
> of lkml emails.  And in my non-scientific method, I think that we
> are suffering from both (a) more patch submittals and (b) fewer
> qualified reviewers (per kernel KLOC) than we had 3-5 years ago.
> 
> I don't see how you can expect Andrew to review these or any other
> specific patchset.  Do you have some suggestions on how to clone
> Andrew?

Ingo was talking to Andi, the x86_64 maintainer, not to Andrew.

And I share his opinion that the maintainer of the subsystem, which is
affected by such a fundamental patch, could have at least shown any
public sign of interest, disgust, comment or what ever in a 3+ month
time frame.

Especially about a patch, which is a logical consequence of an almost
two years public and transparent effort to consolidate the time code in
the kernel.

I for my part have no problem maintaining the set for another round out
of tree and weed out eventually problems in -mm, but my expectation for
qualified response of the responsible maintainer is exactly zero right
now.

Thanks,

	tglx

Re: x86 status was Re: -mm merge plans for 2.6.23

[Linus Torvalds]

On Wed, 11 Jul 2007, Ingo Molnar wrote:
> 
> What you just did here is a slap in the face to a lot of contributors 
> who worked hard on this code :(

Ingo, I'm sorry to say so, but your answer just convinced me that you're 
wrong, and we MUST NOT take that code.

That was *exactly* the same thing you talked about when I refused to take 
the original timer changes into 2.6.20. You were talking about how lots of 
people had worked really hard, and how it was really tested.

And it damn well was NOT really tested, and 2.6.21 ended up being a 
horribly painful experience (one of the more painful kernel releases in 
recent times), and we ended up havign to fix a *lot* of stuff.

And you admitted you were wrong at the time.

Now you do the *exact* same thing.

Here's a big clue: it doesn't matter one _whit_ how much face-slapping you 
get, or how much effort some programmers have put into the code. It's 
untested. And no, we are *not* going to do another "rip everything out, 
and replace it with new code" again.

Over my dead body.

We're going to do this thing gradually, or not at all.

And if somebody feels slighted by the face-slap, and thinks he has already 
done enough, and isn't interested in doing it gradually, then good 
riddance. The "not at all" seems like a good idea, and maybe we can 
re-visit this in a year or two.

I'm not going to have another 2.6.21 on my hands.

		Linus

Re: x86 status was Re: -mm merge plans for 2.6.23

[Valdis.Kletnieks]

[-- Attachment #1: Type: text/plain, Size: 1125 bytes --]

On Wed, 11 Jul 2007 23:16:38 +0200, Andi Kleen said:

(Note - I'm just a usually-confused crash test dummy here...)

> Well I spent a lot of time making the x86-64 timing code work
> well on a variety of machines; working around a wide variety
> of hardware and platform bugs. I obviously don't agree on your description
> of its maintenance state. 

I'm seeing a bit of a disconnect here.  If you spent all that time making it
work, how come the guys who developed the patch are saying you didn't provide
any feedback about the patchset?

> > What contribution do we have from you instead? A week before the .23 
> 
> I told him my objections privately earlier. Basically i would
> like to see an actually debuggable step-by-step change, not a rip everything 
> out.

Odd, I looked at the patchset fairly closely a number of times, as I was
hand-retrofitting the -rc[1-4] versions onto -rc[1-4]-mm kernels, and it looked
to *me* like it was a nice set of 20 or so step-by-step changes (bisectable
and everything - I got to do that once trying to figure out which one I botched).
Was there something in there that I missed?


[-- Attachment #2: Type: application/pgp-signature, Size: 226 bytes --]

Re: x86 status was Re: -mm merge plans for 2.6.23

[Thomas Gleixner]

Andi,

On Wed, 2007-07-11 at 23:16 +0200, Andi Kleen wrote: 
> > What contribution do we have from you instead? A week before the .23 
> 
> I told him my objections privately earlier. Basically i would
> like to see an actually debuggable step-by-step change, not a rip everything 
> out.

You promised privately to do a thorough review as well, which I'm still
waiting for since months.

> If that isn't possible it needs very careful review which just hasn't
> happened yet. But I'm not convinced even step by step is not possible
> here.

There is no step by step thing. You convert an arch to clock events or
you convert it not.

> I thought it was clear that rip everything out is rarely a good idea
> in Linux land?  That's really not something I should need to harp on 
> repeatedly.

If you have technical objections, put them on the table. Point by point.

All I heard so far from you are platitudes, which are not worth the
electrons to transport them.

	tglx

Re: x86 status was Re: -mm merge plans for 2.6.23

[Andrea Arcangeli]

Hi Andi,

On Wed, Jul 11, 2007 at 11:16:38PM +0200, Andi Kleen wrote:
> I thought it was clear that rip everything out is rarely a good idea
> in Linux land?  That's really not something I should need to harp on 
> repeatedly.

I'm going to change topic big time because your sentence above
perfectly applies to the O(1) scheduler too. It's not like process
schedulers are sacred and there shall be only one, while I/O
schedulers and packet schedulers are profane and there can be many of
them. FWIW IMHO the right way would have been to make the new
scheduler pluggable and switchable at runtime, too bad it was ripped
off instead. The difficulty of making the scheduler pluggable isn't
really enormous, there have been patches floating around to achieve
it, some I even deal with them myself once.

The only positive side of being forced to CFS I can imagine, is that
more testing will make it more stable and more tuned more quickly. But
I'm fairly certain Ingo's good enough to achieve without it, perhaps
with a few more weeks.

Personally I very much like the unfariness of O(1), I'm afraid CFS
will overschedule under a certain number of workloads in its attempt
to provide a complete fair queieing at all costs, and it won't deal
with the X server as nicely as O(1), but I may as well be wrong. The
only thing I'm more sure about is that the computational complexity is
higher, and that reason alone is a good technical reason to provide
both and let the java folks stick with O(1) if they want.

Re: x86 status was Re: -mm merge plans for 2.6.23

[Chris Wright]

* Thomas Gleixner (tglx@linutronix.de) wrote:
> > If that isn't possible it needs very careful review which just hasn't
> > happened yet. But I'm not convinced even step by step is not possible
> > here.
> 
> There is no step by step thing. You convert an arch to clock events or
> you convert it not.

Indeed, about the only thing can be done is to take a slower approach
to converging the arch specific implementations (hpet, pit, etc).

thanks,
-chris

Re: x86 status was Re: -mm merge plans for 2.6.23

[Chris Wright]

* Valdis.Kletnieks@vt.edu (Valdis.Kletnieks@vt.edu) wrote:
> On Wed, 11 Jul 2007 23:16:38 +0200, Andi Kleen said:
> (Note - I'm just a usually-confused crash test dummy here...)
> 
> > Well I spent a lot of time making the x86-64 timing code work
> > well on a variety of machines; working around a wide variety
> > of hardware and platform bugs. I obviously don't agree on your description
> > of its maintenance state. 
> 
> I'm seeing a bit of a disconnect here.  If you spent all that time making it
> work, how come the guys who developed the patch are saying you didn't provide
> any feedback about the patchset?

I think Andi's referring to the existing x86_64 code, which gets
replaced by the patchset in question.

Re: x86 status was Re: -mm merge plans for 2.6.23

[Thomas Gleixner]

Linus,

On Wed, 2007-07-11 at 14:42 -0700, Linus Torvalds wrote: 
> Here's a big clue: it doesn't matter one _whit_ how much face-slapping you 
> get, or how much effort some programmers have put into the code. It's 
> untested. And no, we are *not* going to do another "rip everything out, 
> and replace it with new code" again.
> 
> Over my dead body.
>
> We're going to do this thing gradually, or not at all.

Can you please shed some light on me, how exactly you switch an
architecture gradually to clock events.

You simply can not convert PIT today and the HPET next week followed by
the local APIC in three month. 

At least not to my knowledge.

> And if somebody feels slighted by the face-slap, and thinks he has already 
> done enough, and isn't interested in doing it gradually, then good 
> riddance. The "not at all" seems like a good idea, and maybe we can 
> re-visit this in a year or two.

I have no problem to brew this for some more time. I got not repulsed by
the 2.6.20 decision, but I have no clue how to communicate with a black
hole.

	tglx

Re: x86 status was Re: -mm merge plans for 2.6.23

[Linus Torvalds]

On Wed, 11 Jul 2007, Andrea Arcangeli wrote:
>
> I'm going to change topic big time because your sentence above
> perfectly applies to the O(1) scheduler too.

I disagree to a large degree.

We almost never have problems with code you can "think about".

Sure, bugs happen, but code that everybody runs the same generally doesn't 
break. So a CPU scheduler doesn't worry me all that much. CPU schedulers 
are "easy".

What worries me is interfaces to hardware that we know looks different for 
different people. That means that any testing that one person has done 
doesn't necessarily translate to anything at *all* on another persons 
machine.

The timer problems we had when merging the stuff in 2.6.21 just scarred 
me. I'd _really_ hate to have to go through that again. And no, the 
"gradual" thing where the patch that actually *enables* something isn't 
very gradual at all, so that's the absolutely worst kind of thing, because 
then people can "git bisect" to the point where it got enabled and tell us 
that's where things broke, but that doesn't actually say anything at all 
about the patch that actually implements the new behaviour.

So the "enable" kind of patch is actually the worst of the lot, when it 
comes to hardware.

When it comes to pure software algorithms, and things like schedulers, 
you'll still obviously have timing issues and tuning, but generally things 
*work*, which makes it a lot easier to debug and describe.

		Linus

Re: x86 status was Re: -mm merge plans for 2.6.23

[Valdis.Kletnieks]

[-- Attachment #1: Type: text/plain, Size: 1348 bytes --]

On Wed, 11 Jul 2007 14:54:12 PDT, Chris Wright said:
> * Valdis.Kletnieks@vt.edu (Valdis.Kletnieks@vt.edu) wrote:
> > On Wed, 11 Jul 2007 23:16:38 +0200, Andi Kleen said:
> > (Note - I'm just a usually-confused crash test dummy here...)
> > 
> > > Well I spent a lot of time making the x86-64 timing code work
> > > well on a variety of machines; working around a wide variety
> > > of hardware and platform bugs. I obviously don't agree on your description
> > > of its maintenance state. 
> > 
> > I'm seeing a bit of a disconnect here.  If you spent all that time making it
> > work, how come the guys who developed the patch are saying you didn't provide
> > any feedback about the patchset?
> 
> I think Andi's referring to the existing x86_64 code, which gets
> replaced by the patchset in question.

<Takes a closer look at the patches>  D'Oh! :)  Yeah, the -rc4 version I'm
looking at is like a dozen 1-3K patches setting up and cleaning up, and then
one monster 65K patch doing the clockevents conversion, then another 6 or 8
small ones.

Yeah, that one big patch really doesn't look separable to me.  But as I said,
I'm just a crash test dummy here. :)

Andrew - how do you feel about keeping this in the -mm tree until Linus,
Andi, Ingo, and Thomas get on the same page (which may be around the 2.6.24
merge window, by my guesstimate)?


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Re: x86 status was Re: -mm merge plans for 2.6.23

[Linus Torvalds]

On Wed, 11 Jul 2007, Valdis.Kletnieks@vt.edu wrote:
> 
> Odd, I looked at the patchset fairly closely a number of times, as I was
> hand-retrofitting the -rc[1-4] versions onto -rc[1-4]-mm kernels, and it looked
> to *me* like it was a nice set of 20 or so step-by-step changes (bisectable
> and everything - I got to do that once trying to figure out which one I botched).
> Was there something in there that I missed?

The patch-set itself actually looks fine, as far as I'm concerned.

But it does seem to have that "enable everything in one go" problem.

I'd much rather see one time source at a time being converted, and enabled 
then and there, so that when people report problems and do a bisection, if 
it was HPET that broke, you get the commit that changed HPET.

As it is, looking at that set, it *looks* like you'd get the "ok, now 
enable it all" as the commit that breaks, which tells you hardly anything, 
since the commit that _shows_ the behaviour has absolutely nothing to do 
with the code that actually causes it.

But yeah, the patch series per se doesn't look bad. If it wasn't for me 
being burnt by the last big switch-over for timers, I probably wouldn't 
mind it at all, personally.

		Linus

Re: x86 status was Re: -mm merge plans for 2.6.23

[Andi Kleen]

On Wed, Jul 11, 2007 at 11:46:41PM +0200, Thomas Gleixner wrote:
> Andi,
> 
> On Wed, 2007-07-11 at 23:16 +0200, Andi Kleen wrote: 
> > > What contribution do we have from you instead? A week before the .23 
> > 
> > I told him my objections privately earlier. Basically i would
> > like to see an actually debuggable step-by-step change, not a rip everything 
> > out.
> 
> You promised privately to do a thorough review as well, which I'm still
> waiting for since months.

I did some reviewing, but never the big write up and feedback. That was my
fault, sorry.

-Andi

Re: x86 status was Re: -mm merge plans for 2.6.23

[Linus Torvalds]

On Thu, 12 Jul 2007, Thomas Gleixner wrote:
> 
> Can you please shed some light on me, how exactly you switch an
> architecture gradually to clock events.

For example, we can make sure that the code in question that actually 
touches the hardware stays exactly the same, and then just move the 
interfaces around - and basically guarantee that _zero_ hardware-specific 
issues pop up when you switch over, for example.

That way there is a gradual change-over.

The other approach (which would be nice _too_) is to actually try to 
convert one clock source at a time. Why is that not an option? 

		Linus

Re: x86 status was Re: -mm merge plans for 2.6.23

[Chris Wright]

* Valdis.Kletnieks@vt.edu (Valdis.Kletnieks@vt.edu) wrote:
> Andrew - how do you feel about keeping this in the -mm tree until Linus,
> Andi, Ingo, and Thomas get on the same page (which may be around the 2.6.24
> merge window, by my guesstimate)?

Well, that's supposed to be Andi's tree and aggregated by Andrew into -mm.
But keeping it in -mm isn't the hard part.  It's getting enough testing
to convince Linus it's safe, since there's no simple way to enable
clockevents in a slow manner.  IOW, keeping it in -mm just postpones the
issue.

Re: x86 status was Re: -mm merge plans for 2.6.23

[Linus Torvalds]

On Wed, 11 Jul 2007, Valdis.Kletnieks@vt.edu wrote:
> 
> <Takes a closer look at the patches>  D'Oh! :)  Yeah, the -rc4 version I'm
> looking at is like a dozen 1-3K patches setting up and cleaning up, and then
> one monster 65K patch doing the clockevents conversion, then another 6 or 8
> small ones.
> 
> Yeah, that one big patch really doesn't look separable to me. 

I think it should be.

That big patch really does do a *lot* more than just the "clockevents 
conversion". It does all the hpet clock setup changes etc that are about 
the hardware, and have *nothing* to do with actually changing the 
interfaces.

For example, look at the hpet.c part of that patch. Totally independent 
cleanups of everything else.

Or look at the changes to __setup_APIC_LVTT(). Same thing. 

All the actual hardware interface changes are *totally* independent of the 
software interface changes, and a lot of them are just cleanups.

But those hardware interface changes are easily the things that can break, 
where some cleanup results in register writes being done in a different 
order or something, and so if there's a bug there (and it's not visible on 
most setups), now you cannot tell where the bug is.

Another example: setup_APIC_timer() used to wait for a timer interrupt 
trigger to happen on the i8259 timer (or HPET). That code just got 
removed (or maybe it got moved so subtly that I just don't see it). 

What has that got to do with switching from the old timer interface to the 
new one?

NOTHING.

So those kinds of changes that change hardware access functions should 
have been done separately. Maybe there's a machine where that early 
synchronization was necessary for some subtle timing reason. If so, 
removing it sounds like a bug, no? Wouldn't it have been nice to see that 
removal as a separate patch that was independent of the interface switch- 
over?

I'd be a *lot* happier with switching over interfaces if I thought that 
the low-level hardware drivers didn't change at the same time. But they 
*do* change, afaik.

		Linus

Re: x86 status was Re: -mm merge plans for 2.6.23

[Thomas Gleixner]

Linus,

On Wed, 2007-07-11 at 15:20 -0700, Linus Torvalds wrote:
> For example, we can make sure that the code in question that actually 
> touches the hardware stays exactly the same, and then just move the 
> interfaces around - and basically guarantee that _zero_ hardware-specific 
> issues pop up when you switch over, for example.
> 
> That way there is a gradual change-over.

Ok, I can try to split this down further.

> The other approach (which would be nice _too_) is to actually try to 
> convert one clock source at a time. Why is that not an option? 

We need to give control to the clock events core code once we convert
one clock event device. Having two competing subsystems controlling
different devices (e.g. PIT and APIC) is not really desirable.

The HPET change, which is the larger part of the conversion set simply
because we now share the code with i386, might be split out by disabling
HPET in the first step, doing the PIT / APIC conversion and then the
HPET one in a separate step.

Thanks,

	tglx

Re: x86 status was Re: -mm merge plans for 2.6.23

[Chris Wright]

* Linus Torvalds (torvalds@linux-foundation.org) wrote:
> For example, we can make sure that the code in question that actually 
> touches the hardware stays exactly the same, and then just move the 
> interfaces around - and basically guarantee that _zero_ hardware-specific 
> issues pop up when you switch over, for example.

That's not quite right.  Leaving the code unchanged caused breakage
already.  The PIT is damn stupid and can be sensitive to how quickly it's
programmed.  So code that enable/disable didn't change, but frequency
with which it is called did and broke some random boxes.

> The other approach (which would be nice _too_) is to actually try to 
> convert one clock source at a time. Why is that not an option? 

It was that way for x86_64, that's the first thing I fixed (since it was
done by fully disabling all other timers but the one coverted ;-)

Re: x86 status was Re: -mm merge plans for 2.6.23

[Linus Torvalds]

On Wed, 11 Jul 2007, Chris Wright wrote:
> 
> That's not quite right.  Leaving the code unchanged caused breakage
> already.  The PIT is damn stupid and can be sensitive to how quickly it's
> programmed.  So code that enable/disable didn't change, but frequency
> with which it is called did and broke some random boxes.

Sure. We cannot avoid *all* problems. Bugs happen. 

But at least we could try to make sure that there aren't totally 
unnecessary changes in that switch-over patch. Which there definitely 
were, as far as I can tell.

		Linus

generic clockevents/ (hr)time(r) patches was Re: -mm merge plans for 2.6.23

[Thomas Gleixner]

Andrew, Linus, 

On Tue, 2007-07-10 at 01:31 -0700, Andrew Morton wrote:
> When replying, please rewrite the subject suitably and try to Cc: the
> appropriate developer(s).

> i386-hpet-check-if-the-counter-works.patch
> nohz-fix-nohz-x86-dyntick-idle-handling.patch
> acpi-move-timer-broadcast-and-pmtimer-access-before-c3-arbiter-shutdown.patch
> clockevents-fix-typo-in-acpi_pmc.patch
> timekeeping-fixup-shadow-variable-argument.patch
> timerc-cleanup-recently-introduced-whitespace-damage.patch
> clockevents-remove-prototypes-of-removed-functions.patch
> clockevents-fix-resume-logic.patch
> clockevents-fix-device-replacement.patch
> tick-management-spread-timer-interrupt.patch
> highres-improve-debug-output.patch
> hrtimer-speedup-hrtimer_enqueue.patch
> pcspkr-use-the-global-pit-lock.patch
> ntp-move-the-cmos-update-code-into-ntpc.patch
> i386-pit-stop-only-when-in-periodic-or-oneshot-mode.patch
> i386-remove-volatile-in-apicc.patch
> i386-hpet-assumes-boot-cpu-is-0.patch
> i386-move-pit-function-declarations-and-constants-to-correct-header-file.patch

These got sent to Andi as well, but the patches are independent of the
x86_64 conversion.

These are bugfixes (nohz-fix-nohz-x86-dyntick-idle-handling.patch) and
general improvements of the core code and the existing i386 code.

Can we please merge the above now ?

I can resend them or setup a git repo if you want.

Andi, any objections against the above i386 fixlets ?

Thanks,

	tglx

Re: x86 status was Re: -mm merge plans for 2.6.23

[Chris Wright]

* Thomas Gleixner (tglx@linutronix.de) wrote:
> The HPET change, which is the larger part of the conversion set simply
> because we now share the code with i386, might be split out by disabling
> HPET in the first step, doing the PIT / APIC conversion and then the
> HPET one in a separate step.

The timer specific changes (i.e. the merges between arches) can be
done more slowly, but the setup above is basically where I started,
and it was already broken on one of my test boxes.  Anyway, I'll help
you however I can, because it's important to me to get this merged.

thanks,
-chris

Re: x86 status was Re: -mm merge plans for 2.6.23

[Linus Torvalds]

On Thu, 12 Jul 2007, Thomas Gleixner wrote:
>
> The HPET change, which is the larger part of the conversion set simply
> because we now share the code with i386, might be split out by disabling
> HPET in the first step, doing the PIT / APIC conversion and then the
> HPET one in a separate step.

But that misses the point. It means that the commit that actually 
*changes* the code never actually gets tested on its own

Why not just fix up the HPET code so that it can be shared *first*. 
Without the other conversion? Really - What's so wrong with the hpet.c 
changes in the *absense* of conversion to clockevents? Those changes seem 
to be totally independent - just abstracting ou tthe 
"hpet_get_virt_address()" stuff etc.

None of that has anything to do with clockevents, as far as I can see.

In other words, you now change a i386-only file, and maybe it breaks 
subtly on i386 as a result. Wouldn't it be nicer to see that breakage as a 
separate event?

Then, the x86-64 clockevents code will switch over entirely, but now it 
switches over to something we can say has gotten testing, and we know the 
switch-over won't break any 32-bit code, because the switch-over literally 
didn't change anything at all for that case.

See? THAT is what I mean by "gradual". Bugs happen, but if we can make 
_independent_ bugs show up in _independent_ commits, that will make it 
much easier to figure out what happened.

The same is true of a lot of the APIC timer code. Sure, that patch has the 
actual conversion in it, and you don't have the cross-architecture issues, 
but more than 50% of the patch seems to be just cleanup that is 
independent of the actual switch-over, no?

Again, if it was done as a "one patch for cleanup, and another patch that 
actually switches the higher-level interfaces around", then the two mostly 
independent issues (of "hardware access/initialization" vs "higher-level 
changes in how it got called") get done as two independent commits.

And no, I really probably wouldn't ask for this, but 2.6.21 showed 
*exactly* this problem. Trivial debugging helps like "git bisect" didn't 
help at all, because all the problems started when the new code was 
"activated", not when it was actually brought in.

		Linus

Re: x86 status was Re: -mm merge plans for 2.6.23

[Ingo Molnar]

* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> That was *exactly* the same thing you talked about when I refused to 
> take the original timer changes into 2.6.20. You were talking about 
> how lots of people had worked really hard, and how it was really 
> tested.

yes - i was (way too!) upset about it, and your reasoning for the 
rejection was hard (on us) but fair: you wanted a quiet 2.6.20, and you 
felt fundamentally uneasy about the patches.

> And it damn well was NOT really tested, and 2.6.21 ended up being a 
> horribly painful experience (one of the more painful kernel releases 
> in recent times), and we ended up havign to fix a *lot* of stuff.

yes. We had 12 -hrt/dynticks merge related regressions between 
2.6.21-rc1 and -final, and 4 after final. Here's a quick post-mortem:

12 fixes after -rc1:

    [PATCH] i386: Fix bogus return value in hpet_next_event()
    [PATCH] clockevents: remove bad designed sysfs support for now
    [PATCH] clocksource: Fix thinko in watchdog selection
    [PATCH] dynticks: fix hrtimer rounding error in next_timer_interrupt
    [PATCH] i386: add command line option "local_apic_timer_c2_ok"
    [PATCH] i386: disable local apic timer via command line or dmi quirk
    [PATCH] i386: clockevents fix breakage on Geode/Cyrix PIT     
    [PATCH] i386: trust the PM-Timer calibration of the local APIC timer
    [PATCH] clockevents: Fix suspend/resume to disk hangs
    [PATCH] highres: do not run the TIMER_SOFTIRQ after switching to highres mode
    [PATCH] hrtimer: prevent overrun DoS in hrtimer_forward()
    [PATCH] Save/restore periodic tick information over suspend/resume implementations

4 fixes after -final:

 2.6.21.1: -
 2.6.21.2:
    [PATCH] clocksource: fix resume logic
 2.6.21.3: -
 2.6.21.4: -
 2.6.21.5:
    [PATCH] NOHZ: Rate limit the local softirq pending warning output
    [PATCH] Ignore bogus ACPI info for offline CPUs
    [PATCH] i386: HPET, check if the counter works
 2.6.21.6: -

it's all pretty quiet today on the dynticks regressions front. (there 
are no open regressions in either the upstream i386 code or in the devel 
patches we are aware of. Forced-HPET in -mm, which is not part of this 
queue in question [but which is done for dynticks], has one open 
regression.)

The majority of the above bugs were in the infrastructure code. (the 
worst was the generic resume/suspend one fixed in 2.6.21.2) And sadly, a 
fair number of the infrastructure bugs we introduced during the frentic 
clockevents/dynticks rewrites/redesigns we did between .20 and .21. That 
was a royally stupid mistake for us to do - instead of patiently waiting 
for the bugs to be shaken out we destabilized the infrastructure. (it 
was a "lets make this thing so nice that it's impossible to reject" 
instintic gut reaction.)

In the 'weird arch bugs' category, out of the 6 i386 breakages listed 
above, 'i386 legacy systems' was/is by far the worst offender: 4-5 were 
on such old (not 64-bit-capable) systems. (this is not really a 
surprise) While x86_64 certainly has weird crap hardware too, it 
probably is an order of magnitude fewer than i386 - just due to the 
sheer volume, time and diversity difference. (On the other hand if 
there's crap then it will be debugged/tested slower than on 32-bit, 
which offsets that advantage.)

The most prominent bugs were the ones that were in the infrastructure - 
they affected many machines. (But i'd expect the infrastructure to be 
pretty robust by now.)

The x86_64 hrt/dynticks code makes the x86_64 PIT driver (and hpet too) 
shared between the two architectures - which is perhaps another 
difference to the original i386 clockevents merge.

We also integrated _all_ feedback we got, and we had the capacity and 
capability to fix whatever other feedback comes back - it just never 
came ... until today.

But i fully agree with you that the cleanups should be done separately - 
it's just so hard to actually hack on the old hpet code (and to 
understand it to begin with) without first cleaning it up a bit so that 
it does not cause permanent brain damage ;)

	Ingo

Re: x86 status was Re: -mm merge plans for 2.6.23

[Randy Dunlap]

On Wed, 11 Jul 2007 23:39:19 +0200 Thomas Gleixner wrote:

> Randy,
> 
> On Wed, 2007-07-11 at 14:02 -0700, Randy Dunlap wrote: 
> > I certainly haven't.  I can barely keep up with reading about 1/2
> > of lkml emails.  And in my non-scientific method, I think that we
> > are suffering from both (a) more patch submittals and (b) fewer
> > qualified reviewers (per kernel KLOC) than we had 3-5 years ago.
> > 
> > I don't see how you can expect Andrew to review these or any other
> > specific patchset.  Do you have some suggestions on how to clone
> > Andrew?
> 
> Ingo was talking to Andi, the x86_64 maintainer, not to Andrew.

Yep, I see that when I re-read it.  I apologize.

---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***

Re: x86 status was Re: -mm merge plans for 2.6.23

[Thomas Gleixner]

Linus,

On Wed, 2007-07-11 at 16:07 -0700, Linus Torvalds wrote:
> Why not just fix up the HPET code so that it can be shared *first*. 
> Without the other conversion? Really - What's so wrong with the hpet.c 
> changes in the *absense* of conversion to clockevents? Those changes seem 
> to be totally independent - just abstracting ou tthe 
> "hpet_get_virt_address()" stuff etc.
> 
> None of that has anything to do with clockevents, as far as I can see.
>
> In other words, you now change a i386-only file, and maybe it breaks 
> subtly on i386 as a result. Wouldn't it be nicer to see that breakage as a 
> separate event?

Sure, I meant to do the HPET changes to i386 separate as a preparatory
patch.

Sharing HPET before the conversion is nasty at best (it involves a ton
of ifdeffery at least).

> Then, the x86-64 clockevents code will switch over entirely, but now it 
> switches over to something we can say has gotten testing, and we know the 
> switch-over won't break any 32-bit code, because the switch-over literally 
> didn't change anything at all for that case.

Well, we know that it works on i386, but once we turn on the x64 switch
we have not tested the shared code for x64 yet.

I try to find some practicable compromise between the big bang patch and
the theoretical gradual optimum.

> The same is true of a lot of the APIC timer code. Sure, that patch has the 
> actual conversion in it, and you don't have the cross-architecture issues, 
> but more than 50% of the patch seems to be just cleanup that is 
> independent of the actual switch-over, no?

I said before, that I'm going to split them further.

	tglx

Re: x86 status was Re: -mm merge plans for 2.6.23

[Andi Kleen]

> The same is true of a lot of the APIC timer code. Sure, that patch has the 
> actual conversion in it, and you don't have the cross-architecture issues, 
> but more than 50% of the patch seems to be just cleanup that is 
> independent of the actual switch-over, no?

I don't think it's that much cleanup. One of my goals for x86-64 was always
to have it support modern x86 only; this means in particularly most of the
old bug workaround removed. With the APIC timer merging a lot of that crap
gets back in.

I would prefer to keep APIC code separate.

-Andi

Re: x86 status was Re: -mm merge plans for 2.6.23

[Linus Torvalds]

On Thu, 12 Jul 2007, Ingo Molnar wrote:
> 
> We also integrated _all_ feedback we got, and we had the capacity and 
> capability to fix whatever other feedback comes back - it just never 
> came ... until today.

One thing I'll happily talk about is that while 2.6.21 was painful, you 
and Thomas in particular were both very responsible about the thing, so 
no, I'm not at all complaining or worried about it in that sense!

I just really _really_ wish we could have two fairly stable releases in a 
row. I think 2.6.22 has the potential to be a pretty good setup, and I'd 
really like to avoid having another 2.6.21 immediately afterwards.

So I'm not worried about integration and getting fixes when things break 
per se, but I *am* worried that this is an area where we've traditionally 
had lots of unexpected problems.

And hey, maybe this time there will be none. I just still smart from the 
last time, so I'd prefer it to go more smoothly this time around.

		Linus

Re: x86 status was Re: -mm merge plans for 2.6.23

[Thomas Gleixner]

Andi,

On Thu, 2007-07-12 at 01:36 +0200, Andi Kleen wrote:
> > The same is true of a lot of the APIC timer code. Sure, that patch has the 
> > actual conversion in it, and you don't have the cross-architecture issues, 
> > but more than 50% of the patch seems to be just cleanup that is 
> > independent of the actual switch-over, no?
> 
> I don't think it's that much cleanup. One of my goals for x86-64 was always
> to have it support modern x86 only; this means in particularly most of the
> old bug workaround removed. With the APIC timer merging a lot of that crap
> gets back in.
> 
> I would prefer to keep APIC code separate.

Care to look at the patch ? It _IS_ seperate.

Only HPET and PIT got shared.

	tglx

Re: generic clockevents/ (hr)time(r) patches was Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Thu, 12 Jul 2007 01:03:28 +0200
Thomas Gleixner <tglx@linutronix.de> wrote:

> Andrew, Linus, 
> 
> On Tue, 2007-07-10 at 01:31 -0700, Andrew Morton wrote:
> > When replying, please rewrite the subject suitably and try to Cc: the
> > appropriate developer(s).
> 
> > i386-hpet-check-if-the-counter-works.patch
> > nohz-fix-nohz-x86-dyntick-idle-handling.patch
> > acpi-move-timer-broadcast-and-pmtimer-access-before-c3-arbiter-shutdown.patch
> > clockevents-fix-typo-in-acpi_pmc.patch
> > timekeeping-fixup-shadow-variable-argument.patch
> > timerc-cleanup-recently-introduced-whitespace-damage.patch
> > clockevents-remove-prototypes-of-removed-functions.patch
> > clockevents-fix-resume-logic.patch
> > clockevents-fix-device-replacement.patch
> > tick-management-spread-timer-interrupt.patch
> > highres-improve-debug-output.patch
> > hrtimer-speedup-hrtimer_enqueue.patch
> > pcspkr-use-the-global-pit-lock.patch
> > ntp-move-the-cmos-update-code-into-ntpc.patch
> > i386-pit-stop-only-when-in-periodic-or-oneshot-mode.patch
> > i386-remove-volatile-in-apicc.patch
> > i386-hpet-assumes-boot-cpu-is-0.patch
> > i386-move-pit-function-declarations-and-constants-to-correct-header-file.patch
> 
> These got sent to Andi as well, but the patches are independent of the
> x86_64 conversion.
> 
> These are bugfixes (nohz-fix-nohz-x86-dyntick-idle-handling.patch) and
> general improvements of the core code and the existing i386 code.
> 
> Can we please merge the above now ?
> 
> I can resend them or setup a git repo if you want.
> 
> Andi, any objections against the above i386 fixlets ?
> 

They all look pretty innocuous to me.

Could you please take a second look, decide if any of them should also be
in 2.6.22.x and let me know?

Re: x86 status was Re: -mm merge plans for 2.6.23

[Ingo Molnar]

* Andi Kleen <andi@firstfloor.org> wrote:

> > The same is true of a lot of the APIC timer code. Sure, that patch 
> > has the actual conversion in it, and you don't have the 
> > cross-architecture issues, but more than 50% of the patch seems to 
> > be just cleanup that is independent of the actual switch-over, no?
> 
> I don't think it's that much cleanup. One of my goals for x86-64 was 
> always to have it support modern x86 only; this means in particularly 
> most of the old bug workaround removed. With the APIC timer merging a 
> lot of that crap gets back in.

i dont think "clean, modern x86 code" will ever happen - x86_64 has and 
is going to have the exact same type of crap. And i'll say a weird thing 
now: that is a _blessing_. Why? Because this crap in question originates 
from the _diversity_ of the platform, and that is a much larger asset 
than the cost of the quirks can ever be!

What you suggest does not end up in "clean 64-bit code", it ends up in 
"a bit less crappy 64-bit code", plus a lot of unnecessary duplication 
of effort and duplication of code - which easily introduces more crap 
total than it gets rid of ...

The x86 architecture isnt fully analogous to a random piece of device 
hardware that evolves. It is more of a collector of random pieces of 
hardware that evolve independently, and as such it will always be 
exposed to human messups in a factorized way. "The pristine, clean 
architecture" is an utopia and it will never come until humans design 
hardware.

Under your scheme we'll end up with is two sets of code which share some 
of the workarounds and dont share some others. No, in fact we _already_ 
ended up with two sets of code that is crappy in different ways. We had 
countless cases of bugs fixed in i386 but not fixed in x86_64. (and vice 
versa) Sharing code for similar hardware is almost always good.

I think the PowerPC experience (although it is not a fully equivalent 
case) about them merging their 32-bit and 64-bit architectures was an 
overwhelmingly positive move, and x86 could learn a thing or two from 
that.

The only way to fight crappy hardware is to map it, to understand it and 
to design as cleanly in the presence of it as possible. Having two sets 
of code for the same thing hardly serves that purpose. In fact, having 
_more_ crappy hardware _forces_ us to do a cleaner design (up to a pain 
threshold).

	Ingo

Re: generic clockevents/ (hr)time(r) patches was Re: -mm merge plans for 2.6.23

[Andi Kleen]

> Andi, any objections against the above i386 fixlets ?

No, they are fine for me.

-Andi

Re: generic clockevents/ (hr)time(r) patches was Re: -mm merge plans for 2.6.23

[Thomas Gleixner]

Andrew,

On Wed, 2007-07-11 at 16:57 -0700, Andrew Morton wrote:
> They all look pretty innocuous to me.
> 
> Could you please take a second look, decide if any of them should also be
> in 2.6.22.x and let me know?

i386-hpet-check-if-the-counter-works.patch
pcspkr-use-the-global-pit-lock.patch

are the only candidates.

	tglx

Re: x86 status was Re: -mm merge plans for 2.6.23

[Andi Kleen]

> i dont think "clean, modern x86 code" will ever happen - x86_64 has and 
> is going to have the exact same type of crap. And i'll say a weird thing 

Yes, but it will be new crap, but no old crap anymore.

If you always pile the new crap on the old crap at some point
the whole thing might fall over. 64bit was intended as a fresh start.

Admittedly we're getting more and more workarounds too and sometimes
when I want to remove cruft i find out it is still needed on some
64bit boxes (e.g. see my repeated attempts to clean up the irq 0
routing), but it's still much better than i386.

> I think the PowerPC experience (although it is not a fully equivalent 
> case) about them merging their 32-bit and 64-bit architectures was an 
> overwhelmingly positive move, and x86 could learn a thing or two from 
> that.

The equivalent to the powerpc way would be essentially to report i386
into the x86-64 code base and leave the really old hardware only
in arch/i386. I've considered doing it, but it would be an awful
lot of work and to tempt distributions to actually use the new
port would require going back quite a long time. And at least
immediately it would end up with three cases to do things instead
of two like currently.

-Andi

Re: x86 status was Re: -mm merge plans for 2.6.23

[Chris Wright]

* Andi Kleen (andi@firstfloor.org) wrote:
> The equivalent to the powerpc way would be essentially to report i386
> into the x86-64 code base and leave the really old hardware only
> in arch/i386. I've considered doing it, but it would be an awful
> lot of work and to tempt distributions to actually use the new
> port would require going back quite a long time. And at least
> immediately it would end up with three cases to do things instead
> of two like currently.

Well that's just silly.  The right way will never create 3 ways, but
always keep the limit to the existing 2 where the differences aren't
worth reconciling, and 1 for anything that is common.

It will be a fair amount of work, so any constructive input you have
upfront would be helpful.

thanks,
-chris

Re: [stable] generic clockevents/ (hr)time(r) patches was Re: -mm merge plans for 2.6.23

[Chris Wright]

* Thomas Gleixner (tglx@linutronix.de) wrote:
> Andrew,
> 
> On Wed, 2007-07-11 at 16:57 -0700, Andrew Morton wrote:
> > They all look pretty innocuous to me.
> > 
> > Could you please take a second look, decide if any of them should also be
> > in 2.6.22.x and let me know?
> 
> i386-hpet-check-if-the-counter-works.patch
> pcspkr-use-the-global-pit-lock.patch
> 
> are the only candidates.

yup, come through -stable a few times, be great to get them upstream,
and into .22.y

thanks,
-chris

Re: x86 status was Re: -mm merge plans for 2.6.23

[Ingo Molnar]

* Andi Kleen <andi@firstfloor.org> wrote:

> > i dont think "clean, modern x86 code" will ever happen - x86_64 has 
> > and is going to have the exact same type of crap. And i'll say a 
> > weird thing
> 
> Yes, but it will be new crap, but no old crap anymore.
> 
> If you always pile the new crap on the old crap at some point the 
> whole thing might fall over. 64bit was intended as a fresh start.

I think there's no such thing as a fresh start for a diverse 
architecture - the ia64 failure has proven that. x86_64 CPUs still do 
A20 emulation today (!). We still have people running industrial boards 
on real i386 DX CPUs, with the latest upstream kernel. 15 years ago an 
i386 DX was already quite obsolete. 32-bit is not going to go away in 
our lifetime, and we'll want to support it in a first-grade way. We 
better realize that prospect and have it right before our eyes in a 
single tree wherever it makes sense to share code - i'm certainly not 
talking about sharing mtrr/centaur.c or k8.c. (and i'm not necessarily 
suggesting to share io_apic.c either - although it's certainly 
borderline.)

	Ingo

Re: generic clockevents/ (hr)time(r) patches was Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Thu, 12 Jul 2007 01:59:23 +0200
Andi Kleen <ak@suse.de> wrote:

> 
> > Andi, any objections against the above i386 fixlets ?
> 
> No, they are fine for me.
> 

OK, I queued them up for an akpm->linus transfer.  Which will of course be
abandoned if an akpm->andi or andi->linus merge happens in the next week or
so.

Re: x86 status was Re: -mm merge plans for 2.6.23

[Andi Kleen]

On Thu, Jul 12, 2007 at 02:18:07AM +0200, Ingo Molnar wrote:
> > > i dont think "clean, modern x86 code" will ever happen - x86_64 has 
> > > and is going to have the exact same type of crap. And i'll say a 
> > > weird thing
> > 
> > Yes, but it will be new crap, but no old crap anymore.
> > 
> > If you always pile the new crap on the old crap at some point the 
> > whole thing might fall over. 64bit was intended as a fresh start.
> 
> I think there's no such thing as a fresh start for a diverse 
> architecture - the ia64 failure has proven that. x86_64 CPUs still do 
> A20 emulation today (!). 

x86-64 doesn't care about a lot of x86 baggage and a lot of
things have been even obsoleted in the platform.

In practice the backwards compatibility on x86 isn't that
great either.  For example a significant number of new systems don't 
even work correctly in PIC mode anymore.

> We still have people running industrial boards 
> on real i386 DX CPUs, with the latest upstream kernel. 15 years ago an 

Yes, but those for example would be perfectly happy with an arch/i386
with all APIC and SMP code stripped out.

Only the few people who still run dual P5s might not, but
those could continue using old kernels.

But eventually I think that would be the right clean way: 

arch/i386 stripped down port for truly old systems like the embedded 386
upto 586 or early 686. No SMP or APIC.
arch/x86 supporting 32bit and 64bit for reasonably modern systems.
NUMAQ/Voyager/P5-SMP/visual workstation gone [frankly the user
base of those is too small to justify the code impact]

It's just quite ugly to get there and when you think through it
the actual advantages of such a setup it is likely not enough to 
justify the significant work to make it work.

Also I wouldn't have any idea how to regression test significant
changes to arch/i386 aimed at old systems. e.g. I don't think
the powerpc people actually tried to still support really
old systems where it is hard to do regression tests anymore,
only really supported platforms.

So while such a setup would be quite nice the practical
problems of getting there are nasty. Also I must admit I prefer
hacking on new code instead.

-Andi

Re: generic clockevents/ (hr)time(r) patches was Re: -mm merge plans for 2.6.23

[Andi Kleen]

On Thursday 12 July 2007 02:04, Thomas Gleixner wrote:
> Andrew,
>
> On Wed, 2007-07-11 at 16:57 -0700, Andrew Morton wrote:
> > They all look pretty innocuous to me.
> >
> > Could you please take a second look, decide if any of them should also be
> > in 2.6.22.x and let me know?
>
> i386-hpet-check-if-the-counter-works.patch
> pcspkr-use-the-global-pit-lock.patch

Ok by me, although I suspect a lot of the cases where the hpet one
was needed got resolved with the PCI HPET resource fix But it's still
safer to check.

However I don't think patches should go into stable before they 
hit Linus' tree.

-Andi

Re: [stable] generic clockevents/ (hr)time(r) patches was Re: -mm merge plans for 2.6.23

[Chris Wright]

* Andi Kleen (ak@suse.de) wrote:
> Ok by me, although I suspect a lot of the cases where the hpet one
> was needed got resolved with the PCI HPET resource fix But it's still
> safer to check.
> 
> However I don't think patches should go into stable before they 
> hit Linus' tree.

Agreed, we're just waiting ;-)

thanks,
-chris

fault vs invalidate race (Re: -mm merge plans for 2.6.23)

[Nick Piggin]

Andrew Morton wrote:

> mm-fix-fault-vs-invalidate-race-for-linear-mappings.patch
> mm-merge-populate-and-nopage-into-fault-fixes-nonlinear.patch
> mm-merge-nopfn-into-fault.patch
> convert-hugetlbfs-to-use-vm_ops-fault.patch
> mm-remove-legacy-cruft.patch
> mm-debug-check-for-the-fault-vs-invalidate-race.patch
> mm-fix-clear_page_dirty_for_io-vs-fault-race.patch
> invalidate_mapping_pages-add-cond_resched.patch
> ocfs2-release-page-lock-before-calling-page_mkwrite.patch
> document-page_mkwrite-locking.patch
> 
>  The fault-vs-invalidate race fix.  I have belatedly learned that these need
>  more work, so their state is uncertain.

The more work may turn out being too much for you (although it is nothing
exactly tricky that would introduce subtle bugs, it is a fair amont of churn).

However, in that case we can still merge these two:

mm-fix-fault-vs-invalidate-race-for-linear-mappings.patch
mm-fix-clear_page_dirty_for_io-vs-fault-race.patch

Which fix real bugs that need fixing (and will at least help to get some of
my patches off your hands).

-- 
SUSE Labs, Novell Inc.

Re: lguest, Re: -mm merge plans for 2.6.23

[Rusty Russell]

On Wed, 2007-07-11 at 14:23 +0200, Christoph Hellwig wrote:
> > lguest-export-symbols-for-lguest-as-a-module.patch
> 
> __put_task_struct is one of those no way in hell should this be exported
> things because we don't want modules messing with task lifetimes.
> 
> Fortunately I can't find anything actually using this in lguest, so
> it looks the issue has been solved in the meantime.

To do inter-guest (ie. inter-process) I/O you really have to make sure
the other side doesn't go away.

> I also have a rather bad feeling about exporting access_process_vm.
> This is the proverbial sledge hammer for access to user vm addresses
> and I'd rather keep it away from module programmers with "if all
> you have is a hammer ..." in mind.
> 
> In lguest this is used by send_dma which from my short reading of the
> code seems to be the central IPC mechanism.  The double copy here
> doesn't look very efficient to me either.  Maybe some VM folks could
> look into a better way to archive this that might be both more
> efficient and not require the export.

It's not a double copy: it's a map & copy.

If KVM develops inter-guest I/O then this could all be extracted into a
helper function and made more efficient.

> Just started to reading this (again) so no useful comment here, but it
> would be nice if the code could follow CodingStyle and place the || and
> && at the end of the line in multiline conditionals instead of at the
> beginning of the new one.

Surprisingly, you have a point here.  Since the key purpose of lguest is
as demonstration code, it meticulously match kernel style.

I shall immediately prepare a patch to convert the rest of the kernel to
the correct "&& at beginning of line" style.

Rusty.

Re: lguest, Re: -mm merge plans for 2.6.23

[David Miller]

From: Rusty Russell <rusty@rustcorp.com.au>
Date: Thu, 12 Jul 2007 11:21:51 +1000

> To do inter-guest (ie. inter-process) I/O you really have to make sure
> the other side doesn't go away.

You should just let it exit and when it does you receive some kind of
exit notification that resets your virtual device channel.

I think the reference counting approach is error and deadlock prone.
Be more loose and let the events reset the virtual devices when
guests go splat.

block_page_mkwrite? (Re: fault vs invalidate race (Re: -mm merge plans for 2.6.23))

[David Chinner]

On Thu, Jul 12, 2007 at 10:54:57AM +1000, Nick Piggin wrote:
> Andrew Morton wrote:
> > The fault-vs-invalidate race fix.  I have belatedly learned that these 
> > need
> > more work, so their state is uncertain.
> 
> The more work may turn out being too much for you (although it is nothing
> exactly tricky that would introduce subtle bugs, it is a fair amont of 
> churn).

OK, so does that mean we can finally get the block_page_mkwrite
patches merged?

i.e.:

http://marc.info/?l=linux-kernel&m=117426058311032&w=2
http://marc.info/?l=linux-kernel&m=117426070111136&w=2

I've got up-to-date versions of them ready to go and they've been
consistently tested thanks to the XFSQA test I wrote for the bug
that it fixes. I've been holding them out-of-tree for months now
because ->fault was supposed to supercede this interface.....

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group

Re: block_page_mkwrite? (Re: fault vs invalidate race (Re: -mm merge plans for 2.6.23))

[Nick Piggin]

David Chinner wrote:
> On Thu, Jul 12, 2007 at 10:54:57AM +1000, Nick Piggin wrote:
> 
>>Andrew Morton wrote:
>>
>>>The fault-vs-invalidate race fix.  I have belatedly learned that these 
>>>need
>>>more work, so their state is uncertain.
>>
>>The more work may turn out being too much for you (although it is nothing
>>exactly tricky that would introduce subtle bugs, it is a fair amont of 
>>churn).
> 
> 
> OK, so does that mean we can finally get the block_page_mkwrite
> patches merged?
> 
> i.e.:
> 
> http://marc.info/?l=linux-kernel&m=117426058311032&w=2
> http://marc.info/?l=linux-kernel&m=117426070111136&w=2
> 
> I've got up-to-date versions of them ready to go and they've been
> consistently tested thanks to the XFSQA test I wrote for the bug
> that it fixes. I've been holding them out-of-tree for months now
> because ->fault was supposed to supercede this interface.....

Yeah, as I've said, don't hold them back because of me. They are
relatively simple enough that I don't see why they couldn't be
merged in this window.

-- 
SUSE Labs, Novell Inc.

Re: lguest, Re: -mm merge plans for 2.6.23

[Rusty Russell]

On Wed, 2007-07-11 at 19:28 -0700, David Miller wrote:
> From: Rusty Russell <rusty@rustcorp.com.au>
> Date: Thu, 12 Jul 2007 11:21:51 +1000
> 
> > To do inter-guest (ie. inter-process) I/O you really have to make sure
> > the other side doesn't go away.
> 
> You should just let it exit and when it does you receive some kind of
> exit notification that resets your virtual device channel.
> 
> I think the reference counting approach is error and deadlock prone.
> Be more loose and let the events reset the virtual devices when
> guests go splat.

There are two places where we grab task refcnt.  One might be avoidable
(will test and get back) but the deferred wakeup isn't really:

        /* We cache one process to wakeup: helps for batching & wakes outside locks. */
        void set_wakeup_process(struct lguest *lg, struct task_struct *p)
        {
        	if (p == lg->wake)
        		return;
        
        	if (lg->wake) {
        		wake_up_process(lg->wake);
        		put_task_struct(lg->wake);
        	}
        	lg->wake = p;
        	if (lg->wake)
        		get_task_struct(lg->wake);
        }

We drop the lock after I/O, and then do this wakeup.  Meanwhile the
other task might have exited.

I could get rid of it, but I don't think there's anything wrong with the
code...

Cheers,
Rusty.

Re: lguest, Re: -mm merge plans for 2.6.23

[David Miller]

From: Rusty Russell <rusty@rustcorp.com.au>
Date: Thu, 12 Jul 2007 12:48:41 +1000

> We drop the lock after I/O, and then do this wakeup.  Meanwhile the
> other task might have exited.

I already understand what you're doing.

Is it possible to use exit notifiers to handle this case?
That's what I'm trying to suggest. :)

Re: x86 status was Re: -mm merge plans for 2.6.23

[Arjan van de Ven]

On Wed, 2007-07-11 at 15:58 -0700, Linus Torvalds wrote:
> 
> On Wed, 11 Jul 2007, Chris Wright wrote:
> > 
> > That's not quite right.  Leaving the code unchanged caused breakage
> > already.  The PIT is damn stupid and can be sensitive to how quickly it's
> > programmed.  So code that enable/disable didn't change, but frequency
> > with which it is called did and broke some random boxes.
> 
> Sure. We cannot avoid *all* problems. Bugs happen. 
> 
> But at least we could try to make sure that there aren't totally 
> unnecessary changes in that switch-over patch. Which there definitely 
> were, as far as I can tell.


one note is that the "talk differently to hardware" thing is in part
already tested with the 32 bit tickless code; a lot of people (80% ?)
are still using the 32 bit OS on their 64 bit machines, and the 32 bit
code already talks in the "new way" to this hardware.... 
(and since Fedora 7 already ships tickless for 32 bit there are quite a
lot of people using that in practice, in addition to the kernel.org
kernel users)

I would expect just about all the hardware interaction issues to have
popped up already because of this "run 32 bit on 64 bit hardware" thing.
-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org

Re: lguest, Re: -mm merge plans for 2.6.23

[Rusty Russell]

On Wed, 2007-07-11 at 19:51 -0700, David Miller wrote:
> From: Rusty Russell <rusty@rustcorp.com.au>
> Date: Thu, 12 Jul 2007 12:48:41 +1000
> 
> > We drop the lock after I/O, and then do this wakeup.  Meanwhile the
> > other task might have exited.
> 
> I already understand what you're doing.
> 
> Is it possible to use exit notifiers to handle this case?
> That's what I'm trying to suggest. :)

Sure, the process has /dev/lguest open, so I can do something in the
close routine.  Instead of keeping a reference to the tsk, I can keep a
reference to the struct lguest (currently it doesn't have or need a
refcnt).  Then I need another lock, to protect lg->tsk.

This seems like a lot of dancing to avoid one export.  If it's that
important I'd far rather drop the code and do a normal wakeup under the
big lguest lock for 2.6.23.

Cheers,
Rusty.

Re: lguest, Re: -mm merge plans for 2.6.23

[David Miller]

From: Rusty Russell <rusty@rustcorp.com.au>
Date: Thu, 12 Jul 2007 13:15:18 +1000

> Sure, the process has /dev/lguest open, so I can do something in the
> close routine.  Instead of keeping a reference to the tsk, I can keep a
> reference to the struct lguest (currently it doesn't have or need a
> refcnt).  Then I need another lock, to protect lg->tsk.
> 
> This seems like a lot of dancing to avoid one export.  If it's that
> important I'd far rather drop the code and do a normal wakeup under the
> big lguest lock for 2.6.23.

I'm not against the export, so use if it really helps.

Ref-counting just seems clumsy to me given how the hw assisted
virtualization stuff works on platforms I am intimately familiar with
:)

Re: lguest, Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Thu, 12 Jul 2007 12:48:41 +1000 Rusty Russell <rusty@rustcorp.com.au> wrote:

> On Wed, 2007-07-11 at 19:28 -0700, David Miller wrote:
> > From: Rusty Russell <rusty@rustcorp.com.au>
> > Date: Thu, 12 Jul 2007 11:21:51 +1000
> > 
> > > To do inter-guest (ie. inter-process) I/O you really have to make sure
> > > the other side doesn't go away.
> > 
> > You should just let it exit and when it does you receive some kind of
> > exit notification that resets your virtual device channel.
> > 
> > I think the reference counting approach is error and deadlock prone.
> > Be more loose and let the events reset the virtual devices when
> > guests go splat.
> 
> There are two places where we grab task refcnt.  One might be avoidable
> (will test and get back) but the deferred wakeup isn't really:
> 
>         /* We cache one process to wakeup: helps for batching & wakes outside locks. */
>         void set_wakeup_process(struct lguest *lg, struct task_struct *p)
>         {
>         	if (p == lg->wake)
>         		return;
>         
>         	if (lg->wake) {
>         		wake_up_process(lg->wake);
>         		put_task_struct(lg->wake);
>         	}
>         	lg->wake = p;
>         	if (lg->wake)
>         		get_task_struct(lg->wake);
>         }

<handwaving>

We seem to be taking the reference against the wrong thing here.  It should
be against the mm, not against a task_struct?

Re: lguest, Re: -mm merge plans for 2.6.23

[Rusty Russell]

On Wed, 2007-07-11 at 21:24 -0700, Andrew Morton wrote:
> We seem to be taking the reference against the wrong thing here.  It should
> be against the mm, not against a task_struct?

This is solely for the wakeup: you don't wake an mm 8)

The mm reference is held as well under the big lguest_mutex (mm gets
destroyed before files get closed, so we definitely do need to hold a
reference).

I just completed benchmarking: the cached wakeup with the current naive
drivers makes no difference (at one stage I was playing with batched
hypercalls, where it seemed to help).

Thanks Christoph, DaveM!
===
Remove export of __put_task_struct, and usage in lguest

lguest takes a reference count of tasks for two reasons.  The first is
bogus: the /dev/lguest close callback will be called before the task
is destroyed anyway, so no need to take a reference on open.

The second is code to defer waking up tasks for inter-guest I/O, but
the current lguest drivers are too simplistic to benefit (only batched
hypercalls will see an effect, and it's likely that lguests' entire
I/O model will be replaced with virtio and ringbuffers anyway).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 drivers/lguest/hypercalls.c  |    1 -
 drivers/lguest/io.c          |   18 +-----------------
 drivers/lguest/lg.h          |    1 -
 drivers/lguest/lguest_user.c |    2 --
 kernel/fork.c                |    1 -
 5 files changed, 1 insertion(+), 22 deletions(-)

===================================================================
--- a/drivers/lguest/hypercalls.c
+++ b/drivers/lguest/hypercalls.c
@@ -189,5 +189,4 @@ void do_hypercalls(struct lguest *lg)
 		do_hcall(lg, lg->regs);
 		clear_hcall(lg);
 	}
-	set_wakeup_process(lg, NULL);
 }
===================================================================
--- a/drivers/lguest/io.c
+++ b/drivers/lguest/io.c
@@ -296,7 +296,7 @@ static int dma_transfer(struct lguest *s
 
 	/* Do this last so dst doesn't simply sleep on lock. */
 	set_bit(dst->interrupt, dstlg->irqs_pending);
-	set_wakeup_process(srclg, dstlg->tsk);
+	wake_up_process(dstlg->tsk);
 	return i == dst->num_dmas;
 
 fail:
@@ -333,7 +333,6 @@ again:
 			/* Give any recipients one chance to restock. */
 			up_read(&current->mm->mmap_sem);
 			mutex_unlock(&lguest_lock);
-			set_wakeup_process(lg, NULL);
 			empty++;
 			goto again;
 		}
@@ -360,21 +359,6 @@ void release_all_dma(struct lguest *lg)
 			unlink_dma(&lg->dma[i]);
 	}
 	up_read(&lg->mm->mmap_sem);
-}
-
-/* We cache one process to wakeup: helps for batching & wakes outside locks. */
-void set_wakeup_process(struct lguest *lg, struct task_struct *p)
-{
-	if (p == lg->wake)
-		return;
-
-	if (lg->wake) {
-		wake_up_process(lg->wake);
-		put_task_struct(lg->wake);
-	}
-	lg->wake = p;
-	if (lg->wake)
-		get_task_struct(lg->wake);
 }
 
 /* Userspace wants a dma buffer from this guest. */
===================================================================
--- a/drivers/lguest/lg.h
+++ b/drivers/lguest/lg.h
@@ -240,7 +240,6 @@ void release_all_dma(struct lguest *lg);
 void release_all_dma(struct lguest *lg);
 unsigned long get_dma_buffer(struct lguest *lg, unsigned long key,
 			     unsigned long *interrupt);
-void set_wakeup_process(struct lguest *lg, struct task_struct *p);
 
 /* hypercalls.c: */
 void do_hypercalls(struct lguest *lg);
===================================================================
--- a/drivers/lguest/lguest_user.c
+++ b/drivers/lguest/lguest_user.c
@@ -141,7 +141,6 @@ static int initialize(struct file *file,
 	setup_guest_gdt(lg);
 	init_clockdev(lg);
 	lg->tsk = current;
-	get_task_struct(lg->tsk);
 	lg->mm = get_task_mm(lg->tsk);
 	init_waitqueue_head(&lg->break_wq);
 	lg->last_pages = NULL;
@@ -205,7 +204,6 @@ static int close(struct inode *inode, st
 	hrtimer_cancel(&lg->hrt);
 	release_all_dma(lg);
 	free_guest_pagetable(lg);
-	put_task_struct(lg->tsk);
 	mmput(lg->mm);
 	if (!IS_ERR(lg->dead))
 		kfree(lg->dead);
===================================================================
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -128,7 +128,6 @@ void __put_task_struct(struct task_struc
 	if (!profile_handoff_task(tsk))
 		free_task(tsk);
 }
-EXPORT_SYMBOL_GPL(__put_task_struct);
 
 void __init fork_init(unsigned long mempages)
 {

Re: containers (was Re: -mm merge plans for 2.6.23)

[Srivatsa Vaddagiri]

On Wed, Jul 11, 2007 at 12:44:42PM -0700, Paul Menage wrote:
> >I'm inclined to take the cautious route here - I don't think people will be
> >dying for the CFS thingy (which I didn't even know about?) in .23, and it's
> >rather a lot of infrastructure to add for a CPU scheduler configurator
> 
> Selecting the relevant patches to give enough of the container
> framework to support a CFS container subsystem (slightly
> tweaked/updated versions of the base patch, procfs interface patch and
> tasks file interface patch) is about 1600 lines in kernel/container.c
> and another 200 in kernel/container.h, which is about 99% of the
> non-documentation changes.
> 
> So not tiny, but it's not very intrusive on the rest of the kernel,
> and would avoid having to introduce a temporary API based on uids.

Yes that would be good. As long as the user-land interface for process
containers doesn't change (much?) between 2.6.23 and later releases this
should be a good workaround for us.

-- 
Regards,
vatsa

Re: lguest, Re: -mm merge plans for 2.6.23

[Avi Kivity]

Rusty Russell wrote:
> Remove export of __put_task_struct, and usage in lguest
>
> lguest takes a reference count of tasks for two reasons.  The first is
> bogus: the /dev/lguest close callback will be called before the task
> is destroyed anyway, so no need to take a reference on open.
>
>   

What about

  Open /dev/lguest
  transfer fd using SCM_RIGHTS (or clone()?)
  close fd in original task
  exit()

?

My feeling is that if you want to be bound to a task, not a file, you 
need to use syscalls, not ioctls.

-- 
error compiling committee.c: too many arguments to function

Re: [ck] Re: -mm merge plans for 2.6.23

[Kacper Wysocki]

On 7/11/07, Andrew Morton <akpm@linux-foundation.org> wrote:
> On Wed, 11 Jul 2007 11:02:56 +1000 "Matthew Hawkins" <darthmdh@gmail.com> wrote:
>
> > We all know swap prefetch has been tested out the wazoo since Moses was a
> > little boy, is compile-time and runtime selectable, and gives an important
> > and quantifiable performance increase to desktop systems.
>
> Always interested.  Please provide us more details on your usage and
> testing of that code.  Amount of memory, workload, observed results,
> etc?

Swap prefetch has been around for years, and it's a complete boon for
the desktop user and a noop in any other situation. In addition to the
sp_tester tool which consistently shows a definite advantage, there
are many user reports that show the noticeable improvements it has.
The many people who have tried it out have generally chosen to switch
to patched kernels because of the performance increase.

It's been discussed on the lkml many times before, we've been over
performance, testing and impact. The big question is: why *don't* we
merge it?

-Kacper

Re: [ck] Re: -mm merge plans for 2.6.23

[Avuton Olrich]

On 7/12/07, Kacper Wysocki <kacperw@online.no> wrote:
> performance, testing and impact. The big question is: why *don't* we
> merge it?

Stranger thing to me is that this is like Déjà Vu. Many have asked
this same question. When users were asked for their comment before
many end users and some developers have given rave reviews. I don't
remember anyone giving it the heavy thumbs-down, with exception of
when things needed fixing (over 6 months ago?). It continues to go
unmerged. Is there a clear answer on what needs to happen for it to
get merged?
-- 
avuton
--
 Anyone who quotes me in their sig is an idiot. -- Rusty Russell.

Re: x86 status was Re: -mm merge plans for 2.6.23

[Oleg Verych]

* Linus Torvalds "Wed, 11 Jul 2007 15:09:28 -0700 (PDT)"
>
> On Wed, 11 Jul 2007, Andrea Arcangeli wrote:
>>
>> I'm going to change topic big time because your sentence above
>> perfectly applies to the O(1) scheduler too.
>
> I disagree to a large degree.
>
> We almost never have problems with code you can "think about".
>
> Sure, bugs happen, but code that everybody runs the same generally doesn't 
> break. So a CPU scheduler doesn't worry me all that much. CPU schedulers 
> are "easy".
>
> What worries me is interfaces to hardware that we know looks different for 
> different people. That means that any testing that one person has done 
> doesn't necessarily translate to anything at *all* on another persons 
> machine.
>
> The timer problems we had when merging the stuff in 2.6.21 just scarred 
> me. I'd _really_ hate to have to go through that again. And no, the 
> "gradual" thing where the patch that actually *enables* something isn't 
> very gradual at all, so that's the absolutely worst kind of thing, because 
> then people can "git bisect" to the point where it got enabled and tell us 
> that's where things broke, but that doesn't actually say anything at all 
> about the patch that actually implements the new behaviour.
>
> So the "enable" kind of patch is actually the worst of the lot, when it 
> comes to hardware.
>
> When it comes to pure software algorithms, and things like schedulers, 
> you'll still obviously have timing issues and tuning, but generally things 
> *work*, which makes it a lot easier to debug and describe.
>
> 		Linus

Seconded (obviously).

--
-o--=O`C
 #oo'L O
<___=E M

Re: x86 status was Re: -mm merge plans for 2.6.23

[Christoph Lameter]

On Wed, 11 Jul 2007, Andi Kleen wrote:

> These all need re-review:
> 
> > i386-add-support-for-picopower-irq-router.patch
> > make-arch-i386-kernel-setupcremapped_pgdat_init-static.patch
> > arch-i386-kernel-i8253c-should-include-asm-timerh.patch
> > make-arch-i386-kernel-io_apicctimer_irq_works-static-again.patch


> > quicklist-support-for-x86_64.patch

^^^ That patch was supposed to be merged for 2.6.22 (you told me you 
forgot to merge it) and has been for a long time in mm. Does it now 
need to be rereviewed for 2.6.23? The other pieces of the quicklist patch 
for core and other arches were merged for 2.6.22.

Re: x86 status was Re: -mm merge plans for 2.6.23

[Matt Mackall]

On Thu, Jul 12, 2007 at 12:50:19AM +0200, Thomas Gleixner wrote:
> Linus,
> 
> On Wed, 2007-07-11 at 15:20 -0700, Linus Torvalds wrote:
> > For example, we can make sure that the code in question that actually 
> > touches the hardware stays exactly the same, and then just move the 
> > interfaces around - and basically guarantee that _zero_ hardware-specific 
> > issues pop up when you switch over, for example.
> > 
> > That way there is a gradual change-over.
> 
> Ok, I can try to split this down further.
> 
> > The other approach (which would be nice _too_) is to actually try to 
> > convert one clock source at a time. Why is that not an option? 
> 
> We need to give control to the clock events core code once we convert
> one clock event device. Having two competing subsystems controlling
> different devices (e.g. PIT and APIC) is not really desirable.

Can't you take the entire legacy clock system and wrap it as a single
legacy clock source? Then you take bits out of the old system and put
them as independent sources in the new system? When the legacy clock
system is empty, you remove the legacy clock source.

-- 
Mathematics is the supreme nostalgia of our time.

Re: x86 status was Re: -mm merge plans for 2.6.23

[Andi Kleen]

On Thu, Jul 12, 2007 at 12:33:43PM -0700, Christoph Lameter wrote:
> On Wed, 11 Jul 2007, Andi Kleen wrote:
> 
> > These all need re-review:
> > 
> > > i386-add-support-for-picopower-irq-router.patch
> > > make-arch-i386-kernel-setupcremapped_pgdat_init-static.patch
> > > arch-i386-kernel-i8253c-should-include-asm-timerh.patch
> > > make-arch-i386-kernel-io_apicctimer_irq_works-static-again.patch
> 
> 
> > > quicklist-support-for-x86_64.patch
> 
> ^^^ That patch was supposed to be merged for 2.6.22 (you told me you 
> forgot to merge it) and has been for a long time in mm. Does it now 
> need to be rereviewed for 2.6.23? The other pieces of the quicklist patch 
> for core and other arches were merged for 2.6.22.

It's just on the normal re-review list. But it'll likely go in.

-Andi

Re: lguest, Re: -mm merge plans for 2.6.23

[Rusty Russell]

On Thu, 2007-07-12 at 14:10 +0300, Avi Kivity wrote:
> Rusty Russell wrote:
> > Remove export of __put_task_struct, and usage in lguest
> >
> > lguest takes a reference count of tasks for two reasons.  The first is
> > bogus: the /dev/lguest close callback will be called before the task
> > is destroyed anyway, so no need to take a reference on open.
> >
> >   
> 
> What about
> 
>   Open /dev/lguest
>   transfer fd using SCM_RIGHTS (or clone()?)
>   close fd in original task
>   exit()
> 
> ?
> 
> My feeling is that if you want to be bound to a task, not a file, you 
> need to use syscalls, not ioctls.

"Don't do that".  You'll lose the ability to access the operations on
the fd once you are no longer the original task (explicit check).,

It's not an exact match, but a file is a remarkably convenient
abstraction for a non-ABI such as lguest.  Of course, Carsten was
talking about unifying the lguest & kvm userspace interface, so this
could well change anyway.

Cheers,
Rusty.

Re: x86 status was Re: -mm merge plans for 2.6.23

[Roman Zippel]

Hi,

On Wed, 11 Jul 2007, Linus Torvalds wrote:

> Sure, bugs happen, but code that everybody runs the same generally doesn't 
> break. So a CPU scheduler doesn't worry me all that much. CPU schedulers 
> are "easy".

A little more advance warning wouldn't have hurt though.
The new scheduler does _a_lot_ of heavy 64 bit calculations without any 
attempt to scale that down a little...
One can blame me now for not having it brought up earlier, but discussions 
with Ingo are not something I'm looking forward to. :(

bye, Roman

Re: x86 status was Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Fri, 13 Jul 2007 04:23:43 +0200 (CEST) Roman Zippel <zippel@linux-m68k.org> wrote:

> Hi,
> 
> On Wed, 11 Jul 2007, Linus Torvalds wrote:
> 
> > Sure, bugs happen, but code that everybody runs the same generally doesn't 
> > break. So a CPU scheduler doesn't worry me all that much. CPU schedulers 
> > are "easy".
> 
> A little more advance warning wouldn't have hurt though.
> The new scheduler does _a_lot_ of heavy 64 bit calculations without any 
> attempt to scale that down a little...
> One can blame me now for not having it brought up earlier, but discussions 
> with Ingo are not something I'm looking forward to. :(
> 

I brought that up a couple of weeks ago, got handwaved at and gave up.

It still isn't obvious to me that all that arith needs to be 64-bit
on 32-bit machines, or even on 64-bit.  4e9 is a big number.

Re: x86 status was Re: -mm merge plans for 2.6.23

[Mike Galbraith]

On Fri, 2007-07-13 at 04:23 +0200, Roman Zippel wrote:
> Hi,

Hi,

> The new scheduler does _a_lot_ of heavy 64 bit calculations without any 
> attempt to scale that down a little...

See prio_to_weight[], prio_to_wmult[] and sysctl_sched_stat_granularity.
Perhaps more can be done, but "without any attempt..." isn't accurate.

	-Mike

Re: -mm merge plans for 2.6.23

[Jan Engelhardt]

On Jul 10 2007 01:31, Andrew Morton wrote:

>use-menuconfig-objects-isdn-config_isdn_i4l.patch
>
> tilman didn't like it - might drop

Or replace by his suggestion patch ( http://lkml.org/lkml/2007/5/31/222 )


	Jan
-- 

Re: x86 status was Re: -mm merge plans for 2.6.23

[Roman Zippel]

Hi,

On Fri, 13 Jul 2007, Mike Galbraith wrote:

> > The new scheduler does _a_lot_ of heavy 64 bit calculations without any 
> > attempt to scale that down a little...
> 
> See prio_to_weight[], prio_to_wmult[] and sysctl_sched_stat_granularity.
> Perhaps more can be done, but "without any attempt..." isn't accurate.

Calculating these values at runtime would have been completely insane, the 
alternative would be a crummy approximation, so using a lookup table is 
actually a good thing. That's not the problem.
BTW could someone please verify the prio_to_wmult table, especially [16] 
and [21] look a little off, like a digit was cut off.

While I'm at this, the 10% scaling there looks a little much (unless there 
are other changes I haven't looked at yet), the old code used more like 
5%. This would mean a prio -20 task would get 98.86% cpu time compared to 
a prio 0 task, that was previously about the difference between -20 and 
19 (and it would have previously gotten only 88.89%), now a prio -20 task 
would get 99.98% cpu time compared to a prio 19 task.
The individual levels are unfortunately not that easily comparable, but at 
the overall scale the change looks IMHO a little drastic.

bye, Roman

[PATCH] CFS: Fix missing digit off in wmult table

[Thomas Gleixner]

Roman Zippel noticed inconsistency of the wmult table.

wmult[16] has a missing digit.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/sched.c b/kernel/sched.c
index 0559665..3332bbb 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -750,7 +750,7 @@ static const u32 prio_to_wmult[40] = {
 	48356,   60446,   75558,   94446,  118058,  147573,
 	184467,  230589,  288233,  360285,  450347,
 	562979,  703746,  879575, 1099582, 1374389,
-	717986, 2147483, 2684354, 3355443, 4194304,
+	1717986, 2147483, 2684354, 3355443, 4194304,
 	5244160, 6557201, 8196502, 10250518, 12782640,
 	16025997, 19976592, 24970740, 31350126, 39045157,
 	49367440, 61356675, 76695844, 95443717, 119304647,

Re: -mm merge plans for 2.6.23

[Tilman Schmidt]

[-- Attachment #1: Type: text/plain, Size: 786 bytes --]

Am 13.07.2007 11:46 schrieb Jan Engelhardt:
> On Jul 10 2007 01:31, Andrew Morton wrote:
> 
>> use-menuconfig-objects-isdn-config_isdn_i4l.patch
>>
>> tilman didn't like it - might drop
> 
> Or replace by his suggestion patch ( http://lkml.org/lkml/2007/5/31/222 )

That posting was just a change proposal for the drivers/isdn/Kconfig
part, not a complete replacement for the entire patch. If you'd care to
reissue that patch with the modification I proposed, I'll gladly ack it.
Alternatively I can also send a full replacement patch if you prefer.

Regards,
Tilman

-- 
Tilman Schmidt                          E-Mail: tilman@imap.cc
Bonn, Germany
Diese Nachricht besteht zu 100% aus wiederverwerteten Bits.
Ungeöffnet mindestens haltbar bis: (siehe Rückseite)


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 253 bytes --]

Re: x86 status was Re: -mm merge plans for 2.6.23

[Mike Galbraith]

On Fri, 2007-07-13 at 19:23 +0200, Roman Zippel wrote:
> Hi,
> 
> On Fri, 13 Jul 2007, Mike Galbraith wrote:
> 
> > > The new scheduler does _a_lot_ of heavy 64 bit calculations without any 
> > > attempt to scale that down a little...
> > 
> > See prio_to_weight[], prio_to_wmult[] and sysctl_sched_stat_granularity.
> > Perhaps more can be done, but "without any attempt..." isn't accurate.
> 
> Calculating these values at runtime would have been completely insane, the 
> alternative would be a crummy approximation, so using a lookup table is 
> actually a good thing. That's not the problem.

I meant see usage.

	-Mike

Re: -mm merge plans for 2.6.23

[Jan Engelhardt]

On Jul 14 2007 01:09, Tilman Schmidt wrote:
>Am 13.07.2007 11:46 schrieb Jan Engelhardt:
>> On Jul 10 2007 01:31, Andrew Morton wrote:
>> 
>>> use-menuconfig-objects-isdn-config_isdn_i4l.patch
>>>
>>> tilman didn't like it - might drop
>> 
>> Or replace by his suggestion patch ( http://lkml.org/lkml/2007/5/31/222 )
>
>That posting was just a change proposal for the drivers/isdn/Kconfig
>part, not a complete replacement for the entire patch. If you'd care to
>reissue that patch with the modification I proposed, I'll gladly ack it.
>Alternatively I can also send a full replacement patch if you prefer.

Since I did not really see much of a difference between our two
approaches, I'd be grateful if you could send a full replacement in
the hopes that I see the global picture.


Thanks,
	Jan
-- 

Re: [PATCH] CFS: Fix missing digit off in wmult table

[James Bruce]

Thomas Gleixner wrote:
> Roman Zippel noticed inconsistency of the wmult table.
> wmult[16] has a missing digit.
[snip]

While we're at it, isn't the comment above the wmult table incorrect?
The multiplier is 1.25, meaning a 25% change per nice level, not 10%.

  - Jim

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Ingo Molnar]

* James Bruce <bruce@andrew.cmu.edu> wrote:

> While we're at it, isn't the comment above the wmult table incorrect? 
> The multiplier is 1.25, meaning a 25% change per nice level, not 10%.

yes, the weight multiplier 1.25, but the actual difference in CPU 
utilization, when running two CPU intense tasks, is ~10%:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 8246 mingo     20   0  1576  244  196 R   55  0.0   0:11.96 loop
 8247 mingo     21   1  1576  244  196 R   45  0.0   0:10.52 loop

so the first task 'wins' +10% CPU utilization (relative to the 50% it 
had before), the second task 'loses' -10% CPU utilization (relative to 
the 50% it had before).

so what the comment says is true:

 * The "10% effect" is relative and cumulative: from _any_ nice level,
 * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
 * it's +10% CPU usage.

for there to be a ~+10% change in CPU utilization for a task that races 
against another CPU-intense task there needs to be a ~25% change in the 
weight.

	Ingo

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Ingo Molnar]

* Ingo Molnar <mingo@elte.hu> wrote:

> * James Bruce <bruce@andrew.cmu.edu> wrote:
> 
> > While we're at it, isn't the comment above the wmult table incorrect? 
> > The multiplier is 1.25, meaning a 25% change per nice level, not 10%.
> 
> yes, the weight multiplier 1.25, but the actual difference in CPU 
> utilization, when running two CPU intense tasks, is ~10%:
> 
>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>  8246 mingo     20   0  1576  244  196 R   55  0.0   0:11.96 loop
>  8247 mingo     21   1  1576  244  196 R   45  0.0   0:10.52 loop
> 
> so the first task 'wins' +10% CPU utilization (relative to the 50% it 
> had before), the second task 'loses' -10% CPU utilization (relative to 
> the 50% it had before).
> 
> so what the comment says is true:
> 
>  * The "10% effect" is relative and cumulative: from _any_ nice level,
>  * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
>  * it's +10% CPU usage.
> 
> for there to be a ~+10% change in CPU utilization for a task that 
> races against another CPU-intense task there needs to be a ~25% change 
> in the weight.

in any case more documentation is justified, so i've added some 
clarification to the comments - see the patch below.

	Ingo

------------------------>
Subject: sched: improve weight-array comments
From: Ingo Molnar <mingo@elte.hu>

improve the comments around the wmult array (which controls the weight
of niced tasks). Clarify that to achieve a 10% difference in CPU
utilization, a weight multiplier of 1.25 has to be used.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 kernel/sched.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Index: linux/kernel/sched.c
===================================================================
--- linux.orig/kernel/sched.c
+++ linux/kernel/sched.c
@@ -736,7 +736,9 @@ static void update_curr_load(struct rq *
  *
  * The "10% effect" is relative and cumulative: from _any_ nice level,
  * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
- * it's +10% CPU usage.
+ * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
+ * If a task goes up by ~10% and another task goes down by ~10% then
+ * the relative distance between them is ~25%.)
  */
 static const int prio_to_weight[40] = {
 /* -20 */ 88818, 71054, 56843, 45475, 36380, 29104, 23283, 18626, 14901, 11921,

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Mon, 16 Jul 2007, Ingo Molnar wrote:

> yes, the weight multiplier 1.25, but the actual difference in CPU 
> utilization, when running two CPU intense tasks, is ~10%:
> 
>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>  8246 mingo     20   0  1576  244  196 R   55  0.0   0:11.96 loop
>  8247 mingo     21   1  1576  244  196 R   45  0.0   0:10.52 loop
> 
> so the first task 'wins' +10% CPU utilization (relative to the 50% it 
> had before), the second task 'loses' -10% CPU utilization (relative to 
> the 50% it had before).

As soon as you add another loop the difference changes again, while it's 
always correct to say it gets 25% more cpu time (which I still think is a 
little too much).

bye, Roman

Re: -mm merge plans -- lumpy reclaim

[Mel Gorman]

On (11/07/07 09:46), Andrew Morton didst pronounce:
> On Wed, 11 Jul 2007 10:34:31 +0100 Andy Whitcroft <apw@shadowen.org> wrote:
> 
> > [Seems a PEBKAC occured on the subject line, resending lest it become a
> > victim of "oh thats spam".]
> > 
> > Andy Whitcroft wrote:
> > > Andrew Morton wrote:
> > > 
> > > [...]
> > >> lumpy-reclaim-v4.patch
> > >> have-kswapd-keep-a-minimum-order-free-other-than-order-0.patch
> > >> only-check-absolute-watermarks-for-alloc_high-and-alloc_harder-allocations.patch
> > >>
> > >>  Lumpy reclaim.  In a similar situation to Mel's patches.  Stuck due to
> > >>  general lack or interest and effort.
> > > 
> > > The lumpy reclaim patches originally came out of work to support Mel's
> > > anti-fragmentation work.  As such I think they have become somewhat
> > > attached to those patches.  Whilst lumpy is most effective where
> > > placement controls are in place as offered by Mel's work, we see benefit
> > > from reduction in the "blunderbuss" effect when we reclaim at higher
> > > orders.  While placement control is pretty much required for the very
> > > highest orders such as huge page size, lower order allocations are
> > > benefited in terms of lower collateral damage.
> > > 
> > > There are now a few areas other than huge page allocations which can
> > > benefit.  Stacks are still order 1.  Jumbo frames want higher order
> > > contiguous pages for there incoming hardware buffers.  SLUB is showing
> > > performance benefits from moving to a higher allocation order.  All of
> > > these should benefit from more aggressive targeted reclaim, indeed I
> > > have been surprised just how often my test workloads trigger lumpy at
> > > order 1 to get new stacks.
> > > 
> > > Truly representative work loads are hard to generate for some of these.
> > >  Though we have heard some encouraging noises from those who can
> > > reproduce these problems.
> 
> I'd expect that the main application for lumpy-reclaim is in keeping a pool
> of order-2 (say) pages in reserve for GFP_ATOMIC allocators.  ie: jumbo
> frames.
> 
> At present this relies upon the wakeup_kswapd(..., order) mechanism.
> 
> How effective is this at solving the jumbo frame problem?
> 
> (And do we still have a jumbo frame problem?  Reports seems to have subsided)

The patches have an application with hugepage pool resizing.

When lumpy-reclaim is used used with ZONE_MOVABLE, the hugepages pool can
be resized with greater reliability. Testing on a desktop machine with 2GB
of RAM showed that growing the hugepage pool with ZONE_MOVABLE on it's own
was very slow as the success rate was quite low. Without lumpy-reclaim, each
attempt to grow the pool by 100 pages would yield 1 or 2 hugepages. With
lumpy-reclaim, getting 40 to 70 hugepages on each attempt was typical.

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> > yes, the weight multiplier 1.25, but the actual difference in CPU 
> > utilization, when running two CPU intense tasks, is ~10%:
> > 
> >   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
> >  8246 mingo     20   0  1576  244  196 R   55  0.0   0:11.96 loop
> >  8247 mingo     21   1  1576  244  196 R   45  0.0   0:10.52 loop
> > 
> > so the first task 'wins' +10% CPU utilization (relative to the 50% 
> > it had before), the second task 'loses' -10% CPU utilization 
> > (relative to the 50% it had before).
> 
> As soon as you add another loop the difference changes again, while 
> it's always correct to say it gets 25% more cpu time [...]

yep, and i'll add the relative effect to the comment too.

	Ingo

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Mon, 16 Jul 2007, Ingo Molnar wrote:

> > As soon as you add another loop the difference changes again, while 
> > it's always correct to say it gets 25% more cpu time [...]
> 
> yep, and i'll add the relative effect to the comment too.

Why did you cut off the rest of the sentence?
To illustrate the problem a little different: a task with a nice level -20 
got around 700% more cpu time (or 8 times more), now it gets 8500% more 
cpu time (or 86.7 times more).
You don't think that change to the nice levels is a little drastic?

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> On Mon, 16 Jul 2007, Ingo Molnar wrote:
> 
> > > As soon as you add another loop the difference changes again, 
> > > while it's always correct to say it gets 25% more cpu time [...]
> > 
> > yep, and i'll add the relative effect to the comment too.
> 
> Why did you cut off the rest of the sentence?

(no need to become hostile, i answered to that portion of your sentence 
separately, which was logically detached from the other portion of your 
sentence. I marked the cut with the '[...]' sign. )

> To illustrate the problem a little different: a task with a nice level 
> -20 got around 700% more cpu time (or 8 times more), now it gets 8500% 
> more cpu time (or 86.7 times more). You don't think that change to the 
> nice levels is a little drastic?

This was discussed on lkml in detail, see the CFS threads. It has been a 
common request for nice levels to be more logical (i.e. to make them 
universal and to detach them from HZ) and for them to be more effective 
as well.

	Ingo

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Mon, 16 Jul 2007, Ingo Molnar wrote:

> > > > As soon as you add another loop the difference changes again, 
> > > > while it's always correct to say it gets 25% more cpu time [...]
> > > 
> > > yep, and i'll add the relative effect to the comment too.
> > 
> > Why did you cut off the rest of the sentence?
> 
> (no need to become hostile, i answered to that portion of your sentence 
> separately, which was logically detached from the other portion of your 
> sentence. I marked the cut with the '[...]' sign. )

Could you please stop with these accusations?
Could you please point me to the mail with the separate answer?

> > To illustrate the problem a little different: a task with a nice level 
> > -20 got around 700% more cpu time (or 8 times more), now it gets 8500% 
> > more cpu time (or 86.7 times more). You don't think that change to the 
> > nice levels is a little drastic?
> 
> This was discussed on lkml in detail, see the CFS threads.

Which are quite big, so I skipped most of it, a more precise pointer would 
be appreciated.

> It has been a 
> common request for nice levels to be more logical (i.e. to make them 
> universal and to detach them from HZ) and for them to be more effective 
> as well.

Huh? What has this to do with HZ? The scheduler used ticks internally, but 
it's irrelevant to what the user sees via the nice levels.
So the question still stands that this change may be a little drastic, as 
you changed the nice levels of _all_ users, not just of those who were 
previously interested in CFS.

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> > It has been a common request for nice levels to be more logical 
> > (i.e. to make them universal and to detach them from HZ) and for 
> > them to be more effective as well.
> 
> Huh? What has this to do with HZ? The scheduler used ticks internally, 
> but it's irrelevant to what the user sees via the nice levels. [...]

unfortunately you are wrong again - there are various HZ related 
artifacts in the nice level support code of the old scheduler.

v2.6.22, CONFIG_HZ=100, nice +19 task against a nice-0 CPU-intense task:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 2446 mingo     25   0  1576  244  196 R 90.9  0.0   0:32.79 loop
 2448 mingo     39  19  1580  248  196 R  9.1  0.0   0:02.94 loop

v2.6.22, CONFIG_HZ=250, nice +19 task against a nice-0 CPU-intense task:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 2358 mingo     25   0  1576  248  196 R 96.1  0.0   0:31.97 loop_silent
 2363 mingo     39  19  1576  244  196 R  3.9  0.0   0:01.24 loop_silent

v2.6.22, CONFIG_HZ=300, nice +19 task against a nice-0 CPU-intense task:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 2332 mingo     25   0  1580  248  196 R 95.1  0.0   0:11.84 loop_silent
 2335 mingo     39  19  1576  244  196 R  3.1  0.0   0:00.39 loop_silent

to sum it up: a nice +19 task (the most commonly used nice level in 
practice) gets 9.1%, 3.9%, 3.1% of CPU time on the old scheduler, 
depending on the value of HZ. This is quite inconsistent and illogical.

this HZ dependency of nice levels existed for many years, and the new 
scheduler solves that inconsistency - every nice level will get the same 
amount of time, regardless of HZ.

	Ingo

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Mon, 16 Jul 2007, Ingo Molnar wrote:

> to sum it up: a nice +19 task (the most commonly used nice level in 
> practice) gets 9.1%, 3.9%, 3.1% of CPU time on the old scheduler, 
> depending on the value of HZ. This is quite inconsistent and illogical.

You're correct that you can find artifacts in the extreme cases, it's 
subjective whether this is a serious problem.
It's nice that these artifacts are gone, but that still doesn't explain 
why this ratio had to be increase that much from around 1:10 to 1:69.

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[James Bruce]

Ingo Molnar wrote:
> * Ingo Molnar <mingo@elte.hu> wrote:
>> * James Bruce <bruce@andrew.cmu.edu> wrote:
>>> While we're at it, isn't the comment above the wmult table incorrect? 
>>> The multiplier is 1.25, meaning a 25% change per nice level, not 10%.
>> yes, the weight multiplier 1.25, but the actual difference in CPU 
>> utilization, when running two CPU intense tasks, is ~10%:
>>
>>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>>  8246 mingo     20   0  1576  244  196 R   55  0.0   0:11.96 loop
>>  8247 mingo     21   1  1576  244  196 R   45  0.0   0:10.52 loop
>>
>> so the first task 'wins' +10% CPU utilization (relative to the 50% it 
>> had before), the second task 'loses' -10% CPU utilization (relative to 
>> the 50% it had before).
>>
>> so what the comment says is true:
>>
>>  * The "10% effect" is relative and cumulative: from _any_ nice level,
>>  * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
>>  * it's +10% CPU usage.
>>
>> for there to be a ~+10% change in CPU utilization for a task that 
>> races against another CPU-intense task there needs to be a ~25% change 
>> in the weight.
> 
> in any case more documentation is justified, so i've added some 
> clarification to the comments - see the patch below.

Ah ok so it's 10% of the original CPU usage, not relative to a tasks
share from before.  While I guess I still think in terms of relative CPU
share, your comments now make sense to me.  Thanks for the
clarification.

  - Jim

> ------------------------>
> Subject: sched: improve weight-array comments
> From: Ingo Molnar <mingo@elte.hu>
> 
> improve the comments around the wmult array (which controls the weight
> of niced tasks). Clarify that to achieve a 10% difference in CPU
> utilization, a weight multiplier of 1.25 has to be used.
> 
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
> ---
>  kernel/sched.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> Index: linux/kernel/sched.c
> ===================================================================
> --- linux.orig/kernel/sched.c
> +++ linux/kernel/sched.c
> @@ -736,7 +736,9 @@ static void update_curr_load(struct rq *
>   *
>   * The "10% effect" is relative and cumulative: from _any_ nice level,
>   * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
> - * it's +10% CPU usage.
> + * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
> + * If a task goes up by ~10% and another task goes down by ~10% then
> + * the relative distance between them is ~25%.)
>   */
>  static const int prio_to_weight[40] = {
>  /* -20 */ 88818, 71054, 56843, 45475, 36380, 29104, 23283, 18626, 14901, 11921,

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Linus Torvalds]

On Mon, 16 Jul 2007, Roman Zippel wrote:
>
> To illustrate the problem a little different: a task with a nice level -20 
> got around 700% more cpu time (or 8 times more), now it gets 8500% more 
> cpu time (or 86.7 times more).

Ingo, that _does_ sound excessive. 

How about trying a much less aggressive nice-level (and preferably linear, 
not exponential)?

		Linus

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Mon, 16 Jul 2007, Linus Torvalds wrote:

> How about trying a much less aggressive nice-level (and preferably linear, 
> not exponential)?

I think the exponential increase isn't the problem. The old code did 
approximate something like this rather crudely with the result that there 
was a big gap between level 0 and -1.

Something like this:

echo 'for (i=-20;i<=20;i++) print i, " : ", 1024*e(l(2)*(-i/20*3)), "\n";' | bc -l

would produce a range similiar to the old code. Replacing the factor 3 
with 4 would be IMO a more reasonable increase and had the advantage for 
the user that it's easier to understand that every 5 levels the time a 
process gets is doubled.

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Matt Mackall]

On Mon, Jul 16, 2007 at 04:01:17PM +0200, Roman Zippel wrote:
> Hi,
> 
> On Mon, 16 Jul 2007, Ingo Molnar wrote:
> 
> > to sum it up: a nice +19 task (the most commonly used nice level in 
> > practice) gets 9.1%, 3.9%, 3.1% of CPU time on the old scheduler, 
> > depending on the value of HZ. This is quite inconsistent and illogical.
> 
> You're correct that you can find artifacts in the extreme cases, it's 
> subjective whether this is a serious problem.
> It's nice that these artifacts are gone, but that still doesn't explain 
> why this ratio had to be increase that much from around 1:10 to 1:69.

More dynamic range is better? If you actually want a task to get 20x
the CPU time of another, the older scheduler doesn't really allow it.

Getting 1/69th of a modern CPU is still a fair number of cycles.
Nevermind 1/69th of a machine with > 64 cores.

-- 
Mathematics is the supreme nostalgia of our time.

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Ingo Molnar]

* Matt Mackall <mpm@selenic.com> wrote:

> More dynamic range is better? If you actually want a task to get 20x 
> the CPU time of another, the older scheduler doesn't really allow it.
> 
> Getting 1/69th of a modern CPU is still a fair number of cycles. 
> Nevermind 1/69th of a machine with > 64 cores.

yeah. furthermore, nice -20 is only admin-selectable.

Here are the current CPU-use values for positive nice levels:

 nice  0: 100.00%
 nice  1: 80.00%
 nice  2: 64.10%
 nice  3: 51.28%
 nice  4: 40.98%
 nice  5: 32.78%
 nice  6: 26.24%
 nice  7: 21.00%
 nice  8: 16.77%
 nice  9: 13.42%
 nice 10: 10.74%
 nice 11: 8.59%
 nice 12: 6.87%
 nice 13: 5.50%
 nice 14: 4.39%
 nice 15: 3.51%
 nice 16: 2.81%
 nice 17: 2.25%
 nice 18: 1.80%
 nice 19: 1.44%

here's the CPU utilization table for negative nice levels (relative to a 
nice -20 task):

 nice  0: 1.15%
 nice -1: 1.44%
 nice -2: 1.80%
 nice -3: 2.25%
 nice -4: 2.81%
 nice -5: 3.51%
 nice -6: 4.39%
 nice -7: 5.50%
 nice -8: 6.87%
 nice -9: 8.59%
 nice -10: 10.74%
 nice -11: 13.42%
 nice -12: 16.77%
 nice -13: 21.00%
 nice -14: 26.24%
 nice -15: 32.78%
 nice -16: 40.98%
 nice -17: 51.28%
 nice -18: 64.10%
 nice -19: 80.00%
 nice -20: 100.00%

these are pretty sane, and symmetric across the origo. Nice -20 is the 
odd one out, because there is no nice +20. But its value is still 
logical, it's the mirror image of an imaginery nice +20.

and note that even on the old scheduler, nice-0 was "3200% more 
powerful" than nice +19 (with CONFIG_HZ=300), and nice -19 was only 700% 
more powerful than nice-0. So not only was it inconsistent (and i can 
create scary numbers too ;), it gave the admin-controlled negative nice 
levels less of a punch than to user-controlled nice +19. A number of 
people complainted about that, and CFS addresses this.

in fact i like it that nice -20 has a slightly bigger punch than it used 
to have before: it might remove the need to run audio apps (and other 
multimedia apps) under SCHED_FIFO. (SCHED_FIFO is unprotected against 
lockups, while under CFS a nice 0 task is still starvation protected 
against a nice -20 task.)

furthermore, there is a quality of implementation issue as well, look at 
the definition of the nice system call:

   asmlinkage long sys_nice(int increment)

the "increment" is relative. So nice(1) has the same behavioral effect 
under CFS, regardless of which nice level you start out from. Under the 
old scheduler, the result depended on which nice level you started out 
from.

	Ingo

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Mon, 16 Jul 2007, Matt Mackall wrote:

> > It's nice that these artifacts are gone, but that still doesn't explain 
> > why this ratio had to be increase that much from around 1:10 to 1:69.
> 
> More dynamic range is better? If you actually want a task to get 20x
> the CPU time of another, the older scheduler doesn't really allow it.

You can already have that, the complete range level from 19 to -20 was 
about 1:80.
There is also something like too much range, I tried it with top at 19 and 
as soon as something runs at -20 it's practically dead, because it gets 
now only 1/5900 of cpu time.

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Mon, 16 Jul 2007, Ingo Molnar wrote:

> and note that even on the old scheduler, nice-0 was "3200% more 
> powerful" than nice +19 (with CONFIG_HZ=300),

How did you get that value? At any HZ the ratio should be around 1:10
(+- rounding error).

> in fact i like it that nice -20 has a slightly bigger punch than it used 
> to have before:

"Slightly bigger"??? You're joking, right?
Especially the user levels are doing something completely different now, 
which may break user expectation. While the user couldn't expect anything 
precise, it's still a big difference whether a process at nice 5 gets 75% 
of the time or only 30%.

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> Hi,
> 
> On Mon, 16 Jul 2007, Ingo Molnar wrote:
> 
> > and note that even on the old scheduler, nice-0 was "3200% more 
> > powerful" than nice +19 (with CONFIG_HZ=300),
> 
> How did you get that value? At any HZ the ratio should be around 1:10 
> (+- rounding error).

you are wrong again. I sent you the numbers earlier today already:

|   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
|  2332 mingo     25   0  1580  248  196 R 95.1  0.0   0:11.84 loop
|  2335 mingo     39  19  1576  244  196 R  3.1  0.0   0:00.39 loop

3.1% is 3067% more than 95.1%, and the ratio is 1:30.67. You again deny 
above that this is the case, and there's nothing i can do about your 
denial of facts - that is your own private problem.

	Ingo

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Tue, 17 Jul 2007, Ingo Molnar wrote:

> * Roman Zippel <zippel@linux-m68k.org> wrote:
> 
> > Hi,
> > 
> > On Mon, 16 Jul 2007, Ingo Molnar wrote:
> > 
> > > and note that even on the old scheduler, nice-0 was "3200% more 
> > > powerful" than nice +19 (with CONFIG_HZ=300),
> > 
> > How did you get that value? At any HZ the ratio should be around 1:10 
> > (+- rounding error).
> 
> you are wrong again. I sent you the numbers earlier today already:
> 
> |   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
> |  2332 mingo     25   0  1580  248  196 R 95.1  0.0   0:11.84 loop
> |  2335 mingo     39  19  1576  244  196 R  3.1  0.0   0:00.39 loop
> 
> 3.1% is 3067% more than 95.1%, and the ratio is 1:30.67. You again deny 
> above that this is the case, and there's nothing i can do about your 
> denial of facts - that is your own private problem.

Ingo, how am I supposed to react to this? I'm asking a simple question
and I get this? I'm at serious loss how to deal with you. :-(

Above is based on theoritical values, for a 300HZ kernel these two 
processes should get 30 and 3 ticks. Should there be any rounding error or 
off by one error so that the processes get one tick less than they should 
get or one tick is accounted to the wrong process, my theoritical value is 
still within the possible error range and doesn't contradict your
practical values.
Playing around with some other nice levels, confirms the theory that 
something is a little off, so I'm quite correct at saying that the ratio 
_should_ be 1:10.
OTOH you are the one who is wrong about me (again). :-(

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Tue, 17 Jul 2007, I wrote:

> Playing around with some other nice levels, confirms the theory that 
> something is a little off, so I'm quite correct at saying that the ratio 
> _should_ be 1:10.

Rechecking everything there was actually a small error in my test program, 
so the ratio should be at 1:20. Sorry about that mistake.
Nice level 19 shows the largest artifacts, as that level only gets a 
single tick, so the ratio is often 1:HZ/10 (except for 1000HZ where it's 
5:100). Nevertheless it's still true that in general nice levels were 
independent of HZ (that's all I wanted to say a couple of mails ago).

Ingo, you can start now gloating, but contrary to you I have no problems 
with admitting mistakes and apologizing for them. The point is just that 
I'm reacting better to factual arguments instead of flames (and I think 
it's not just me), so I'm pretty sure I'm still correct about this:

> OTOH you are the one who is wrong about me (again). :-(

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> > > It's nice that these artifacts are gone, but that still doesn't 
> > > explain why this ratio had to be increase that much from around 
> > > 1:10 to 1:69.
> > 
> > More dynamic range is better? If you actually want a task to get 20x 
> > the CPU time of another, the older scheduler doesn't really allow 
> > it.
> 
> You can already have that, the complete range level from 19 to -20 was 
> about 1:80.

But that is irrelevant: all tasks start out at nice 0, and what matters 
is the dynamic range around 0.

So the dynamic range has been made uniform in the positive from 
1:10...1:20...1:30 to 1:69 for nice +19, and from 1:8 to 1:69 in the 
minus. (with 1:86 nice -20) If you look at the negative nice levels 
alone it's a substantial increase but if you compare it with positive 
nice levels you'll similar kinds of dynamic ranges were already present 
in the old scheduler and you'll see why we've done it.

Negative nice levels are admin-controlled, the increase in the negative 
levels is is not a big issue and people actually like the increased 
dynamic range and the consistency. The positive range _might_ be a 
bigger issue but there we were largely inconsistent anyway, and again, 
people like the increased dynamic range.

	Ingo

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> Nice level 19 shows the largest artifacts, as that level only gets a 
> single tick, so the ratio is often 1:HZ/10 (except for 1000HZ where 
> it's 5:100). [...]

Roman, please do me a favor, and ask me the following question:

 " Ingo, you've been maintaining the scheduler for years. In fact you 
   wrote the old nice code we are talking about here. You changed it a
   number of times since then. So you really know what's going on here. 
   Why does the old nice code behave like that for nice +19 levels? "

I've been waiting for that obvious question, and i _might_ be able to 
answer it, but somehow it never occured to you ;-) Thanks,

	Ingo

unprivileged mounts (was: Re: -mm merge plans for 2.6.23)

[Andrew Morton]

On Tue, 10 Jul 2007 01:31:52 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:

> unprivileged-mounts-add-user-mounts-to-the-kernel.patch
> unprivileged-mounts-allow-unprivileged-umount.patch
> unprivileged-mounts-account-user-mounts.patch
> unprivileged-mounts-propagate-error-values-from-clone_mnt.patch
> unprivileged-mounts-allow-unprivileged-bind-mounts.patch
> unprivileged-mounts-put-declaration-of-put_filesystem-in-fsh.patch
> unprivileged-mounts-allow-unprivileged-mounts.patch
> unprivileged-mounts-allow-unprivileged-fuse-mounts.patch
> unprivileged-mounts-propagation-inherit-owner-from-parent.patch
> unprivileged-mounts-add-no-submounts-flag.patch
> 
>  Don't know.  Need to ping suitable developers over this work.

ping.

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Tue, 17 Jul 2007, Ingo Molnar wrote:

> Roman, please do me a favor, and ask me the following question:
> 
>  " Ingo, you've been maintaining the scheduler for years. In fact you 
>    wrote the old nice code we are talking about here. You changed it a
>    number of times since then. So you really know what's going on here. 
>    Why does the old nice code behave like that for nice +19 levels? "
> 
> I've been waiting for that obvious question, and i _might_ be able to 
> answer it, but somehow it never occured to you ;-) Thanks,

Do you have any idea how insulting and arrogant this is?
Let me translate for you, how this arrived:

"O Ingo, who art our god of the scheduler. You have blessed the paths I 
walked in. You kept me from sinning numerous times. Your wisdom is 
infinite. Guide me on the journey that layeth ahead of me into this world 
knowledge of Your truth."

(I apologize already in advance, if I should have hurt anyones religious 
feelings.)

It's obvious that you have more experience with the scheduler code, but 
does that make you unfailable? Does that give you the right to act like a 
jerk?
I do make mistakes, I try to learn from them and life goes on, I have no 
problem with that, but what I have a problem with is if someone is abusing 
this to his own advantage. I have to be extremely carful what I say to 
you, because you jump on the first small mistake and I have to bear your 
insults like "there's nothing i can do about your denial of facts - that 
is your own private problem." I have no problems with facts, I'm only 
trying very hard to ignore your arrogant behaviour...
If you have something to contribute to this discussion which might clear 
things up, then just say it, but I'm not going to beg for it.

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Tue, 17 Jul 2007, Ingo Molnar wrote:

> * Roman Zippel <zippel@linux-m68k.org> wrote:
> 
> > > > It's nice that these artifacts are gone, but that still doesn't 
> > > > explain why this ratio had to be increase that much from around 
> > > > 1:10 to 1:69.
> > > 
> > > More dynamic range is better? If you actually want a task to get 20x 
> > > the CPU time of another, the older scheduler doesn't really allow 
> > > it.
> > 
> > You can already have that, the complete range level from 19 to -20 was 
> > about 1:80.
> 
> But that is irrelevant: all tasks start out at nice 0, and what matters 
> is the dynamic range around 0.
> 
> So the dynamic range has been made uniform in the positive from 
> 1:10...1:20...1:30 to 1:69 for nice +19, and from 1:8 to 1:69 in the 
> minus. (with 1:86 nice -20) If you look at the negative nice levels 
> alone it's a substantial increase but if you compare it with positive 
> nice levels you'll similar kinds of dynamic ranges were already present 
> in the old scheduler and you'll see why we've done it.

So let's look at them:

for (i=0;i<20;i++) print i, " : ", (20-i)*5, " : ", 100*1.25^-i, " : ", e(l(2)*(-i/5))*100, "\n";
0 : 100 : 100 : 100.00000000000000000000
1 : 95 : 80.00000000000000000000 : 87.05505632961241391300
2 : 90 : 64.00000000000000000000 : 75.78582832551990411700
3 : 85 : 51.20000000000000000000 : 65.97539553864471296900
4 : 80 : 40.96000000000000000000 : 57.43491774985175034000
5 : 75 : 32.76800000000000000000 : 50.00000000000000000000
6 : 70 : 26.21440000000000000000 : 43.52752816480620695700
7 : 65 : 20.97152000000000000000 : 37.89291416275995205900
8 : 60 : 16.77721600000000000000 : 32.98769776932235648400
9 : 55 : 13.42177280000000000000 : 28.71745887492587517000
10 : 50 : 10.73741824000000000000 : 25.00000000000000000000
11 : 45 : 8.58993459200000000000 : 21.76376408240310347800
12 : 40 : 6.87194767360000000000 : 18.94645708137997602900
13 : 35 : 5.49755813888000000000 : 16.49384888466117824200
14 : 30 : 4.39804651110400000000 : 14.35872943746293758500
15 : 25 : 3.51843720888320000000 : 12.50000000000000000000
16 : 20 : 2.81474976710656000000 : 10.88188204120155173900
17 : 15 : 2.25179981368524800000 : 9.47322854068998801400
18 : 10 : 1.80143985094819840000 : 8.24692444233058912100
19 : 5 : 1.44115188075855872000 : 7.17936471873146879200

(nice level : old % : new % : my suggested %)

Your levels divert very quickly from what they used to be (upto a factor 
of 7), it's also not really easy to remember what the individual levels 
mean.
I at least try to keep them somewhat in the range they used to be (and 
the difference is limited to a factor of about 2), also every 5 levels the 
amount of cpu time is halved, which is very easy to remember.

If you need more dynamic range, is there a law that prevents us from going 
beyond 19? For example:

for (i=20;i<=30;i++) print i, " : ", (20-i)*5, " : ", 100*1.25^-i, " : ", e(l(2)*(-i/5))*100, "\n";
20 : 0 : 1.15292150460684697600 : 6.25000000000000000000
21 : -5 : .92233720368547758000 : 5.44094102060077586900
22 : -10 : .73786976294838206400 : 4.73661427034499400700
23 : -15 : .59029581035870565100 : 4.12346222116529456000
24 : -20 : .47223664828696452100 : 3.58968235936573439600
25 : -25 : .37778931862957161700 : 3.12500000000000000000
26 : -30 : .30223145490365729300 : 2.72047051030038793400
27 : -35 : .24178516392292583400 : 2.36830713517249700300
28 : -40 : .19342813113834066700 : 2.06173111058264728000
29 : -45 : .15474250491067253400 : 1.79484117968286719800
30 : -50 : .12379400392853802700 : 1.56250000000000000000

setpriority() accepts such values without error.

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Peter Zijlstra]

On Mon, 2007-07-16 at 10:47 -0700, Linus Torvalds wrote:
> 
> On Mon, 16 Jul 2007, Roman Zippel wrote:
> >
> > To illustrate the problem a little different: a task with a nice level -20 
> > got around 700% more cpu time (or 8 times more), now it gets 8500% more 
> > cpu time (or 86.7 times more).
> 
> Ingo, that _does_ sound excessive. 
> 
> How about trying a much less aggressive nice-level (and preferably linear, 
> not exponential)?

I actually like the extra range, it allows for a much softer punch of
background tasks even on somewhat slower boxen.

I've been testing CFS on my 1200 MHz lappy for some time and a strongly
niced kbuild leaves a very usable system. 

The old scheduler would leave the thing rather jumpy. And while CFS
fully fixes the jumpyness, I just did a nice +13 (which should be
equivalent to the old schedulers nice +19 for my HZ) and did a nice +19
kbuild and I can definitely feel the difference between them.

Early CFS versions had an pretty aggressive nice range (0.1% for +19),
and that has been toned down based on feedback. The current levels seem
to work well, at least on my boxen.

- Peter

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> On Tue, 17 Jul 2007, Ingo Molnar wrote:
> 
> > Roman, please do me a favor, and ask me the following question:
> > 
> >  " Ingo, you've been maintaining the scheduler for years. In fact you 
> >    wrote the old nice code we are talking about here. You changed it a
> >    number of times since then. So you really know what's going on here. 
> >    Why does the old nice code behave like that for nice +19 levels? "
> > 
> > I've been waiting for that obvious question, and i _might_ be able 
> > to answer it, but somehow it never occured to you ;-) Thanks,

[...]
> It's obvious that you have more experience with the scheduler code, 
> but does that make you unfailable? [...]

Roman, it is really not about 'experience', and yes, we all make 
frequent mistakes.

it's about the plain fact that i happened to write _both_ the old and 
the new code you were talking about all along. In this discussion about 
nice levels you were (very) agressively asserting things that were 
untrue, you were suggesting that i dont understand the code, instead of 
simply asking me why the code was written in such a way and what the 
motivation behind it was. I'd be glad to attempt to answer such a 
friendly question, if you are interested in asking it and if you are 
interested in my answer. Thanks,

	Ingo

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Wed, 18 Jul 2007, Ingo Molnar wrote:

> > > Roman, please do me a favor, and ask me the following question:
> > > 
> > >  [insult deleted]


> In this discussion about 
> nice levels you were (very) agressively asserting things that were 
> untrue,

Instead of simply asserting things, how about you provide some examples?
I made so far a single mistake of mixing up nice levels 18 and 19.
If you would point me to such examples, I could learn how to tone it down 
a little, since the nice levels are not the only issue I have with the new 
scheduler, the heavy stuff is still about to come. The problem here is 
there is too much burnt ground so I can't just present raw ideas, which 
get flamed by you, I have to be sufficiently confident they are valid, 
what you might then interpret as "agressive assertion".

> you were suggesting that i dont understand the code,

Again, please point me to examples, so I at least have a chance to clear 
things up, since it was never my intention to make such a suggestion, but 
this gives me no chance to defend myself.

OTOH I can tell you exactly how you continuously insult me, e.g. by 
suggesting I ask "stupid questions" or that I'm in "denial of facts".
Don't make such suggestions if you have no idea how insulting they are. 
Especially the one deleted insult above where you have the impertinence to 
quote it, such tone is more appropriate between lord and inferior, where 
the latter have to make a request and the former "might" grant it. 
_Never_ make me beg. :-(

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Wed, 18 Jul 2007, Peter Zijlstra wrote:

> I actually like the extra range, it allows for a much softer punch of
> background tasks even on somewhat slower boxen.

The extra range is not really a problem, in 

http://www.ussg.iu.edu/hypermail/linux/kernel/0707.2/0850.html

I suggested how we can have both.

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Peter Zijlstra]

On Wed, 2007-07-18 at 14:45 +0200, Roman Zippel wrote:
> Hi,
> 
> On Wed, 18 Jul 2007, Peter Zijlstra wrote:
> 
> > I actually like the extra range, it allows for a much softer punch of
> > background tasks even on somewhat slower boxen.
> 
> The extra range is not really a problem, in 
> 
> http://www.ussg.iu.edu/hypermail/linux/kernel/0707.2/0850.html
> 
> I suggested how we can have both.

By breaking the UNIX model of nice levels. Not an option in my book.

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Ingo Molnar]

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Wed, 2007-07-18 at 14:45 +0200, Roman Zippel wrote:
> > Hi,
> > 
> > On Wed, 18 Jul 2007, Peter Zijlstra wrote:
> > 
> > > I actually like the extra range, it allows for a much softer punch of
> > > background tasks even on somewhat slower boxen.
> > 
> > The extra range is not really a problem, in 
> > 
> > http://www.ussg.iu.edu/hypermail/linux/kernel/0707.2/0850.html
> > 
> > I suggested how we can have both.
> 
> By breaking the UNIX model of nice levels. Not an option in my book.

yeah, that's pretty much out of question.

	Ingo

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Wed, 18 Jul 2007, Peter Zijlstra wrote:

> By breaking the UNIX model of nice levels. Not an option in my book.

Breaking user expectations of nice levels is?

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Wed, 18 Jul 2007, Peter Zijlstra wrote:

> By breaking the UNIX model of nice levels. Not an option in my book.

BTW what is the "UNIX model of nice levels"?

SUS specifies the limit via NZERO, which is defined as "Minimum Acceptable 
Value: 20", I can't find any information that it must be 20.

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Peter Zijlstra]

On Wed, 2007-07-18 at 15:07 +0200, Roman Zippel wrote:
> Hi,
> 
> On Wed, 18 Jul 2007, Peter Zijlstra wrote:
> 
> > By breaking the UNIX model of nice levels. Not an option in my book.
> 
> Breaking user expectations of nice levels is?

http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap03.html

specifically:

"3.239 Nice Value

  A number used as advice to the system to alter process scheduling.
  Numerically smaller values give a process additional preference when
  scheduling a process to run. Numerically larger values reduce the
  preference and make a process less likely to run. Typically, a process
  with a smaller nice value runs to completion more quickly than an
  equivalent process with a higher nice value. The symbol {NZERO}
  specifies the default nice value of the system."


The only expectation is that a process with a lower nice level gets more
time. Any other expectation is a bug.

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Peter Zijlstra]

On Wed, 2007-07-18 at 15:26 +0200, Roman Zippel wrote:
> Hi,
> 
> On Wed, 18 Jul 2007, Peter Zijlstra wrote:
> 
> > By breaking the UNIX model of nice levels. Not an option in my book.
> 
> BTW what is the "UNIX model of nice levels"?
> 
> SUS specifies the limit via NZERO, which is defined as "Minimum Acceptable 
> Value: 20", I can't find any information that it must be 20.

I have never encountered a UNIX where it is anything other than 20.
Convention (alas not specification) does dictate 20.

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> > By breaking the UNIX model of nice levels. Not an option in my book.
> 
> Breaking user expectations of nice levels is?

_changing_ it is an option within reason, and we've done it a couple of 
times already in the past, and even within CFS (as Peter correctly 
observed) we've been through a couple of iterations already. And as i 
mentioned it before, the outer edge of nice levels (+19, by far the most 
commonly used nice level) was inconsistent to begin with: 3%, 5%, 9% of 
nice-0, depending on HZ. So changing that to a consistent (and 
user-requested) 1.5% is a much smaller change than you seem to make it 
out to be. CFS itself is a far larger "change of expectations" than this 
tweak to nice levels. So by your standard we could never change the 
scheduler. (which your ultimate argument might be after all =B-)

	Ingo

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Wed, 18 Jul 2007, Peter Zijlstra wrote:

> The only expectation is that a process with a lower nice level gets more
> time. Any other expectation is a bug.

Yes, users are buggy, they expect a lot of stupid things...
Is this really reason enough to break this?

What exactly is the damage if setpriority() accepts a few more levels?

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Wed, 18 Jul 2007, Ingo Molnar wrote:

> _changing_ it is an option within reason, and we've done it a couple of 
> times already in the past, and even within CFS (as Peter correctly 
> observed) we've been through a couple of iterations already. And as i 
> mentioned it before, the outer edge of nice levels (+19, by far the most 
> commonly used nice level) was inconsistent to begin with: 3%, 5%, 9% of 
> nice-0, depending on HZ.

Why do you constantly stress level 19? Yes, that one is special, all other 
positive levels were already relatively consistent.

> So changing that to a consistent (and 
> user-requested)

How old is CFS and how many users did it have so far? How many users has 
the old scheduler, which will be exposed to the new one soon?

> 1.5% is a much smaller change than you seem to make it 
> out to be.

The percentage levels are off by a factor of upto _seven_, sorry I fail 
see how you can characterize this as "small".

> So by your standard we could never change the 
> scheduler. (which your ultimate argument might be after all =B-)

Careful, you make assertion about me, for which you have absolutely no 
base, adding a smiley doesn't make this any funnier.

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> > _changing_ it is an option within reason, and we've done it a couple 
> > of times already in the past, and even within CFS (as Peter 
> > correctly observed) we've been through a couple of iterations 
> > already. And as i mentioned it before, the outer edge of nice levels 
> > (+19, by far the most commonly used nice level) was inconsistent to 
> > begin with: 3%, 5%, 9% of nice-0, depending on HZ.
> 
> Why do you constantly stress level 19? Yes, that one is special, all 
> other positive levels were already relatively consistent.

i constantly stress it for the reason i mentioned a good number of 
times: because it's by far the most commonly used (and complained about) 
nice level. =B-)

but because you are asking, i'm glad to give you some first-hand 
historic background about Linux nice levels (in case you are interested) 
and the motivations behind their old and new implementations:

nice levels were always so weak under Linux (just read Peter's report) 
that people continuously bugged me about making nice +19 tasks use up 
much less CPU time. Unfortunately that was not that easy to implement 
(otherwise we'd have done it long ago) because nice level support was 
historically coupled to timeslice length, and timeslice units were 
driven by the HZ tick, so the smallest timeslice was 1/HZ.

In the O(1) scheduler (about 4 years ago) i changed negative nice levels 
to be much stronger than they were before in 2.4 (and people were happy 
about that change), and i also intentionally calibrated the linear 
timeslice rule so that nice +19 level would be _exactly_ 1 jiffy. To 
better understand it, the timeslice graph went like this (cheesy ASCII 
art alert!):


                   A
             \     | [timeslice length]
              \    |
               \   |
                \  |
                 \ |
                  \|___100msecs
                   |^ . _
                   |      ^ . _
                   |            ^ . _
 -*----------------------------------*-----> [nice level]
 -20               |                +19
                   |
                   |

so that if someone wants to really renice tasks, +19 would give a much 
bigger hit than the normal linear rule would do. (The solution of 
changing the ABI to extend priorities was discarded early on.)

This approach worked to some degree for some time, but later on with 
HZ=1000 it caused 1 jiffy to be 1 msec, which meant 0.1% CPU usage which 
we felt to be a bit excessive. Excessive _not_ because it's too small of 
a CPU utilization, but because it causes too frequent (once per 
millisec) rescheduling. (and would thus trash the cache, etc. Remember, 
this was 4-5 years ago when hardware was weaker and caches were smaller, 
and people were running number crunching apps at nice +19.)

So for HZ=1000 i changed nice +19 to 5msecs, because that felt like the 
right minimal granularity - and this translates to 5% CPU utilization. 
But the fundamental HZ-sensitive property for nice+19 still remained, 
and i never got a single complaint about nice +19 being too _weak_ in 
terms of CPU utilization, i only got complaints about it (still) being 
way too _strong_.

To sum it up: i always wanted to make nice levels more consistent, but 
within the constraints of HZ and jiffies and their nasty design level 
coupling to timeslices and granularity it was not really viable.

The second (less frequent but still periodically occuring) complaint 
about Linux's nice level support was its assymetry around the origo 
(which you can see demonstrated in the picture above), or more 
accurately: the fact that nice level behavior depended on the _absolute_ 
nice level as well, while the nice API itself is fundamentally 
"relative":

   int nice(int inc);

   asmlinkage long sys_nice(int increment)

(the first one is the glibc API, the second one is the syscall API.) 
Note that the 'inc' is relative to the current nice level. Tools like 
bash's "nice" command mirror this relative API.

With the old scheduler, if you for example started a niced task with +1 
and another task with +2, the CPU split between the two tasks would 
depend on the nice level of the parent shell - if it was at nice -10 the 
CPU split was different than if it was at +5 or +10.

A third complaint against Linux's nice level support was that negative 
nice levels were not 'punchy enough', so lots of people had to resort to 
run audio (and other multimedia) apps under RT priorities such as 
SCHED_FIFO. But this caused other problems: SCHED_FIFO is not starvation 
proof, and a buggy SCHED_FIFO app can also lock up the system for good.

CFS addresses all three types of complaints:

To address the first complaint (of nice levels being not "punchy" 
enough), i decoupled the scheduler from 'time slice' and HZ concepts 
(and made granularity a separate concept from nice levels) and thus CFS 
was able to implement better and more consistent nice +19 support: now 
in CFS nice +19 tasks get a HZ-independent 1.5%, instead of the variable 
3%-5%-9% range they got in the old scheduler.

To address the second complaint (of nice levels not being consistent), i 
made nice(1) have the same CPU utilization effect on tasks, regardless 
of their absolute nice levels. So on CFS, running a nice +10 and a nice 
+11 task has the same CPU utilization "split" between them as running a 
nice -5 and a nice -4 task. (one will get 55% of the CPU, the other 
45%.) That is why I changed nice levels to be "multiplicative" (or 
exponential) - that way it does not matter which nice level you start 
out from, the 'relative result' will always be the same.

The third complaint (of negative nice levels not being "punchy" enough 
and forcing audio apps to run under the more dangerous SCHED_FIFO 
scheduling policy) is addressed by CFS almost automatically: stronger 
negative nice levels are an automatic side-effect of the recalibrated 
dynamic range of nice levels.

Hope this helps,

	Ingo

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> Don't make such suggestions if you have no idea how insulting they 
> are. Especially the one deleted insult above where you have the 
> impertinence to quote it, such tone is more appropriate between lord 
> and inferior, where the latter have to make a request and the former 
> "might" grant it. [...]

uhm, [and the uninterested reader might want to skip to the next mail 
;-)], i'm really confused about your reply. Do you really mean this:

> > Roman, please do me a favor, and ask me the following question:
> >
> >  " Ingo, you've been maintaining the scheduler for years. In fact you
> >    wrote the old nice code we are talking about here. You changed it a
> >    number of times since then. So you really know what's going on here.
> >    Why does the old nice code behave like that for nice +19 levels? "
> >
> > I've been waiting for that obvious question, and i _might_ be able
> > to answer it, but somehow it never occured to you ;-) Thanks,

the ";-)" emoticon (and its contents) clearly signals this as a 
sarcastic, tongue-in-cheek remark. To make it even clearer, please 
re-read it with the <sarcastic> tag added as well for clarity:

> > <sarcastic>
> >
> > Roman, please do me a favor, and ask me the following question:
> >
> >  " Ingo, you've been maintaining the scheduler for years. In fact you
> >    wrote the old nice code we are talking about here. You changed it a
> >    number of times since then. So you really know what's going on here.
> >    Why does the old nice code behave like that for nice +19 levels? "
> >
> > I've been waiting for that obvious question, and i _might_ be able
> > to answer it, but somehow it never occured to you ;-) Thanks,
> >
> > </sarcastic>

ok? (If you didnt see/read it as sarcastic straight away then my 
apologies for insulting you!)

The "_might_ be able to answer" bit is of course sarcastic too, and 
contrary to your (i have to say, pretty absurd) suggestion i did not 
suggest that i "might be _willing_ to answer" - which would be quite 
arrogant indeed and which i never said or suggested. To make it even 
clearer: i'm definitely able to answer questions about code i wrote 
originally and which i just changed, were you to show genuine interest 
in hearing my opinion :-)

	Ingo

Re: [PATCH] Use menuconfig objects - CONFIG_ISDN_I4L [v2]

[Jan Engelhardt]

>Remove a menu statement and several dependencies from the Kconfig files in
>the drivers/isdn tree as they have become unnecessary by the transformation
>of CONFIG_ISDN from "menu, config" into "menuconfig".
>(Modified version of a patch originally proposed by Jan Engelhardt.)
>
>Signed-off-by: Tilman Schmidt <tilman@imap.cc>
>---
>
>This is my alternative proposal for
>use-menuconfig-objects-isdn-config_isdn_i4l.patch (patch 2 of 6 in Jan's
>"Use menuconfig objects 4 - ISDN" series). It must go between patch 1 and
>3 of that series because they touch some of the same files.

This looks good to me. (Applies on top of today's git.)


Thanks,
	Jan
-- 

Re: [more PATCHes] Use menuconfig objects - CONFIG_ISDN_I4L

[Jan Engelhardt]

Hi,


here are two more changes I propose for the isdn submenu(s).
They go on top of Tilman's patch; each of the two following patches is 
independent of another.
Opinions please :)


	Jan
-- 

[patch 1/2] Use menuconfig objects - ISDN

[Jan Engelhardt]

Unclutter the ISDN menu a tiny bit by moving ISDN4Linux and the CAPI2.0
layers into their own menu.

Signed-off-by: Jan Engelhardt <jengelh@gmx.de>

---
 drivers/isdn/Kconfig |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux-2.6.23/drivers/isdn/Kconfig
===================================================================
--- linux-2.6.23.orig/drivers/isdn/Kconfig
+++ linux-2.6.23/drivers/isdn/Kconfig
@@ -21,7 +21,7 @@ menuconfig ISDN
 
 if ISDN
 
-config ISDN_I4L
+menuconfig ISDN_I4L
 	tristate "Old ISDN4Linux (deprecated)"
 	---help---
 	  This driver allows you to use an ISDN adapter for networking
@@ -43,7 +43,7 @@ if ISDN_I4L
 source "drivers/isdn/i4l/Kconfig"
 endif
 
-config ISDN_CAPI
+menuconfig ISDN_CAPI
 	tristate "CAPI 2.0 subsystem"
 	help
 	  This provides the CAPI (Common ISDN Application Programming

[patch 2/2] Use menuconfig objects - ISDN/Gigaset

[Jan Engelhardt]

Change Kconfig objects from "menu, config" into "menuconfig" so
that the user can disable the whole feature without having to
enter the menu first.

Signed-off-by: Jan Engelhardt <jengelh@gmx.de>

---
 drivers/isdn/gigaset/Kconfig |    8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

Index: linux-2.6.23/drivers/isdn/gigaset/Kconfig
===================================================================
--- linux-2.6.23.orig/drivers/isdn/gigaset/Kconfig
+++ linux-2.6.23/drivers/isdn/gigaset/Kconfig
@@ -1,6 +1,4 @@
-menu "Siemens Gigaset"
-
-config ISDN_DRV_GIGASET
+menuconfig ISDN_DRV_GIGASET
 	tristate "Siemens Gigaset support (isdn)"
 	select CRC_CCITT
 	select BITREVERSE
@@ -53,6 +51,4 @@ config GIGASET_UNDOCREQ
 	  features like configuration mode of M105, say yes. If you
 	  care about your device, say no.
 
-endif
-
-endmenu
+endif # ISDN_DRV_GIGASET != n

Re: lguest, Re: -mm merge plans for 2.6.23

[Christoph Hellwig]

On Thu, Jul 12, 2007 at 02:52:23PM +1000, Rusty Russell wrote:
> This is solely for the wakeup: you don't wake an mm 8)
> 
> The mm reference is held as well under the big lguest_mutex (mm gets
> destroyed before files get closed, so we definitely do need to hold a
> reference).
> 
> I just completed benchmarking: the cached wakeup with the current naive
> drivers makes no difference (at one stage I was playing with batched
> hypercalls, where it seemed to help).
> 
> Thanks Christoph, DaveM!

The version that just got into mainline still has the __put_task_struct
export despite not needing it anymore.  Care to fix this up?

Re: lguest, Re: -mm merge plans for 2.6.23

[Rusty Russell]

On Thu, 2007-07-19 at 19:27 +0200, Christoph Hellwig wrote:
> The version that just got into mainline still has the __put_task_struct
> export despite not needing it anymore.  Care to fix this up?

No, it got patched in then immediately patched out again.  Andrew
mis-mixed my patches, but there have been so many of them I find it hard
to blame him.

Rusty.

Re: lguest, Re: -mm merge plans for 2.6.23

[Christoph Hellwig]

On Fri, Jul 20, 2007 at 01:27:26PM +1000, Rusty Russell wrote:
> On Thu, 2007-07-19 at 19:27 +0200, Christoph Hellwig wrote:
> > The version that just got into mainline still has the __put_task_struct
> > export despite not needing it anymore.  Care to fix this up?
> 
> No, it got patched in then immediately patched out again.  Andrew
> mis-mixed my patches, but there have been so many of them I find it hard
> to blame him.

Indeed, the export is gone in last mainline gone.

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Wed, 18 Jul 2007, Ingo Molnar wrote:

> > > [more rude insults deleted]
> > > I've been waiting for that obvious question, and i _might_ be able
> > > to answer it, but somehow it never occured to you ;-) Thanks,
> 
> the ";-)" emoticon (and its contents) clearly signals this as a 
> sarcastic, tongue-in-cheek remark.

To take another example why is this still insulting and inappropriate, 
this is a behaviour I would characterize as school bullying:
A bully attacks someone obviously weaker than himself and for example 
takes something away and than continues like "If you ask nicely I'll give 
it back to you.", this often accompied by laughter to signal he's enjoying 
himself and the power he has, but for the other person it's everything but 
funny.

Maybe you don't know what it feels like, but I do and I can't find 
anything funny, sarcastic or whatever about this, no matter how many 
smileys or other tags you add there. If the communication is already that 
troubled as this, such "humor" is really the worst thing you can do and I 
find it rather sad that you can't realize this yourself.

> ok? (If you didnt see/read it as sarcastic straight away then my 
> apologies for insulting you!)

Sorry, that is too little too late. You've apologized before and you 
continued to make fun of me personally to the point of spreading wrong 
information about me, which you could have very easily verified yourself, 
if you only wanted.
What I want from you is that you treat me with respect and to keep your 
"sarcasm" to yourself.

I told you very clearly how I think about you requoting this crap and yet 
you repeat it again _twice_, so on the one hand I get this apology attempt 
and on the other hand you continue to kick me in the crotch? How do you 
think am I supposed to feel about this?

It's also always interesting what you don't respond to. I asked you for 
examples which would prove the (rather strong) assertions you made about 
me, what does it tell me now if you can't back up your statements?

bye, Roman

Re: [PATCH] CFS: Fix missing digit off in wmult table

[Roman Zippel]

Hi,

On Wed, 18 Jul 2007, Ingo Molnar wrote:

> > Why do you constantly stress level 19? Yes, that one is special, all 
> > other positive levels were already relatively consistent.
> 
> i constantly stress it for the reason i mentioned a good number of 
> times: because it's by far the most commonly used (and complained about) 
> nice level. =B-)

How do you know that? Most complained about makes most commonly used?

> but because you are asking, i'm glad to give you some first-hand 
> historic background about Linux nice levels (in case you are interested) 
> and the motivations behind their old and new implementations:

I guess I should be thankful now?
I'm curious why you post this now, after I "asked" about this. Most of the 
information is either rather generic or not specific enough for the 
problem at hand. If you had posted this information earlier, it had been 
far more valueable as it could have been a nice base for a discussion.
But posting it this late I can't lose the feeling you're more interested 
in "teaching" me.

> nice levels were always so weak under Linux (just read Peter's report) 

-ENOLINK

> Hope this helps,

Not completely.

For negative nice levels you mentioned audio apps, but these aren't really 
interested in a fair share, they would use the higher percentage only to 
guarantee they get the amount of time they need independent of the 
current load. I think they would be better served with e.g. a deadline 
scheduler, which guarantees them an absolute time share not a relative 
one.
On the other end with positive levels I more remember requests for 
something closer to idle scheduling, where a process only runs when 
nothing else is running.

So assuming we had scheduling classes for the above use cases, what other 
reasons are left for such extreme nice levels?

My proposed nice levels have otherwise the same properties as yours (e.g. 
being consistent). There is one propery you haven't commented on at all 
yet. My proposed levels give the average use a far better idea what they 
actually mean, i.e. that every 5 levels the process gets double/halve the 
cpu time. This is IMO a considerable advantage.

bye, Roman

Re: [more PATCHes] Use menuconfig objects - CONFIG_ISDN_I4L

[Tilman Schmidt]

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Hi,

sorry for the late reply.
On 18.07.2007 20:22 Jan Engelhardt wrote:
> here are two more changes I propose for the isdn submenu(s).
> They go on top of Tilman's patch; each of the two following patches is 
> independent of another.
> Opinions please :)

These are fine by me.

Thanks
Tilman

-- 
Tilman Schmidt                          E-Mail: tilman@imap.cc
Bonn, Germany
Diese Nachricht besteht zu 100% aus wiederverwerteten Bits.
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Re: -mm merge plans for 2.6.23

[Jesper Juhl]

On 10/07/07, Con Kolivas <kernel@kolivas.org> wrote:
> On Tuesday 10 July 2007 18:31, Andrew Morton wrote:
> > When replying, please rewrite the subject suitably and try to Cc: the
> > appropriate developer(s).
>
> ~swap prefetch
>
> Nick's only remaining issue which I could remotely identify was to make it
> cpuset aware:
> http://marc.info/?l=linux-mm&m=117875557014098&w=2
> as discussed with Paul Jackson it was cpuset aware:
> http://marc.info/?l=linux-mm&m=117895463120843&w=2
>
> I fixed all bugs I could find and improved it as much as I could last kernel
> cycle.
>
> Put me and the users out of our misery and merge it now or delete it forever
> please. And if the meaningless handwaving that I 100% expect as a response
> begins again, then that's fine. I'll take that as a no and you can dump it.
>
For what it's worth; put me down as supporting the merger of swap
prefetch. I've found it useful in the past, Con has maintained it
nicely and cleaned up everything that people have pointed out - it's
mature, does no harm - let's just get it merged.  It's too late for
2.6.23-rc1 now, but let's try and get this in by -rc2 - it's long
overdue...

-- 
Jesper Juhl <jesper.juhl@gmail.com>
Don't top-post  http://www.catb.org/~esr/jargon/html/T/top-post.html
Plain text mails only, please      http://www.expita.com/nomime.html

Re: -mm merge plans for 2.6.23

[Con Kolivas]

On Tuesday 10 July 2007 20:15, Con Kolivas wrote:
> On Tuesday 10 July 2007 18:31, Andrew Morton wrote:
> > When replying, please rewrite the subject suitably and try to Cc: the
> > appropriate developer(s).
>
> ~swap prefetch
>
> Nick's only remaining issue which I could remotely identify was to make it
> cpuset aware:
> http://marc.info/?l=linux-mm&m=117875557014098&w=2
> as discussed with Paul Jackson it was cpuset aware:
> http://marc.info/?l=linux-mm&m=117895463120843&w=2
>
> I fixed all bugs I could find and improved it as much as I could last
> kernel cycle.
>
> Put me and the users out of our misery and merge it now or delete it
> forever please. And if the meaningless handwaving that I 100% expect as a
> response begins again, then that's fine. I'll take that as a no and you can
> dump it.

The window for 2.6.23 has now closed and your position on this is clear. I've 
been supporting this code in -mm for 21 months since 16-Oct-2005 without any 
obvious decision for this code forwards or backwards.

I am no longer part of your operating system's kernel's world; thus I cannot 
support this code any longer. Unless someone takes over the code base for 
swap prefetch you have to assume it is now unmaintained and should delete it.

Please respect my request to not be contacted further regarding this or any 
other kernel code.

-- 
-ck

Re: -mm merge plans for 2.6.23

[Nick Piggin]

Jesper Juhl wrote:
> On 10/07/07, Con Kolivas <kernel@kolivas.org> wrote:
> 
>> On Tuesday 10 July 2007 18:31, Andrew Morton wrote:
>> > When replying, please rewrite the subject suitably and try to Cc: the
>> > appropriate developer(s).
>>
>> ~swap prefetch
>>
>> Nick's only remaining issue which I could remotely identify was to 
>> make it
>> cpuset aware:
>> http://marc.info/?l=linux-mm&m=117875557014098&w=2
>> as discussed with Paul Jackson it was cpuset aware:
>> http://marc.info/?l=linux-mm&m=117895463120843&w=2
>>
>> I fixed all bugs I could find and improved it as much as I could last 
>> kernel
>> cycle.
>>
>> Put me and the users out of our misery and merge it now or delete it 
>> forever
>> please. And if the meaningless handwaving that I 100% expect as a 
>> response
>> begins again, then that's fine. I'll take that as a no and you can 
>> dump it.
>>
> For what it's worth; put me down as supporting the merger of swap
> prefetch. I've found it useful in the past, Con has maintained it
> nicely and cleaned up everything that people have pointed out - it's
> mature, does no harm - let's just get it merged.  It's too late for
> 2.6.23-rc1 now, but let's try and get this in by -rc2 - it's long
> overdue...


Not talking about swap prefetch itself, but everytime I have asked
anyone to instrument or produce some workload where swap prefetch
helps, they never do.

Fair enough if swap prefetch helps them, but I also want to look at
why that is the case and try to improve page reclaim in some of
these situations (for example standard overnight cron jobs shouldn't
need swap prefetch on a 1 or 2GB system, I would hope).

Anyway, back to swap prefetch, I don't know why I've been singled out
as the bad guy here. I'm one of the only people who has had a look at
the damn thing and tried to point out areas where it could be improved
to the point of being included, and outlining things that are needed
for it to be merged (ie. numbers). If anyone thinks that makes me the
bad guy then they have an utterly inverted understanding of what peer
review is for.

Finally, everyone who has ever hacked on these heuristicy parts of the
VM has heaps of patches that help some workload or some silly test
case or (real or percieved) shortfall but have not been merged. It
really isn't anything personal.

If something really works, then it should be possible to get real
numbers in real situations where it helps (OK, swap prefetching won't
be as easy as a straight line performance improvement, but still much
easier than trying to measure something like scheduler interactivity).

Numbers are the best way to add weight to the pro-merge argument, so
for all the people who a whining about merging this and don't want
to actually work on the code -- post some numbers for where it helps
you!!

-- 
SUSE Labs, Novell Inc.

Re: -mm merge plans for 2.6.23

[Ray Lee]

On 7/23/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> Not talking about swap prefetch itself, but everytime I have asked
> anyone to instrument or produce some workload where swap prefetch
> helps, they never do.
[...]
> so for all the people who a whining about merging this and don't want
> to actually work on the code -- post some numbers for where it helps
> you!!

<Raised eyebrow> You sound frustrated. Perhaps we could be
communicating better. I'll start.

Unlike others on the cc: line, I don't get paid to hack on the kernel,
not even indirectly. So if you find that my lack of providing numbers
is giving you heartache, I can only apologize and point at my paying
work that requires my attention.

That said, I'm willing to run my day to day life through both a swap
prefetch kernel and a normal one. *However*, before I go through all
the work of instrumenting the damn thing, I'd really like Andrew (or
Linus) to lay out his acceptance criteria on the feature. Exactly what
*should* I be paying attention to? I've suggested keeping track of
process swapin delay total time, and comparing with and without. Is
that reasonable? Is it incomplete?

Without Andrew's criteria, we're back to where we've been for a long
time: lots of work, no forward motion. Perhaps it's a character flaw
of mine, but I'd really like to know what would constitute proof here
before I invest the effort. Especially given that Con has already
written a test case that shows that swap prefetch works, and that I've
given you a clear argument for why better (or even perfect) page
reclaim can't provide full coverage to all the situations that swap
prefetch helps. (Also, it's not like I've got tons free time, y'know?
Just like all the rest of you all, I have to pick and choose my
battles if I'm going to be effective.)

Since this merge period has appeared particularly frazzling for
Andrew, I've been keeping silent and waiting for him to get to a point
where there's a breather. I didn't feel it would be polite to request
yet more work out of him while he had a mess on his hands.

But, given this has come to a head, I'm asking now.

Andrew? You've always given the impression that you want this run more
as an engineering effort than an artistic endeavour, so help us out
here. What are your concerns with swap prefetch? What sort of
comparative data would you like to see to justify its inclusion, or to
prove that it's not needed?

Or are we reading too much into the fact that it isn't merged? In
short, communicate please, it will help.

Re: -mm merge plans for 2.6.23

[Jeremy Fitzhardinge]

Ray Lee wrote:
> That said, I'm willing to run my day to day life through both a swap
> prefetch kernel and a normal one. *However*, before I go through all
> the work of instrumenting the damn thing, I'd really like Andrew (or
> Linus) to lay out his acceptance criteria on the feature. Exactly what
> *should* I be paying attention to? I've suggested keeping track of
> process swapin delay total time, and comparing with and without. Is
> that reasonable? Is it incomplete?

Um, isn't it up to you?  The questions that need to be answered are:

   1. What are you trying to achieve?  Presumably you have some intended
      or desired effect you're trying to get.  What's the intended
      audience?  Who would be expected to see a benefit?  Who suffers?
   2. How does the code achieve that end?  Is it nasty or nice?  Has
      everyone who's interested in the affected areas at least looked at
      the changes, or ideally given them a good review?  Does it need
      lots of tunables, or is it set-and-forget?
   3. Does it achieve the intended end?  Numbers are helpful here.
   4. Does it make anything worse?  A lot or a little?  Rare corner
      cases, or a real world usage?  Again, numbers make the case most
      strongly.


I can't say I've been following this particular feature very closely,
but these are the fundamental questions that need to be dealt with in
merging any significant change.  And as Nick says, historically point 4
is very important in VM tuning changes, because "obvious" improvements
have often ended up giving pathologically bad results on unexpected
workloads.

    J

Re: -mm merge plans for 2.6.23

[Nick Piggin]

Ray Lee wrote:
> On 7/23/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> That said, I'm willing to run my day to day life through both a swap
> prefetch kernel and a normal one. *However*, before I go through all
> the work of instrumenting the damn thing, I'd really like Andrew (or
> Linus) to lay out his acceptance criteria on the feature. Exactly what
> *should* I be paying attention to? I've suggested keeping track of
> process swapin delay total time, and comparing with and without. Is
> that reasonable? Is it incomplete?

I don't feel it is so useful without more context. For example, in
most situations where pages get pushed to swap, there will *also* be
useful file backed pages being thrown out. Swap prefetch might
improve the total swapin delay time very significantly but that may
be just a tiny portion of the real problem.

Also a random day at the desktop, it is quite a broad scope and
pretty well impossible to analyse. If we can first try looking at
some specific problems that are easily identified.

Looking at your past email, you have a 1GB desktop system and your
overnight updatedb run is causing stuff to get swapped out such that
swap prefetch makes it significantly better. This is really
intriguing to me, and I would hope we can start by making this
particular workload "not suck" without swap prefetch (and hopefully
make it even better than it currently is with swap prefetch because
we'll try not to evict useful file backed pages as well).

After that we can look at other problems that swap prefetch helps
with, or think of some ways to measure your "whole day" scenario.

So when/if you have time, I can cook up a list of things to monitor
and possibly a patch to add some instrumentation over this updatedb
run.

Anyway, I realise swap prefetching has some situations where it will
fundamentally outperform even the page replacement oracle. This is
why I haven't asked for it to be dropped: it isn't a bad idea at all.

However, if we can improve basic page reclaim where it is obviously
lacking, that is always preferable. eg: being a highly speculative
operation, swap prefetch is not great for power efficiency -- but we
still want laptop users to have a good experience as well, right?

-- 
SUSE Labs, Novell Inc.

Re: -mm merge plans for 2.6.23

[Ray Lee]

On 7/23/07, Jeremy Fitzhardinge <jeremy@goop.org> wrote:
> Ray Lee wrote:
> > That said, I'm willing to run my day to day life through both a swap
> > prefetch kernel and a normal one. *However*, before I go through all
> > the work of instrumenting the damn thing, I'd really like Andrew (or
> > Linus) to lay out his acceptance criteria on the feature. Exactly what
> > *should* I be paying attention to? I've suggested keeping track of
> > process swapin delay total time, and comparing with and without. Is
> > that reasonable? Is it incomplete?
>
> Um, isn't it up to you?

Huh? I'm not Linus or Andrew, with the power to merge a patch to the
2.6 kernel, so I think that the answer to that is a really clear 'No.'

> 4. Does it make anything worse?  A lot or a little?  Rare corner
> cases, or a real world usage?  Again, numbers make the case most
> strongly.
>
> I can't say I've been following this particular feature very closely,
> but these are the fundamental questions that need to be dealt with in
> merging any significant change.  And as Nick says, historically point 4
> is very important in VM tuning changes, because "obvious" improvements
> have often ended up giving pathologically bad results on unexpected
> workloads.

Dude. My whole question was *what* numbers. Please go back and read it
all again. Maybe I was unclear, but I really don't think so.

Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Mon, 23 Jul 2007 21:53:38 -0700 "Ray Lee" <ray-lk@madrabbit.org> wrote:

> 
> Since this merge period has appeared particularly frazzling for
> Andrew, I've been keeping silent and waiting for him to get to a point
> where there's a breather. I didn't feel it would be polite to request
> yet more work out of him while he had a mess on his hands.

Let it just be noted that Con is not the only one who has expended effort
on this patch.  It's been in -mm for nearly two years and it has meant
ongoing effort for me and, to a lesser extent, other MM developers to keep
it alive.

> But, given this has come to a head, I'm asking now.
> 
> Andrew? You've always given the impression that you want this run more
> as an engineering effort than an artistic endeavour, so help us out
> here. What are your concerns with swap prefetch? What sort of
> comparative data would you like to see to justify its inclusion, or to
> prove that it's not needed?

Critera are different for each patch, but it usually comes down to a
cost/benefit judgement.  Does the benefit of the patch exceed its
maintenance cost over the lifetime of the kernel (whatever that is).

In this case the answer to that has never been clear to me.  The (much
older) fs-aio patches were (are) in a similar situation.

The other consideration here is, as Nick points out, are the problems which
people see this patch solving for them solveable in other, better ways? 
IOW, is this patch fixing up preexisting deficiencies post-facto?

To attack the second question we could start out with bug reports: system A
with workload B produces result C.  I think result C is wrong for <reasons>
and would prefer to see result D.

> Or are we reading too much into the fact that it isn't merged? In
> short, communicate please, it will help.

Well.  The above, plus there's always a lot of stuff happening in MM land,
and I haven't seen much in the way of enthusiasm from the usual MM
developers.

Re: -mm merge plans for 2.6.23

[Ray Lee]

On 7/23/07, Andrew Morton <akpm@linux-foundation.org> wrote:
> Let it just be noted that Con is not the only one who has expended effort
> on this patch.  It's been in -mm for nearly two years and it has meant
> ongoing effort for me and, to a lesser extent, other MM developers to keep
> it alive.

<nods> Yes, keeping patches from crufting up and stepping on other
patches' toes is hard work; I did it for a bit, and it was one of the
more thankless tasks I've tried a hand at.

So, thanks.

> Critera are different for each patch, but it usually comes down to a
> cost/benefit judgement.  Does the benefit of the patch exceed its
> maintenance cost over the lifetime of the kernel (whatever that is).

Well, I suspect it's 'lifetime of the feature,' in this case as it's
no more user visible than the page replacement algorithm in the first
place.

> The other consideration here is, as Nick points out, are the problems which
> people see this patch solving for them solveable in other, better ways?
> IOW, is this patch fixing up preexisting deficiencies post-facto?

In some cases, it almost certainly is. It also has the troubling
aspect of mitigating future regressions without anyone terribly
noticing, due to it being able to paper over those hypothetical future
deficiencies when they're introduced.

> To attack the second question we could start out with bug reports: system A
> with workload B produces result C.  I think result C is wrong for <reasons>
> and would prefer to see result D.

I spend a lot of time each day watching my computer fault my
workingset back in when I switch contexts. I'd rather I didn't have to
do that. Unfortunately, that's a pretty subjective problem report. For
whatever it's worth, we have pretty subjective solution reports
pointing to swap prefetch as providing a fix for them.

My concern is that a subjective problem report may not be good enough.
So, what do I measure to make this an objective problem report? And if
I do that (and it shows a positive result), will that be good enough
to argue for inclusion?

Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Mon, 23 Jul 2007 23:01:41 -0700 "Ray Lee" <ray-lk@madrabbit.org> wrote:

> So, what do I measure to make this an objective problem report?

Ideal would be to find a reproducible-by-others testcase which does what you
believe to be the wrong thing.

> And if
> I do that (and it shows a positive result), will that be good enough
> to argue for inclusion?

That depends upon whether there are more suitable ways of fixing "the
wrong thing".

There may not be - it could well be that present behaviour
is correct for the testcase, but it leaves the system in the wrong
state for your large workload shift.  In that case, prefetching (ie:
restoring system state approximately to that which prevailed prior to
"testcase") might well be a suitable fix.

Re: -mm merge plans for 2.6.23

[Tilman Schmidt]

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Ray Lee schrieb:
> I spend a lot of time each day watching my computer fault my
> workingset back in when I switch contexts. I'd rather I didn't have to
> do that. Unfortunately, that's a pretty subjective problem report. For
> whatever it's worth, we have pretty subjective solution reports
> pointing to swap prefetch as providing a fix for them.

Add me.

> My concern is that a subjective problem report may not be good enough.

That's my impression too, seeing the insistence on numbers.

> So, what do I measure to make this an objective problem report?

That seems to be the crux of the matter: how to measure subjective
usability issues (aka user experience) when simple reports along the
lines of "A is much better than B for everyday work" are not enough.
The same problem already impaired the "fair scheduler" discussion.
It would really help to have a clear direction there.

-- 
Tilman Schmidt                    E-Mail: tilman@imap.cc
Bonn, Germany
Diese Nachricht besteht zu 100% aus wiederverwerteten Bits.
Ungeöffnet mindestens haltbar bis: (siehe Rückseite)


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Re: -mm merge plans for 2.6.23

[Ray Lee]

On 7/23/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> Ray Lee wrote:
> > That said, I'm willing to run my day to day life through both a swap
> > prefetch kernel and a normal one. *However*, before I go through all
> > the work of instrumenting the damn thing, I'd really like Andrew (or
> > Linus) to lay out his acceptance criteria on the feature. Exactly what
> > *should* I be paying attention to? I've suggested keeping track of
> > process swapin delay total time, and comparing with and without. Is
> > that reasonable? Is it incomplete?
>
> I don't feel it is so useful without more context. For example, in
> most situations where pages get pushed to swap, there will *also* be
> useful file backed pages being thrown out. Swap prefetch might
> improve the total swapin delay time very significantly but that may
> be just a tiny portion of the real problem.

Agreed, it's important to make sure we're not being penny-wise and
pound-foolish here.

> Also a random day at the desktop, it is quite a broad scope and
> pretty well impossible to analyse.

It is pretty broad, but that's also what swap prefetch is targetting.
As for hard to analyze, I'm not sure I agree. One can black-box test
this stuff with only a few controls. e.g., if I use the same apps each
day (mercurial, firefox, xorg, gcc), and the total I/O wait time
consistently goes down on a swap prefetch kernel (normalized by some
control statistic, such as application CPU time or total I/O, or
something), then that's a useful measurement.

> If we can first try looking at
> some specific problems that are easily identified.

Always easier, true. Let's start with "My mouse jerks around under
memory load." A Google Summer of Code student working on X.Org claims
that mlocking the mouse handling routines gives a smooth cursor under
load ([1]). It's surprising that the kernel would swap that out in the
first place.

[1] http://vignatti.wordpress.com/2007/07/06/xorg-input-thread-summary-or-something/

> Looking at your past email, you have a 1GB desktop system and your
> overnight updatedb run is causing stuff to get swapped out such that
> swap prefetch makes it significantly better. This is really
> intriguing to me, and I would hope we can start by making this
> particular workload "not suck" without swap prefetch (and hopefully
> make it even better than it currently is with swap prefetch because
> we'll try not to evict useful file backed pages as well).

updatedb is an annoying case, because one would hope that there would
be a better way to deal with that highly specific workload. It's also
pretty stat dominant, which puts it roughly in the same category as a
git diff. (They differ in that updatedb does a lot of open()s and
getdents on directories, git merely does a ton of lstat()s instead.)

Anyway, my point is that I worry that tuning for an unusual and
infrequent workload (which updatedb certainly is), is the wrong way to
go.

> After that we can look at other problems that swap prefetch helps
> with, or think of some ways to measure your "whole day" scenario.
>
> So when/if you have time, I can cook up a list of things to monitor
> and possibly a patch to add some instrumentation over this updatedb
> run.

That would be appreciated. Don't spend huge amounts of time on it,
okay? Point me the right direction, and we'll see how far I can run
with it.

> Anyway, I realise swap prefetching has some situations where it will
> fundamentally outperform even the page replacement oracle. This is
> why I haven't asked for it to be dropped: it isn't a bad idea at all.

<nod>

> However, if we can improve basic page reclaim where it is obviously
> lacking, that is always preferable. eg: being a highly speculative
> operation, swap prefetch is not great for power efficiency -- but we
> still want laptop users to have a good experience as well, right?

Absolutely. Disk I/O is the enemy, and the best I/O is one you never
had to do in the first place.

Re: [ck] Re: -mm merge plans for 2.6.23

[Rashkae]

> 
>> However, if we can improve basic page reclaim where it is obviously
>> lacking, that is always preferable. eg: being a highly speculative
>> operation, swap prefetch is not great for power efficiency -- but we
>> still want laptop users to have a good experience as well, right?
>

Sounds like something that can be altered with a tuneable for workloads 
where power efficiency is more important than performance.

As far as performance goes, empty memory is wasted memory.  I think the 
most important 'measurement' people can make for swap prefetch, if this 
is even possible to capture, is a positive hit ratio.  Under everyman's 
typical workload, what percentage of pages prefetched end up being used? 
And what percentage end up discarded?  I'm pulling these numbers out of 
thin air, but I would say, if > 10% is referenced, and < 70% discarded, 
then that would be significant performance boost well worthwhile.


To be clear, I don't know what I'm talking about.  It just seems to me 
however, that debating whether or not to implement a performance boost 
because we can better tune corner cases is silly.  For as long as 
computers have used swap and unused memory, there will be a performance 
gain to background prefetching.  That doesn't preclude developers from 
tuning the specific workloads that lead to such.  It's not like this 
were a theoretical discussion of should we develop this or not.. 
Prefetch is here, now, and working.  The only questions I see are:

Does the performance gain from Prefetch compensate for the prefetch code 
memory requirements?

Is there someone who's comfortable with lkml politics willing to 
maintain the thing?

Re: [ck] Re: -mm merge plans for 2.6.23

[Matthew Hawkins]

On 7/24/07, Andrew Morton <akpm@linux-foundation.org> wrote:
> The other consideration here is, as Nick points out, are the problems which
> people see this patch solving for them solveable in other, better ways?
> IOW, is this patch fixing up preexisting deficiencies post-facto?

So let me get this straight - you don't want to merge swap prefetch
which exists now and solves issues many people are seeing, and has
been tested more than a gazillion other bits & pieces that do get
merged - because it could be possible that in the future some other
patch, which doesn't yet exist and nobody is working on, may solve the
problem better?

You know what, just release Linux 0.02 as 2.6.23 because, using your
logic, everything that was merged since October 5, 1991 could be
replaced by something better.  Perhaps.  So there's obviously no point
having it there in the first place & there'll be untold savings in
storage costs and compilation time for the kernel tree, also bandwidth
for the mirror sites etc. in the mean time while we wait for the magic
pixies to come and deliver the one true piece of code that cannot be
improved upon.

> Well.  The above, plus there's always a lot of stuff happening in MM land,
> and I haven't seen much in the way of enthusiasm from the usual MM
> developers.

I haven't seen much in the way of enthusiasm from developers, period.
People are tired of maintaining patches for years that never get
merged into mainline because of totally bullshit reasons (usually
amounting to NIH syndrome)

-- 
Matt

Re: [ck] Re: -mm merge plans for 2.6.23

[David Miller]

From: "Matthew Hawkins" <darthmdh@gmail.com>
Date: Wed, 25 Jul 2007 11:26:57 +1000

> On 7/24/07, Andrew Morton <akpm@linux-foundation.org> wrote:
> > The other consideration here is, as Nick points out, are the problems which
> > people see this patch solving for them solveable in other, better ways?
> > IOW, is this patch fixing up preexisting deficiencies post-facto?
> 
> So let me get this straight - you don't want to merge swap prefetch
> which exists now and solves issues many people are seeing, and has
> been tested more than a gazillion other bits & pieces that do get
> merged - because it could be possible that in the future some other
> patch, which doesn't yet exist and nobody is working on, may solve the
> problem better?

I have to generally agree that the objections to the swap prefetch
patches have been conjecture and in general wasting time and
frustrating people.

There is a point at which it might be wise to just step back and let
the river run it's course and see what happens.  Initially, it's good
to play games of "what if", but after several months it's not a
productive thing and slows down progress for no good reason.

If a better mechanism gets implemented, great!  We'll can easily
replace the swap prefetch stuff at such time.  But until then swap
prefetch is what we have and it's sat long enough in -mm with no major
problems to merge it.

Re: -mm merge plans for 2.6.23

[Nick Piggin]

Ray Lee wrote:
> On 7/23/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:

>> Also a random day at the desktop, it is quite a broad scope and
>> pretty well impossible to analyse.
> 
> 
> It is pretty broad, but that's also what swap prefetch is targetting.
> As for hard to analyze, I'm not sure I agree. One can black-box test
> this stuff with only a few controls. e.g., if I use the same apps each
> day (mercurial, firefox, xorg, gcc), and the total I/O wait time
> consistently goes down on a swap prefetch kernel (normalized by some
> control statistic, such as application CPU time or total I/O, or
> something), then that's a useful measurement.

I'm not saying that we can't try to tackle that problem, but first of
all you have a really nice narrow problem where updatedb seems to be
causing the kernel to completely do the wrong thing. So we start on
that.


>> If we can first try looking at
>> some specific problems that are easily identified.
> 
> 
> Always easier, true. Let's start with "My mouse jerks around under
> memory load." A Google Summer of Code student working on X.Org claims
> that mlocking the mouse handling routines gives a smooth cursor under
> load ([1]). It's surprising that the kernel would swap that out in the
> first place.
> 
> [1] 
> http://vignatti.wordpress.com/2007/07/06/xorg-input-thread-summary-or-something/ 

OK, I'm not sure what the point is though. Under heavy memory load,
things are going to get swapped out... and swap prefetch isn't going
to help there (at least, not during the memory load).

There are also other issues like whether the CPU scheduler is at fault,
etc. Interactive workloads are always the hardest to work out. updatedb
is a walk in the park by comparison.


>> Looking at your past email, you have a 1GB desktop system and your
>> overnight updatedb run is causing stuff to get swapped out such that
>> swap prefetch makes it significantly better. This is really
>> intriguing to me, and I would hope we can start by making this
>> particular workload "not suck" without swap prefetch (and hopefully
>> make it even better than it currently is with swap prefetch because
>> we'll try not to evict useful file backed pages as well).
> 
> 
> updatedb is an annoying case, because one would hope that there would
> be a better way to deal with that highly specific workload. It's also
> pretty stat dominant, which puts it roughly in the same category as a
> git diff. (They differ in that updatedb does a lot of open()s and
> getdents on directories, git merely does a ton of lstat()s instead.)

Yeah, and I suspect we might be able to do better use-once of
inode and dentry caches. It isn't really highly specific: lots
of things tend to just scan over a few files once -- updatedb
just scans a lot so the problem becomes more noticable.


> Anyway, my point is that I worry that tuning for an unusual and
> infrequent workload (which updatedb certainly is), is the wrong way to
> go.

Well it runs every day or so for every desktop Linux user, and
it has similarities with other workloads. We don't want to optimise
it at the expense of other things, but it _really_ should not be
pushing a 1-2GB desktop into swap, I don't think.


>> After that we can look at other problems that swap prefetch helps
>> with, or think of some ways to measure your "whole day" scenario.
>>
>> So when/if you have time, I can cook up a list of things to monitor
>> and possibly a patch to add some instrumentation over this updatedb
>> run.
> 
> 
> That would be appreciated. Don't spend huge amounts of time on it,
> okay? Point me the right direction, and we'll see how far I can run
> with it.

I guess /proc/meminfo, /proc/zoneinfo, /proc/vmstat, /proc/slabinfo
before and after the updatedb run with the latest kernel would be a
first step. top and vmstat output during the run wouldn't hurt either.

Thanks,
Nick

-- 
SUSE Labs, Novell Inc.

Re: -mm merge plans for 2.6.23

[david]

On Tue, 24 Jul 2007, Ray Lee wrote:

> On 7/23/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
>>  Ray Lee wrote:
>
>>  Looking at your past email, you have a 1GB desktop system and your
>>  overnight updatedb run is causing stuff to get swapped out such that
>>  swap prefetch makes it significantly better. This is really
>>  intriguing to me, and I would hope we can start by making this
>>  particular workload "not suck" without swap prefetch (and hopefully
>>  make it even better than it currently is with swap prefetch because
>>  we'll try not to evict useful file backed pages as well).
>
> updatedb is an annoying case, because one would hope that there would
> be a better way to deal with that highly specific workload. It's also
> pretty stat dominant, which puts it roughly in the same category as a
> git diff. (They differ in that updatedb does a lot of open()s and
> getdents on directories, git merely does a ton of lstat()s instead.)
>
> Anyway, my point is that I worry that tuning for an unusual and
> infrequent workload (which updatedb certainly is), is the wrong way to
> go.

updatedb pushing out program data may be able to be improved on with drop 
behind or similar.

however another scenerio that causes a similar problem is when a user is 
busy useing one of the big memory hogs and then switches to another (think 
switching between openoffice and firefox)

>>  After that we can look at other problems that swap prefetch helps
>>  with, or think of some ways to measure your "whole day" scenario.
>>
>>  So when/if you have time, I can cook up a list of things to monitor
>>  and possibly a patch to add some instrumentation over this updatedb
>>  run.
>
> That would be appreciated. Don't spend huge amounts of time on it,
> okay? Point me the right direction, and we'll see how far I can run
> with it.

you could make a synthetic test by writing a memory hog that allocates 3/4 
of your ram then pauses waiting for input and then randomly accesses the 
memory for a while (say randomly accessing 2x # of pages allocated) and 
then pausing again before repeating

run two of these, alternating which one is running at any one time. time 
how long it takes to do the random accesses.

the difference in this time should be a fair example of how much it would 
impact the user.

by the way, I've also seen comments on the Postgres performance mailing 
list about how slow linux is compared to other OS's in pulling data back 
in that's been pushed out to swap (not a factor on dedicated database 
machines, but a big factor on multi-purpose machines)

>>  Anyway, I realise swap prefetching has some situations where it will
>>  fundamentally outperform even the page replacement oracle. This is
>>  why I haven't asked for it to be dropped: it isn't a bad idea at all.
>
> <nod>
>
>>  However, if we can improve basic page reclaim where it is obviously
>>  lacking, that is always preferable. eg: being a highly speculative
>>  operation, swap prefetch is not great for power efficiency -- but we
>>  still want laptop users to have a good experience as well, right?
>
> Absolutely. Disk I/O is the enemy, and the best I/O is one you never
> had to do in the first place.

almost always true, however there is some amount of I/O that is free with 
todays drives (remember, they read the entire track into ram and then 
give you the sectors on the track that you asked for). and if you have a 
raid array this is even more true.

if you read one sector in from a raid5 array you have done all the same 
I/O that you would have to do to read in the entire stripe, but I don't 
believe that the current system will keep it all around if it exceeds the 
readahead limit.

so in many cases readahead may end up being significantly cheaper then you 
expect.

David Lang

Re: -mm merge plans for 2.6.23

[Rene Herman]

On 07/25/2007 06:06 AM, Nick Piggin wrote:

> Ray Lee wrote:

>> Anyway, my point is that I worry that tuning for an unusual and 
>> infrequent workload (which updatedb certainly is), is the wrong way to 
>> go.
> 
> Well it runs every day or so for every desktop Linux user, and it has
> similarities with other workloads.

It certainly doesn't run for me ever. Always kind of a "that's not the 
point" comment but I just keep wondering whenever I see anyone complain 
about updatedb why the _hell_ they are running it in the first place. If 
anyone who never uses "locate" for anything simply disable updatedb, the 
problem will for a large part be solved.

This not just meant as a cheap comment; while I can think of a few similar 
loads even on the desktop (scanning a browser cache, a media player indexing 
a large amount of media files, ...) I've never heard of problems _other_ 
than updatedb. So just junk that crap and be happy.

Rene.

Re: -mm merge plans for 2.6.23

[Nick Piggin]

Rene Herman wrote:
> On 07/25/2007 06:06 AM, Nick Piggin wrote:
> 
>> Ray Lee wrote:
> 
> 
>>> Anyway, my point is that I worry that tuning for an unusual and 
>>> infrequent workload (which updatedb certainly is), is the wrong way 
>>> to go.
>>
>>
>> Well it runs every day or so for every desktop Linux user, and it has
>> similarities with other workloads.
> 
> 
> It certainly doesn't run for me ever. Always kind of a "that's not the 
> point" comment but I just keep wondering whenever I see anyone complain 
> about updatedb why the _hell_ they are running it in the first place. If 
> anyone who never uses "locate" for anything simply disable updatedb, the 
> problem will for a large part be solved.
> 
> This not just meant as a cheap comment; while I can think of a few 
> similar loads even on the desktop (scanning a browser cache, a media 
> player indexing a large amount of media files, ...) I've never heard of 
> problems _other_ than updatedb. So just junk that crap and be happy.

OK fair point, but the counter point that there are real patterns
that just use-once a lot of metadata (ls, for example. grep even.)

-- 
SUSE Labs, Novell Inc.

Re: -mm merge plans for 2.6.23

[david]

On Wed, 25 Jul 2007, Rene Herman wrote:

> On 07/25/2007 06:06 AM, Nick Piggin wrote:
>
>>  Ray Lee wrote:
>
>> >  Anyway, my point is that I worry that tuning for an unusual and 
>> >  infrequent workload (which updatedb certainly is), is the wrong way to 
>> >  go.
>>
>>  Well it runs every day or so for every desktop Linux user, and it has
>>  similarities with other workloads.
>
> It certainly doesn't run for me ever. Always kind of a "that's not the point" 
> comment but I just keep wondering whenever I see anyone complain about 
> updatedb why the _hell_ they are running it in the first place. If anyone who 
> never uses "locate" for anything simply disable updatedb, the problem will 
> for a large part be solved.
>
> This not just meant as a cheap comment; while I can think of a few similar 
> loads even on the desktop (scanning a browser cache, a media player indexing 
> a large amount of media files, ...) I've never heard of problems _other_ than 
> updatedb. So just junk that crap and be happy.

but if you do use locate then the alturnative becomes sitting around and 
waiting for find to complete on a regular basis.

David Lang

Re: -mm merge plans for 2.6.23

[Rene Herman]

On 07/25/2007 07:12 AM, david@lang.hm wrote:

> On Wed, 25 Jul 2007, Rene Herman wrote:

>> It certainly doesn't run for me ever. Always kind of a "that's not the 
>> point" comment but I just keep wondering whenever I see anyone 
>> complain about updatedb why the _hell_ they are running it in the 
>> first place. If anyone who never uses "locate" for anything simply 
>> disable updatedb, the problem will for a large part be solved.
>>
>> This not just meant as a cheap comment; while I can think of a few 
>> similar loads even on the desktop (scanning a browser cache, a media 
>> player indexing a large amount of media files, ...) I've never heard 
>> of problems _other_ than updatedb. So just junk that crap and be happy.
> 
> but if you do use locate then the alturnative becomes sitting around and 
> waiting for find to complete on a regular basis.

Yes, but what's locate's usage scenario? I've never, ever wanted to use it. 
When do you know the name of something but not where it's located, other 
than situations which "which" wouldn't cover and after just having 
installed/unpacked something meaning locate doesn't know about it yet either?

Rene.

Re: -mm merge plans for 2.6.23

[Eric St-Laurent]

On Wed, 2007-25-07 at 06:55 +0200, Rene Herman wrote:

> It certainly doesn't run for me ever. Always kind of a "that's not the 
> point" comment but I just keep wondering whenever I see anyone complain 
> about updatedb why the _hell_ they are running it in the first place. If 
> anyone who never uses "locate" for anything simply disable updatedb, the 
> problem will for a large part be solved.
> 
> This not just meant as a cheap comment; while I can think of a few similar 
> loads even on the desktop (scanning a browser cache, a media player indexing 
> a large amount of media files, ...) I've never heard of problems _other_ 
> than updatedb. So just junk that crap and be happy.

>From my POV there's two different problems discussed recently:

- updatedb type of workloads that add tons of inodes and dentries in the
slab caches which of course use the pagecache.

- streaming large files (read or copying) that fill the pagecache with
useless used-once data

swap prefetch fix the first case, drop-behind fix the second case.

Both have the same symptoms but the cause is different.

Personally updatedb doesn't really hurt me.  But I don't have that many
files on my desktop.  I've tried the swap prefetch patch in the past and
it was not so noticeable for me. (I don't doubt it's helpful for others)

But every time I read or copy a large file around (usually from a
server) the slowdown is noticeable for some moments.

I just wanted to point this out, if it wasn't clean enough for everyone.
I hope both problems get fixed.


Best regards,

- Eric

Re: -mm merge plans for 2.6.23

[Nick Piggin]

Eric St-Laurent wrote:
> On Wed, 2007-25-07 at 06:55 +0200, Rene Herman wrote:
> 
> 
>>It certainly doesn't run for me ever. Always kind of a "that's not the 
>>point" comment but I just keep wondering whenever I see anyone complain 
>>about updatedb why the _hell_ they are running it in the first place. If 
>>anyone who never uses "locate" for anything simply disable updatedb, the 
>>problem will for a large part be solved.
>>
>>This not just meant as a cheap comment; while I can think of a few similar 
>>loads even on the desktop (scanning a browser cache, a media player indexing 
>>a large amount of media files, ...) I've never heard of problems _other_ 
>>than updatedb. So just junk that crap and be happy.
> 
> 
>>From my POV there's two different problems discussed recently:
> 
> - updatedb type of workloads that add tons of inodes and dentries in the
> slab caches which of course use the pagecache.
> 
> - streaming large files (read or copying) that fill the pagecache with
> useless used-once data
> 
> swap prefetch fix the first case, drop-behind fix the second case.

OK, this is where I start to worry. Swap prefetch AFAIKS doesn't fix
the updatedb problem very well, because if updatedb has caused swapout
then it has filled memory, and swap prefetch doesn't run unless there
is free memory (not to mention that updatedb would have paged out other
files as well).

And drop behind doesn't fix your usual problem where you are downloading
from a server, because that is use-once write(2) data which is the
problem. And this readahead-based drop behind also doesn't help if data
you were reading happened to be a sequence of small files, or otherwise
not in good readahead order.

Not to say that neither fix some problems, but for such conceptually
big changes, it should take a little more effort than a constructed test
case and no consideration of the alternatives to get it merged.

-- 
SUSE Labs, Novell Inc.

Re: -mm merge plans for 2.6.23

[david]

On Wed, 25 Jul 2007, Rene Herman wrote:

> On 07/25/2007 07:12 AM, david@lang.hm wrote:
>
>>  On Wed, 25 Jul 2007, Rene Herman wrote:
>
>> >  It certainly doesn't run for me ever. Always kind of a "that's not the 
>> >  point" comment but I just keep wondering whenever I see anyone complain 
>> >  about updatedb why the _hell_ they are running it in the first place. If 
>> >  anyone who never uses "locate" for anything simply disable updatedb, the 
>> >  problem will for a large part be solved.
>> > 
>> >  This not just meant as a cheap comment; while I can think of a few 
>> >  similar loads even on the desktop (scanning a browser cache, a media 
>> >  player indexing a large amount of media files, ...) I've never heard of 
>> >  problems _other_ than updatedb. So just junk that crap and be happy.
>>
>>  but if you do use locate then the alturnative becomes sitting around and
>>  waiting for find to complete on a regular basis.
>
> Yes, but what's locate's usage scenario? I've never, ever wanted to use it. 
> When do you know the name of something but not where it's located, other than 
> situations which "which" wouldn't cover and after just having 
> installed/unpacked something meaning locate doesn't know about it yet either?

which only finds executables that are in the path.

I commonly use locate to find config files (or sample config files) for 
packages that were installed at some point in the past with fairly default 
configs and now I want to go and tweak them. so I start reading 
documentation and then need to find out where $disto moved the files to 
this release (I commonly am working on machines with over a half dozen 
different distro releases, and none of them RedHat)

David Lang

Re: -mm merge plans for 2.6.23

[david]

On Wed, 25 Jul 2007, Nick Piggin wrote:

> Eric St-Laurent wrote:
>>  On Wed, 2007-25-07 at 06:55 +0200, Rene Herman wrote:
>>
>> 
>> > It certainly doesn't run for me ever. Always kind of a "that's not the 
>> > point" comment but I just keep wondering whenever I see anyone complain 
>> > about updatedb why the _hell_ they are running it in the first place. If 
>> > anyone who never uses "locate" for anything simply disable updatedb, the 
>> > problem will for a large part be solved.
>> > 
>> > This not just meant as a cheap comment; while I can think of a few 
>> > similar loads even on the desktop (scanning a browser cache, a media 
>> > player indexing a large amount of media files, ...) I've never heard of 
>> > problems _other_ than updatedb. So just junk that crap and be happy.
>>
>> 
>> >From my POV there's two different problems discussed recently:
>>
>>  - updatedb type of workloads that add tons of inodes and dentries in the
>>  slab caches which of course use the pagecache.
>>
>>  - streaming large files (read or copying) that fill the pagecache with
>>  useless used-once data
>>
>>  swap prefetch fix the first case, drop-behind fix the second case.
>
> OK, this is where I start to worry. Swap prefetch AFAIKS doesn't fix
> the updatedb problem very well, because if updatedb has caused swapout
> then it has filled memory, and swap prefetch doesn't run unless there
> is free memory (not to mention that updatedb would have paged out other
> files as well).
>
> And drop behind doesn't fix your usual problem where you are downloading
> from a server, because that is use-once write(2) data which is the
> problem. And this readahead-based drop behind also doesn't help if data
> you were reading happened to be a sequence of small files, or otherwise
> not in good readahead order.
>
> Not to say that neither fix some problems, but for such conceptually
> big changes, it should take a little more effort than a constructed test
> case and no consideration of the alternatives to get it merged.

well, there appears to be a fairly large group of people who have 
subjective opinions that it helps them. but those were dismissed becouse 
they aren't measurements.

so now the measurements of the constructed test case aren't acceptable.

what sort of test case would be acceptable?

David Lang

Re: -mm merge plans for 2.6.23

[Nick Piggin]

david@lang.hm wrote:
> On Wed, 25 Jul 2007, Nick Piggin wrote:

>> OK, this is where I start to worry. Swap prefetch AFAIKS doesn't fix
>> the updatedb problem very well, because if updatedb has caused swapout
>> then it has filled memory, and swap prefetch doesn't run unless there
>> is free memory (not to mention that updatedb would have paged out other
>> files as well).
>>
>> And drop behind doesn't fix your usual problem where you are downloading
>> from a server, because that is use-once write(2) data which is the
>> problem. And this readahead-based drop behind also doesn't help if data
>> you were reading happened to be a sequence of small files, or otherwise
>> not in good readahead order.
>>
>> Not to say that neither fix some problems, but for such conceptually
>> big changes, it should take a little more effort than a constructed test
>> case and no consideration of the alternatives to get it merged.
> 
> 
> well, there appears to be a fairly large group of people who have 
> subjective opinions that it helps them. but those were dismissed becouse 
> they aren't measurements.

Not at all. But there is also seems to be some people also experiencing
problems with basic page reclaim on some of the workloads where these
things help. I am not dismissing anybody's claims about anything; I want
to try to solve some of these problems.

Interestingly, some of the people ranting the most about how the VM sucks
are the ones helping least in solving these basic problems.


> so now the measurements of the constructed test case aren't acceptable.
> 
> what sort of test case would be acceptable?

Well I never said real world tests aren't acceptable, they are. There is
a difference between an "it feels better for me", and some actual real
measurement and analysis of said workload.

And constructed test cases of course are useful as well, I didn't say
they weren't. I don't know what you mean by "acceptable", but you should
read my last paragraph again.

-- 
SUSE Labs, Novell Inc.

Re: [ck] Re: -mm merge plans for 2.6.23

[Matthew Hawkins]

On 7/25/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> I'm not saying that we can't try to tackle that problem, but first of
> all you have a really nice narrow problem where updatedb seems to be
> causing the kernel to completely do the wrong thing. So we start on
> that.

updatedb isn't the only problem, its just an obvious one.  I like the
idea of looking into the vfs for this and other one-shot applications
(rather than looking at updatedb itself specifically)

Many modern applications have a lot of open file handles.  For
example, I just fired up my usual audio player and sys/fs/file-nr
showed another 600 open files (funnily enough, I have roughly that
many audio files :)  I'm not exactly sure what happens when this one
gets swapped out for whatever reason (firefox/java/vmware/etc chews
ram, updatedb, whatever) but I'm fairly confident what happens between
kswapd and the vfs and whatever else we're caching is not optimal come
time for this process to context-switch back in.  We're not running a
highly-optimised number-crunching scientific app on desktops, we're
running a full herd of poorly-coded hogs simultaneously through
smaller pens.

I don't think anyone is trying to claim that swap prefetch is the be
all and end all of this problem's solution, however without it the
effects are an order of magnitude worse (I've cited numbers elsewhere,
as have several others); its relatively non-intrusive (600+ lines of
the 755 changed ones are self-contained), is compile and runtime
selectable, and still has a maintainer now that Con has retired.  If
there was a better solution, it should have been developed sometime in
the past 23 months that swap prefetch has addressed it.  That's how we
got rmap versus aa, and so on.  But nobody chose to do so, and
continuing to hold out on merging it on the promise of vapourware is
ridiculous.  That has never been the way linux kernel development has
operated.

-- 
Matt

Re: [ck] Re: -mm merge plans for 2.6.23

[Nick Piggin]

Matthew Hawkins wrote:
> On 7/25/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> 
>> I'm not saying that we can't try to tackle that problem, but first of
>> all you have a really nice narrow problem where updatedb seems to be
>> causing the kernel to completely do the wrong thing. So we start on
>> that.
> 
> 
> updatedb isn't the only problem, its just an obvious one.  I like the
> idea of looking into the vfs for this and other one-shot applications
> (rather than looking at updatedb itself specifically)

That's the point, it is an obvious one. So it should be easy to work
out why it is going wrong, and fix it. (And hopefully that fixes some
of the less obvious problems too.)


> Many modern applications have a lot of open file handles.  For
> example, I just fired up my usual audio player and sys/fs/file-nr
> showed another 600 open files (funnily enough, I have roughly that
> many audio files :)  I'm not exactly sure what happens when this one
> gets swapped out for whatever reason (firefox/java/vmware/etc chews
> ram, updatedb, whatever) but I'm fairly confident what happens between
> kswapd and the vfs and whatever else we're caching is not optimal come
> time for this process to context-switch back in.  We're not running a
> highly-optimised number-crunching scientific app on desktops, we're
> running a full herd of poorly-coded hogs simultaneously through
> smaller pens.

And yet nobody wants to take the time to properly analyse why these
things are going wrong and reporting their findings? Or if they have,
where is that documented?

-- 
SUSE Labs, Novell Inc.

Re: [ck] Re: -mm merge plans for 2.6.23

[Matthew Hawkins]

On 7/25/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> Not to say that neither fix some problems, but for such conceptually
> big changes, it should take a little more effort than a constructed test
> case and no consideration of the alternatives to get it merged.

Swap Prefetch has existed since September 5, 2005.  Please Nick,
enlighten us all with your "alternatives" which have been offered (in
practical, not theoretical form) in the past 23 months, along with
their non-constructed benchmarks proving their case and the hordes of
happy users and kernel developers who have tested them out the wazoo
and given their backing.  Or just take a nice steaming jug of STFU.

-- 
Matt

Re: -mm merge plans for 2.6.23

[david]

On Wed, 25 Jul 2007, Nick Piggin wrote:

> david@lang.hm wrote:
>>  On Wed, 25 Jul 2007, Nick Piggin wrote:
>
>> >  OK, this is where I start to worry. Swap prefetch AFAIKS doesn't fix
>> >  the updatedb problem very well, because if updatedb has caused swapout
>> >  then it has filled memory, and swap prefetch doesn't run unless there
>> >  is free memory (not to mention that updatedb would have paged out other
>> >  files as well).
>> > 
>> >  And drop behind doesn't fix your usual problem where you are downloading
>> >  from a server, because that is use-once write(2) data which is the
>> >  problem. And this readahead-based drop behind also doesn't help if data
>> >  you were reading happened to be a sequence of small files, or otherwise
>> >  not in good readahead order.
>> > 
>> >  Not to say that neither fix some problems, but for such conceptually
>> >  big changes, it should take a little more effort than a constructed test
>> >  case and no consideration of the alternatives to get it merged.
>>
>>
>>  well, there appears to be a fairly large group of people who have
>>  subjective opinions that it helps them. but those were dismissed becouse
>>  they aren't measurements.
>
> Not at all. But there is also seems to be some people also experiencing
> problems with basic page reclaim on some of the workloads where these
> things help. I am not dismissing anybody's claims about anything; I want
> to try to solve some of these problems.
>
> Interestingly, some of the people ranting the most about how the VM sucks
> are the ones helping least in solving these basic problems.
>
>
>>  so now the measurements of the constructed test case aren't acceptable.
>>
>>  what sort of test case would be acceptable?
>
> Well I never said real world tests aren't acceptable, they are. There is
> a difference between an "it feels better for me", and some actual real
> measurement and analysis of said workload.
>
> And constructed test cases of course are useful as well, I didn't say
> they weren't. I don't know what you mean by "acceptable", but you should
> read my last paragraph again.

this problem has been around for many years, with many different people 
working on solutions. it's hardly a case of getting a proposal and trying 
to get it in without anyone looking at other options.

it seems that there are some people (not nessasarily including you) who 
will oppose this feature until a test is created that shows that it's 
better. the question is what sort of test will be accepted as valid? I'm 
not useing this patch, but it sounds as if the people who are useing it 
are interested in doing whatever testing is required, but so far the 
situation seems to be a series of "here's a test", "that test isn't valid, 
try again" loops. which don't seem to be doing anyone any good and are 
frustrating lots of people, so like several people over the last few days 
O'm asking the question, "what sort of test would be acceptable as proof 
that this patch does some good?"

David Lang

Re: [ck] Re: -mm merge plans for 2.6.23

[Nick Piggin]

Matthew Hawkins wrote:
> On 7/25/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> 
>> Not to say that neither fix some problems, but for such conceptually
>> big changes, it should take a little more effort than a constructed test
>> case and no consideration of the alternatives to get it merged.
> 
> 
> Swap Prefetch has existed since September 5, 2005.  Please Nick,
> enlighten us all with your "alternatives" which have been offered (in
> practical, not theoretical form) in the past 23 months, along with
> their non-constructed benchmarks proving their case and the hordes of
> happy users and kernel developers who have tested them out the wazoo
> and given their backing.  Or just take a nice steaming jug of STFU.

The alternatives comment was in relation to the readahead based drop
behind patch,for which an alternative would be improving use-once,
possibly in the way I described.

As for swap prefetch, I don't know, I'm not in charge of it being
merged or not merged. I do know some people have reported that their
updatedb problem gets much better with swap prefetch turned on, and
I am trying to work on that too.

For you? You also have the alternative to help improve things yourself,
and you can modify your own kernel.

-- 
SUSE Labs, Novell Inc.

Re: -mm merge plans for 2.6.23

[Eric St-Laurent]

On Wed, 2007-25-07 at 15:37 +1000, Nick Piggin wrote:

> OK, this is where I start to worry. Swap prefetch AFAIKS doesn't fix
> the updatedb problem very well, because if updatedb has caused swapout
> then it has filled memory, and swap prefetch doesn't run unless there
> is free memory (not to mention that updatedb would have paged out other
> files as well).
> 
> And drop behind doesn't fix your usual problem where you are downloading
> from a server, because that is use-once write(2) data which is the
> problem. And this readahead-based drop behind also doesn't help if data
> you were reading happened to be a sequence of small files, or otherwise
> not in good readahead order.
> 
> Not to say that neither fix some problems, but for such conceptually
> big changes, it should take a little more effort than a constructed test
> case and no consideration of the alternatives to get it merged.


Sorry for the confusion.

For swap prefetch I should have said "some people claim that it fix
their problem". I didn't want to hurt anybody feelings, some people are
tired to hear others speak hypothetically about this patch, as it
work-for-them (TM).

I don't experience the problem. Can't help.

For drop behind it fix half the problem. The read case is handled
perfectly by Peter's patch. And the copy (read+write) is unchanged. My
test case demonstrate it very easily, just look at the numbers.

So, I agree with you that drop behind doesn't fix the write() case.
Peter has said so himself when I offered to test his patch.

As I do experience this problem, I have written a small test program and
batch file to help push the patch for acceptance.  I'm very willing to
help improve the test cases, test patches and write code, time
permitting.

About this very subject, earlier this year this Andrew suggested me to
came up with a test case to demonstrate my problem, well finally I've
done so.

http://lkml.org/lkml/2007/3/3/164
http://lkml.org/lkml/2007/3/3/166

Lastly, I would go as far to say that the use-once read then copy fix
must also work with copies over NFS. I don't know if NFS change the
workload on the client station versus the local case, and I don't know
if it's still possible to consider data copied this way as use-once.


- Eric

Re: [ck] Re: -mm merge plans for 2.6.23

[Mike Galbraith]

On Wed, 2007-07-25 at 16:19 +1000, Matthew Hawkins wrote:
> On 7/25/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> > Not to say that neither fix some problems, but for such conceptually
> > big changes, it should take a little more effort than a constructed test
> > case and no consideration of the alternatives to get it merged.
> 
> Swap Prefetch has existed since September 5, 2005.  Please Nick,
> enlighten us all with your "alternatives" which have been offered (in
> practical, not theoretical form) in the past 23 months, along with
> their non-constructed benchmarks proving their case and the hordes of
> happy users and kernel developers who have tested them out the wazoo
> and given their backing.  Or just take a nice steaming jug of STFU.

Heh.  Here we have a VM developer expressing his interest in the problem
space, and you offer him a steaming jug of STFU because he doesn't say
what you want to hear.  I wonder how many killfiles you just entered.

	-Mike

Re: -mm merge plans for 2.6.23

[Valdis.Kletnieks]

[-- Attachment #1: Type: text/plain, Size: 1659 bytes --]

On Wed, 25 Jul 2007 07:30:37 +0200, Rene Herman said:

> Yes, but what's locate's usage scenario? I've never, ever wanted to use it. 
> When do you know the name of something but not where it's located, other 
> than situations which "which" wouldn't cover and after just having 
> installed/unpacked something meaning locate doesn't know about it yet either?

My favorite use - with 5 Fedora kernels and as many -mm kernels on my laptop,
doing a 'locate moby' finds all the moby.c and moby.o and moby.ko for
the various releases. For bonus points, something like:

ls -lt `locate iwl3945.ko`

to find all 19 copies that are on my system, and remind me which ones were
compiled when.  Or just when you remember the name of some one-off 100-line
Perl program that you wrote 6 months ago, but not sure which directory you
left it in... ;)

You want hard numbers? Here you go - 'locate' versus 'find'
(/usr/src/ has about 290K files on it):

%  strace locate iwl3945.ko  >| /tmp/foo3 2>&1
% wc /tmp/foo3
  96  592 6252 /tmp/foo3
% strace find /usr/src /lib -name iwl3945.ko >| /tmp/foo4 2>&1
% wc /tmp/foo4
  328380  1550032 15708205 /tmp/foo4

# echo 1 > /proc/sys/vm/drop_caches     (to empty the caches

% time locate iwl3945.ko > /dev/null

real    0m0.872s
user    0m0.867s
sys     0m0.008s

% time find /usr/src /lib -name iwl3945.ko > /dev/null
find: /usr/src/lost+found: Permission denied

real    1m12.241s
user    0m1.128s
sys     0m3.566s

So 96 system calls in 1 second, against 328K calls in a minute.  There's your
use case, right there.  Now if we can just find a way for that find/updatedb
to not be as painful to the rest of the system.....





[-- Attachment #2: Type: application/pgp-signature, Size: 226 bytes --]

Re: [ck] Re: -mm merge plans for 2.6.23

[Eric St-Laurent]

On Wed, 2007-25-07 at 08:47 +0200, Mike Galbraith wrote:

> Heh.  Here we have a VM developer expressing his interest in the problem
> space, and you offer him a steaming jug of STFU because he doesn't say
> what you want to hear.  I wonder how many killfiles you just entered.
> 

Agreed.

(a bit OT)

People should understand that it's not (I think) about a desktop
workload vs enterprise workloads war.

I see it mostly as a progression versus regressions trade-off. And
adding potentially useless or unmaintained code is a regression from the
maintainers POV.

The best way to justify a patch and have it integrated is to have a
scientific testing method with repeatable numbers.

Con has done so for his patch, his benchmark demonstrated good
improvements.

But I feel some of his supporters have indirectly harmed his cause by
their comments.  Also, the fact that Con recently stopped maintaining
his work out of frustration also don't help having his patch merged. 

Again I'm not personally pushing this patch, I don't need it.

Con has worked for many years on two area that still cause problems for
desktop users: scheduler interactivity and pagecache trashing.  Now that
the scheduler has been fixed, let's have the VM fixed too.

Sorry for the slightly OT post, and please don't start a flame war...


- Eric

Re: -mm merge plans for 2.6.23

[Nick Piggin]

david@lang.hm wrote:
> On Wed, 25 Jul 2007, Nick Piggin wrote:

>> And constructed test cases of course are useful as well, I didn't say
>> they weren't. I don't know what you mean by "acceptable", but you should
>> read my last paragraph again.
> 
> 
> this problem has been around for many years, with many different people 
> working on solutions. it's hardly a case of getting a proposal and 
> trying to get it in without anyone looking at other options.

What is "this problem"? People have an updatedb problem that is solved
by swap prefetching which I want to fix in a different way.

There would be a different problem of "run something that uses heaps of
memory and swap everything else out, then quit it, wait for a while, and
swap prefetching helps". OK, definitely swap prefetching would help there.
How much? I don't know. I'd be slightly surprised if it was like an order
of magnitude, because not only swap but everything else has been thrown
out too.


> it seems that there are some people (not nessasarily including you) who 
> will oppose this feature until a test is created that shows that it's 
> better. the question is what sort of test will be accepted as valid? I'm 
> not useing this patch, but it sounds as if the people who are useing it 
> are interested in doing whatever testing is required, but so far the 
> situation seems to be a series of "here's a test", "that test isn't 
> valid, try again" loops. which don't seem to be doing anyone any good 

And yet despite my repeated pleas, none of those people has yet spent a
bit of time with me to help analyse what is happening.


> and are frustrating lots of people, so like several people over the last 
> few days O'm asking the question, "what sort of test would be acceptable 
> as proof that this patch does some good?"

I don't think any further proof is needed that the patch does "some"
good. Rig up a test case and you could see some seconds shaved off it.
Maybe you want to know "how to get this patch merged"? And I don't know
that one. I do know that it is fuzzy, and probably doesn't include
demanding things of Andrew or Linus.

BTW. If you find out the answer to that one, let me know because I have
this lockless pagecache patch that has also been around for years, is
also just a few hundred lines in the VM, and does do some good too. I'm
sure the buffered AIO people and many others would also like to know.

-- 
SUSE Labs, Novell Inc.

Re: -mm merge plans for 2.6.23

[Ingo Molnar]

* Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> And yet despite my repeated pleas, none of those people has yet spent 
> a bit of time with me to help analyse what is happening.

btw., it might help to give specific, precise instructions about what 
people should do to help you analyze this problem.

	Ingo

Re: -mm merge plans for 2.6.23

[Nick Piggin]

Ingo Molnar wrote:
> * Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> 
> 
>>And yet despite my repeated pleas, none of those people has yet spent 
>>a bit of time with me to help analyse what is happening.
> 
> 
> btw., it might help to give specific, precise instructions about what 
> people should do to help you analyze this problem.

Ray has been the first one to offer (thank you), and yes I have asked
him for precise details of info to collect to hopefully work out what
is happening with his first problem.

For the general "it feels better for me" it is harder, but not as hard
as CPU scheduler. We can measure various types of IO waits, swap in/out
events, swap prefetch events and successfulness; see what happens to
those as we change swappiness or vfs_cache_pressure etc.

-- 
SUSE Labs, Novell Inc.

Re: -mm merge plans for 2.6.23

[Rene Herman]

[-- Attachment #1: Type: text/plain, Size: 760 bytes --]

On 07/25/2007 06:46 AM, david@lang.hm wrote:

> you could make a synthetic test by writing a memory hog that allocates 
> 3/4 of your ram then pauses waiting for input and then randomly accesses 
> the memory for a while (say randomly accessing 2x # of pages allocated) 
> and then pausing again before repeating

Something like this?

> run two of these, alternating which one is running at any one time. time 
> how long it takes to do the random accesses.
> 
> the difference in this time should be a fair example of how much it 
> would impact the user.

Notenotenote, not sure what you're going to show with it (times are simply 
as horrendous as I'd expect) but thought I'd try to inject something other 
than steaming cups of 4-letter beverages.

Rene.

[-- Attachment #2: hog.c --]
[-- Type: text/plain, Size: 974 bytes --]

/* gcc -W -Wall -o hog hog.c */

#include <stdlib.h>
#include <stdio.h>

#include <sys/time.h>
#include <unistd.h>

int main(void)
{
	int pages, pagesize, i;
	unsigned char *mem;
	struct timeval tv;
	
	pages = sysconf(_SC_PHYS_PAGES);
	if (pages < 0) {
		perror("_SC_PHYS_PAGES");
		return EXIT_FAILURE;
	}
	pages = (3 * pages) / 4;

	pagesize = sysconf(_SC_PAGESIZE);
	if (pagesize < 0) {
		perror("_SC_PAGESIZE");
		return EXIT_FAILURE;
	}

	mem = malloc(pages * pagesize);
	if (!mem) {
		fprintf(stderr, "out of memory\n");
		return EXIT_FAILURE;
	}
	for (i = 0; i < pages; i++)
		mem[i * pagesize] = 0;

	gettimeofday(&tv, NULL);
	srand((unsigned int)tv.tv_sec);

	while (1) {
		struct timeval start;

		getchar();

		gettimeofday(&start, NULL);
		for (i = 0; i < 2 * pages; i++)
			mem[(rand() / (RAND_MAX / pages + 1)) * pagesize] = 0;
		gettimeofday(&tv, NULL);

		timersub(&tv, &start, &tv);
		printf("%lu.%lu\n", tv.tv_sec, tv.tv_usec);
	}

	return EXIT_SUCCESS;
}

Re: -mm merge plans for 2.6.23

[david]

On Wed, 25 Jul 2007, Rene Herman wrote:

> On 07/25/2007 06:46 AM, david@lang.hm wrote:
>
>>  you could make a synthetic test by writing a memory hog that allocates 3/4
>>  of your ram then pauses waiting for input and then randomly accesses the
>>  memory for a while (say randomly accessing 2x # of pages allocated) and
>>  then pausing again before repeating
>
> Something like this?
>
>>  run two of these, alternating which one is running at any one time. time
>>  how long it takes to do the random accesses.
>>
>>  the difference in this time should be a fair example of how much it would
>>  impact the user.
>
> Notenotenote, not sure what you're going to show with it (times are simply as 
> horrendous as I'd expect) but thought I'd try to inject something other than 
> steaming cups of 4-letter beverages.

when the swap readahead is enabled does it make a significant difference 
in the time to do the random access?

if it does that should show a direct benifit of the patch in a simulation 
of a relativly common workflow (startup a memory hog like openoffice then 
try and go back to your prior work)

David Lang

Re: -mm merge plans for 2.6.23

[Ingo Molnar]

* Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> > > And yet despite my repeated pleas, none of those people has yet 
> > > spent a bit of time with me to help analyse what is happening.
> >
> > btw., it might help to give specific, precise instructions about 
> > what people should do to help you analyze this problem.
> 
> Ray has been the first one to offer (thank you), and yes I have asked 
> him for precise details of info to collect to hopefully work out what 
> is happening with his first problem.

do you mean this paragraph:

| I guess /proc/meminfo, /proc/zoneinfo, /proc/vmstat, /proc/slabinfo 
| before and after the updatedb run with the latest kernel would be a 
| first step. top and vmstat output during the run wouldn't hurt either.

correct? Does "latest kernel" mean v2.6.22.1, or does it have to be 
v2.6.23-rc1? I guess v2.6.22.1 would be fine as this is a VM problem, 
not a scheduling problem.

the following script will gather all the above information for a 10 
seconds interval:

  http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh

Ray, please run this script before the updatedb run, once during the 
updatedb run and once after the updatedb run, and send Nick the 3 files 
it creates. (feel free to Cc: me too)

	Ingo

Re: -mm merge plans for 2.6.23

[Rene Herman]

On 07/25/2007 09:14 AM, Valdis.Kletnieks@vt.edu wrote:

> On Wed, 25 Jul 2007 07:30:37 +0200, Rene Herman said:
> 
>> Yes, but what's locate's usage scenario? I've never, ever wanted to use
>> it. When do you know the name of something but not where it's located,
>> other than situations which "which" wouldn't cover and after just
>> having installed/unpacked something meaning locate doesn't know about
>> it yet either?
> 
> My favorite use - with 5 Fedora kernels and as many -mm kernels on my
> laptop, doing a 'locate moby' finds all the moby.c and moby.o and moby.ko
> for the various releases.

Supposing you know the path in one tree, you know the path in all of them, 
right? :-?

> You want hard numbers? Here you go - 'locate' versus 'find'

These are ofcourse not necesary. If you discount the time updatedb itself 
takes it's utterly obvious that _if_ you use it, it's going to be wildly 
faster than find.

Regardless, I'll stand by "[by disabling updatedb] the problem will for a 
large part be solved" as I expect approximately 94.372 percent of Linux 
desktop users couldn't care less about locate.

Rene.

Re: -mm merge plans for 2.6.23

[Ingo Molnar]

* Rene Herman <rene.herman@gmail.com> wrote:

> Regardless, I'll stand by "[by disabling updatedb] the problem will 
> for a large part be solved" as I expect approximately 94.372 percent 
> of Linux desktop users couldn't care less about locate.

i think that approach is illogical: because Linux mis-handled a mixed 
workload the answer is to ... remove a portion of that workload?

To bring your approach to the extreme: what if Linux sucked at running 
more than two CPU-intense tasks at once. Most desktop users dont do 
that, so a probably larger than 94.372 percent of Linux desktop users 
couldn't care less about a proper scheduler. Still, anyone who builds a 
kernel (the average desktop user wont do that) while using firefox will 
attest to the fact that it's quite handy that the Linux scheduler can 
handle mixed workloads pretty well.

now, it might be the case that this mixed VM/VFS workload cannot be 
handled any more intelligently - but that wasnt your argument! The 
swap-prefetch patch certainly tried to do things more intelligently and 
the test-case (measurement app) Con provided showed visible improvements 
in swap-in latency. (and a good number of people posted those results)

	Ingo

Re: -mm merge plans for 2.6.23

[Rene Herman]

On 07/25/2007 10:07 AM, david@lang.hm wrote:

> On Wed, 25 Jul 2007, Rene Herman wrote:

>> Something like this?

[ ... ]

> when the swap readahead is enabled does it make a significant difference 
> in the time to do the random access?

I don't use swap prefetch (nor -ck or -mm). If someone who has the patch 
applied waits to hit enter until swap prefetch has prefetched it all back in 
again, it certainly will.

Swap prefetch's potential to do larger reads back from swapspace than a 
random segfaulting app could well be very significant. Reads are dwarved by 
seeks. If this program does what you wanted, please use it to show us.

Rene.

Re: -mm merge plans for 2.6.23

[david]

On Wed, 25 Jul 2007, Rene Herman wrote:

> On 07/25/2007 10:07 AM, david@lang.hm wrote:
>
>>  On Wed, 25 Jul 2007, Rene Herman wrote:
>
>> >  Something like this?
>
> [ ... ]
>
>>  when the swap readahead is enabled does it make a significant difference
>>  in the time to do the random access?
>
> I don't use swap prefetch (nor -ck or -mm). If someone who has the patch 
> applied waits to hit enter until swap prefetch has prefetched it all back in 
> again, it certainly will.
>
> Swap prefetch's potential to do larger reads back from swapspace than a 
> random segfaulting app could well be very significant. Reads are dwarved by 
> seeks. If this program does what you wanted, please use it to show us.

I haven't used swap prefetch either, the call was put out for what could 
be used to test the performance, and I was suggesting a test.

if nobody else follows up on this I'll try to get some time to test it 
myself in a day or two.

David Lang

Re: -mm merge plans for 2.6.23

[david]

On Wed, 25 Jul 2007, david@lang.hm wrote:

> Subject: Re: -mm merge plans for 2.6.23
> 
> On Wed, 25 Jul 2007, Rene Herman wrote:
>
>>  On 07/25/2007 10:07 AM, david@lang.hm wrote:
>> 
>> >   On Wed, 25 Jul 2007, Rene Herman wrote:
>> 
>> > >   Something like this?
>>
>>  [ ... ]
>> 
>> >   when the swap readahead is enabled does it make a significant 
>> >   difference
>> >   in the time to do the random access?
>>
>>  I don't use swap prefetch (nor -ck or -mm). If someone who has the patch
>>  applied waits to hit enter until swap prefetch has prefetched it all back
>>  in again, it certainly will.
>>
>>  Swap prefetch's potential to do larger reads back from swapspace than a
>>  random segfaulting app could well be very significant. Reads are dwarved
>>  by seeks. If this program does what you wanted, please use it to show us.
>
> I haven't used swap prefetch either, the call was put out for what could be 
> used to test the performance, and I was suggesting a test.
>
> if nobody else follows up on this I'll try to get some time to test it myself 
> in a day or two.

this assumes that this isn't ruled an invalid test in the meantime.

in any case thanks for codeing this up so quickly.

David Lang

Re: -mm merge plans for 2.6.23

[Rene Herman]

On 07/25/2007 10:28 AM, Ingo Molnar wrote:

>> Regardless, I'll stand by "[by disabling updatedb] the problem will 
>> for a large part be solved" as I expect approximately 94.372 percent 
>> of Linux desktop users couldn't care less about locate.
> 
> i think that approach is illogical: because Linux mis-handled a mixed 
> workload the answer is to ... remove a portion of that workload?

No. It got snipped but I introduced the comment by saying it was a "that's 
not the point" kind of thing. Sometimes things that aren't the point are 
still true though and in the case of Linux desktop users complaining about 
updatedb runs, a comment that says that for many an obvious solution would 
be to stop running the damned thing is not in any sense illogical.

Also note I'm not against swap prefetch or anything. I don't use it and do 
not believe I have a pressing need for it, but do suspect it has potential 
to make quite a bit of difference on some things -- if only to drastically 
reduce seeks if it means it's swapping in larger chunks than a randomly 
faulting program would.

Rene.

Re: -mm merge plans for 2.6.23

[Jesper Juhl]

On 25/07/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
[snip]
>
> Well I never said real world tests aren't acceptable, they are. There is
> a difference between an "it feels better for me", and some actual real
> measurement and analysis of said workload.
>

Let me tell you about the use-case where swap prefetch helps me. I
don't have actual numbers currently, only a subjective "it feels
better", but when I get home from work tonight I'll try to collect
some actual numbers for you.

Anyway, here's a description of the scenario (machine is a AMD
Athlon64 X2 4400+, 2GB RAM, 1GB swap, running 32bit kernel &
userspace):

A KDE desktop with the following running is common for me
 - A few (konsole) shells open running vim, pine, less, ssh sessions etc.
 - Eclipse (with CDT) with 20-30 files open in a project.
 - Firefox with 30+ tabs open.
 - LyX with a 200+ page document I'm working on open, is running.
 - Gimp running, usually with at least one or two images open (~1280x1024).
 - Amarok open and playing my playlist (a few days worth of music).
 - At least one Konqueror window in filemanager mode running.
 - More often than not OpenOffice is running with a spreadsheet or
text document open.
 - In the background the machine is running Apache, MySQL, BIND and
NFS services for my local LAN, but they see very little actual use.

Now, a thing I commonly do is fire up a new shell, pull the latest
changes from Linus' git tree and start a script running that builds a
allnoconfig kernel, a allmodconfig kernel, a allyesconfig kernel and
then 30 randconfig kernels.  Obviously that script takes quite a while
to run and loads the box quite a bit, so I usually just leave the box
alone for a few hours until it is done (sometimes I leave it over
night, in which case updatedb also gets added to the mix during the
night). This usually pushes the box to use some amount of swap.

Without swap prefetch; when I start working with one of the apps I had
running before starting the compile job it always feels a little laggy
at first. With swap prefetch app response time is not laggy when I
come back.  The "laggyness" doesn't last too long and is hard to
quantify, but I'll try getting some numbers (if in no other way, then
perhaps by using a stop watch)....

Fact is, this is a scenario that is common to me and one where swap
prefetch definately makes the box feel nicer to work with.


-- 
Jesper Juhl <jesper.juhl@gmail.com>
Don't top-post  http://www.catb.org/~esr/jargon/html/T/top-post.html
Plain text mails only, please      http://www.expita.com/nomime.html

Re: -mm merge plans for 2.6.23

[Rene Herman]

On 07/25/2007 10:33 AM, david@lang.hm wrote:

>> I haven't used swap prefetch either, the call was put out for what 
>> could be used to test the performance, and I was suggesting a test.
>>
>> if nobody else follows up on this I'll try to get some time to test it 
>> myself in a day or two.
> 
> this assumes that this isn't ruled an invalid test in the meantime.

Let's save a little time and guess. While two instances of the hog are 
running no physical memory is free (as together they take up 1.5x physical) 
meaning that swap-prefetch wouldn't get a change to do anything and wouldn't 
make a difference. As such, the two instances test as you suggested would in 
fact not be testing anything it seems.

However, if you quit one, and idle long enough to continue with the other 
one until swap-prefetch prefetched all its memory back in, it should be a 
difference on the order of minutes, even total if swap prefetch fetched it 
back in without seeking al over swap-space, and "total" isn't applicable if 
the idle time really is free.

A program randomly touching single pages all over memory is a contrived 
worst case scenario and not a real-world issue. It is a boundary condition 
though, and it's simply quite impossible to think of any example where 
swap-prefetch would _not_ give you a snappier feeling machine after you've 
been idling.

So really the only question would seem to be -- does it hurt any if you have 
_not_ been?

Rene.

Re: [ck] Re: -mm merge plans for 2.6.23

[Nick Piggin]

Jos Poortvliet wrote:

> Nick
> has been talking about 'fixing the updatedb thing' for years now, no patch
> yet.

Wrong Nick, I think.

First I heard about the updatedb problem was a few months ago with people
saying updatedb was causing their system to swap (that is, swap prefetching
helped after updatedb). I haven't been able to even try to fix it because I
can't reproduce it (I'm sitting on a machine with 256MB RAM), and nobody
has wanted to help me.


> Besides, he won't fix OO.o nor all other userspace stuff - so 
> actually,
> he does NOT even promise an alternative. Not that I think fixing updatedb
> would be cool, btw - it sure would, but it's no reason not to include swap
> prefetch - it's mostly unrelated.
> 
> I think everyone with >1 gb ram should stop saying 'I don't need it' 
> because
> that's obvious for that hardware. Just like ppl having a dual- or quadcore
> shouldn't even talk about scheduler interactivity stuff...

Actually there are people with >1GB of ram who are saying it helps. Why do
you want to shut people out of the discussion?


> Desktop users want it, tests show it works, there is no alternative and the
> maybe-promised-one won't even fix all cornercases. It's small, mostly
> selfcontained. There is a maintainer. It's been stable for a long time. 
> It's
> been in MM for a long time.
> 
> Yet it doesn't make it. Andrew says 'some ppl have objections' (he means
> Nick) and he doesn't see an advantage in it (at least 4 gig ram, right,
> Andrew?).
> 
> Do I miss things?

You could try constructively contributing?


> Apparently, it didn't get in yet - and I find it hard to believe Andrew
> holds swapprefetch for reasons like the above. So it must be something 
> else.
> 
> 
> Nick is saying tests have already proven swap prefetch to be helpfull,
> that's not the problem. He calls the requirements to get in 'fuzzy'. OK.

The test I have seen is the one that forces a huge amount of memory to
swap out, waits, then touches it. That speeds up, and that's fine. That's
a good sanity test to ensure it is working. Beyond that there are other
considerations to getting something merged.

-- 
SUSE Labs, Novell Inc.

Re: -mm merge plans for 2.6.23

[Ingo Molnar]

* Rene Herman <rene.herman@gmail.com> wrote:

> On 07/25/2007 10:28 AM, Ingo Molnar wrote:
> 
> >>Regardless, I'll stand by "[by disabling updatedb] the problem will 
> >>for a large part be solved" as I expect approximately 94.372 percent 
> >>of Linux desktop users couldn't care less about locate.
> >
> > i think that approach is illogical: because Linux mis-handled a 
> > mixed workload the answer is to ... remove a portion of that 
> > workload?
> 
> No. It got snipped but I introduced the comment by saying it was a 
> "that's not the point" kind of thing. [...]

ok - with that qualification i understand.

still, especially for someone like me who frequently deals with source 
code, 'locate' is indispensible.

and the fact is: updatedb discards a considerable portion of the cache 
completely unnecessarily: on a reasonably complex box no way do all the 
inodes and dentries fit into all of RAM, so we just trash everything. 
Maybe the kernel could be extended with a method of opening files in a 
'drop from the dcache after use' way. (beagled and backup tools could 
make use of that facility too.) (Or some other sort of 
file-cache-invalidation syscall that already exist, which would _also_ 
result in the immediate zapping of the dentry+inode from the dcache.)

	Ingo

Re: -mm merge plans for 2.6.23

[Rene Herman]

On 07/25/2007 01:34 PM, Ingo Molnar wrote:

> and the fact is: updatedb discards a considerable portion of the cache 
> completely unnecessarily: on a reasonably complex box no way do all the 
> inodes and dentries fit into all of RAM, so we just trash everything.

Okay, but unless I've now managed to really quite horribly confuse myself, 
that wouldn't have anything to do with _swap_ prefetch would it?

Rene.

Re: -mm merge plans for 2.6.23

[Ingo Molnar]

* Rene Herman <rene.herman@gmail.com> wrote:

> > and the fact is: updatedb discards a considerable portion of the 
> > cache completely unnecessarily: on a reasonably complex box no way 
> > do all the inodes and dentries fit into all of RAM, so we just trash 
> > everything.
> 
> Okay, but unless I've now managed to really quite horribly confuse 
> myself, that wouldn't have anything to do with _swap_ prefetch would 
> it?

it's connected: it would remove updatedb from the VM picture altogether. 
(updatedb would just cycle through the files with leaving minimal cache 
disturbance.)

hence swap-prefetch could concentrate on the cases where it makes sense 
to start swap prefetching _without_ destroying other, already cached 
content: such as when a large app exits and frees gobs of memory back 
into the buddy allocator. _That_ would be a definitive "no costs and 
side-effects" point for swap-prefetch to kick in, and it would eliminate 
this pretty artificial (and unnecessary) 'desktop versus server' 
controversy and would turn it into a 'helps everyone' feature.

	Ingo

Re: [ck] Re: -mm merge plans for 2.6.23

[Rene Herman]

On 07/25/2007 12:53 PM, Jos Poortvliet wrote:

> On 7/25/07, *Rene Herman* <rene.herman@gmail.com 
> <mailto:rene.herman@gmail.com>> wrote:

>> Also note I'm not against swap prefetch or anything. I don't use it and
>> do not believe I have a pressing need for it, but do suspect it has 
>> potential to make quite a bit of difference on some things -- if only
>> to drastically reduce seeks if it means it's swapping in larger chunks
>> than a randomly faulting program would.
> 
> I wonder what your hardware is. Con talked about the diff in hardware 
> between most endusers and the kernel developers. 

I'm afraid you will need to categorize me more as an innocent bystander than 
a kernel developer and, as such, I have an endusery x86 with 768M (but I 
still think of myself as one of the cool kids!)

> Yes, swap prefetch doesn't help if you have 3 GB ram, but it DOES do a
> lot on a 256 mb laptop...

Rather, it does not help if you are not swapping or idling. Probably largely 
due to me being a rather serial person I seem to never even push my git tree 
from cache. Hence my belief that "I don't have a pressing need for it".

Taking a laptop as an example is interesting in itself by the way since a 
spundown disk (most applicable to laptops) is an argument against swap 
prefetch even when idle and when I'm not mistaken the feature actually 
disables itself when the machine's set to laptop mode...

> After using OO.o, the system continues to be slow for a long time. With
> swap prefetch, it's back up speed much faster. Con has showed a benchmark
> for this with speedups of 10 times and more, users mentioned they liked
> it.

After using and quiting OO.o. If you simply don't have any memory free to 
prefetch into swap prefetch won't help any. The fact that it helps the case 
of OO.o having pushed out firefox is fairly obvious.

> Nick has been talking about 'fixing the updatedb thing' for years now, no
> patch yet. Besides, he won't fix OO.o nor all other userspace stuff - so
> actually, he does NOT even promise an alternative. Not that I think
> fixing updatedb would be cool, btw - it sure would, but it's no reason
> not to include swap prefetch - it's mostly unrelated.

Well, the trouble at least to some is that they indeed seem to be rather 
unrelated. Why does the updatedb run even cause swapout? (itself ofcourse a 
pre-condition for swap-prefetch to help).

> I think everyone with >1 gb ram should stop saying 'I don't need it' 
> because that's obvious for that hardware. Just like ppl having a dual- 
> or quadcore shouldn't even talk about scheduler interactivity stuff...

Actually, interactivity is largely about latency and latency is largely or 
partly independent of CPU speed -- if something's keeping the system from 
scheduling for too long it's likely that it's hogging the CPU for a fixed 
number of usecs and those pass in the same amount of time on all CPUs (we 
hope...).

But that's a tangent anyway. I'm just glad that I get to say that I believe 
I don't need it with my 768M!

> Apparently, it didn't get in yet - and I find it hard to believe Andrew 
> holds swapprefetch for reasons like the above. So it must be something 
> else.
> 
> Nick is saying tests have already proven swap prefetch to be helpfull, 
> that's not the problem. He calls the requirements to get in 'fuzzy'. OK.
> Beer is fuzzy, do we need to offer beer to someone? If Andrew promises 
> to come to FOSDEM again next year, I'll offer him a beer, if that 
> helps... Anything else? A nice massage?

Personally I'd go for sexual favours directly (but then again, I always do).

But please also note that I even _literally_ said above that I myself am not 
against swap-prefetch or anything and yet I get what appears to be an least 
somewhat adversary rant directed at me. Which in itself is fine, but not too 
helpful...

Nick Piggin is the person to convince it seems and if I've read things right 
(I only stepped into this thing at the updatedb mention, so maybe I haven't) 
his main question is _why_ the hell it helps updatedb. As long as you don't 
know this, then even a solution that helps could be papering over a problem 
which you'd much rather fix at the root rather than at the symptom.

Rene.

Re: [ck] Re: -mm merge plans for 2.6.23

[Ingo Molnar]

* Rene Herman <rene.herman@gmail.com> wrote:

> Nick Piggin is the person to convince it seems and if I've read things 
> right (I only stepped into this thing at the updatedb mention, so 
> maybe I haven't) his main question is _why_ the hell it helps 
> updatedb. [...]

btw., i'd like to make this clear: if you want stuff to go upstream, do 
not concentrate on 'convincing the maintainer'.

Instead concentrate on understanding the _problem_, concentrate on 
making sure that both you and the maintainer understands the problem 
correctly, possibly write some testcase that clearly exposes it, and 
help the maintainer debug the problem. _Optionally_, if you find joy in 
it, you are also free to write a proposed solution for that problem and 
submit it to the maintainer.

But a "here is a solution, take it or leave it" approach, before having 
communicated the problem to the maintainer and before having debugged 
the problem is the wrong way around. It might still work out fine if the 
solution is correct (especially if the patch is small and obvious), but 
if there are any non-trivial tradeoffs involved, or if nontrivial amount 
of code is involved, you might see your patch at the end of a really 
long (and constantly growing) waiting list of patches.

	Ingo

Re: -mm merge plans for 2.6.23

[Ray Lee]

Hoo boy, lots of messages this morning.

(Al? I've added you to the CC: because of your swap-in vs swap-out
speed report from January. See below -- half-way down or so -- for
more detals.)

On 7/24/07, david@lang.hm <david@lang.hm> wrote:
> On Tue, 24 Jul 2007, Ray Lee wrote:
>
> > On 7/23/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> >>  Ray Lee wrote:
> >
> >>  Looking at your past email, you have a 1GB desktop system and your
> >>  overnight updatedb run is causing stuff to get swapped out such that
> >>  swap prefetch makes it significantly better. This is really
> >>  intriguing to me, and I would hope we can start by making this
> >>  particular workload "not suck" without swap prefetch (and hopefully
> >>  make it even better than it currently is with swap prefetch because
> >>  we'll try not to evict useful file backed pages as well).
> >
> > updatedb is an annoying case, because one would hope that there would
> > be a better way to deal with that highly specific workload. It's also
> > pretty stat dominant, which puts it roughly in the same category as a
> > git diff. (They differ in that updatedb does a lot of open()s and
> > getdents on directories, git merely does a ton of lstat()s instead.)
> >
> > Anyway, my point is that I worry that tuning for an unusual and
> > infrequent workload (which updatedb certainly is), is the wrong way to
> > go.
>
> updatedb pushing out program data may be able to be improved on with drop
> behind or similar.

Hmm, I thought drop-behind wasn't going to be able to target metadata?

> however another scenerio that causes a similar problem is when a user is
> busy useing one of the big memory hogs and then switches to another (think
> switching between openoffice and firefox)

Yes, and that was the core of my original report months ago. I'm
working for a while on one task, go to openoffice to view a report, or
gimp to tweak the colors on a photo before uploading it, and then go
back to my email and... and... and... there we go. The faults that
occur when I context switch is what's most annoying.

> >>  After that we can look at other problems that swap prefetch helps
> >>  with, or think of some ways to measure your "whole day" scenario.
> >>
> >>  So when/if you have time, I can cook up a list of things to monitor
> >>  and possibly a patch to add some instrumentation over this updatedb
> >>  run.
> >
> > That would be appreciated. Don't spend huge amounts of time on it,
> > okay? Point me the right direction, and we'll see how far I can run
> > with it.
>
> you could make a synthetic test by writing a memory hog that allocates 3/4
> of your ram then pauses waiting for input and then randomly accesses the
> memory for a while (say randomly accessing 2x # of pages allocated) and
> then pausing again before repeating

Con wrote a benchmark much like that. It showed measurable improvement
with swap prefetch.

> by the way, I've also seen comments on the Postgres performance mailing
> list about how slow linux is compared to other OS's in pulling data back
> in that's been pushed out to swap (not a factor on dedicated database
> machines, but a big factor on multi-purpose machines)

Yeah, akpm and... one of the usual suspects, had mentioned something
such as 2.6 is half the speed of 2.4 for swapin. (Let's see if I can
find a reference for that, it's been a year or more...) Okay,
misremembered. Swap in is half the speed of swap out (
http://lkml.org/lkml/2007/1/22/173 ). Al Boldi (added to the CC:, poor
sod), is the one who knows how to measure that, I'm guessing.

Al? How are you coming up with those figures? I'm interested in
reproducing it. It could be due to something stupid, such as the VM
faulting things out in reverse order or something...

> >>  Anyway, I realise swap prefetching has some situations where it will
> >>  fundamentally outperform even the page replacement oracle. This is
> >>  why I haven't asked for it to be dropped: it isn't a bad idea at all.
> >
> > <nod>
> >
> >>  However, if we can improve basic page reclaim where it is obviously
> >>  lacking, that is always preferable. eg: being a highly speculative
> >>  operation, swap prefetch is not great for power efficiency -- but we
> >>  still want laptop users to have a good experience as well, right?
> >
> > Absolutely. Disk I/O is the enemy, and the best I/O is one you never
> > had to do in the first place.
>
> almost always true, however there is some amount of I/O that is free with
> todays drives (remember, they read the entire track into ram and then
> give you the sectors on the track that you asked for). and if you have a
> raid array this is even more true.

Yeah, I knew I'd get called on that one :-). It's the seeks that'll
really kill you, and as you say once you're on the track the rest is
practically free (which is why the VM should prefer to evict larger
chunks at a time rather than lots of small things, see
http://lkml.org/lkml/2007/7/23/214 for something that's heading the
right direction, though the side-effects are unfortunate.

> if you read one sector in from a raid5 array you have done all the same
> I/O that you would have to do to read in the entire stripe, but I don't
> believe that the current system will keep it all around if it exceeds the
> readahead limit.

Fengguang Wu is doing lots of active work on making the readahead suck
less. Ping him and he'll likely take an active interest in the RAID
stuff.

Ray

Re: -mm merge plans for 2.6.23

[Ray Lee]

On 7/24/07, Rene Herman <rene.herman@gmail.com> wrote:
> Yes, but what's locate's usage scenario? I've never, ever wanted to use it.
> When do you know the name of something but not where it's located, other
> than situations which "which" wouldn't cover and after just having
> installed/unpacked something meaning locate doesn't know about it yet either?

I use it to find source files and documents all the time. One of my
work boxes has <runs a locate work | wc -l> ~38500 files and
directories under my source directory. And then there's the "I wrote
that tech doc two years ago, where was that. Hmm, what did I name it?
Bet it had 323 in the name, and doc in the path."

I'd just like updatedb to amortize its work better. If we had some way
to track all filesystem events, updatedb could keep a live and
accurate index on the filesystem. And this isn't just updatedb that
wants that, beagle and tracker et al also want to know filesystem
events so that they can index the documents themselves as well as the
metadata. And if they do it live, that spreads the cost out, including
the VM pressure.

Ray

Re: -mm merge plans for 2.6.23

[Valdis.Kletnieks]

[-- Attachment #1: Type: text/plain, Size: 860 bytes --]

On Wed, 25 Jul 2007 13:34:01 +0200, Ingo Molnar said:

> Maybe the kernel could be extended with a method of opening files in a 
> 'drop from the dcache after use' way. (beagled and backup tools could 
> make use of that facility too.) (Or some other sort of 
> file-cache-invalidation syscall that already exist, which would _also_ 
> result in the immediate zapping of the dentry+inode from the dcache.)

The semantic that would benefit my work patterns the most would not be
"immediate zapping" - I have 2G of RAM, so often there's no memory pressure,
and often a 'find' will be followed by another similar 'find' that will hit a
lot of the same dentries and inodes, so may as well save them if we can.
Flagging it as "the first to be heaved over the side the instant there *is*
pressure" would suit just fine.

Or is that the semantic you actually meant?


[-- Attachment #2: Type: application/pgp-signature, Size: 226 bytes --]

Re: -mm merge plans for 2.6.23

[Ray Lee]

Hey Eric,

On 7/24/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> Eric St-Laurent wrote:
> > On Wed, 2007-25-07 at 06:55 +0200, Rene Herman wrote:
> >
> >
> >>It certainly doesn't run for me ever. Always kind of a "that's not the
> >>point" comment but I just keep wondering whenever I see anyone complain
> >>about updatedb why the _hell_ they are running it in the first place. If
> >>anyone who never uses "locate" for anything simply disable updatedb, the
> >>problem will for a large part be solved.
> >>
> >>This not just meant as a cheap comment; while I can think of a few similar
> >>loads even on the desktop (scanning a browser cache, a media player indexing
> >>a large amount of media files, ...) I've never heard of problems _other_
> >>than updatedb. So just junk that crap and be happy.
> >
> >
> >>From my POV there's two different problems discussed recently:
> >
> > - updatedb type of workloads that add tons of inodes and dentries in the
> > slab caches which of course use the pagecache.
> >
> > - streaming large files (read or copying) that fill the pagecache with
> > useless used-once data

No, there's a third case which I find the most annoying. I have
multiple working sets, the sum of which won't fit into RAM. When I
finish one, the kernel had time to preemptively swap back in the
other, and yet it didn't. So, I sit around, twiddling my thumbs,
waiting for my music player to come back to life, or thunderbird,
or...

Re: -mm merge plans for 2.6.23

[Ray Lee]

On 7/24/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> Ray Lee wrote:
> > On 7/23/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> >> If we can first try looking at
> >> some specific problems that are easily identified.
> >
> > Always easier, true. Let's start with "My mouse jerks around under
> > memory load." A Google Summer of Code student working on X.Org claims
> > that mlocking the mouse handling routines gives a smooth cursor under
> > load ([1]). It's surprising that the kernel would swap that out in the
> > first place.
> >
> > [1]
> > http://vignatti.wordpress.com/2007/07/06/xorg-input-thread-summary-or-something/
>
> OK, I'm not sure what the point is though. Under heavy memory load,
> things are going to get swapped out... and swap prefetch isn't going
> to help there (at least, not during the memory load).

Sorry, I headed slightly off-topic. Or perhaps 'up-topic' to the
larger issue, which is that the desktop experience has some suckiness
to it.

My point is that the page replacement algorithm has some choice as to
what to evict. The xorg input handler never should have been evicted.
It was hopefully a hard example of where the current page replacement
policy is falling flat on its face.

All that said, this could really easily be handled by xorg mlocking
the critical realtime stuff.

> There are also other issues like whether the CPU scheduler is at fault,
> etc. Interactive workloads are always the hardest to work out.

This one is not a scheduler issue, as mlock()ing the mouse handling
routines gives a smooth cursor. It's just a pure page replacement
problem, as the kernel should never have swapped that out in the first
place.

<snip things I agreed with>

<snip list of things to watch during updatedb run>

Ray

Re: [ck] Re: -mm merge plans for 2.6.23

[Satyam Sharma]

Hi Ingo,

[ Going off-topic, nothing related to swap/prefetch/etc. Just getting
a hang of how development goes on here ... ]

On 7/25/07, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Rene Herman <rene.herman@gmail.com> wrote:
>
> > Nick Piggin is the person to convince it seems and if I've read things
> > right (I only stepped into this thing at the updatedb mention, so
> > maybe I haven't) his main question is _why_ the hell it helps
> > updatedb. [...]
>
> btw., i'd like to make this clear: if you want stuff to go upstream, do
> not concentrate on 'convincing the maintainer'.

It's not so easy or clear-cut, see below.

> Instead concentrate on understanding the _problem_,

Of course -- that's a given.

> concentrate on
> making sure that both you and the maintainer understands the problem
> correctly,

This itself may require some "convincing" to do. What if the maintainer
just doesn't recognize the problem? Note that the development model
here is more about the "social" thing than purely a "technical" thing.
People do handwave, possibly due to innocent misunderstandings,
possibly without. Often it's just a case of seeing different reasons behind
the "problematic behaviour". Or it could be a case of all of the above.

> possibly write some testcase that clearly exposes it, and

Oh yes -- that'll be helpful, but definitely not necessarily a prerequisite
for all issues, and then you can't even expect everybody to write or
test/benchmark with testcases. (oh, btw, this is assuming you do find
consensus on a testcase)

> help the maintainer debug the problem.

Umm ... well. Should this "dance-with-the-maintainer" and all be really
necessary? What you're saying is easy if a "bug" is simple and objective,
with mathematically few (probably just one) possible correct solutions.
Often (most often, in fact) it's a subjective issue -- could be about APIs,
high level design, tradeoffs, even little implementation nits ... with one
person wanting to do it one way, another thinks there's something hacky
or "band-aidy" about it and a more beautiful/elegant solution exists elsewhere.
I think there's a similar deadlock here (?)

> _Optionally_, if you find joy in
> it, you are also free to write a proposed solution for that problem

Oh yes. But why "optionally"? This is *precisely* what the spirit of
development in such open / distributed projects is ... unless Linux
wants to die the same, slow, ivory-towered, miserable death that
*BSD have.

> and
> submit it to the maintainer.

Umm, ok ... pretty unlikely Linus or Andrew would take patches for any
kernel subsystem (that isn't obvious/trivial) from anybody just like that,
so you do need to Cc: the ones they trust (maintainer) to ensure they
review/ack your work and pick it up.

> But a "here is a solution, take it or leave it" approach,

Agreed. That's definitely not the way to go.

> before having
> communicated the problem to the maintainer

Umm, well this could depend from problem-to-problem.

> and before having debugged
> the problem

Again, agreed -- but people can plausibly see different root causes for
the same symptoms -- and different solutions.

> is the wrong way around. It might still work out fine if the
> solution is correct (especially if the patch is small and obvious), but
> if there are any non-trivial tradeoffs involved, or if nontrivial amount
> of code is involved, you might see your patch at the end of a really
> long (and constantly growing) waiting list of patches.

That's the whole point. For non-trivial / non-obvious / subjective issues,
the "process" you laid out above could itself become a problem ...

Satyam

Re: -mm merge plans for 2.6.23

[Frank A. Kingswood]

Nick Piggin wrote:
> OK, this is where I start to worry. Swap prefetch AFAIKS doesn't fix
> the updatedb problem very well, because if updatedb has caused swapout
> then it has filled memory, and swap prefetch doesn't run unless there
> is free memory (not to mention that updatedb would have paged out other
> files as well).

It is *not* about updatedb. That is just a trivial case which people 
notice. Therefore fixing updatedb to be nicer, as was discussed at 
various points in this thread, is *not* the solution.
Most users are also *not*at*all* interested in kernel builds as a metric 
of system performance.

When I'm at work, I run a large, commercial, engineering application. 
While running, it takes most of the system memory (4GB and up), and it 
reads and writes very large files. Swap prefetch noticeably helps my 
desktop too. Can I measure it? Not sure. Can people on lkml fix the 
application? Certainly not.

Frank

Re: -mm merge plans for 2.6.23

[Al Boldi]

Ray Lee wrote:
> On 7/24/07, david@lang.hm <david@lang.hm> wrote:
> > by the way, I've also seen comments on the Postgres performance mailing
> > list about how slow linux is compared to other OS's in pulling data back
> > in that's been pushed out to swap (not a factor on dedicated database
> > machines, but a big factor on multi-purpose machines)
>
> Yeah, akpm and... one of the usual suspects, had mentioned something
> such as 2.6 is half the speed of 2.4 for swapin. (Let's see if I can
> find a reference for that, it's been a year or more...) Okay,
> misremembered. Swap in is half the speed of swap out (
> http://lkml.org/lkml/2007/1/22/173 ). Al Boldi (added to the CC:, poor
> sod), is the one who knows how to measure that, I'm guessing.
>
> Al? How are you coming up with those figures? I'm interested in
> reproducing it. It could be due to something stupid, such as the VM
> faulting things out in reverse order or something...

Thanks for asking.  I'm rather surprised why nobody's noticing any of this 
slowdown.  To be fair, it's not really a regression, on the contrary, 2.4 is 
lot worse wrt swapin and swapout, and Rik van Riel even considers a 50% 
swapin slowdown wrt swapout something like better than expected (see thread 
'[RFC] kswapd: Kernel Swapper performance').  He probably meant random 
swapin, which seems to offer a 4x slowdown.

There are two ways to reproduce this:

1. swsusp to disk reports ~44mb/s swapout, and ~25mb/s swapin during resume

2. tmpfs swapout is superfast, whereas swapin is really slow
(see thread '[PATCH] free swap space when (re)activating page')

Here is an excerpt from that thread (note machine config in first line):

============================================
 RAM 512mb , SWAP 1G
 #mount -t tmpfs -o size=1G none /dev/shm
 #time cat /dev/full > /dev/shm/x.dmp
 15sec
 #time cat /dev/shm/x.dmp > /dev/null
 58sec
 #time cat /dev/shm/x.dmp > /dev/null
 72sec
 #time cat /dev/shm/x.dmp > /dev/null
 85sec
 #time cat /dev/shm/x.dmp > /dev/null
 93sec
 #time cat /dev/shm/x.dmp > /dev/null
 99sec
============================================

As you can see, swapout is running full wirespeed, whereas swapin not only is 
4x slower, but increasingly gets the VM tangled up to end at a ~6x slowdown.

So again, I'm really surprised people haven't noticed.


Thanks!

--
Al

Re: [ck] Re: -mm merge plans for 2.6.23

[Ingo Molnar]

* Satyam Sharma <satyam.sharma@gmail.com> wrote:

> > concentrate on making sure that both you and the maintainer 
> > understands the problem correctly,
> 
> This itself may require some "convincing" to do. What if the 
> maintainer just doesn't recognize the problem? Note that the 
> development model here is more about the "social" thing than purely a 
> "technical" thing. People do handwave, possibly due to innocent 
> misunderstandings, possibly without. Often it's just a case of seeing 
> different reasons behind the "problematic behaviour". Or it could be a 
> case of all of the above.

sure - but i was really not talking about from the user's perspective, 
but from the enterprising kernel developer's perspective who'd like to 
solve a particular problem. And the nice thing about concentrating on 
the problem: if you do that well, it does not really matter what the 
maintainer thinks!

( Talking to the maintainer can of course be of enormous help in the 
  quest for understanding the problem and figuring out the best fix - 
  the maintainer will most likely know more about the subject than 
  yourself. More communication never hurts. It's an additional bonus if 
  you manage to convince the maintainer to take up the matter for 
  himself. It's not a given right though - a maintainer's main task is 
  to judge code that is being submitted, to keep a subsystem running
  smoothly and to not let it regress - but otherwise there can easily be
  different priorities of what tasks to tackle first, and in that sense 
  the maintainer is just one of the many overworked kernel developers 
  who has no real obligation what to tackle first. )

If the maintainer rejects something despite it being well-reasoned, 
well-researched and robustly implemented with no tradeoffs and 
maintainance problems at all then it's a bad maintainer. (but from all 
i've seen in the past few years the VM maintainers do their job pretty 
damn fine.) And note that i _do_ disagree with them in this particular 
swap-prefetch case, but still, the non-merging of swap-prefetch was not 
a final decision at all. It was more of a "hm, dunno, i still dont 
really like it - shouldnt this be done differently? Could we debug this 
a bit better?" reaction. Yes, it can be frustrating after more than one 
year.

> > possibly write some testcase that clearly exposes it, and
> 
> Oh yes -- that'll be helpful, but definitely not necessarily a 
> prerequisite for all issues, and then you can't even expect everybody 
> to write or test/benchmark with testcases. (oh, btw, this is assuming 
> you do find consensus on a testcase)

no, but Con is/was certainly more than capable to write testcases and to 
debug various scenarios. That's the way how new maintainers are found 
within Linux: people take matters in their own hands and improve a 
subsystem so that they'll either peacefully co-work with the other 
maintainers or they replace them (sometimes not so peacefully - like in 
the IDE/SATA/PATA saga).

> > help the maintainer debug the problem.
> 
> Umm ... well. Should this "dance-with-the-maintainer" and all be 
> really necessary? What you're saying is easy if a "bug" is simple and 
> objective, with mathematically few (probably just one) possible 
> correct solutions. Often (most often, in fact) it's a subjective issue 
> -- could be about APIs, high level design, tradeoffs, even little 
> implementation nits ... with one person wanting to do it one way, 
> another thinks there's something hacky or "band-aidy" about it and a 
> more beautiful/elegant solution exists elsewhere. I think there's a 
> similar deadlock here (?)

you dont _have to_ cooperative with the maintainer, but it's certainly 
useful to work with good maintainers, if your goal is to improve Linux. 
Or if for some reason communication is not working out fine then grow 
into the job and replace the maintainer by doing a better job.

> > _Optionally_, if you find joy in it, you are also free to write a 
> > proposed solution for that problem
> 
> Oh yes. But why "optionally"? This is *precisely* what the spirit of 
> development in such open / distributed projects is ... unless Linux 
> wants to die the same, slow, ivory-towered, miserable death that *BSD 
> have.

perhaps you misunderstood how i meant the 'optional': it is certainly 
not required to write a solution for every problem you are reporting. 
Best-case the maintainer picks the issue up and solves it. Worst-case 
you get ignored. But you always have the option to take matters into 
your own hands and solve the problem.

> >and submit it to the maintainer.
> 
> Umm, ok ... pretty unlikely Linus or Andrew would take patches for any 
> kernel subsystem (that isn't obvious/trivial) from anybody just like 
> that, so you do need to Cc: the ones they trust (maintainer) to ensure 
> they review/ack your work and pick it up.

actually, it happens pretty frequently, and NACK-ing perfectly 
reasonable patches is a sure way towards getting replaced as a 
maintainer.

> > is the wrong way around. It might still work out fine if the 
> > solution is correct (especially if the patch is small and obvious), 
> > but if there are any non-trivial tradeoffs involved, or if 
> > nontrivial amount of code is involved, you might see your patch at 
> > the end of a really long (and constantly growing) waiting list of 
> > patches.
> 
> That's the whole point. For non-trivial / non-obvious / subjective 
> issues, the "process" you laid out above could itself become a problem 
> ...

firstly, there's rarely any 'subjective' issue in maintainance 
decisions, even when it comes to complex patches. The 'subjective' issue 
becomes a factor mostly when a problem has not been researched well 
enough, when it becomes more of a faith thing ('i believe it helps me') 
than a fully fact-backed argument. Maintainers tend to dodge such issues 
until they become more clearly fact-backed.

providing more and more facts gradually reduces the 'judgement/taste' 
leeway of maintainers, down to an almost algorithmic level.

but in any case there's always the ultimate way out: prove that you can 
do a better job yourself and replace the maintainer. But providing an 
overwhelming, irresistable body of facts in favor of a patch does the 
trick too in 99.9% of the cases.

	Ingo

Re: -mm merge plans for 2.6.23

[Andi Kleen]

Nick Piggin <nickpiggin@yahoo.com.au> writes:

> Ray Lee wrote:
> > On 7/23/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> 
> >> Also a random day at the desktop, it is quite a broad scope and
> >> pretty well impossible to analyse.
> > It is pretty broad, but that's also what swap prefetch is targetting.
> > As for hard to analyze, I'm not sure I agree. One can black-box test
> > this stuff with only a few controls. e.g., if I use the same apps each
> > day (mercurial, firefox, xorg, gcc), and the total I/O wait time
> > consistently goes down on a swap prefetch kernel (normalized by some
> > control statistic, such as application CPU time or total I/O, or
> > something), then that's a useful measurement.
> 
> I'm not saying that we can't try to tackle that problem, but first of
> all you have a really nice narrow problem where updatedb seems to be
> causing the kernel to completely do the wrong thing. So we start on
> that.

One simple way to fix this would be to implement a fadvise() flag
that puts the dentry/inode on a "soon to be expired" list if there
are no other references. Then if a dentry allocation needs more
memory try to reuse dentries from that list (or better queue) first. Any other
access will remove the dentry from the list. 

Disadvantage would be that the userland would need to be patched,
but I guess it's better than adding very dubious heuristics to the
kernel.

Similar thing could be done for directory buffers although they
are probably less of a problem.

I expect that C.Lameter's directed dentry/inode freeing in slub will also
make a big difference. People who have problems with updatedb should
definitely try mm which has it I believe and enable SLUB.

-Andi (who always thought swap prefetch was just a workaround, not
a real solution) 

Re: -mm merge plans for 2.6.23

[Zan Lynx]

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On Wed, 2007-07-25 at 09:02 -0700, Ray Lee wrote:

> I'd just like updatedb to amortize its work better. If we had some way
> to track all filesystem events, updatedb could keep a live and
> accurate index on the filesystem. And this isn't just updatedb that
> wants that, beagle and tracker et al also want to know filesystem
> events so that they can index the documents themselves as well as the
> metadata. And if they do it live, that spreads the cost out, including
> the VM pressure.

That would be nice.  It'd be great if there was a per-filesystem inotify
mode.  I can't help but think it'd be more efficient than recursing
every directory and adding a watch.

Or maybe a netlink thing that could buffer events since filesystem mount
until a daemon could get around to starting, so none were lost.
-- 
Zan Lynx <zlynx@acm.org>

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Re: -mm merge plans for 2.6.23

[Ray Lee]

On 7/25/07, Zan Lynx <zlynx@acm.org> wrote:
> On Wed, 2007-07-25 at 09:02 -0700, Ray Lee wrote:
>
> > I'd just like updatedb to amortize its work better. If we had some way
> > to track all filesystem events, updatedb could keep a live and
> > accurate index on the filesystem. And this isn't just updatedb that
> > wants that, beagle and tracker et al also want to know filesystem
> > events so that they can index the documents themselves as well as the
> > metadata. And if they do it live, that spreads the cost out, including
> > the VM pressure.
>
> That would be nice.  It'd be great if there was a per-filesystem inotify
> mode.  I can't help but think it'd be more efficient than recursing
> every directory and adding a watch.
>
> Or maybe a netlink thing that could buffer events since filesystem mount
> until a daemon could get around to starting, so none were lost.

See "Filesystem Event Reporter" by Yi Yang, that does pretty much
exactly that. http://lkml.org/lkml/2006/9/30/98 . Author had things to
update, never resubmitted it as far as I can tell.

Ray

Re: -mm merge plans for 2.6.23

[Paul Jackson]

> and the fact is: updatedb discards a considerable portion of the cache 
> completely unnecessarily: on a reasonably complex box no way do all the 

I'm wondering how much of this updatedb problem is due to poor layout
of swap and other file systems across disk spindles.

I'll wager that those most impacted by updatedb have just one disk.

I have the following three boxes - three different setups, each with
different updatedb behaviour:

    The first box, with 1 GB ram, becomes dog slow as soon as it
    breaths on the swap device.  Updatedb and backups are painful
    intrusions on any interactive work on that system.  I sometimes
    wait a half minute for a response from an interactive application
    anytime it has to go to disk.  This box has a single disk spindle,
    on an old cheap slow disk, with swap on the opposite end of the
    disk from root and the main usr partition.  It's a worst case
    disk seek test device.

    The second box, also with 1 GB ram, has multiple disk spindles,
    and swap on its own spindle.  I can still notice updatedb and
    backup, but it's far far less painful.

    The third box has dual CPU cores and 4 GB ram.  Updatedb runs
    over the entire system in perhaps 30 seconds with no perceptible
    impact at all on interactive uses.  Everything is still in memory
    from the previous updatedb run; the disk is just used to write
    out new stuff.  Swap is never used on this (sweet) rig.

I'd think that prefetch would help in the single disk spindle
configuration, because it does the swap accesses separately, instead
of intermingling them with root or usr partition accesses, which
would require alot of disk head seeking.

Pretty much anytime that ordinary desktop users complain about
performance as much as they have about this one, it's either disk
head seeks or network delays.  Nothing else is -that- slow, to be so
noticeable to so many users just doing ordinary work.

Question:
  Could those who have found this prefetch helps them alot say how
  many disks they have?  In particular, is their swap on the same
  disk spindle as their root and user files?

Answer - for me:
  On my system where updatedb is a big problem, I have one, slow, disk.
  On my system where updatedb is a small problem, swap is on a separate
    spindle.
  On my system where updatedb is -no- problem, I have so much memory
    I never use swap.

I'd expect the laptop crowd to mostly have a single, slow, disk, and
hence to find updatedb more painful.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.925.600.0401

Re: -mm merge plans for 2.6.23

[Zan Lynx]

[-- Attachment #1: Type: text/plain, Size: 953 bytes --]

On Wed, 2007-07-25 at 15:05 -0700, Paul Jackson wrote:
[snip]
> Question:
>   Could those who have found this prefetch helps them alot say how
>   many disks they have?  In particular, is their swap on the same
>   disk spindle as their root and user files?
> 
> Answer - for me:
>   On my system where updatedb is a big problem, I have one, slow, disk.
>   On my system where updatedb is a small problem, swap is on a separate
>     spindle.
>   On my system where updatedb is -no- problem, I have so much memory
>     I never use swap.
> 
> I'd expect the laptop crowd to mostly have a single, slow, disk, and
> hence to find updatedb more painful.

A well done swap-to-flash would help here.  I sometimes do it anyway to
a 4GB CF card but I can tell it's hitting the read/update/write cycles
on the flash blocks.  The sad thing is that it is still a speed
improvement over swapping to laptop disk.
-- 
Zan Lynx <zlynx@acm.org>

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Re: -mm merge plans for 2.6.23

[Jesper Juhl]

On 26/07/07, Paul Jackson <pj@sgi.com> wrote:
> > and the fact is: updatedb discards a considerable portion of the cache
> > completely unnecessarily: on a reasonably complex box no way do all the
>
> I'm wondering how much of this updatedb problem is due to poor layout
> of swap and other file systems across disk spindles.
>
> I'll wager that those most impacted by updatedb have just one disk.
>
[snip]
>
> Question:
>   Could those who have found this prefetch helps them alot say how
>   many disks they have?  In particular, is their swap on the same
>   disk spindle as their root and user files?
>

Swap prefetch helps me.

In my case I have a single (10K RPM, Ultra 160 SCSI) disk.

# fdisk -l /dev/sda

Disk /dev/sda: 36.7 GB, 36703918080 bytes
255 heads, 63 sectors/track, 4462 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1         974     7823623+  83  Linux
/dev/sda2             975        1218     1959930   83  Linux
/dev/sda3            1219        1341      987997+  82  Linux swap
/dev/sda4            1342        4462    25069432+  83  Linux

sda1 is "/", sda2 is "/usr/local/" and sda4 is "/home/"


But, I don't think updatedb is the problem, at least not just updatedb
on its own.
My machine has 2GB of RAM, so a single updatedb on its own will not
cause it to start swapping, but it does eat up a chunk of mem no doubt
about that.
The problem with updatedb is simply that it can be a contributing
factor to stuff being swapped out, but any memory hungry application
can do that - just try building an allyesconfig kernel and see how
much the linker eats towards the end.

What swap prefetch helps is not updatedb specifically, In my
experience it helps any case where you have applications running, then
start some memory hungry job that runs for a limited time, push the
previously started apps out to swap and then dies (like updatedb or a
compile job).

Without swap prefetch those apps that were pushed to swap won't be
brought back in before they are used (at which time the user is going
to have to sit there and wait for them).
With swap prefetch, the apps that got swapped out will slowly make
their way back once the mem hungry app has died and will then be fully
or partly back in memory when the user comes back to them.

That's how swap prefetch helps, it's got nothing to do with updatedb
as such - at least not as I see it.

-- 
Jesper Juhl <jesper.juhl@gmail.com>
Don't top-post  http://www.catb.org/~esr/jargon/html/T/top-post.html
Plain text mails only, please      http://www.expita.com/nomime.html

Re: [ck] Re: -mm merge plans for 2.6.23

[Michael Chang]

On 7/25/07, Paul Jackson <pj@sgi.com> wrote:
> Question:
>   Could those who have found this prefetch helps them alot say how
>   many disks they have?  In particular, is their swap on the same
>   disk spindle as their root and user files?

I have found that swap prefetch helped on all of the four machines
machine I have, although the effect is more noticeable on machines
with slower disks. They all have one hard disk, and root and swap were
always on the same disk. I have no idea how to determine how many disk
spindles they have, but since the drives are mainly low-end consumer
models sold with low-end sub $500 PCs...

-- 
Michael Chang

Please avoid sending me Word or PowerPoint attachments. Send me ODT,
RTF, or HTML instead.
See http://www.gnu.org/philosophy/no-word-attachments.html
Thank you.

Re: [ck] Re: -mm merge plans for 2.6.23

[André Goddard Rosa]

> Question:
>   Could those who have found this prefetch helps them alot say how
>   many disks they have?  In particular, is their swap on the same
>   disk spindle as their root and user files?
>
> Answer - for me:
>   On my system where updatedb is a big problem, I have one, slow, disk.

On both desktop and laptop.

Cheers,
-- 
[]s,
André Goddard

Re: [ck] Re: -mm merge plans for 2.6.23

[Matthew Hawkins]

On 7/26/07, Ray Lee <ray-lk@madrabbit.org> wrote:
> I'd just like updatedb to amortize its work better. If we had some way
> to track all filesystem events, updatedb could keep a live and
> accurate index on the filesystem. And this isn't just updatedb that
> wants that, beagle and tracker et al also want to know filesystem
> events so that they can index the documents themselves as well as the
> metadata. And if they do it live, that spreads the cost out, including
> the VM pressure.

We already have this, its called inotify (and if I'm not mistaken,
beagle already uses it).  Several years ago when it was still a little
flakey patch, I built a custom filesystem indexer into an enterprise
search engine using it (I needed to pull apart Unix mbox files).  The
only trouble of course is the action is triggered immediately, which
may not always be ideal (but that's a userspace problem)

-- 
Matt

Re: [ck] Re: -mm merge plans for 2.6.23

[Ray Lee]

On 7/25/07, Matthew Hawkins <darthmdh@gmail.com> wrote:
> On 7/26/07, Ray Lee <ray-lk@madrabbit.org> wrote:
> > I'd just like updatedb to amortize its work better. If we had some way
> > to track all filesystem events, updatedb could keep a live and
> > accurate index on the filesystem. And this isn't just updatedb that
> > wants that, beagle and tracker et al also want to know filesystem
> > events so that they can index the documents themselves as well as the
> > metadata. And if they do it live, that spreads the cost out, including
> > the VM pressure.
>
> We already have this, its called inotify (and if I'm not mistaken,
> beagle already uses it).

Yeah, I know about inotify, but it doesn't scale.

ray@phoenix:~$ find ~ -type d | wc -l
17933
ray@phoenix:~$

That's not fun with inotify, and that's just my home directory. The
vast majority of those are quiet the vast majority of the time, which
is the crux of the problem, and why inotify isn't a great fit for
on-demand virus scanners or indexers.

Ray

Re: [ck] Re: -mm merge plans for 2.6.23

[Bartlomiej Zolnierkiewicz]

Hi,

Some general thoughts about submitter/maintainer responsibilities,
not necessarily connected with the recents events (I hasn't been
following them closely - some people don't have that much free time
to burn at their hands ;)...

On Wednesday 25 July 2007, Ingo Molnar wrote:
> 
> * Satyam Sharma <satyam.sharma@gmail.com> wrote:
> 
> > > concentrate on making sure that both you and the maintainer 
> > > understands the problem correctly,
> > 
> > This itself may require some "convincing" to do. What if the 
> > maintainer just doesn't recognize the problem? Note that the 
> > development model here is more about the "social" thing than purely a 
> > "technical" thing. People do handwave, possibly due to innocent 
> > misunderstandings, possibly without. Often it's just a case of seeing 
> > different reasons behind the "problematic behaviour". Or it could be a 
> > case of all of the above.
> 
> sure - but i was really not talking about from the user's perspective, 
> but from the enterprising kernel developer's perspective who'd like to 
> solve a particular problem. And the nice thing about concentrating on 
> the problem: if you do that well, it does not really matter what the 
> maintainer thinks!

Yes, this is a really good strategy to get you changes upstream (and it
works) - just make changes so perfect that nobody can really complain. :)

The only problem is that the bigger the change becomes the less likely it
is to get it perfect so for really big changes it is also useful to show
maintainer that you take responsibility of your changes (by taking bugreports
and potential review issues very seriously instead of ignoring them, past
history of your merged changes has also a big influence here) so he will
know that you won't leave him in the cold with your code when bugreports
happen and be _sure_ that they will happen with bigger changes.

> ( Talking to the maintainer can of course be of enormous help in the 
>   quest for understanding the problem and figuring out the best fix - 
>   the maintainer will most likely know more about the subject than 
>   yourself. More communication never hurts. It's an additional bonus if 
>   you manage to convince the maintainer to take up the matter for 
>   himself. It's not a given right though - a maintainer's main task is 
>   to judge code that is being submitted, to keep a subsystem running
>   smoothly and to not let it regress - but otherwise there can easily be
>   different priorities of what tasks to tackle first, and in that sense 
>   the maintainer is just one of the many overworked kernel developers 
>   who has no real obligation what to tackle first. )

Yep, and patch author should try to help maintainer understand both the
problem he is trying to fix and the solution, i.e. throwing some undocumented
patches and screaming at maintainer to merge them is not a way to go.

> If the maintainer rejects something despite it being well-reasoned, 
> well-researched and robustly implemented with no tradeoffs and 
> maintainance problems at all then it's a bad maintainer. (but from all 
> i've seen in the past few years the VM maintainers do their job pretty 
> damn fine.) And note that i _do_ disagree with them in this particular 
> swap-prefetch case, but still, the non-merging of swap-prefetch was not 
> a final decision at all. It was more of a "hm, dunno, i still dont 
> really like it - shouldnt this be done differently? Could we debug this 
> a bit better?" reaction. Yes, it can be frustrating after more than one 
> year.
> 
> > > possibly write some testcase that clearly exposes it, and
> > 
> > Oh yes -- that'll be helpful, but definitely not necessarily a 
> > prerequisite for all issues, and then you can't even expect everybody 
> > to write or test/benchmark with testcases. (oh, btw, this is assuming 
> > you do find consensus on a testcase)
> 
> no, but Con is/was certainly more than capable to write testcases and to 
> debug various scenarios. That's the way how new maintainers are found 
> within Linux: people take matters in their own hands and improve a 
> subsystem so that they'll either peacefully co-work with the other 
> maintainers or they replace them (sometimes not so peacefully - like in 
> the IDE/SATA/PATA saga).

Heh, now that you've raised IDE saga I feel obligated to stand up
and say a few words...

The latest opening of IDE saga was quite interesting in the current context
because we had exactly the reversed situation there - "independent" maintainer
and "enterprise" developer (imagine the amount of frustration on both sides)
but the root source was quite similar (inability to get changes merged).

IMO the source root of the conflict lied in coming from different perspectives
and having a bit different priorities (stabilising/cleaning current code vs
adding new features on top of pile of crap).  In such situations it is very
important to be able to stop for a moment and look at the situation from
the other person's perspective.

In summary:

The IDE-wars are the thing of the past and lets learn from IDE-world
mistakes instead of repeating them in other subsystems, OK? :)

> > > help the maintainer debug the problem.
> > 
> > Umm ... well. Should this "dance-with-the-maintainer" and all be 
> > really necessary? What you're saying is easy if a "bug" is simple and 
> > objective, with mathematically few (probably just one) possible 
> > correct solutions. Often (most often, in fact) it's a subjective issue 
> > -- could be about APIs, high level design, tradeoffs, even little 
> > implementation nits ... with one person wanting to do it one way, 
> > another thinks there's something hacky or "band-aidy" about it and a 
> > more beautiful/elegant solution exists elsewhere. I think there's a 
> > similar deadlock here (?)
> 
> you dont _have to_ cooperative with the maintainer, but it's certainly 
> useful to work with good maintainers, if your goal is to improve Linux. 
> Or if for some reason communication is not working out fine then grow 
> into the job and replace the maintainer by doing a better job.

The idea of growing into the job and replacing the maintainer by proving
the you are doing better job was viable few years ago but may not be
feasible today.

If maintainer is "enterprise" developer and maintaining is part of his
job replacing him may be not possible et all because you simply lack
the time to do the job.  You may be actually better but you can't afford
to show it and without showing it you won't replace him (catch 22).

Oh, and it could happen that if maintainer works for a distro he sticks
his competing solution to the problem to the distro kernel and suddenly
gets order of magnitude more testers and sometimes even contributors.

How are you supposed to win such competition?  [ A: You can't. ]

I'm not even mentioning the situation when the maintainer is just a genius
and one of the best kernel hackers ever (I'm talking about you actually :)
so your chances are pretty slim from the start...

> > > _Optionally_, if you find joy in it, you are also free to write a 
> > > proposed solution for that problem
> > 
> > Oh yes. But why "optionally"? This is *precisely* what the spirit of 
> > development in such open / distributed projects is ... unless Linux 
> > wants to die the same, slow, ivory-towered, miserable death that *BSD 
> > have.
> 
> perhaps you misunderstood how i meant the 'optional': it is certainly 
> not required to write a solution for every problem you are reporting. 
> Best-case the maintainer picks the issue up and solves it. Worst-case 
> you get ignored. But you always have the option to take matters into 
> your own hands and solve the problem.
> 
> > >and submit it to the maintainer.
> > 
> > Umm, ok ... pretty unlikely Linus or Andrew would take patches for any 
> > kernel subsystem (that isn't obvious/trivial) from anybody just like 
> > that, so you do need to Cc: the ones they trust (maintainer) to ensure 
> > they review/ack your work and pick it up.
> 
> actually, it happens pretty frequently, and NACK-ing perfectly 

It actually happens really rarely (there are pretty good reasons for that).

> reasonable patches is a sure way towards getting replaced as a 
> maintainer.

"reasonable" is highly subjective

> > > is the wrong way around. It might still work out fine if the 
> > > solution is correct (especially if the patch is small and obvious), 
> > > but if there are any non-trivial tradeoffs involved, or if 
> > > nontrivial amount of code is involved, you might see your patch at 
> > > the end of a really long (and constantly growing) waiting list of 
> > > patches.
> > 
> > That's the whole point. For non-trivial / non-obvious / subjective 
> > issues, the "process" you laid out above could itself become a problem 
> > ...
> 
> firstly, there's rarely any 'subjective' issue in maintainance 
> decisions, even when it comes to complex patches. The 'subjective' issue 
> becomes a factor mostly when a problem has not been researched well 
> enough, when it becomes more of a faith thing ('i believe it helps me') 
> than a fully fact-backed argument. Maintainers tend to dodge such issues 
> until they become more clearly fact-backed.

Yep.

However there is a some reasonable time limit for this dodging, two years
isn't reasonable.  By being a maintainer you frequently have to sacrifice
your own goals and instead work on other people changes first (sometimes
even on changes that you don't find particulary interesting or important).
Sure it doesn't give you the same credit you'll get for your own changes
but you're investing in people who will help you in a long-term.

Could you allow the luxury of losing these people?

The another problem is that sometimes it seems that independent developers
has to go through more hops than entreprise ones and it is really frustrating
experience for them.  There is no conspiracy here - it is only the natural
mechanism of trusting more in the code of people who you are working with more.

> providing more and more facts gradually reduces the 'judgement/taste' 
> leeway of maintainers, down to an almost algorithmic level.
> but in any case there's always the ultimate way out: prove that you can 
> do a better job yourself and replace the maintainer. But providing an 

As stated before - this is nearly impossible in some cases.

I'm not proposing any kind of justice or fair chances here I'm just saying
that in the long-term it is gonna hurt said maintainer because he will lose
talented people willing to work on the code that he maintains.

> overwhelming, irresistable body of facts in favor of a patch does the 
> trick too in 99.9% of the cases.

Now could I ask people to stop all this -ck threads and give the developers
involved in the recent events some time to calmly rethink the whole case.

Please?

Thanks,
Bart

Re: [ck] Re: -mm merge plans for 2.6.23

[Matthew Hawkins]

On 7/26/07, Ray Lee <ray-lk@madrabbit.org> wrote:
> Yeah, I know about inotify, but it doesn't scale.

Yeah, the nonrecursive behaviour is a bugger.  Also I found it helped
to queue operations in userspace and execute periodically rather than
trying to execute on every single notification.  Worked well for
indexing, for virus scanning though you'd want to do some risk
analysis.

It'd be nice to have a filesystem that handled that sort of thing
internally *cough*winfs*cough*.  That was my hope for reiserfs a very
long time ago with its pluggable fs modules feature.

-- 
Matt

Re: [ck] Re: -mm merge plans for 2.6.23

[Jeff Garzik]

Bartlomiej Zolnierkiewicz wrote:
> On Wednesday 25 July 2007, Ingo Molnar wrote:
>> you dont _have to_ cooperative with the maintainer, but it's certainly 
>> useful to work with good maintainers, if your goal is to improve Linux. 
>> Or if for some reason communication is not working out fine then grow 
>> into the job and replace the maintainer by doing a better job.
> 
> The idea of growing into the job and replacing the maintainer by proving
> the you are doing better job was viable few years ago but may not be
> feasible today.

IMO...  Tejun is an excellent counter-example.  He showed up as an 
independent developer, put a bunch of his own spare time and energy into 
the codebase, and is probably libata's main engineer (in terms of code 
output) today.  If I get hit by a bus tomorrow, I think the Linux 
community would be quite happy with him as the libata maintainer.


> The another problem is that sometimes it seems that independent developers
> has to go through more hops than entreprise ones and it is really frustrating
> experience for them.  There is no conspiracy here - it is only the natural
> mechanism of trusting more in the code of people who you are working with more.

I think Tejun is a counter-example here too :)  Everyone's experience is 
different, but from my perspective, Tejun "appeared out of nowhere" 
producing good code, and so, it got merged rapidly.

Personally, for merging code, I tend to trust people who are most in 
tune with "the Linux Way(tm)."  It is hard to quantify, but quite often, 
independent developers "get it" when enterprise developers do not.


> Now could I ask people to stop all this -ck threads and give the developers
> involved in the recent events some time to calmly rethink the whole case.

Indeed...

	Jeff

Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Wed, 25 Jul 2007 09:09:01 -0700
"Ray Lee" <ray-lk@madrabbit.org> wrote:

> No, there's a third case which I find the most annoying. I have
> multiple working sets, the sum of which won't fit into RAM. When I
> finish one, the kernel had time to preemptively swap back in the
> other, and yet it didn't. So, I sit around, twiddling my thumbs,
> waiting for my music player to come back to life, or thunderbird,
> or...

Yes, I'm thinking that's a good problem statement and it isn't something
which the kernel even vaguely attempts to address, apart from normal
demand paging.

We could perhaps improve things with larger and smarter fault readaround,
perhaps guided by refault-rate measurement.  But that's still demand-paged
rather than being proactive/predictive/whatever.

None of this is swap-specific though: exactly the same problem would need
to be solved for mmapped files and even plain old pagecache.

In fact I'd restate the problem as "system is in steady state A, then there
is a workload shift causing transition to state B, then the system goes
idle.  We now wish to reinstate state A in anticipation of a resumption of
the original workload".

swap-prefetch solves a part of that.

A complete solution for anon and file-backed memory could be implemented
(ta-da) in userspace using the kernel inspection tools in -mm's maps2-*
patches.  We would need to add a means by which userspace can repopulate
swapcache, but that doesn't sound too hard (especially when you haven't
thought about it).

And userspace can right now work out which pages from which files are in
pagecache so this application can handle pagecache, swap and file-backed
memory.  (file-backed memory might not even need special treatment, given
that it's pagecache anyway).


And userspace can do a much better implementation of this
how-to-handle-large-load-shifts problem, because it is really quite
complex.  The system needs to be monitored to determine what is the "usual"
state (ie: the thing we wish to reestablish when the transient workload
subsides).  The system then needs to be monitored to determine when the
exceptional workload has started, and when it has subsided, and userspace
then needs to decide when to start reestablishing the old working set, at
what rate, when to abort doing that, etc.

All this would end up needing runtime configurability and tweakability and
customisability.  All standard fare for userspace stuff - much easier than
patching the kernel.


So.  We can

a) provide a way for userspace to reload pagecache and

b) merge maps2 (once it's finished) (pokes mpm)

and we're done?

Re: -mm merge plans for 2.6.23

[Nick Piggin]

Andrew Morton wrote:

> All this would end up needing runtime configurability and tweakability and
> customisability.  All standard fare for userspace stuff - much easier than
> patching the kernel.
> 
> 
> So.  We can
> 
> a) provide a way for userspace to reload pagecache and
> 
> b) merge maps2 (once it's finished) (pokes mpm)
> 
> and we're done?


The userspace solution has been brought up before. It could be a good way
to go. I was thinking about how to do refetching of file backed pages from
the kernel, and it isn't impossible, but it it seems like locking would be
quite hard and it would be pretty complex and inflexible compared to a
userspace solution. Userspace might know what to chuck out, what to keep,
what access patterns to use...

Not that I want to say anything about swap prefetch getting merged: my
inbox is already full of enough "helpful suggestions" about that, so I'll
just be happy to have a look at little things like updatedb.

-- 
SUSE Labs, Novell Inc.

Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Thu, 26 Jul 2007 15:53:37 +1000 Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> Not that I want to say anything about swap prefetch getting merged: my
> inbox is already full of enough "helpful suggestions" about that,

give them the kernel interfaces, they can do it themselves ;)

> so I'll
> just be happy to have a look at little things like updatedb.

Yes, that is a little thing.  I mean, even if the kernel's behaviour
during an updatedb run was "perfect" (ie: does what we the designers
curently intend it to do (whatever that is)) then the core problem isn't
solved: short-term workload evicts your working set and you have to
synchronously reestablish it.

Re: -mm merge plans for 2.6.23

[Nick Piggin]

Andrew Morton wrote:
> On Thu, 26 Jul 2007 15:53:37 +1000 Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> 
> 
>>Not that I want to say anything about swap prefetch getting merged: my
>>inbox is already full of enough "helpful suggestions" about that,
> 
> 
> give them the kernel interfaces, they can do it themselves ;)

It is a good idea if we can give enough to get started. Then if
they run into something they really need to do in the kernel, we
can take a look.

Page eviction order / prefetch-back-in-order might be tricky to
expose.


>>so I'll
>>just be happy to have a look at little things like updatedb.
> 
> 
> Yes, that is a little thing.  I mean, even if the kernel's behaviour
> during an updatedb run was "perfect" (ie: does what we the designers
> curently intend it to do (whatever that is)) then the core problem isn't
> solved: short-term workload evicts your working set and you have to
> synchronously reestablish it.

Sure, I know and I was never against swap (and/or file) prefetching to
solve this problem. I'm just saying, I'm staying out of that :)

-- 
SUSE Labs, Novell Inc.

Re: -mm merge plans for 2.6.23

[Ray Lee]

On 7/25/07, Andrew Morton <akpm@linux-foundation.org> wrote:
> On Wed, 25 Jul 2007 09:09:01 -0700
> "Ray Lee" <ray-lk@madrabbit.org> wrote:
>
> > No, there's a third case which I find the most annoying. I have
> > multiple working sets, the sum of which won't fit into RAM. When I
> > finish one, the kernel had time to preemptively swap back in the
> > other, and yet it didn't. So, I sit around, twiddling my thumbs,
> > waiting for my music player to come back to life, or thunderbird,
> > or...
>
> Yes, I'm thinking that's a good problem statement and it isn't something
> which the kernel even vaguely attempts to address, apart from normal
> demand paging.
>
> We could perhaps improve things with larger and smarter fault readaround,
> perhaps guided by refault-rate measurement.  But that's still demand-paged
> rather than being proactive/predictive/whatever.
>
> None of this is swap-specific though: exactly the same problem would need
> to be solved for mmapped files and even plain old pagecache.

<nod> Could be what I'm noticing, but it's important to note that as
others have shown improvement with Con's swap prefetch, it's easily
arguable that targeting just swap is good enough for a first
approximation.

> In fact I'd restate the problem as "system is in steady state A, then there
> is a workload shift causing transition to state B, then the system goes
> idle.  We now wish to reinstate state A in anticipation of a resumption of
> the original workload".

Yes, that's a fair transformation / generalization. It's always nice
talking to someone with more clarity than one's self.

> swap-prefetch solves a part of that.
>
> A complete solution for anon and file-backed memory could be implemented
> (ta-da) in userspace using the kernel inspection tools in -mm's maps2-*
> patches.
> We would need to add a means by which userspace can repopulate
> swapcache,

Okay, let's run with that for argument's sake.

> but that doesn't sound too hard (especially when you haven't
> thought about it).

I've always thought your sense of humor was underappreciated.

> And userspace can right now work out which pages from which files are in
> pagecache so this application can handle pagecache, swap and file-backed
> memory.  (file-backed memory might not even need special treatment, given
> that it's pagecache anyway).

So in your proposed scheme, would userspace be polling, er, <goes and
looks through email for maps2 stuff, only finds Rusty's patches to
it>, well, /proc/<pids>/something_or_another?

A userspace daemon that wakes up regularly to poll a bunch of proc
files fills me with glee. Wait, is that glee? I think, no... wait...
horror, yes, horror is what I'm feeling.

I'm wrong, right? I love being wrong about this kind of stuff.

> And userspace can do a much better implementation of this
> how-to-handle-large-load-shifts problem, because it is really quite
> complex.  The system needs to be monitored to determine what is the "usual"
> state (ie: the thing we wish to reestablish when the transient workload
> subsides).  The system then needs to be monitored to determine when the
> exceptional workload has started, and when it has subsided, and userspace
> then needs to decide when to start reestablishing the old working set, at
> what rate, when to abort doing that, etc.

Oy. I mean this in the most respectful way possible, but you're too
smart for your own good.

I mean, sure, it's possible one could have multiply-chained transient
workloads each of which have their optimum workingset, of which
there's little overlap with the previous. Mainframes made their names
on such loads. Workingset A starts, generates data, finishes and
invokes workingset B, of which the only thing they share in common is
said data. B finishes and invokes C, etc.

So, yeah, that's way too complex to stuff into the kernel. Even if it
were possible to do so, I cringe at the thought. And I can't believe
that would be a common enough pattern nowadays to justify any
hueristics on anyone's part. It's certainly complex enough that I'd
like to punt that scenario out of the conversation entirely -- I think
it has the potential to give a false impression as to how involved of
a process we're talking about here.

Let's go back to your restatement:

> In fact I'd restate the problem as "system is in steady state A, then there
> is a workload shift causing transition to state B, then the system goes
> idle.  We now wish to reinstate state A in anticipation of a resumption of
> the original workload".

I'll take an 80% solution for that one problem, and happily declare
that the kernel's job is done. In particular, when a resource hog
exits (or whatever hueristics prefetch is currently hooking in to),
the kernel (or userspace, if that interface could be made sane) could
exercise a completely workload agnostic refetch of the last n things
evicted, where n is determined by what's suddenly become free (or
whatever Con came up with).

Just, y'know, MRU style.

> All this would end up needing runtime configurability and tweakability and
> customisability.  All standard fare for userspace stuff - much easier than
> patching the kernel.

We're talking about patching the kernel for whatever API you're coming
up with to repopulate pagecache, swap, and inodes, aren't we? If we
are, it doesn't seem like we're saving any work here. Also we're
talking about a creating a new user-visible API instead of augmenting
a pre-existing hueristic -- page replacement -- that the kernel
doesn't export and so can change at a moment's notice. Augmenting an
opaque hueristic seems a lot more friendly to long-term maintenance.

> So.  We can
>
> a) provide a way for userspace to reload pagecache and
>
> b) merge maps2 (once it's finished) (pokes mpm)
>
> and we're done?

Eh, dunno. Maybe?

We're assuming we come up with an API for userspace to get
notifications of evictions (without polling, though poll() would be
fine -- you know what I mean), and an API for re-victing those things
on demand. If you think that adding that API and maintaining it is
simpler/better than including a variation on the above hueristic I
offered, then yeah, I guess we are. It'll all have that vague
userspace s2ram odor about it, but I'm sure it could be made to work.

As I think I've successfully Peter Principled my way through this
conversation to my level of incompetence, I'll shut up now.

Ray

Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Wed, 25 Jul 2007 23:33:24 -0700 "Ray Lee" <ray-lk@madrabbit.org> wrote:

> > So.  We can
> >
> > a) provide a way for userspace to reload pagecache and
> >
> > b) merge maps2 (once it's finished) (pokes mpm)
> >
> > and we're done?
> 
> Eh, dunno. Maybe?
> 
> We're assuming we come up with an API for userspace to get
> notifications of evictions (without polling, though poll() would be
> fine -- you know what I mean), and an API for re-victing those things
> on demand.

I was assuming that polling would work OK.  I expect it would.

> If you think that adding that API and maintaining it is
> simpler/better than including a variation on the above hueristic I
> offered, then yeah, I guess we are. It'll all have that vague
> userspace s2ram odor about it, but I'm sure it could be made to work.

Actually, I overdesigned the API, I suspect.  What we _could_ do is to
provide a way of allowing userspace to say "pretend process A touched page
B": adopt its mm and go touch the page.  We in fact already have that:
PTRACE_PEEKTEXT.

So I suspect this could all be done by polling maps2 and using PEEKTEXT. 
The tricky part would be working out when to poll, and when to reestablish.

A neater implementation than PEEKTEXT would be to make the maps2 files
writeable(!) so as a party trick you could tar 'em up and then, when you
want to reestablish firefox's previous working set, do a untar in
/proc/$(pidof firefox)/

Re: -mm merge plans for 2.6.23

[Ray Lee]

On 7/25/07, Andrew Morton <akpm@linux-foundation.org> wrote:
> On Wed, 25 Jul 2007 23:33:24 -0700 "Ray Lee" <ray-lk@madrabbit.org> wrote:
> > If you think that adding that API and maintaining it is
> > simpler/better than including a variation on the above hueristic I
> > offered, then yeah, I guess we are. It'll all have that vague
> > userspace s2ram odor about it, but I'm sure it could be made to work.
>
> Actually, I overdesigned the API, I suspect.  What we _could_ do is to
> provide a way of allowing userspace to say "pretend process A touched page
> B": adopt its mm and go touch the page.  We in fact already have that:
> PTRACE_PEEKTEXT.

Huh. All right.

> So I suspect this could all be done by polling maps2 and using PEEKTEXT.
> The tricky part would be working out when to poll, and when to reestablish.

Welllllll.... there is the taskstats interface. It's not required
right now, though, and lacks most of what userspace would need, I
think. It does at least currently provide a notification of process
exit, which is a clue for when to start reestablishment. Gotta be
another way we can get at that...

Oh, stat on /proc, does that work? Huh, it does, sort of. It seems to
be off by 12 or 13, but hey, that's something.

Wish I had the time to look at the maps2 stuff, but regardless, it
probably currently provides too much detail for continual polling? I
suspect what we'd want to do is to take a detailed snapshot a little
after the beginning of a process's lifetime (once the block-in counts
subside), then poll aggregate residency or evicition counts to know
which processes are suffering the burden of the transient workload.

Eh, wait, that doesn't help with inodes. No matter, I guess; I'm the
one who said targetting swap-in would be good enough for a first pass.

On process exit, if userspace can get a hold of an estimate of the
size of what just freed up, it could then spend
min(that,evicted_count) on repopulation. That's probably already
available by polling whatever `free` calls.

> A neater implementation than PEEKTEXT would be to make the maps2 files
> writeable(!) so as a party trick you could tar 'em up and then, when you
> want to reestablish firefox's previous working set, do a untar in
> /proc/$(pidof firefox)/

I'm going to get into trouble if I wake up the other person in the
house with my laughter. That's laughter in a positive sense, not a
"you're daft" kind of way.

Huh. <thinks> So, to go back a little bit, I guess one of my problems
with polling is that it means that userspace can only approximate an
MRU of what's been evicted. Perhaps an approximation is good enough, I
don't know, but that's something to keep in mind. (Hmm, how many pages
can an average desktop evict per second? If we poll everything once
per second, that's how off we could be.)

Another is a more philosophical hangup -- running a process that polls
periodically to improve system performance seems backward. Okay, so
that's my problem to get over, not yours.

Another problem is what poor sod would be willing to write and test
this, given that there's already a written and tested kernel patch to
do much the same thing? Yeah, that's sorta rhetorical, but it's sorta
not. Given that swap prefetch could be ripped out of 2.6.n+1 if it's
introduced in 2.6.n, and nothing in userspace would be the wiser,
where's the burden?  There is some, just as any kernel code has some,
and as it's core code (versus, say, a driver), the burden is
correspondingly greater per line, but given the massive changesets
flowing through each release now, I have to think that the burden this
introduces is marginal compared to the rest of the bulk sweeping
through the kernel weekly.

This is obviously where I'm totally conjecturing, and you'll know far,
far better than I.

Offline for about 20 hours or so, not that anyone would probably notice :-).

Ray

Re: -mm merge plans for 2.6.23

[Nick Piggin]

Ray Lee wrote:

> Another is a more philosophical hangup -- running a process that polls
> periodically to improve system performance seems backward.

You mean like the kprefetchd of swap prefetch? ;)


> Okay, so
> that's my problem to get over, not yours.

If it was a problem you could add some event trigger to wake it up.

-- 
SUSE Labs, Novell Inc.

Re: -mm merge plans for 2.6.23

[Frank Kingswood]

Andi Kleen wrote:
> One simple way to fix this would be to implement a fadvise() flag
> that puts the dentry/inode on a "soon to be expired" list if there
> are no other references. Then if a dentry allocation needs more
> memory try to reuse dentries from that list (or better queue) first. Any other
> access will remove the dentry from the list. 
> 
> Disadvantage would be that the userland would need to be patched,
> but I guess it's better than adding very dubious heuristics to the
> kernel.

Are you going to change every single large memory application in the 
world? As I wrote before, it is *not* about updatedb, but about all 
applications that use a lot of memory, and then terminate.

Frank

Re: -mm merge plans for 2.6.23

[Ingo Molnar]

* Frank Kingswood <frank@kingswood-consulting.co.uk> wrote:

> > Disadvantage would be that the userland would need to be patched, 
> > but I guess it's better than adding very dubious heuristics to the 
> > kernel.
> 
> Are you going to change every single large memory application in the 
> world? As I wrote before, it is *not* about updatedb, but about all 
> applications that use a lot of memory, and then terminate.

it is about multiple problems, _one_ problem is updatedb. The _second_ 
problem is large memory applications.

note that updatedb is not a "large memory application". It simply scans 
through the filesystem and has pretty minimal memory footprint.

the _kernel_ ends up blowing up the dentry cache to a rather large size 
(because it has no idea that updatedb uses every dentry only once).

Once we give the kernel the knowledge that the dentry wont be used again 
by this app, the kernel can do a lot more intelligent decision and not 
baloon the dentry cache.

( we _do_ want to baloon the dentry cache otherwise - for things like 
  "find" - having a fast VFS is important. But known-use-once things 
  like the daily updatedb job can clearly be annotated properly. )

the 'large memory apps' are a second category of problems. And those are 
where swap-prefetch could indeed help. (as long as it only 'fills up' 
the free memory that a large-memory-exit left behind it.)

the 'morning after' phenomenon that the majority of testers complained 
about will likely be resolved by the updatedb change. The second 
category is likely an improvement too, for swap-happy desktop (and 
server) workloads.

	Ingo

Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Thu, 26 Jul 2007 11:20:25 +0200 Ingo Molnar <mingo@elte.hu> wrote:

> Once we give the kernel the knowledge that the dentry wont be used again 
> by this app, the kernel can do a lot more intelligent decision and not 
> baloon the dentry cache.
> 
> ( we _do_ want to baloon the dentry cache otherwise - for things like 
>   "find" - having a fast VFS is important. But known-use-once things 
>   like the daily updatedb job can clearly be annotated properly. )

Mutter.  /proc/sys/vm/vfs_cache_pressure has been there for what, three
years?  Are any distros raising it during the updatedb run yet?

RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Ingo Molnar]

* Andrew Morton <akpm@linux-foundation.org> wrote:

> On Thu, 26 Jul 2007 11:20:25 +0200 Ingo Molnar <mingo@elte.hu> wrote:
> 
> > Once we give the kernel the knowledge that the dentry wont be used again 
> > by this app, the kernel can do a lot more intelligent decision and not 
> > baloon the dentry cache.
> > 
> > ( we _do_ want to baloon the dentry cache otherwise - for things like 
> >   "find" - having a fast VFS is important. But known-use-once things 
> >   like the daily updatedb job can clearly be annotated properly. )
> 
> Mutter.  /proc/sys/vm/vfs_cache_pressure has been there for what, 
> three years?  Are any distros raising it during the updatedb run yet?

but ... that's system-wide, and the 'dont baloon the dcache' is only a 
property of updatedb. Still, it's useful to debug this thing.

below is an updatedb hack that sets vfs_cache_pressure down to 0 during 
an updatedb run. Could someone who is affected by the 'morning after' 
problem give it a try? If this works then we can think about any other 
measures ...

	Ingo

--- /etc/cron.daily/mlocate.cron.orig
+++ /etc/cron.daily/mlocate.cron
@@ -1,4 +1,7 @@
 #!/bin/sh
 nodevs=$(< /proc/filesystems awk '$1 == "nodev" { print $2 }')
 renice +19 -p $$ >/dev/null 2>&1
+PREV=`cat /proc/sys/vm/vfs_cache_pressure 2>/dev/null`
+echo 0 > /proc/sys/vm/vfs_cache_pressure 2>/dev/null
 /usr/bin/updatedb -f "$nodevs"
+[ "$PREV" != "" ] && echo $PREV > /proc/sys/vm/vfs_cache_pressure 2>/dev/null

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Andrew Morton]

On Thu, 26 Jul 2007 11:40:24 +0200 Ingo Molnar <mingo@elte.hu> wrote:

> 
> * Andrew Morton <akpm@linux-foundation.org> wrote:
> 
> > On Thu, 26 Jul 2007 11:20:25 +0200 Ingo Molnar <mingo@elte.hu> wrote:
> > 
> > > Once we give the kernel the knowledge that the dentry wont be used again 
> > > by this app, the kernel can do a lot more intelligent decision and not 
> > > baloon the dentry cache.
> > > 
> > > ( we _do_ want to baloon the dentry cache otherwise - for things like 
> > >   "find" - having a fast VFS is important. But known-use-once things 
> > >   like the daily updatedb job can clearly be annotated properly. )
> > 
> > Mutter.  /proc/sys/vm/vfs_cache_pressure has been there for what, 
> > three years?  Are any distros raising it during the updatedb run yet?
> 
> but ... that's system-wide, and the 'dont baloon the dcache' is only a 
> property of updatedb.

Sure, but it's practical, isn't it?  Who runs (and cares about)
vfs-intensive workloads during their wee-small-hours updatedb run?

(OK, I do, but I kill the damn thing if it goes off)

> Still, it's useful to debug this thing.
> 
> below is an updatedb hack that sets vfs_cache_pressure down to 0 during 
> an updatedb run. Could someone who is affected by the 'morning after' 
> problem give it a try? If this works then we can think about any other 
> measures ...
> 
> 	Ingo
> 
> --- /etc/cron.daily/mlocate.cron.orig
> +++ /etc/cron.daily/mlocate.cron
> @@ -1,4 +1,7 @@
>  #!/bin/sh
>  nodevs=$(< /proc/filesystems awk '$1 == "nodev" { print $2 }')
>  renice +19 -p $$ >/dev/null 2>&1
> +PREV=`cat /proc/sys/vm/vfs_cache_pressure 2>/dev/null`
> +echo 0 > /proc/sys/vm/vfs_cache_pressure 2>/dev/null
>  /usr/bin/updatedb -f "$nodevs"
> +[ "$PREV" != "" ] && echo $PREV > /proc/sys/vm/vfs_cache_pressure 2>/dev/null

Setting it to zero will maximise the preservation of the vfs caches.  You
wanted 10000 there.

<bets that nobody will test this>

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Al Viro]

On Thu, Jul 26, 2007 at 11:40:24AM +0200, Ingo Molnar wrote:
> below is an updatedb hack that sets vfs_cache_pressure down to 0 during 
> an updatedb run. Could someone who is affected by the 'morning after' 
> problem give it a try? If this works then we can think about any other 
> measures ...

BTW, I really wonder how much pain could be avoided if updatedb recorded
mtime of directories and checked it.  I.e. instead of just doing blind
find(1), walk the stored directory tree comparing timestamps with those
in filesystem.  If directory mtime has not changed, don't bother rereading
it and just go for (stored) subdirectories.  If it has changed - reread the
sucker.  If we have a match for stored subdirectory of changed directory,
check inumber; if it doesn't match, consider the entire subtree as new
one.  AFAICS, that could eliminate quite a bit of IO...

Re: [ck] Re: -mm merge plans for 2.6.23

[Bartlomiej Zolnierkiewicz]

On Thursday 26 July 2007, Jeff Garzik wrote:
> Bartlomiej Zolnierkiewicz wrote:
> > On Wednesday 25 July 2007, Ingo Molnar wrote:
> >> you dont _have to_ cooperative with the maintainer, but it's certainly 
> >> useful to work with good maintainers, if your goal is to improve Linux. 
> >> Or if for some reason communication is not working out fine then grow 
> >> into the job and replace the maintainer by doing a better job.
> > 
> > The idea of growing into the job and replacing the maintainer by proving
> > the you are doing better job was viable few years ago but may not be
> > feasible today.
> 
> IMO...  Tejun is an excellent counter-example.  He showed up as an 

IMO this doesn't qualify as a counter-example here et all unless
you are trying to say that Tejun does your job much better and that
we should just replace you. ;)

> independent developer, put a bunch of his own spare time and energy into 
> the codebase, and is probably libata's main engineer (in terms of code 
> output) today.  If I get hit by a bus tomorrow, I think the Linux 
> community would be quite happy with him as the libata maintainer.

Fully agreed on this part.

> > The another problem is that sometimes it seems that independent developers
> > has to go through more hops than entreprise ones and it is really frustrating
> > experience for them.  There is no conspiracy here - it is only the natural
> > mechanism of trusting more in the code of people who you are working with more.
> 
> I think Tejun is a counter-example here too :)  Everyone's experience is 
> different, but from my perspective, Tejun "appeared out of nowhere" 
> producing good code, and so, it got merged rapidly.

Tejun (like any of other developers) spent some time in-the-making
and this time was in large part spent in the IDE-land, and yes I'm also
very glad of the effects. :)

Thanks,
Bart

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Ingo Molnar]

* Andrew Morton <akpm@linux-foundation.org> wrote:

> Setting it to zero will maximise the preservation of the vfs caches.  
> You wanted 10000 there.

ok, updated patch below :-)

> <bets that nobody will test this>

wrong, it's active on three of my boxes already :) But then again, i 
never had these hangover problems. (not really expected with gigs of RAM 
anyway)

	Ingo

--- /etc/cron.daily/mlocate.cron.orig
+++ /etc/cron.daily/mlocate.cron
@@ -1,4 +1,7 @@
 #!/bin/sh
 nodevs=$(< /proc/filesystems awk '$1 == "nodev" { print $2 }')
 renice +19 -p $$ >/dev/null 2>&1
+PREV=`cat /proc/sys/vm/vfs_cache_pressure 2>/dev/null`
+echo 10000 > /proc/sys/vm/vfs_cache_pressure 2>/dev/null
 /usr/bin/updatedb -f "$nodevs"
+[ "$PREV" != "" ] && echo $PREV > /proc/sys/vm/vfs_cache_pressure 2>/dev/null

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Ingo Molnar]

* Andrew Morton <akpm@linux-foundation.org> wrote:

> > > > ( we _do_ want to baloon the dentry cache otherwise - for things like 
> > > >   "find" - having a fast VFS is important. But known-use-once things 
> > > >   like the daily updatedb job can clearly be annotated properly. )
> > > 
> > > Mutter.  /proc/sys/vm/vfs_cache_pressure has been there for what, 
> > > three years?  Are any distros raising it during the updatedb run yet?
> > 
> > but ... that's system-wide, and the 'dont baloon the dcache' is only a 
> > property of updatedb.
> 
> Sure, but it's practical, isn't it?  Who runs (and cares about) 
> vfs-intensive workloads during their wee-small-hours updatedb run?

there's another side-effect: it likely results in the zapping of 
thousands of dentries that were cached nicely before. So we might 
exchange 'all my apps are swapped out' experience with 'all file access 
is slow'. The latter is _probably_ still an improvement over the 
balooning, but i'm not sure. What we _really_ want is an updatedb that 
does not disturb the dcache.

	Ingo

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Andrew Morton]

On Thu, 26 Jul 2007 12:27:30 +0200 Ingo Molnar <mingo@elte.hu> wrote:

> 
> * Andrew Morton <akpm@linux-foundation.org> wrote:
> 
> > > > > ( we _do_ want to baloon the dentry cache otherwise - for things like 
> > > > >   "find" - having a fast VFS is important. But known-use-once things 
> > > > >   like the daily updatedb job can clearly be annotated properly. )
> > > > 
> > > > Mutter.  /proc/sys/vm/vfs_cache_pressure has been there for what, 
> > > > three years?  Are any distros raising it during the updatedb run yet?
> > > 
> > > but ... that's system-wide, and the 'dont baloon the dcache' is only a 
> > > property of updatedb.
> > 
> > Sure, but it's practical, isn't it?  Who runs (and cares about) 
> > vfs-intensive workloads during their wee-small-hours updatedb run?
> 
> there's another side-effect: it likely results in the zapping of 
> thousands of dentries that were cached nicely before. So we might 
> exchange 'all my apps are swapped out' experience with 'all file access 
> is slow'. The latter is _probably_ still an improvement over the 
> balooning, but i'm not sure.

Yup.  Nobody has begun to think about preserving dcache/icache across load
shifts yet, afaik.  Hard.

> What we _really_ want is an updatedb that 
> does not disturb the dcache.

Well.  Hopefully this time next year you can prep a 16MB container and toss
your updatedb inside that.  Maybe set its peak disk bandwidth utilisation
too.  However that won't work ;) because I don't think anyone is looking
at containerisation of vfs cache memory yet.  Perhaps full-on openvz has it,
dunno.

But updatedb is a special case, because it is so vfs-intensive.  For lots
of other workloads (those which use heaps of pagecache), resource
management via containerisation will work nicely.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Andi Kleen]

> BTW, I really wonder how much pain could be avoided if updatedb recorded
> mtime of directories and checked it.  I.e. instead of just doing blind
> find(1), walk the stored directory tree comparing timestamps with those
> in filesystem.  If directory mtime has not changed, don't bother rereading
> it and just go for (stored) subdirectories.  If it has changed - reread the
> sucker.  If we have a match for stored subdirectory of changed directory,
> check inumber; if it doesn't match, consider the entire subtree as new
> one.  AFAICS, that could eliminate quite a bit of IO...

That would just save reading the directories. Not sure
it helps that much. Much better would be actually if it didn't stat the 
individual files (and force their dentries/inodes in). I bet it does that to 
find out if they are directories or not. But in a modern system it could just 
check the type in the dirent on file systems that support 
that and not do a stat. Then you would get much less dentries/inodes.

Also I expect in general the new slub dcache freeing that is pending
will improve things a lot.

But even if updatedb was fixed to be more efficient we probably
still need a general solution for other tree walking programs
that cannot be optimized this way.

-Andi

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Mike Galbraith]

On Thu, 2007-07-26 at 03:09 -0700, Andrew Morton wrote:

> Setting it to zero will maximise the preservation of the vfs caches.  You
> wanted 10000 there.
> 
> <bets that nobody will test this>

drops caches prior to both updatedb runs.

root@Homer: df -i
Filesystem            Inodes   IUsed   IFree IUse% Mounted on
/dev/hdc3            12500992 1043544 11457448    9% /
udev                  129162    1567  127595    2% /dev
/dev/hdc1              26104      87   26017    1% /boot
/dev/hda1             108144   90676   17468   84% /windows/C
/dev/hda5              11136    3389    7747   31% /windows/D
/dev/hda6                  0       0       0    -  /windows/E

vfs_cache_pressure=10000, updatedb freshly completed:
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 1  0     48  76348 420356 104748    0    0     0     0 1137  912  3  1 97  0

ext3_inode_cache  315153 316274    524    7    1 : tunables   54   27    8 : slabdata  45182  45182      0
dentry_cache      224829 281358    136   29    1 : tunables  120   60    8 : slabdata   9702   9702      0
buffer_head       156624 159728     56   67    1 : tunables  120   60    8 : slabdata   2384   2384      0

vfs_cache_pressure=100 (stock), updatedb freshly completed:

procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
1  0    148  83824 270088 116340    0    0     0     0 1095  330  2  1 97  0
 
ext3_inode_cache  467257 502495    524    7    1 : tunables   54   27    8 : slabdata  71785  71785      0
dentry_cache      292695 408958    136   29    1 : tunables  120   60    8 : slabdata  14102  14102      0
buffer_head       118329 184384     56   67    1 : tunables  120   60    8 : slabdata   2752   2752      1

Note:  updatedb doesn't bother my box, not running enough leaky apps I
guess.

	-Mike

Re: [ck] Re: -mm merge plans for 2.6.23

[Michael Chang]

On 7/26/07, Andrew Morton <akpm@linux-foundation.org> wrote:
> On Wed, 25 Jul 2007 09:09:01 -0700
> "Ray Lee" <ray-lk@madrabbit.org> wrote:
>
> > No, there's a third case which I find the most annoying. I have
> > multiple working sets, the sum of which won't fit into RAM. When I
> > finish one, the kernel had time to preemptively swap back in the
> > other, and yet it didn't. So, I sit around, twiddling my thumbs,
> > waiting for my music player to come back to life, or thunderbird,
> > or...
>
> In fact I'd restate the problem as "system is in steady state A, then there
> is a workload shift causing transition to state B, then the system goes
> idle.  We now wish to reinstate state A in anticipation of a resumption of
> the original workload".
>
> swap-prefetch solves a part of that.
>
> A complete solution for anon and file-backed memory could be implemented
> (ta-da) in userspace using the kernel inspection tools in -mm's maps2-*
> patches.  We would need to add a means by which userspace can repopulate
> swapcache, but that doesn't sound too hard (especially when you haven't
> thought about it).
>
> And userspace can right now work out which pages from which files are in
> pagecache so this application can handle pagecache, swap and file-backed
> memory.  (file-backed memory might not even need special treatment, given
> that it's pagecache anyway).
>
> And userspace can do a much better implementation of this
> how-to-handle-large-load-shifts problem, because it is really quite
> complex.  The system needs to be monitored to determine what is the "usual"
> state (ie: the thing we wish to reestablish when the transient workload
> subsides).  The system then needs to be monitored to determine when the
> exceptional workload has started, and when it has subsided, and userspace
> then needs to decide when to start reestablishing the old working set, at
> what rate, when to abort doing that, etc.
>
> All this would end up needing runtime configurability and tweakability and
> customisability.  All standard fare for userspace stuff - much easier than
> patching the kernel.

Maybe I'm missing something here, but if the problem is resource
allocation when switching from state A to state B, and from B to C,
etc.; wouldn't it be a bad thing if state B happened to be (in the
future) this state-shifting userspace daemon of which you speak? (Or
is that likely to be impossible/unlikely for some other reason which
alludes me at the moment?)

-- 
Michael Chang

Please avoid sending me Word or PowerPoint attachments. Send me ODT,
RTF, or HTML instead.
See http://www.gnu.org/philosophy/no-word-attachments.html
Thank you.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Al Viro]

On Thu, Jul 26, 2007 at 02:23:30PM +0200, Andi Kleen wrote:
> That would just save reading the directories. Not sure
> it helps that much. Much better would be actually if it didn't stat the 
> individual files (and force their dentries/inodes in). I bet it does that to 
> find out if they are directories or not. But in a modern system it could just 
> check the type in the dirent on file systems that support 
> that and not do a stat. Then you would get much less dentries/inodes.
 
FWIW, find(1) does *not* stat non-directories (and neither would this
approach).  So it's just dentries for directories and you can't realistically
skip those.  OK, you could - if you had banned cross-directory rename
for directories and propagated "dirty since last look" towards root (note
that it would be a boolean, not a timestamp).  Then we could skip unchanged
subtrees completely...

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Andrew Morton]

On Thu, 26 Jul 2007 14:46:58 +0200 Mike Galbraith <efault@gmx.de> wrote:

> On Thu, 2007-07-26 at 03:09 -0700, Andrew Morton wrote:
> 
> > Setting it to zero will maximise the preservation of the vfs caches.  You
> > wanted 10000 there.
> > 
> > <bets that nobody will test this>
> 
> drops caches prior to both updatedb runs.

I think that was the wrong thing to do.  That will leave gobs of free
memory for updatedb to populate with dentries and inodes.

Instead, fill all of memory up with pagecache, then do the updatedb.  See
how much pagecache is left behind and see how large the vfs caches end up.

> root@Homer: df -i
> Filesystem            Inodes   IUsed   IFree IUse% Mounted on
> /dev/hdc3            12500992 1043544 11457448    9% /
> udev                  129162    1567  127595    2% /dev
> /dev/hdc1              26104      87   26017    1% /boot
> /dev/hda1             108144   90676   17468   84% /windows/C
> /dev/hda5              11136    3389    7747   31% /windows/D
> /dev/hda6                  0       0       0    -  /windows/E
> 
> vfs_cache_pressure=10000, updatedb freshly completed:
> procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
>  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
>  1  0     48  76348 420356 104748    0    0     0     0 1137  912  3  1 97  0
> 
> ext3_inode_cache  315153 316274    524    7    1 : tunables   54   27    8 : slabdata  45182  45182      0
> dentry_cache      224829 281358    136   29    1 : tunables  120   60    8 : slabdata   9702   9702      0
> buffer_head       156624 159728     56   67    1 : tunables  120   60    8 : slabdata   2384   2384      0
> 
> vfs_cache_pressure=100 (stock), updatedb freshly completed:
> 
> procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
>  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
> 1  0    148  83824 270088 116340    0    0     0     0 1095  330  2  1 97  0
>  
> ext3_inode_cache  467257 502495    524    7    1 : tunables   54   27    8 : slabdata  71785  71785      0
> dentry_cache      292695 408958    136   29    1 : tunables  120   60    8 : slabdata  14102  14102      0
> buffer_head       118329 184384     56   67    1 : tunables  120   60    8 : slabdata   2752   2752      1
> 
> Note:  updatedb doesn't bother my box, not running enough leaky apps I
> guess.
> 

So you ended up with a couple hundred MB of pagecache preserved.

Capturing before-and-after /proc/meminfo would be nice - it's a useful
summary.

Re: [ck] Re: -mm merge plans for 2.6.23

[Andrew Morton]

On Thu, 26 Jul 2007 10:19:06 -0400 "Michael Chang" <thenewme91@gmail.com> wrote:

> > All this would end up needing runtime configurability and tweakability and
> > customisability.  All standard fare for userspace stuff - much easier than
> > patching the kernel.
> 
> Maybe I'm missing something here, but if the problem is resource
> allocation when switching from state A to state B, and from B to C,
> etc.; wouldn't it be a bad thing if state B happened to be (in the
> future) this state-shifting userspace daemon of which you speak? (Or
> is that likely to be impossible/unlikely for some other reason which
> alludes me at the moment?)

Well.  I was assuming that the daemon wouldn't be a great memory pig. 
I suspect it would do practically zero IO and would use little memory.
It could even be mlocked, but I doubt if that would be needed.

Re: [ck] Re: -mm merge plans for 2.6.23

[Dirk Schoebel]

[-- Attachment #1: Type: text/plain, Size: 1323 bytes --]

I don't really understand the reasons for all those discussions.
As long as you have a maintainer, why don't you just put swap prefetch into 
the kernel, marked experimental, default deactivated so anyone who just 
make[s] oldconfig (or defaultconfig) won't get it. If anyone finds a good 
solution for all those cache 'poisoning' problems and problems concerning 
swapin on workload changes and such swap prefetch can easily taken out again 
and no one has to complain and continuing maintaining it.
Actually the same goes for plugshed (having it might have kept Con as a 
valuable developer).
I am actually waiting for more than 2 years that reiser4 will make it into the 
kernel (sure, marked experimental or even highly experimental) so the 
patch-journey for every new kernel comes to an end. And most things in-kernel 
will surely be tested more intense so bugs will come up much faster. 
(Constantly running MM kernels is not really an option since many things in 
there can't be deactivated if they don't work as expected since lots of 
patches also concern 'vital' parts of the kernel.)

...just 2cents from a happy CK user for it made it possible to watch a movie 
while compiling the system - which was impossible with mainline kernel, even 
on dual core 2.2 GHz AMD64 with 4G RAM !

Dirk.

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Re: -mm merge plans for 2.6.23

[Michael Chang]

On 7/25/07, Matthew Hawkins <darthmdh@gmail.com> wrote:
> On 7/26/07, Ray Lee <ray-lk@madrabbit.org> wrote:
> > I'd just like updatedb to amortize its work better. If we had some way
> > to track all filesystem events, updatedb could keep a live and
> > accurate index on the filesystem. And this isn't just updatedb that
> > wants that, beagle and tracker et al also want to know filesystem
> > events so that they can index the documents themselves as well as the
> > metadata. And if they do it live, that spreads the cost out, including
> > the VM pressure.
>
> We already have this, its called inotify (and if I'm not mistaken,
> beagle already uses it).  Several years ago when it was still a little
> flakey patch, I built a custom filesystem indexer into an enterprise
> search engine using it (I needed to pull apart Unix mbox files).  The
> only trouble of course is the action is triggered immediately, which
> may not always be ideal (but that's a userspace problem)
>

With all this discussion about updatedb and locate and such, I thought
I'd do a Google search, (considering I've never heard of locate before
but I've seen updatedb here and there in ps lists) and I found this:

http://www.linux.com/articles/114029

That page mentions something called "rlocate", which seems to provide
some sort of almost-real-time mechanism, although the method it does
so bothers me -- it uses a 2.6 kernel module AND a userspace daemon.
And from what I can tell, there's no indication that this almost
"real-time" (--I see mentions of a 2 second lag--) system
replaces/eliminates updatedb in any way, shape, or form.

http://rlocate.sourceforge.net/ - Project "Web Site"
http://sourceforge.net/projects/rlocate/ - Source Forge Project Summary

The last release also appears a bit dated on sourceforge... release
0.4.0 on 2006-01-15.

Just thought I'd mention it.


-- 
Michael Chang

Please avoid sending me Word or PowerPoint attachments. Send me ODT,
RTF, or HTML instead.
See http://www.gnu.org/philosophy/no-word-attachments.html
Thank you.

Re: [ck] Re: -mm merge plans for 2.6.23

[Dirk Schoebel]

[-- Attachment #1: Type: text/plain, Size: 1126 bytes --]

...sorry for the reply to myself.

As Gentoo user i'm happy about the freedom of choice in almost every aspect of 
the system.
But with the kernel this freedom is taken away and i'm left with largely 
choices other people did. Sure, i can get the sources and patch and change 
the kernel myself in every aspect but thats more the possibility given by the 
freedom of the open source of the kernel.
I think the kernel should be more open for new ideas, and as long as the 
maintainer follows the kernel development things can be left in, if the 
maintainer can't follow anymore they are taken out quite fast again. (This 
statement mostly counts for parts of the kernel where a choice is possible or 
the coding overhead of making such choice possible is quite low.)
A problem of Linux is there are 100s of patches and patchsets out there but if 
you want to have more than one (since they offer advantages or functionality 
in different places) you are mostly left alone, start to integrate all 
patches by hand and solve so many rejects.

..still a happy CK user, but sad that Con left the scene.

Dirk.

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Re: [ck] Re: -mm merge plans for 2.6.23

[Jeff Garzik]

Dirk Schoebel wrote:
> as long as the 
> maintainer follows the kernel development things can be left in, if the 
> maintainer can't follow anymore they are taken out quite fast again. (This 
> statement mostly counts for parts of the kernel where a choice is possible or 
> the coding overhead of making such choice possible is quite low.)


This is just not good engineering.

It is axiomatic that it is easy to add code, but difficult to remove 
code.  It takes -years- to remove code that no one uses.  Long after the 
maintainer disappears, the users (and bug reports!) remain.

It is also axiomatic that adding code, particularly core code, often 
exponentially increases complexity.

	Jeff

Re: [ck] Re: -mm merge plans for 2.6.23

[david]

On Thu, 26 Jul 2007, Jeff Garzik wrote:

> Dirk Schoebel wrote:
>>  as long as the maintainer follows the kernel development things can be
>>  left in, if the maintainer can't follow anymore they are taken out quite
>>  fast again. (This statement mostly counts for parts of the kernel where a
>>  choice is possible or the coding overhead of making such choice possible
>>  is quite low.)
>
>
> This is just not good engineering.
>
> It is axiomatic that it is easy to add code, but difficult to remove code. 
> It takes -years- to remove code that no one uses.  Long after the maintainer 
> disappears, the users (and bug reports!) remain.

I'll point out that the code that's so hard to remove is the code that 
exposes an API to userspace.

code that's an internal implementation (like a couple of the things being 
discussed) gets removed much faster.

> It is also axiomatic that adding code, particularly core code, often 
> exponentially increases complexity.

this is true and may be a valid argument (depending on how large and how 
intrusive the proposed patch is)

David Lang

Re: [ck] Re: -mm merge plans for 2.6.23

[Jeff Garzik]

david@lang.hm wrote:
> On Thu, 26 Jul 2007, Jeff Garzik wrote:
> 
>> Dirk Schoebel wrote:
>>>  as long as the maintainer follows the kernel development things can be
>>>  left in, if the maintainer can't follow anymore they are taken out 
>>> quite
>>>  fast again. (This statement mostly counts for parts of the kernel 
>>> where a
>>>  choice is possible or the coding overhead of making such choice 
>>> possible
>>>  is quite low.)
>>
>>
>> This is just not good engineering.
>>
>> It is axiomatic that it is easy to add code, but difficult to remove 
>> code. It takes -years- to remove code that no one uses.  Long after 
>> the maintainer disappears, the users (and bug reports!) remain.
> 
> I'll point out that the code that's so hard to remove is the code that 
> exposes an API to userspace.

True.


> code that's an internal implementation (like a couple of the things 
> being discussed) gets removed much faster.

Not true.  It is highly unlikely that code will get removed if it has 
active users, even if the maintainer has disappeared.

The only things that get removed rapidly are those things mathematically 
guaranteed to be dead code.

_Behavior changes_, driver removals, feature removals happen more 
frequently than userspace ABI changes -- true -- but the rate of removal 
is still very, very slow.

It is axiomatic that we are automatically burdened with new code for at 
least 10 years :)  That's what you have to assume, when accepting anything.

	Jeff

Re: [ck] Re: -mm merge plans for 2.6.23

[david]

On Thu, 26 Jul 2007, Jeff Garzik wrote:

> david@lang.hm wrote:
>>  On Thu, 26 Jul 2007, Jeff Garzik wrote:
>> 
>> >  Dirk Schoebel wrote:
>> > >   as long as the maintainer follows the kernel development things can 
>> > >   be
>> > >   left in, if the maintainer can't follow anymore they are taken out 
>> > >  quite
>> > >  fast again. (This statement mostly counts for parts of the kernel 
>> > >  where a
>> > >  choice is possible or the coding overhead of making such choice 
>> > >  possible
>> > >   is quite low.)
>> > 
>> > 
>> >  This is just not good engineering.
>> > 
>> >  It is axiomatic that it is easy to add code, but difficult to remove 
>> >  code. It takes -years- to remove code that no one uses.  Long after the 
>> >  maintainer disappears, the users (and bug reports!) remain.
>>
>>  I'll point out that the code that's so hard to remove is the code that
>>  exposes an API to userspace.
>
> True.
>
>
>>  code that's an internal implementation (like a couple of the things being
>>  discussed) gets removed much faster.
>
> Not true.  It is highly unlikely that code will get removed if it has active 
> users, even if the maintainer has disappeared.

if you propose removing code in such a way that performance suffers then 
yes, it's hard to remove (and it should be).

but if it has no API the code is only visable to the users as a side 
effect of it's use. if the new code works better then it can be replaced.

the scheduler change that we're going through right now is an example, new 
code came along that was better and the old code went away very quickly.

the SLAB/SLOB/SLUB/S**B debate is another example. currently the different 
versions have different performance advantages and disadvantages, as one 
drops behind to the point where one of the others is better at all times, 
it goes away.

> The only things that get removed rapidly are those things mathematically 
> guaranteed to be dead code.
>
> _Behavior changes_, driver removals, feature removals happen more frequently 
> than userspace ABI changes -- true -- but the rate of removal is still very, 
> very slow.

a large part of this is that it's so hard to get a replacement that works 
better (this is very definantly a compliment to the kernel coders :-)



> It is axiomatic that we are automatically burdened with new code for at 
> least 10 years :)  That's what you have to assume, when accepting 
> anything.

for userspace API's 10 years is reasonable, for internal features it's 
not. there is a LOT of internal stuff that was in the kernel 10 (or even 
5) years ago that isn't there now. the key is that the behavior as far as 
users is concerned is better now.

David Lang

Re: -mm merge plans for 2.6.23

[Magnus Naeslund]

Al Boldi wrote:
> 
> Thanks for asking.  I'm rather surprised why nobody's noticing any of this 
> slowdown.  To be fair, it's not really a regression, on the contrary, 2.4 is 
> lot worse wrt swapin and swapout, and Rik van Riel even considers a 50% 
> swapin slowdown wrt swapout something like better than expected (see thread 
> '[RFC] kswapd: Kernel Swapper performance').  He probably meant random 
> swapin, which seems to offer a 4x slowdown.
> 

Sorry for the late reply.
Well I think I reported this or another swap/tmpfs performance issue earlier ( http://marc.info/?t=116542915700004&r=1&w=2 ), we got the suggestion to increase /proc/sys/vm/page-cluster to 5, but we never came around to try it.
Maybe this was the reason for my report to be almost entirely ignored, sorry for that.

Regards,
Magnus

Re: [ck] Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Matthew Hawkins]

On 7/26/07, Ingo Molnar <mingo@elte.hu> wrote:
> wrong, it's active on three of my boxes already :) But then again, i
> never had these hangover problems. (not really expected with gigs of RAM
> anyway)
[...]
> --- /etc/cron.daily/mlocate.cron.orig
[...]

mlocate by design doesn't thrash the cache as much.  People using
slocate (distros other than Redhat ;) are going to be hit worse.  See
http://carolina.mff.cuni.cz/~trmac/blog/mlocate/

updatedb by itself doesn't really bug me, its just that on occasion
its still running at 7am which then doesn't assist my single spindle
come swapin of the other apps!  I'm considering getting one of the old
ide drives out in the garage and shifting swap onto it.  The swap
prefetch patch has mainly assisted me in the "state A -> B -> A"
scenario.  A lot.

-- 
Matt

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Mike Galbraith]

On Thu, 2007-07-26 at 11:05 -0700, Andrew Morton wrote:
> On Thu, 26 Jul 2007 14:46:58 +0200 Mike Galbraith <efault@gmx.de> wrote:
> 
> > On Thu, 2007-07-26 at 03:09 -0700, Andrew Morton wrote:
> > 
> > > Setting it to zero will maximise the preservation of the vfs caches.  You
> > > wanted 10000 there.
> > > 
> > > <bets that nobody will test this>
> > 
> > drops caches prior to both updatedb runs.
> 
> I think that was the wrong thing to do.  That will leave gobs of free
> memory for updatedb to populate with dentries and inodes.
> 
> Instead, fill all of memory up with pagecache, then do the updatedb.  See
> how much pagecache is left behind and see how large the vfs caches end up.

Yeah.  Before these two runs just to see what difference there was in
caches with those two settings, I tried running with a heavier than
normal (for me) desktop application mix, to see if it would start
swapping, but it didn't.   Seems that 1GB ram is enough space for
everything I do, and everything updatedb does as well.  You need a
larger working set to feel the pain I guess.

	-Mike

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Mike Galbraith]

On Fri, 2007-07-27 at 07:13 +0200, Mike Galbraith wrote:
> On Thu, 2007-07-26 at 11:05 -0700, Andrew Morton wrote:
> > > drops caches prior to both updatedb runs.
> > 
> > I think that was the wrong thing to do.  That will leave gobs of free
> > memory for updatedb to populate with dentries and inodes.
> > 
> > Instead, fill all of memory up with pagecache, then do the updatedb.  See
> > how much pagecache is left behind and see how large the vfs caches end up.

I didn't _fill_ memory, but loaded it up a bit with some real workload
data...

I tried time sh -c 'git diff v2.6.11 HEAD > /dev/null' to populate the
cache, and tried different values for vfs_cache_pressure.  Nothing
prevented git's data from being trashed by updatedb.  Turning the knob
downward rapidly became very unpleasant due to swap, (with 0 not
surprisingly being a true horror) but turning it up didn't help git one
bit.  The amount of data that had to be re-read with stock 100 or 10000
was the same, or at least so close that you couldn't see a difference in
vmstat and wall-clock.  Cache sizes varied, but the bottom line didn't.
(wasn't surprised, seems quite reasonable that git's data looks old and
useless to the reclaim logic when updatedb runs in between git runs)

	-Mike

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Andrew Morton]

On Fri, 27 Jul 2007 09:23:41 +0200 Mike Galbraith <efault@gmx.de> wrote:

> On Fri, 2007-07-27 at 07:13 +0200, Mike Galbraith wrote:
> > On Thu, 2007-07-26 at 11:05 -0700, Andrew Morton wrote:
> > > > drops caches prior to both updatedb runs.
> > > 
> > > I think that was the wrong thing to do.  That will leave gobs of free
> > > memory for updatedb to populate with dentries and inodes.
> > > 
> > > Instead, fill all of memory up with pagecache, then do the updatedb.  See
> > > how much pagecache is left behind and see how large the vfs caches end up.
> 
> I didn't _fill_ memory, but loaded it up a bit with some real workload
> data...
> 
> I tried time sh -c 'git diff v2.6.11 HEAD > /dev/null' to populate the
> cache, and tried different values for vfs_cache_pressure.  Nothing
> prevented git's data from being trashed by updatedb.  Turning the knob
> downward rapidly became very unpleasant due to swap, (with 0 not
> surprisingly being a true horror) but turning it up didn't help git one
> bit.  The amount of data that had to be re-read with stock 100 or 10000
> was the same, or at least so close that you couldn't see a difference in
> vmstat and wall-clock.  Cache sizes varied, but the bottom line didn't.
> (wasn't surprised, seems quite reasonable that git's data looks old and
> useless to the reclaim logic when updatedb runs in between git runs)
> 

Did a bit of playing with this with 128MB of memory.

- drop caches
- read a 1MB file
- run slocate.cron

With vfs_cache_pressure=100:

MemTotal:       116316 kB
MemFree:          3196 kB
Buffers:         54408 kB
Cached:           5128 kB
SwapCached:          0 kB
Active:          41728 kB
Inactive:        27540 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:       116316 kB
LowFree:          3196 kB
SwapTotal:     1020116 kB
SwapFree:      1019496 kB
Dirty:               0 kB
Writeback:           0 kB
AnonPages:        9760 kB
Mapped:           3808 kB
Slab:            40468 kB
SReclaimable:    34824 kB
SUnreclaim:       5644 kB
PageTables:        720 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
CommitLimit:   1078272 kB
Committed_AS:    25988 kB
VmallocTotal:   901112 kB
VmallocUsed:       656 kB
VmallocChunk:   900412 kB
HugePages_Total:     0
HugePages_Free:      0
HugePages_Rsvd:      0
Hugepagesize:     4096 kB

WIth vfs_cache_pressure=10000:

MemTotal:       116316 kB
MemFree:          3060 kB
Buffers:         80792 kB
Cached:           5052 kB
SwapCached:          0 kB
Active:          59432 kB
Inactive:        36140 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:       116316 kB
LowFree:          3060 kB
SwapTotal:     1020116 kB
SwapFree:      1019512 kB
Dirty:               0 kB
Writeback:           0 kB
AnonPages:        9756 kB
Mapped:           3832 kB
Slab:            14304 kB
SReclaimable:     7992 kB
SUnreclaim:       6312 kB
PageTables:        732 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
CommitLimit:   1078272 kB
Committed_AS:    26000 kB
VmallocTotal:   901112 kB
VmallocUsed:       656 kB
VmallocChunk:   900412 kB
HugePages_Total:     0
HugePages_Free:      0
HugePages_Rsvd:      0
Hugepagesize:     4096 kB

so we reaped quite a lot more slab with the higher vfs_cache_pressure.

What I think is killing us here is the blockdev pagecache: the pagecache
which backs those directory entries and inodes.  These pages get read
multiple times because they hold multiple directory entries and multiple
inodes.  These multiple touches will put those pages onto the active list
so they stick around for a long time and everything else gets evicted.


I've never been very sure about this policy for the metadata pagecache.  We
read the filesystem objects into the dcache and icache and then we won't
read from that page again for a long time (I expect).  But the page will
still hang around for a long time.

It could be that we should leave those pages inactive.

<tries it>

diff -puN include/linux/buffer_head.h~a include/linux/buffer_head.h
--- a/include/linux/buffer_head.h~a
+++ a/include/linux/buffer_head.h
@@ -130,7 +130,7 @@ BUFFER_FNS(Eopnotsupp, eopnotsupp)
 BUFFER_FNS(Unwritten, unwritten)
 
 #define bh_offset(bh)		((unsigned long)(bh)->b_data & ~PAGE_MASK)
-#define touch_buffer(bh)	mark_page_accessed(bh->b_page)
+#define touch_buffer(bh)	do { } while(0)
 
 /* If we *know* page->private refers to buffer_heads */
 #define page_buffers(page)					\
_

vfs_cache_pressure=100:

vmm:/home/akpm# cat /proc/meminfo 
MemTotal:       116524 kB
MemFree:          2692 kB
Buffers:         51044 kB
Cached:           5440 kB
SwapCached:          0 kB
Active:          19248 kB
Inactive:        46996 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:       116524 kB
LowFree:          2692 kB
SwapTotal:     1020116 kB
SwapFree:      1019492 kB
Dirty:            2008 kB
Writeback:           0 kB
AnonPages:        9772 kB
Mapped:           3812 kB
Slab:            44336 kB
SReclaimable:    38792 kB
SUnreclaim:       5544 kB
PageTables:        720 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
CommitLimit:   1078376 kB
Committed_AS:    26108 kB
VmallocTotal:   901112 kB
VmallocUsed:       648 kB
VmallocChunk:   900412 kB
HugePages_Total:     0
HugePages_Free:      0
HugePages_Rsvd:      0
Hugepagesize:     4096 kB


vfs_cache_pressure=10000

vmm:/home/akpm# cat /proc/meminfo                       
MemTotal:       116524 kB
MemFree:          3720 kB
Buffers:         79832 kB
Cached:           6260 kB
SwapCached:          0 kB
Active:          18276 kB
Inactive:        77584 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:       116524 kB
LowFree:          3720 kB
SwapTotal:     1020116 kB
SwapFree:      1019500 kB
Dirty:            2228 kB
Writeback:           0 kB
AnonPages:        9788 kB
Mapped:           3828 kB
Slab:            13680 kB
SReclaimable:     7676 kB
SUnreclaim:       6004 kB
PageTables:        736 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
CommitLimit:   1078376 kB
Committed_AS:    26112 kB
VmallocTotal:   901112 kB
VmallocUsed:       648 kB
VmallocChunk:   900412 kB
HugePages_Total:     0
HugePages_Free:      0
HugePages_Rsvd:      0
Hugepagesize:     4096 kB


So again, slab was trimmed a lot more, but all our pagecache still got
evicted.

ah, but I started that pagecache out on the inactive list.  Try again. 
This time, instead of reading a 1GB file once, let's read an 80MB file four
times.

<no difference>

OK, I saw what happened then.  The inode for my 80MB file got reclaimed
from icache and that instantly reclaimed all 80MB of pagecache.

A single large file probably isn't a good testcase, but the same will
happen with multiple files.  Higher vfs_cache_pressure will worsen this
effect.  But it won't happen with mapped files because their inodes aren't
reclaimable.  More sophisticated testing is needed - there's something in
ext3-tools which will mmap, page in and hold a file for you.


Anyway, blockdev pagecache is a problem, I expect.  It's worth playing with
that patch.

Another problem is atime updates.  You really do want to mount noatime. 
Because with atimes enabled, each touch of a file will touch its inode and
will keep its backing blockdev pagecache page in core.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Al Viro]

On Fri, Jul 27, 2007 at 01:47:49AM -0700, Andrew Morton wrote:
> What I think is killing us here is the blockdev pagecache: the pagecache
> which backs those directory entries and inodes.  These pages get read
> multiple times because they hold multiple directory entries and multiple
> inodes.  These multiple touches will put those pages onto the active list
> so they stick around for a long time and everything else gets evicted.

I wonder what happens if you try that on ext2.  There we'd get directory
contents in per-directory page cache, so the picture might change...

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Andrew Morton]

On Fri, 27 Jul 2007 09:54:41 +0100 Al Viro <viro@ftp.linux.org.uk> wrote:

> On Fri, Jul 27, 2007 at 01:47:49AM -0700, Andrew Morton wrote:
> > What I think is killing us here is the blockdev pagecache: the pagecache
> > which backs those directory entries and inodes.  These pages get read
> > multiple times because they hold multiple directory entries and multiple
> > inodes.  These multiple touches will put those pages onto the active list
> > so they stick around for a long time and everything else gets evicted.
> 
> I wonder what happens if you try that on ext2.  There we'd get directory
> contents in per-directory page cache, so the picture might change...

afacit ext2 just forgets to run mark_page_accessed for directory pages
altogether, so it'll be equivalent to ext3 with that one-liner, I expect.

The directory pagecache on ext2 might get reclaimed faster because those
pages are eligible for reclaiming via the reclaim of their inodes, whereas
ext3's directories are in blockdev pagecache, for which the reclaim-via-inode
mechanism cannot happen.

I should do some testing with mmapped files.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Mike Galbraith]

On Fri, 2007-07-27 at 01:47 -0700, Andrew Morton wrote:

> Anyway, blockdev pagecache is a problem, I expect.  It's worth playing with
> that patch.

(may tinker a bit, but i'm way rusty.  ain't had the urge to mutilate
anything down there in quite a while... works just fine for me these
days)

> Another problem is atime updates.  You really do want to mount noatime. 
> Because with atimes enabled, each touch of a file will touch its inode and
> will keep its backing blockdev pagecache page in core.

Yeah, I mount noatime,nodiratime,data=writeback.  ext3's journal with my
crusty old disk/fs is painful as heck.

	-Mike

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Andrew Morton]

On Fri, 27 Jul 2007 01:47:49 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:

> More sophisticated testing is needed - there's something in
> ext3-tools which will mmap, page in and hold a file for you.

So much for that theory.  afaict mmapped, active pagecache is immune to
updatedb activity.  It just sits there while updatedb continues munching
away at the slab and blockdev pagecache which it instantiated.  I assume
we're never getting the VM into enough trouble to tip it over the
start-reclaiming-mapped-pages threshold (ie: /proc/sys/vm/swappiness).

Start the updatedb on this 128MB machine with 80MB of mapped pagecache, it
falls to 55MB fairly soon and then never changes.

So hrm.  Are we sure that updatedb is the problem?  There are quite a few
heavyweight things which happen in the wee small hours.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Mike Galbraith]

On Fri, 2007-07-27 at 03:00 -0700, Andrew Morton wrote:
> On Fri, 27 Jul 2007 01:47:49 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:
> 
> > More sophisticated testing is needed - there's something in
> > ext3-tools which will mmap, page in and hold a file for you.
> 
> So much for that theory.  afaict mmapped, active pagecache is immune to
> updatedb activity.  It just sits there while updatedb continues munching
> away at the slab and blockdev pagecache which it instantiated.  I assume
> we're never getting the VM into enough trouble to tip it over the
> start-reclaiming-mapped-pages threshold (ie: /proc/sys/vm/swappiness).
> 
> Start the updatedb on this 128MB machine with 80MB of mapped pagecache, it
> falls to 55MB fairly soon and then never changes.
> 
> So hrm.  Are we sure that updatedb is the problem?  There are quite a few
> heavyweight things which happen in the wee small hours.

The balance in _my_ world seems just fine.  I don't let any of those
system maintenance things run while I'm using the system, and it doesn't
bother me if my working set has to be reconstructed after heavy-weight
maintenance things are allowed to run.  I'm not seeing anything I
wouldn't expect to see when running a job the size of updatedb.

	-Mike

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Daniel Hazelton]

On Friday 27 July 2007 06:25:18 Mike Galbraith wrote:
> On Fri, 2007-07-27 at 03:00 -0700, Andrew Morton wrote:
> > On Fri, 27 Jul 2007 01:47:49 -0700 Andrew Morton 
<akpm@linux-foundation.org> wrote:
> > > More sophisticated testing is needed - there's something in
> > > ext3-tools which will mmap, page in and hold a file for you.
> >
> > So much for that theory.  afaict mmapped, active pagecache is immune to
> > updatedb activity.  It just sits there while updatedb continues munching
> > away at the slab and blockdev pagecache which it instantiated.  I assume
> > we're never getting the VM into enough trouble to tip it over the
> > start-reclaiming-mapped-pages threshold (ie: /proc/sys/vm/swappiness).
> >
> > Start the updatedb on this 128MB machine with 80MB of mapped pagecache,
> > it falls to 55MB fairly soon and then never changes.
> >
> > So hrm.  Are we sure that updatedb is the problem?  There are quite a few
> > heavyweight things which happen in the wee small hours.
>
> The balance in _my_ world seems just fine.  I don't let any of those
> system maintenance things run while I'm using the system, and it doesn't
> bother me if my working set has to be reconstructed after heavy-weight
> maintenance things are allowed to run.  I'm not seeing anything I
> wouldn't expect to see when running a job the size of updatedb.
>
> 	-Mike

Do you realize you've totally missed the point?

It isn't about what is fine in the Kernel Developers world, but what is fine 
in the *USERS* world. 

There are dozens of big businesses pushing Linux for Enterprise performance. 
Rather than discussing the merit of those patches - some of which just 
improve the performance of a specific application by 1 or 2  percent - they 
get a nod and go into the kernel. But when a group of users that don't 
represent one of those businesses says "Hey, this helps with problems I see 
on my system" there is a big discussion and ultimately those patches get 
rejected. Why? Because they'll give an example using a program that they see 
causing part of the problem and be told "Use program X - it does things 
differently and shouldn't cause the problem" or "But what causes the problem 
to happen? The patch treats a symptom of a larger problem".

The fucked up part of that is that the (mass of) kernel developers will see a 
similar report saying "mySQL has a performance problem because of X, this 
fixes it" and not blink twice - even if it is "treating the symptom and not 
the cause". It's this attitude more than anything that caused Con 
to "retire" - at least that is the impression I got from the interviews he's 
given. (The exact impression was "I'm sick of the kernel developers doing 
everything they can to help enterprise users and ignoring the home users")

So...
The problem:
Updatedb or another process that uses the FS heavily runs on a users 256MB 
P3-800 (when it is idle) and the VFS caches grow, causing memory pressure 
that causes other applications to be swapped to disk. In the morning the user 
has to wait for the system to swap those applications back in.

Questions about it:
Q) Does swap-prefetch help with this? 
A) [From all reports I've seen (*)] Yes, it does. 

Q) Why does it help? 
A) Because it pro-actively swaps stuff back-in when the memory pressure that 
caused it to be swapped out is gone. 

Q) What causes the problem? 
A) The VFS layer not keeping a limited cache. Instead the VFS will chew 
through available memory in the name of "increasing performance".

Solution(s) to the problem:
1) Limit the amount of memory the pagecache and other VFS caches can consume
2) Implement swap prefetch

If I had a (more) complete understanding of how the VFS cache(s) work I'd try 
to code a patch to do #1 myself. Patches to do #2 already exist and have been 
shown to work for the users that have tried it. My question is thus, simply: 
What is the reason that it is argued against?(**)

DRH
PS: Yes, I realize I've repeated some people from earlier in this thread, but 
it seems that people have been forgetting the point.

(*) I've followed this thread and all of its splinters. The reports that are 
in them, where the person making the report has a system that has the limited 
memory needed for the problem to exhibit itself, all show that swap-prefetch 
helps.

(**) No, I won't settle for "Its treating a symptom". The fact is that this 
isn't a *SYMPTOM* of anything. It treats the cause of the lag the users that 
have less than (for the sake of argument) 1G of memory are seeing. And no, 
changing userspace isn't a solution - updatedb may be the program that has 
been used as an example, but there are others. The proper fix is to change 
the kernel to either make the situation impossible (limit the VFS and other 
kernel caches) or make the situation as painless as possible (implement swap 
prefetch to alleviate the lag of swapping data back in).

-- 
Dialup is like pissing through a pipette. Slow and excruciatingly painful.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/27/2007 07:45 PM, Daniel Hazelton wrote:

> Updatedb or another process that uses the FS heavily runs on a users
> 256MB P3-800 (when it is idle) and the VFS caches grow, causing memory
> pressure that causes other applications to be swapped to disk. In the
> morning the user has to wait for the system to swap those applications
> back in.
> 
> Questions about it:
> Q) Does swap-prefetch help with this? 
> A) [From all reports I've seen (*)] Yes, it does. 

No it does not. If updatedb filled memory to the point of causing swapping 
(which noone is reproducing anyway) it HAS FILLED MEMORY and swap-prefetch 
hasn't any memory to prefetch into -- updatedb itself doesn't use any 
significant memory.

Here's swap-prefetch's author saying the same:

http://lkml.org/lkml/2007/2/9/112

| It can't help the updatedb scenario. Updatedb leaves the ram full and
| swap prefetch wants to cost as little as possible so it will never
| move anything out of ram in preference for the pages it wants to swap
| back in.

Now please finally either understand this, or tell us how we're wrong.

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Paul Jackson]

Al Viro wrote:
> BTW, I really wonder how much pain could be avoided if updatedb recorded
> mtime of directories and checked it.

Someone mentioned a variant of slocate above that they called mlocate,
and that Red Hat ships, that seems to do this (if I understand you and
what mlocate does correctly.)

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.925.600.0401

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[david]

On Fri, 27 Jul 2007, Rene Herman wrote:

> On 07/27/2007 07:45 PM, Daniel Hazelton wrote:
>
>>  Updatedb or another process that uses the FS heavily runs on a users
>>  256MB P3-800 (when it is idle) and the VFS caches grow, causing memory
>>  pressure that causes other applications to be swapped to disk. In the
>>  morning the user has to wait for the system to swap those applications
>>  back in.
>>
>>  Questions about it:
>>  Q) Does swap-prefetch help with this? A) [From all reports I've seen (*)]
>>  Yes, it does. 
>
> No it does not. If updatedb filled memory to the point of causing swapping 
> (which noone is reproducing anyway) it HAS FILLED MEMORY and swap-prefetch 
> hasn't any memory to prefetch into -- updatedb itself doesn't use any 
> significant memory.

however there are other programs which are known to take up significant 
amounts of memory and will cause the issue being described (openoffice for 
example)

please don't get hung up on the text 'updatedb' and accept that there are 
programs that do run intermittently and do use a significant amount of ram 
and then free it.

David Lang

> Here's swap-prefetch's author saying the same:
>
> http://lkml.org/lkml/2007/2/9/112
>
> |  It can't help the updatedb scenario. Updatedb leaves the ram full and
> |  swap prefetch wants to cost as little as possible so it will never
> |  move anything out of ram in preference for the pages it wants to swap
> |  back in.
>
> Now please finally either understand this, or tell us how we're wrong.
>
> Rene.
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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>

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Daniel Hazelton]

On Friday 27 July 2007 14:16:32 Rene Herman wrote:
> On 07/27/2007 07:45 PM, Daniel Hazelton wrote:
> > Updatedb or another process that uses the FS heavily runs on a users
> > 256MB P3-800 (when it is idle) and the VFS caches grow, causing memory
> > pressure that causes other applications to be swapped to disk. In the
> > morning the user has to wait for the system to swap those applications
> > back in.
> >
> > Questions about it:
> > Q) Does swap-prefetch help with this?
> > A) [From all reports I've seen (*)] Yes, it does.
>
> No it does not. If updatedb filled memory to the point of causing swapping
> (which noone is reproducing anyway) it HAS FILLED MEMORY and swap-prefetch
> hasn't any memory to prefetch into -- updatedb itself doesn't use any
> significant memory.

Check the attitude at the door then re-read what I actually said:
> > Updatedb or another process that uses the FS heavily runs on a users
> > 256MB P3-800 (when it is idle) and the VFS caches grow, causing memory
> > pressure that causes other applications to be swapped to disk. In the
> > morning the user has to wait for the system to swap those applications
> > back in.

I never said that it was the *program* itself - or *any* specific program (I 
used "Updatedb" because it has been the big name in the discussion) - doing 
the filling of memory. I actually said that the problem is that the kernel's 
caches - VFS and others - will grow *WITHOUT* *LIMIT*, filling all available 
memory. 

Swap prefetch on its own will not alleviate *all* of the problem, but it 
appears to fix enough of it that the problem doesn't seem to bother people 
anymore. (As I noted later on there are things that can be changes that would 
also fix things. Those changes, however, are quite tricky and involve changes 
to the page faulting mechanism, the way the various caches work and a number 
of other things)

In light of the fact that swap prefetch appears to solve the problem for the 
people that have been vocal about it, and because it is a less intrusive 
change than the other potential solutions, I'd like to know why all the 
complaints and arguments against it come down to "Its treating the symptom".

I mean it - because I fail to see how it isn't getting at the root of the 
problem - which is, pretty much, that Swap has classically been and, in the 
case of most modern systems, still is damned slow. By prefetching those pages 
that have most recently been evicted the problem of "slow swap" is being 
directly addressed.

You want to know what causes the problem? The current design of the caches. 
They will extend without much limit, to the point of actually pushing pages 
to disk so they can grow even more. 

> Here's swap-prefetch's author saying the same:
>
> http://lkml.org/lkml/2007/2/9/112
>
> | It can't help the updatedb scenario. Updatedb leaves the ram full and
> | swap prefetch wants to cost as little as possible so it will never
> | move anything out of ram in preference for the pages it wants to swap
> | back in.
>
> Now please finally either understand this, or tell us how we're wrong.
>
> Rene.

I already did. You completely ignored it because I happened to use the magic 
words "updatedb" and "swap prefetch". 

Did I ever say it was about "updatedb" in particular? You've got the statement 
in the part of my post that you quoted. Nope, appears that I used the name as 
a specific example - and one that has been used previously in the thread. Now 
drop the damned attitude and start using your brain. Okay?

DRH

-- 
Dialup is like pissing through a pipette. Slow and excruciatingly painful.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Mike Galbraith]

On Fri, 2007-07-27 at 13:45 -0400, Daniel Hazelton wrote:
> On Friday 27 July 2007 06:25:18 Mike Galbraith wrote:
> > On Fri, 2007-07-27 at 03:00 -0700, Andrew Morton wrote:

> > > So hrm.  Are we sure that updatedb is the problem?  There are quite a few
> > > heavyweight things which happen in the wee small hours.
> >
> > The balance in _my_ world seems just fine.  I don't let any of those
> > system maintenance things run while I'm using the system, and it doesn't
> > bother me if my working set has to be reconstructed after heavy-weight
> > maintenance things are allowed to run.  I'm not seeing anything I
> > wouldn't expect to see when running a job the size of updatedb.
> >
> > 	-Mike
> 
> Do you realize you've totally missed the point?

Did you notice that I didn't make one disparaging remark about the patch
or the concept behind it?   Did you notice that I took _my time_  to
test, to actually look at  the problem?  No, you're too busy running
your mouth to appreciate the efforts of others.
 
<snips load of useless spleen venting>

Do yourself a favor, go dig into the VM source.  Read it, understand it
(not terribly easy), _then_ come back and preach to me.

Have a nice day.

	-Mike

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Daniel Hazelton]

On Friday 27 July 2007 18:08:44 Mike Galbraith wrote:
> On Fri, 2007-07-27 at 13:45 -0400, Daniel Hazelton wrote:
> > On Friday 27 July 2007 06:25:18 Mike Galbraith wrote:
> > > On Fri, 2007-07-27 at 03:00 -0700, Andrew Morton wrote:
> > > > So hrm.  Are we sure that updatedb is the problem?  There are quite a
> > > > few heavyweight things which happen in the wee small hours.
> > >
> > > The balance in _my_ world seems just fine.  I don't let any of those
> > > system maintenance things run while I'm using the system, and it
> > > doesn't bother me if my working set has to be reconstructed after
> > > heavy-weight maintenance things are allowed to run.  I'm not seeing
> > > anything I wouldn't expect to see when running a job the size of
> > > updatedb.
> > >
> > > 	-Mike
> >
> > Do you realize you've totally missed the point?
>
> Did you notice that I didn't make one disparaging remark about the patch
> or the concept behind it?   Did you notice that I took _my time_  to
> test, to actually look at  the problem?  No, you're too busy running
> your mouth to appreciate the efforts of others.

If you're done being an ass, take note of the fact that I never even said you 
were doing that. What I was commenting on was the fact that you (and a lot of 
the other developers) seem to keep saying "It doesn't happen here, so it 
doesn't matter!" - ie: If I don't see something happening, it doesn't matter.

> <snips load of useless spleen venting>
>
> Do yourself a favor, go dig into the VM source.  Read it, understand it
> (not terribly easy), _then_ come back and preach to me.

I've been trying to do that since the thread started. Note that you snipped 
where I said (and I'm going to paraphrase myself) "There is another way to 
fix this, but I don't have the understanding necessary".

Now, once more, I'm going to ask: What is so terribly wrong with swap 
prefetch? Why does it seem that everyone against it says "Its treating a 
symptom, so it can't go in"?

Try coming up with an answer that isn't "I don't see the problem on my $10K 
system" or similar - try explaining it based on the *technical* merits. Does 
it cause the processor cache to get thrashed? Does it create locking 
problems?

I stand by my statements, as vitriolic as you and Rene seem to want to get 
over it. So far in this thread I have not seen one bit of *technical* 
discussion over the merits, just the bits I've simplified and stated before.

> Have a nice day.

I am. You being nasty when somebody gets fed up with a line of BS doesn't stop 
me from having a nice day. Only thing that could make my life any better 
would be to have the questions I've asked answered, rather than having 
supposedly intelligent people act like trolls.

DRH

-- 
Dialup is like pissing through a pipette. Slow and excruciatingly painful.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Björn Steinbrink]

On 2007.07.27 20:16:32 +0200, Rene Herman wrote:
> On 07/27/2007 07:45 PM, Daniel Hazelton wrote:
>
>> Updatedb or another process that uses the FS heavily runs on a users
>> 256MB P3-800 (when it is idle) and the VFS caches grow, causing memory
>> pressure that causes other applications to be swapped to disk. In the
>> morning the user has to wait for the system to swap those applications
>> back in.
>> Questions about it:
>> Q) Does swap-prefetch help with this? A) [From all reports I've seen (*)] 
>> Yes, it does. 
>
> No it does not. If updatedb filled memory to the point of causing swapping 
> (which noone is reproducing anyway) it HAS FILLED MEMORY and swap-prefetch 
> hasn't any memory to prefetch into -- updatedb itself doesn't use any 
> significant memory.
>
> Here's swap-prefetch's author saying the same:
>
> http://lkml.org/lkml/2007/2/9/112
>
> | It can't help the updatedb scenario. Updatedb leaves the ram full and
> | swap prefetch wants to cost as little as possible so it will never
> | move anything out of ram in preference for the pages it wants to swap
> | back in.
>
> Now please finally either understand this, or tell us how we're wrong.

Con might have been wrong there for boxes with really little memory.

My desktop box has not even 300k inodes in use (IIRC someone posted a df
-i output showing 1 million inodes in use). Still, the memory footprint
of the "sort" process grows up to about 50MB. Assuming that the average
filename length stays, that would mean 150MB for the 1 million inode
case, just for the "sort" process.

Now, sort cannot produce any output before its got all its input, so
that RSS usage exists at least as long as the VFS cache is growing due
to the ongoing search for files.

And then, all that memory that "sort" uses is required, because sort
needs to output its results. So if there's memory pressure, the VFS
cache is likely to be dropped, because "sort" needs its data, for
sorting and producing output. And then sort terminates and leaves that
whole lot of memory _unused_. The other actions of updatedb only touch
the locate db, which is just a few megs (4.5MB here) big so the cache
won't grow that much again.

OK, so we got about, say, at least 128MB of totally unused memory, maybe
even more. If you look at the vmstat output I sent, you see that I had
between 90MB and 128MB free, depending on the swappiness setting, with
increased inode usage, that could very well scale up.

Conclusion: updatedb does _not_ leave the RAM full. And for a box with
little memory (say 256MB) it might even be 50% or more memory that is
free after updatedb ran. Might that make swap prefetch kick in?


Any faults in that reasoning?

Thanks,
Björn

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Andi Kleen]

> Any faults in that reasoning?

GNU sort uses a merge sort with temporary files on disk. Not sure
how much it keeps in memory during that, but it's probably less
than 150MB. At some point the dirty limit should kick in and write back the 
data of the temporary files; so it's not quite the same as anonymous memory. 
But it's not that different given.

It would be better to measure than to guess. At least Andrew's measurements
on 128MB actually didn't show updatedb being really that big a problem.

Perhaps some people have much more files or simply a less efficient
updatedb implementation?

I guess the people who complain here that loudly really need to supply
some real numbers. 

-Andi

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Björn Steinbrink]

On 2007.07.28 01:29:19 +0200, Andi Kleen wrote:
> > Any faults in that reasoning?
> 
> GNU sort uses a merge sort with temporary files on disk. Not sure
> how much it keeps in memory during that, but it's probably less
> than 150MB. At some point the dirty limit should kick in and write back the 
> data of the temporary files; so it's not quite the same as anonymous memory. 
> But it's not that different given.

Hm, does that change anything? The files need to be read at the end (so
they go into the cache) and are delete afterwards (cache gets freed I
guess?).

> It would be better to measure than to guess. At least Andrew's measurements
> on 128MB actually didn't show updatedb being really that big a problem.

Here's a before/after memory usage for an updatedb run:
root@atjola:~# free -m
             total       used       free     shared    buffers     cached
Mem:          2011       1995         15          0        269        779
-/+ buffers/cache:        946       1064
Swap:         1945          0       1945
root@atjola:~# updatedb
root@atjola:~# free -m
             total       used       free     shared    buffers     cached
Mem:          2011       1914         96          0        209        746
-/+ buffers/cache:        958       1052
Swap:         1945          0       1944

81MB more unused RAM afterwards.

If anyone can make use of that, here's a snippet from /proc/$PID/smaps
of updatedb's sort process, when it was at about its peak memory usage
(according to the RSS column in top), which was about 50MB.

2b90ab3c1000-2b90ae4c3000 rw-p 2b90ab3c1000 00:00 0 
Size:              50184 kB
Rss:               50184 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:     50184 kB
Referenced:        50184 kB

> Perhaps some people have much more files or simply a less efficient
> updatedb implementation?

sort (GNU coreutils) 5.97

GNU updatedb version 4.2.31

> I guess the people who complain here that loudly really need to supply
> some real numbers. 

Just to clarify: I'm not complaining either way, neither about not
merging swap prefetch, nor about someone wanting that to be merge. It
was rather the "discussion" that caught my attention... Just in case ;-)

Björn

Re: -mm merge plans for 2.6.23

[Matt Mackall]

On Wed, Jul 25, 2007 at 09:57:17PM -0700, Andrew Morton wrote:
> So.  We can
> 
> a) provide a way for userspace to reload pagecache and
> 
> b) merge maps2 (once it's finished) (pokes mpm)

Consider me poked, despite not being cc:ed.

-- 
Mathematics is the supreme nostalgia of our time.

Re: -mm merge plans for 2.6.23

[Matt Mackall]

On Wed, Jul 25, 2007 at 11:50:37PM -0700, Andrew Morton wrote:
> On Wed, 25 Jul 2007 23:33:24 -0700 "Ray Lee" <ray-lk@madrabbit.org> wrote:
> 
> > > So.  We can
> > >
> > > a) provide a way for userspace to reload pagecache and
> > >
> > > b) merge maps2 (once it's finished) (pokes mpm)
> > >
> > > and we're done?
> > 
> > Eh, dunno. Maybe?
> > 
> > We're assuming we come up with an API for userspace to get
> > notifications of evictions (without polling, though poll() would be
> > fine -- you know what I mean), and an API for re-victing those things
> > on demand.
> 
> I was assuming that polling would work OK.  I expect it would.
> 
> > If you think that adding that API and maintaining it is
> > simpler/better than including a variation on the above hueristic I
> > offered, then yeah, I guess we are. It'll all have that vague
> > userspace s2ram odor about it, but I'm sure it could be made to work.
> 
> Actually, I overdesigned the API, I suspect.  What we _could_ do is to
> provide a way of allowing userspace to say "pretend process A touched page
> B": adopt its mm and go touch the page.  We in fact already have that:
> PTRACE_PEEKTEXT.
> 
> So I suspect this could all be done by polling maps2 and using PEEKTEXT. 
> The tricky part would be working out when to poll, and when to reestablish.
> 
> A neater implementation than PEEKTEXT would be to make the maps2 files
> writeable(!) so as a party trick you could tar 'em up and then, when you
> want to reestablish firefox's previous working set, do a untar in
> /proc/$(pidof firefox)/

Sick. But thankfully, unnecessary. The pagemaps give you more than
just a present bit, which is all we care about here. We simply need to
record which pages are mapped, then reference them all back to life..

-- 
Mathematics is the supreme nostalgia of our time.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Daniel Hazelton]

On Friday 27 July 2007 19:29:19 Andi Kleen wrote:
> > Any faults in that reasoning?
>
> GNU sort uses a merge sort with temporary files on disk. Not sure
> how much it keeps in memory during that, but it's probably less
> than 150MB. At some point the dirty limit should kick in and write back the
> data of the temporary files; so it's not quite the same as anonymous
> memory. But it's not that different given.

Yes, this should occur. But how many programs use temporary files like that? 
>From what I can tell FireFox and OpenOffice both keep all their data in 
memory, only using a single file for some buffering purposes. When they get 
pushed out by a memory hog (either short term or long term) it takes several 
seconds for them to be swapped back in. (I'm on a P4-1.3GHz machine with 1G 
of ram and rarely run more than four programs (Mail Client, XChat, FireFox 
and a console window) and I've seen this lag in FireFox when switching to it 
after starting OOo. I've also seen the same sort of lag when exiting OOo. 
I'll see about getting some numbers about this)

> It would be better to measure than to guess. At least Andrew's measurements
> on 128MB actually didn't show updatedb being really that big a problem.

I agree. As I've said previously, it isn't updatedb itself which causes the 
problem. It's the way the VFS cache seems to just expand and expand - to the 
point of evicting pages to make room for itself. However, I may be wrong 
about that - I haven't actually tested it for myself, just looked at the 
numbers and other information that has been posted in this thread.

> Perhaps some people have much more files or simply a less efficient
> updatedb implementation?

Yes, it could be the proliferation of files. It could also be some other sort 
of problem that is exposing a corner-case in the VFS cache or the MM. I, 
personally, am of the opinion that it is likely the aforementioned corner 
case for people reporting the "updatedb" problem. If it is, then 
swap-prefetch is just papering over the problem. However I do not have the 
knowledge and understanding of the subsystems involved to be able to do much 
more than make a (probably wrong) guess.

> I guess the people who complain here that loudly really need to supply
> some real numbers.

I've seen numerous "real numbers" posted about this. As was said earlier in 
the thread "every time numbers are posted they are claimed to be no good". 
But hey, nobodies perfect :)

Anyway, the discussion seems to be turning to the technical merits of 
swap-prefetch...

Now, a completely different question:
During the research (and lots of thinking) I've been doing while this thread 
has been going on I've often wondered why swap prefetch wasn't already in the 
kernel. The problem of slow swap-in has long been known, and, given current 
hardware, the optimal solution would be some sort of data prefetch - similar 
to what is done to speed up normal disk reads. Swap prefetch looks like it 
does exactly that. The algo could be argued over and/or improved (to suggest 
ways to do that I'd have to give it more than a 10 minute look) but it does 
provide a speed-up.

This speed increase will probably be enjoyed more by the home users, but the 
performance increase could also help on enterprise systems.

Now I'll be the first one to admit that there is a trade-off there - it will 
cause more power to be used because the disk's don't get a chance to spin 
down (or go through a cycle every time the prefetch system starts) but that 
could, potentially, be alleviated by having "laptop mode" switch it off.

(And no, I'm not claiming that it is perfect - but then, what is when its 
first merged into the kernel?)

DRH

-- 
Dialup is like pissing through a pipette. Slow and excruciatingly painful.

Re: -mm merge plans for 2.6.23

[Daniel Cheng]

Andrew Morton wrote:
[...]
> 
> And userspace can do a much better implementation of this
> how-to-handle-large-load-shifts problem, because it is really quite
> complex.  The system needs to be monitored to determine what is the "usual"
[...]
> All this would end up needing runtime configurability and tweakability and
> customisability.  All standard fare for userspace stuff - much easier than
> patching the kernel.

But a patch already exist.
Which is easier: (1) apply the patch ; or (2) write a new patch?

> 
> So.  We can
> a) provide a way for userspace to reload pagecache and
> b) merge maps2 (once it's finished) (pokes mpm)
> and we're done?

might be.
but merging maps2 have higher risk which should be done in a development
branch (er... 2.7, but we don't have it now).

-- 

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/27/2007 10:28 PM, Daniel Hazelton wrote:

> Check the attitude at the door then re-read what I actually said:

Attitude? You wanted attitude dear boy?

>>> Updatedb or another process that uses the FS heavily runs on a users
>>> 256MB P3-800 (when it is idle) and the VFS caches grow, causing memory
>>> pressure that causes other applications to be swapped to disk. In the
>>> morning the user has to wait for the system to swap those applications
>>> back in.
> 
> I never said that it was the *program* itself - or *any* specific program (I 
> used "Updatedb" because it has been the big name in the discussion) - doing 
> the filling of memory. I actually said that the problem is that the kernel's 
> caches - VFS and others - will grow *WITHOUT* *LIMIT*, filling all available 
> memory. 

WHICH SWAP-PREFETCH DOES NOT HELP WITH.
WHICH SWAP-PREFETCH DOES NOT HELP WITH.
WHICH SWAP-PREFETCH DOES NOT HELP WITH.

And now finally get that through your thick scull or shut up, right fucking now.

> You want to know what causes the problem? The current design of the caches. 
> They will extend without much limit, to the point of actually pushing pages 
> to disk so they can grow even more. 

Due to being a generally nice guy, I am going to try _once_ more to try and 
make you understand. Not twice, once. So pay attention. Right now.

Those caches are NOT causing any problem under discussion. If any caches 
grow to the point of causing swap-out, they have filled memory and 
swap-prefetch cannot and will not do anything since it needs free (as in not 
occupied by caches) memory. As such, people maintaining that swap-prefetch 
helps their situation are not being hit by caches.

The only way swap-prefetch can (and will) do anything is when something that 
by itself takes up lots of memory runs and exits. So can we now please 
finally drop the fucking red herring and start talking about swap-prefetch?

If we accept that some of the people maintaining that swap-prefetch helps 
them are not in fact deluded -- a bit of a stretch seeing as how not a 
single one of them is substantiating anything -- we have a number of 
slightly different possibilities for "something" in the above.

-- 1)

It could be an inefficient updatedb. Although he isn't experiencing the 
problem, Bjoern Steinbrink is posting numbers (weeee!) that show that at 
least the GNU version spawns a large memory "sort" process meaning that on a 
low-memory box updatedb itself can be what causes the observed problem.

While in this situation switching to a different updatedb (slocate, mlocate) 
obviously makes sense it's the kind of situation where swap-prefetch will help.

-- 2)

It could be something else entirely such as a backup run. I suppose people 
would know if they were running anything of the sort though and wouldn't 
blaim anything on updatedb.

Other than that, it's again the situation where swap-prefetch would help.

-- 3)

The something else entirely can also run _after_ updatedb, kicking out the 
VFS caches and leaving free memory upon exit. I still suppose the same thing 
as under (2) but this is the only way how updatedb / VFS caches can even be 
part of any problem, if the _combined_ memory pressure is just enough to 
make the difference.

The direct problem is still just the "something else entirely" and needs 
someone affected to tell us what it is.

> I already did. You completely ignored it because I happened to use the magic 
> words "updatedb" and "swap prefetch". 

No I did not. This thread is about swap-prefetch and you used the magic 
words VFS caches. I don't give a fryin' fuck if their filling is caused by 
updatedb or the cat sleeping on the "find /<enter>" keys on your keyboard, 
they're still not causing anything swap-prefetch helps with.

This thread has seen input from a selection of knowledgeable people and 
Morton was even running benchmarks to look at this supposed VFS cache 
problem and not finding it. The only further input this thread needs is 
someone affected by the supposed problem.

Which I ofcourse notice in a followup of yours you are not either -- you're 
just here to blabber, not to solve anything.

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/27/2007 09:43 PM, david@lang.hm wrote:

> On Fri, 27 Jul 2007, Rene Herman wrote:
> 
>> On 07/27/2007 07:45 PM, Daniel Hazelton wrote:
>>
>>>  Questions about it:
>>>  Q) Does swap-prefetch help with this?
>>>  A) [From all reports I've seen (*)]
>>>  Yes, it does. 
>>
>> No it does not. If updatedb filled memory to the point of causing 
>> swapping (which noone is reproducing anyway) it HAS FILLED MEMORY and 
>> swap-prefetch hasn't any memory to prefetch into -- updatedb itself 
>> doesn't use any significant memory.
> 
> however there are other programs which are known to take up significant 
> amounts of memory and will cause the issue being described (openoffice 
> for example)
> 
> please don't get hung up on the text 'updatedb' and accept that there 
> are programs that do run intermittently and do use a significant amount 
> of ram and then free it.

Different issue. One that's worth pursueing perhaps, but a different issue 
from the VFS caches issue that people have been trying to track down.

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/28/2007 01:15 AM, Björn Steinbrink wrote:

> On 2007.07.27 20:16:32 +0200, Rene Herman wrote:

>> Here's swap-prefetch's author saying the same:
>>
>> http://lkml.org/lkml/2007/2/9/112
>>
>> | It can't help the updatedb scenario. Updatedb leaves the ram full and
>> | swap prefetch wants to cost as little as possible so it will never
>> | move anything out of ram in preference for the pages it wants to swap
>> | back in.
>>
>> Now please finally either understand this, or tell us how we're wrong.
> 
> Con might have been wrong there for boxes with really little memory.

Note -- with "the updatedb scenario" both he in the above and I are talking 
about the "VFS caches filling memory cause the problem" not updatedb in 
particular.

> My desktop box has not even 300k inodes in use (IIRC someone posted a df 
> -i output showing 1 million inodes in use). Still, the memory footprint 
> of the "sort" process grows up to about 50MB. Assuming that the average 
> filename length stays, that would mean 150MB for the 1 million inode 
> case, just for the "sort" process.

Even if it's not 150MB, 50MB is already a lot on a 128 or even a 256MB box. 
So, yes, we're now at the expected scenario of some hog pushing out things 
and freeing it upon exit again and it's something swap-prefetch definitely 
has potential to help with.

Said early in the thread it's hard to imagine how it would not help in any 
such situation so that the discussion may as far as I'm concerned at that 
point concentrate on whether swap-prefetch hurts anything in others.

Some people I believe are not convinced it helps very significantly due to 
at that point _everything_ having been thrown out but a copy of openoffice 
with a large spreadsheet open should come back to life much quicker it would 
seem.

> Any faults in that reasoning?

No. If the machine goes idle after some memory hog _itself_ pushes things 
out and then exits, swap-prefetch helps, at the veryvery least potentially.

By the way -- I'm unable to make my slocate grow substantial here but I'll 
try what GNU locate does. If it's really as bad as I hear then regardless of 
anything else it should really be either fixed or dumped...

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Mike Galbraith]

On Fri, 2007-07-27 at 18:51 -0400, Daniel Hazelton wrote:

> Now, once more, I'm going to ask: What is so terribly wrong with swap 
> prefetch? Why does it seem that everyone against it says "Its treating a 
> symptom, so it can't go in"?

And once again, I personally have nothing against swap-prefetch, or
something like it. I can see how it or something like it could be made
to improve the lives of people who get up in the morning to find their
apps sitting on disk due to memory pressure generated by over-night
system maintenance operations.

The author himself however, says his implementation can't help with
updatedb (though people seem to be saying that it does), or anything
else that leaves memory full.  That IMHO, makes it of questionable value
toward solving what people are saying they want swap-prefetch for in the
first place.

I personally don't care if swap-prefetch goes in or not.

	-Mike

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/28/2007 09:35 AM, Rene Herman wrote:

> By the way -- I'm unable to make my slocate grow substantial here but 
> I'll try what GNU locate does. If it's really as bad as I hear then 
> regardless of anything else it should really be either fixed or dumped...

Yes. GNU locate is broken and nobody should be using it. The updatedb from 
(my distribution standard) "slocate" uses around 2M allocated total during 
an entire run while GNU locate allocates some 30M to the sort process alone.

GNU locate is also close to 4 times as slow (although that ofcourse only 
matters on cached runs anyways).

So, GNU locate is just a pig pushing things out, with or without any added 
VFS cache pressure from the things it does by design. As such, we can trust 
people complaining about it but should first tell them to switch to halfway 
sane locate implementation. If you run memory hogs on small memory boxes, 
you're going to suffer.

Leaves the fact that swap-prefetch sometimes helps alleviate these and other 
kinds of memory-hog situations and as such, might not (again) be a bad idea 
in itself.

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[david]

On Sat, 28 Jul 2007, Rene Herman wrote:

> On 07/27/2007 09:43 PM, david@lang.hm wrote:
>
>>  On Fri, 27 Jul 2007, Rene Herman wrote:
>> 
>> >  On 07/27/2007 07:45 PM, Daniel Hazelton wrote:
>> > 
>> > >   Questions about it:
>> > >   Q) Does swap-prefetch help with this?
>> > >   A) [From all reports I've seen (*)]
>> > >   Yes, it does. 
>> > 
>> >  No it does not. If updatedb filled memory to the point of causing 
>> >  swapping (which noone is reproducing anyway) it HAS FILLED MEMORY and 
>> >  swap-prefetch hasn't any memory to prefetch into -- updatedb itself 
>> >  doesn't use any significant memory.
>>
>>  however there are other programs which are known to take up significant
>>  amounts of memory and will cause the issue being described (openoffice for
>>  example)
>>
>>  please don't get hung up on the text 'updatedb' and accept that there are
>>  programs that do run intermittently and do use a significant amount of ram
>>  and then free it.
>
> Different issue. One that's worth pursueing perhaps, but a different issue 
> from the VFS caches issue that people have been trying to track down.

people are trying to track down the problem of their machine being slow 
until enough data is swapped back in to operate normally.

in at some situations swap prefetch can help becouse something that used 
memory freed it so there is free memory that could be filled with data 
(which is something that Linux does agressivly in most other situations)

in some other situations swap prefetch cannot help becouse useless data is 
getting cached at the expense of useful data.

nobody is arguing that swap prefetch helps in the second cast.

what people are arguing is that there are situations where it helps for 
the first case. on some machines and version of updatedb the nighly run of 
updatedb can cause both sets of problems. but the nightly updatedb run is 
not the only thing that can cause problems


but let's talk about the concept here for a little bit

the design is to use CPU and I/O capacity that's otherwise idle to fill 
free memory with data from swap.

pro:
   more ram has potentially useful data in it

con:
   it takes a little extra effort to give this memory to another app (the 
page must be removed from the list and zeroed at the time it's needed, I 
assume that the data is left in swap so that it doesn't have to be written 
out again)

   it adds some complexity to the kernel (~500 lines IIRC from this thread)

   by undoing recent swapouts it can potentially mask problems with swapout

it looks to me like unless the code was really bad (and after 23 months in 
-mm it doesn't sound like it is) that the only significant con left is the 
potential to mask other problems.

however there are many legitimate cases where it is definantly dong the 
right thing (swapout was correct in pushing out the pages, but now the 
cause of that preasure is gone). the amount of benifit from this will vary 
from situation to situation, but it's not reasonable to claim that this 
provides no benifit (you have benchmark numbers that show it in synthetic 
benchmarks, and you have user reports that show it in the real-worlk)

there are lots of things in the kernel who's job is to pre-fill the memroy 
with data that may (or may not) be useful in the future. this is just 
another method of filling the cache. it does so my saying "the user wanted 
these pages in the recent past, so it's a reasonable guess to say that the 
user will want them again in the future"

David Lang

Re: -mm merge plans for 2.6.23

[Stefan Richter]

Daniel Cheng wrote:
> but merging maps2 have higher risk which should be done in a development
> branch (er... 2.7, but we don't have it now).

This is off-topic and has been discussed to death, but:  Rather than one
stable branch and one development branch, we have a few stable branches
and a lot of development branches.  Some are located at git.kernel.org.
Among else, this gives you a predictable release rythm and very timely
updated stable branches.
-- 
Stefan Richter
-=====-=-=== -=== ===--
http://arcgraph.de/sr/

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/28/2007 10:55 AM, david@lang.hm wrote:

> in at some situations swap prefetch can help becouse something that used 
> memory freed it so there is free memory that could be filled with data 
> (which is something that Linux does agressivly in most other situations)
> 
> in some other situations swap prefetch cannot help becouse useless data 
> is getting cached at the expense of useful data.
> 
> nobody is arguing that swap prefetch helps in the second cast.

Oh yes they are. Daniel for example did twice, telling me to turn my brain 
on in between (if you read it, you may have noticed I got a little annoyed 
at that point).

> but let's talk about the concept here for a little bit
> 
> the design is to use CPU and I/O capacity that's otherwise idle to fill 
> free memory with data from swap.
> 
> pro:
>   more ram has potentially useful data in it
> 
> con:
>   it takes a little extra effort to give this memory to another app (the 
> page must be removed from the list and zeroed at the time it's needed, I 
> assume that the data is left in swap so that it doesn't have to be 
> written out again)

It is. Prefetched pages can be dropped on the floor without additional I/O.

>   it adds some complexity to the kernel (~500 lines IIRC from this thread)
> 
>   by undoing recent swapouts it can potentially mask problems with swapout
> 
> it looks to me like unless the code was really bad (and after 23 months 
> in -mm it doesn't sound like it is)

Not to sound pretentious or anything but I assume that Andrew has a fairly 
good overview of exactly how broken -mm can be at times. How many -mm users 
use it anyway? He himself said he's not convinced of usefulness having not 
seen it help for him (and notice that most developers are also users), 
turned it off due to it annoying him at some point and hasn't seen a serious 
investigation into potential downsides.

> that the only significant con left is the potential to mask other
> problems.

Which is not a madeup issue, mind you. As an example, I just now tried GNU 
locate and saw it's a complete pig and specifically unsuitable for the low 
memory boxes under discussion. Upon completion, it actually frees enough 
memory that swap-prefetch _could_ help on some boxes, while the real issue 
is that they should first and foremost dump GNU locate.

> however there are many legitimate cases where it is definantly dong the 
> right thing (swapout was correct in pushing out the pages, but now the 
> cause of that preasure is gone). the amount of benifit from this will 
> vary from situation to situation, but it's not reasonable to claim that 
> this provides no benifit (you have benchmark numbers that show it in 
> synthetic benchmarks, and you have user reports that show it in the 
> real-worlk)

I certainly would not want to argue anything of the sort no. As said a few 
times, I agree that swap-prefetch makes sense and has at least the potential 
to help some situations that you really wouldnt even want to try and fix any 
other way, simply because nothing's broken.

> there are lots of things in the kernel who's job is to pre-fill the 
> memroy with data that may (or may not) be useful in the future. this is 
> just another method of filling the cache. it does so my saying "the user
> wanted these pages in the recent past, so it's a reasonable guess to say
> that the user will want them again in the future"

Well, _that_ is what the kernel is already going to great lengths at doing, 
and it decided that those pages us poor overnight OO.o users want in in the 
morning weren't reasonable guesses. The kernel also won't any time soon be 
reading our minds, so any solution would need either user intervention (we 
could devise a way to tell the kernel "hey ho, I consider these pages to be 
very important -- try not to swap them out" possible even with a "and if you 
do, please pull them back in when possible") or we can let swap-prefetch do 
the "just in case" thing it is doing.

While swap-prefetch may not be the be all end all of solutions I agree that 
having a machine sit around with free memory and applications in swap seems 
not too useful if (as is the case) fetched pages can be dropped immediately 
when it turns out swap-prefetch made the wrong decision.

So that's for the concept. As to implementation, if I try and look at the 
code, it seems to be trying hard to really be free and as such, potential 
downsides seem limited. It's a rather core concept though and as such needs 
someone with a _lot_ more VM clue to ack. Sorry for not knowing, but who's 
maintaining/submitting the thing now that Con's not? He or she should 
preferably address any concerns it seems.

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Alan Cox]

> It is. Prefetched pages can be dropped on the floor without additional I/O.

Which is essentially free for most cases. In addition your disk access
may well have been in idle time (and should be for this sort of stuff)
and if it was in the same chunk as something nearby was effectively free
anyway. 

Actual physical disk ops are precious resource and anything that mostly
reduces the number will be a win - not to stay swap prefetch is the right
answer but accidentally or otherwise there are good reasons it may happen
to help.

Bigger more linear chunks of writeout/readin is much more important I
suspect than swap prefetching. 

> good overview of exactly how broken -mm can be at times. How many -mm users 
> use it anyway? He himself said he's not convinced of usefulness having not 

I've been using it for months with no noticed problem. I turn it on
because it might as well get tested. I've not done comparison tests so I
can't comment on if its worth it.

Lots of -mm testers turn *everything* on because its a test kernel.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Daniel Hazelton]

On Saturday 28 July 2007 03:48:13 Mike Galbraith wrote:
> On Fri, 2007-07-27 at 18:51 -0400, Daniel Hazelton wrote:
> > Now, once more, I'm going to ask: What is so terribly wrong with swap
> > prefetch? Why does it seem that everyone against it says "Its treating a
> > symptom, so it can't go in"?
>
> And once again, I personally have nothing against swap-prefetch, or
> something like it. I can see how it or something like it could be made
> to improve the lives of people who get up in the morning to find their
> apps sitting on disk due to memory pressure generated by over-night
> system maintenance operations.
>
> The author himself however, says his implementation can't help with
> updatedb (though people seem to be saying that it does), or anything
> else that leaves memory full.  That IMHO, makes it of questionable value
> toward solving what people are saying they want swap-prefetch for in the
> first place.

Okay. I have to agree with the author that, in such a situation, it wouldn't 
help. However there are, without a doubt, other situations where it would 
help immensely. (memory hogs forcing everything to disk and quitting, one off 
tasks that don't balloon the cache (kernel compiles, et al) - in those 
situations swap prefetch would really shine.)

DRH

-- 
Dialup is like pissing through a pipette. Slow and excruciatingly painful.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Daniel Hazelton]

On Saturday 28 July 2007 04:55:58 david@lang.hm wrote:
> On Sat, 28 Jul 2007, Rene Herman wrote:
> > On 07/27/2007 09:43 PM, david@lang.hm wrote:
> >>  On Fri, 27 Jul 2007, Rene Herman wrote:
> >> >  On 07/27/2007 07:45 PM, Daniel Hazelton wrote:
> >> > >   Questions about it:
> >> > >   Q) Does swap-prefetch help with this?
> >> > >   A) [From all reports I've seen (*)]
> >> > >   Yes, it does.
> >> >
> >> >  No it does not. If updatedb filled memory to the point of causing
> >> >  swapping (which noone is reproducing anyway) it HAS FILLED MEMORY and
> >> >  swap-prefetch hasn't any memory to prefetch into -- updatedb itself
> >> >  doesn't use any significant memory.
> >>
> >>  however there are other programs which are known to take up significant
> >>  amounts of memory and will cause the issue being described (openoffice
> >> for example)
> >>
> >>  please don't get hung up on the text 'updatedb' and accept that there
> >> are programs that do run intermittently and do use a significant amount
> >> of ram and then free it.
> >
> > Different issue. One that's worth pursueing perhaps, but a different
> > issue from the VFS caches issue that people have been trying to track
> > down.
>
> people are trying to track down the problem of their machine being slow
> until enough data is swapped back in to operate normally.
>
> in at some situations swap prefetch can help becouse something that used
> memory freed it so there is free memory that could be filled with data
> (which is something that Linux does agressivly in most other situations)
>
> in some other situations swap prefetch cannot help becouse useless data is
> getting cached at the expense of useful data.
>
> nobody is arguing that swap prefetch helps in the second cast.

Actually, I made a mistake when tracking the thread and reading the code for 
the patch and started to argue just that. But I have to admit I made a 
mistake - the patches author has stated (as Rene was kind enough to point 
out) that swap prefetch can't help when memory is filled.

> what people are arguing is that there are situations where it helps for
> the first case. on some machines and version of updatedb the nighly run of
> updatedb can cause both sets of problems. but the nightly updatedb run is
> not the only thing that can cause problems

Solving the cache filling memory case is difficult. There have been a number 
of discussions about it. The simplest solution, IMHO, would be to place a 
(configurable) hard limit on the maximum size any of the kernels caches can 
grow to. (The only solution that was discussed, however, is a complex beast)

>
> but let's talk about the concept here for a little bit
>
> the design is to use CPU and I/O capacity that's otherwise idle to fill
> free memory with data from swap.
>
> pro:
>    more ram has potentially useful data in it
>
> con:
>    it takes a little extra effort to give this memory to another app (the
> page must be removed from the list and zeroed at the time it's needed, I
> assume that the data is left in swap so that it doesn't have to be written
> out again)
>
>    it adds some complexity to the kernel (~500 lines IIRC from this thread)
>
>    by undoing recent swapouts it can potentially mask problems with swapout
>
> it looks to me like unless the code was really bad (and after 23 months in
> -mm it doesn't sound like it is) that the only significant con left is the
> potential to mask other problems.

I'll second this. But with the swap system itself having seen as heavy testing 
as it has I don't know if it would be masking other problems.

That is why I've been asking "What is so wrong with it?" - while it definately 
doesn't help with programs that cause caches to balloon (that problem does 
need another solution) it does help to speed things up when a memory hog has 
exited. (And since its a pretty safe assumption that swap is going to be 
noticeably slower than RAM this patch seems to me to be a rather visible and 
obvious solution to that problem)

> however there are many legitimate cases where it is definantly dong the
> right thing (swapout was correct in pushing out the pages, but now the
> cause of that preasure is gone). the amount of benifit from this will vary
> from situation to situation, but it's not reasonable to claim that this
> provides no benifit (you have benchmark numbers that show it in synthetic
> benchmarks, and you have user reports that show it in the real-worlk)

Exactly. Though I have seen posts which (to me at least) appear to claim 
exactly that. It was part of the reason why I got a bit incensed. (The other 
was that it looked like the kernel devs with the ultra-powerful machines were 
claiming 'I don't see the problem on my machine, so it doesn't exist'. That 
sort of attitude is fine, in some cases, but not, IMHO, where performance is 
concerned)

> there are lots of things in the kernel who's job is to pre-fill the memroy
> with data that may (or may not) be useful in the future. this is just
> another method of filling the cache. it does so my saying "the user wanted
> these pages in the recent past, so it's a reasonable guess to say that the
> user will want them again in the future"

Yep. And it's a pretty obvious step forward. The VFS system already does 
readahead and caching for mounted volumes to improve performance - why not do 
similar to improve the performance of swap?

The only real downside is that swap-prefetch won't be effective in all cases 
and it will cause some extra power consumption. (drives can't spin-down as 
soon as the would without it, etc...) While I can only make some suggestions 
as to how to fix the problem of ballooning caches (I've been wading through 
the VM code for a few days now and still don't fully understand any of it), 
the solution to the power consumption seems obvious - swap prefetch doesn't 
work when the system is running on battery (or UPS or whatever)

DRH

-- 
Dialup is like pissing through a pipette. Slow and excruciatingly painful.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Ray Lee]

On 7/28/07, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> Actual physical disk ops are precious resource and anything that mostly
> reduces the number will be a win - not to stay swap prefetch is the right
> answer but accidentally or otherwise there are good reasons it may happen
> to help.
>
> Bigger more linear chunks of writeout/readin is much more important I
> suspect than swap prefetching.

<nod>. The larger the chunks are that we swap out, the less it
actually hurts to swap, which might make all this a moot point. Not
all I/O is created equal...

Ray

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[david]

On Sat, 28 Jul 2007, Rene Herman wrote:

> On 07/28/2007 10:55 AM, david@lang.hm wrote:
>
>>  it looks to me like unless the code was really bad (and after 23 months in
>>  -mm it doesn't sound like it is)
>
> Not to sound pretentious or anything but I assume that Andrew has a fairly 
> good overview of exactly how broken -mm can be at times. How many -mm users 
> use it anyway? He himself said he's not convinced of usefulness having not 
> seen it help for him (and notice that most developers are also users), turned 
> it off due to it annoying him at some point and hasn't seen a serious 
> investigation into potential downsides.

if that was the case then people should be responding to the request to 
get it merged with 'but it caused problems for me when I tried it'

I haven't seen any comments like that.

>>  that the only significant con left is the potential to mask other
>>  problems.
>
> Which is not a madeup issue, mind you. As an example, I just now tried GNU 
> locate and saw it's a complete pig and specifically unsuitable for the low 
> memory boxes under discussion. Upon completion, it actually frees enough 
> memory that swap-prefetch _could_ help on some boxes, while the real issue is 
> that they should first and foremost dump GNU locate.

I see the conclusion as being exactly the opposite.

here is a workload with some badly designed userspace software that the 
kernel can make much more pleasent for users.

arguing that users should never use badly designed software in userspace 
doesn't seem like an argument that will gain much traction. I'm not saying 
the kernel needs to fix the software itself (ala the sched_yeild issues), 
but the kernel should try and keep such software from hurting the rest of 
the system where it can.

in this case it can't help it while the bad software is running, but it 
could minimize the impact after it finishes.

>>  however there are many legitimate cases where it is definantly dong the
>>  right thing (swapout was correct in pushing out the pages, but now the
>>  cause of that preasure is gone). the amount of benifit from this will vary
>>  from situation to situation, but it's not reasonable to claim that this
>>  provides no benifit (you have benchmark numbers that show it in synthetic
>>  benchmarks, and you have user reports that show it in the real-worlk)
>
> I certainly would not want to argue anything of the sort no. As said a few 
> times, I agree that swap-prefetch makes sense and has at least the potential 
> to help some situations that you really wouldnt even want to try and fix any 
> other way, simply because nothing's broken.

so there is a legitimate situation where swap-prefetch will help 
significantly, what is the downside that prevents it from being included? 
(reading this thread it sometimes seems like the downside is that updatedb 
shouldn't cause this problem and so if you fixed updatedb there wold be no 
legitimate benifit, or alturnatly this patch doesn't help updatedb so 
there's no legitimate benifit)

>>  there are lots of things in the kernel who's job is to pre-fill the memroy
>>  with data that may (or may not) be useful in the future. this is just
>>  another method of filling the cache. it does so my saying "the user
>>  wanted these pages in the recent past, so it's a reasonable guess to say
>>  that the user will want them again in the future"
>
> Well, _that_ is what the kernel is already going to great lengths at doing, 
> and it decided that those pages us poor overnight OO.o users want in in the 
> morning weren't reasonable guesses. The kernel also won't any time soon be 
> reading our minds, so any solution would need either user intervention (we 
> could devise a way to tell the kernel "hey ho, I consider these pages to be 
> very important -- try not to swap them out" possible even with a "and if you 
> do, please pull them back in when possible") or we can let swap-prefetch do 
> the "just in case" thing it is doing.

it's not that they shouldn't have been swapped out (they should have 
been), it's that the reason they were swapped out no longer exists.

> While swap-prefetch may not be the be all end all of solutions I agree that 
> having a machine sit around with free memory and applications in swap seems 
> not too useful if (as is the case) fetched pages can be dropped immediately 
> when it turns out swap-prefetch made the wrong decision.
>
> So that's for the concept. As to implementation, if I try and look at the 
> code, it seems to be trying hard to really be free and as such, potential 
> downsides seem limited. It's a rather core concept though and as such needs 
> someone with a _lot_ more VM clue to ack. Sorry for not knowing, but who's 
> maintaining/submitting the thing now that Con's not? He or she should 
> preferably address any concerns it seems.

I've seen it mentioned that there is still a maintainer but I missed who 
it is, but I haven't seen any concerns that can be addressed, they all 
seem to be 'this is a core concept, people need to think about it' or 'but 
someone may find a better answer in the future' type of things. it's 
impossible to address these concerns directly.

David Lang

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[david]

On Sat, 28 Jul 2007, Alan Cox wrote:

>> It is. Prefetched pages can be dropped on the floor without additional I/O.
>
> Which is essentially free for most cases. In addition your disk access
> may well have been in idle time (and should be for this sort of stuff)
> and if it was in the same chunk as something nearby was effectively free
> anyway.

as I understand it the swap-prefetch only kicks in if the device is idle

> Actual physical disk ops are precious resource and anything that mostly
> reduces the number will be a win - not to stay swap prefetch is the right
> answer but accidentally or otherwise there are good reasons it may happen
> to help.
>
> Bigger more linear chunks of writeout/readin is much more important I
> suspect than swap prefetching.

I'm sure this is true while you are doing the swapout or swapin and the 
system is waiting for it. but with prefetch you may be able to avoid doing 
the swapin at a time when the system is waiting for it by doing it at a 
time when the system is otherwise idle.

David Lang

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[david]

On Sat, 28 Jul 2007, Daniel Hazelton wrote:

> 
> On Saturday 28 July 2007 04:55:58 david@lang.hm wrote:
>> On Sat, 28 Jul 2007, Rene Herman wrote:
>>> On 07/27/2007 09:43 PM, david@lang.hm wrote:
>>>>  On Fri, 27 Jul 2007, Rene Herman wrote:
>>>>>  On 07/27/2007 07:45 PM, Daniel Hazelton wrote:
>>
>> nobody is arguing that swap prefetch helps in the second cast.
>
> Actually, I made a mistake when tracking the thread and reading the code for
> the patch and started to argue just that. But I have to admit I made a
> mistake - the patches author has stated (as Rene was kind enough to point
> out) that swap prefetch can't help when memory is filled.

I stand corrected, thaks for speaking up and correcting your position.

>> what people are arguing is that there are situations where it helps for
>> the first case. on some machines and version of updatedb the nighly run of
>> updatedb can cause both sets of problems. but the nightly updatedb run is
>> not the only thing that can cause problems
>
> Solving the cache filling memory case is difficult. There have been a number
> of discussions about it. The simplest solution, IMHO, would be to place a
> (configurable) hard limit on the maximum size any of the kernels caches can
> grow to. (The only solution that was discussed, however, is a complex beast)

limiting the size of the cache is also the wrong thing to do in many 
situations. it's only right if the cache pushes out other data you care 
about, if you are trying to do one thing as fast as you can you really do 
want the system to use all the memory it can for the cache.

David Lang

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Daniel Hazelton]

On Saturday 28 July 2007 17:06:50 david@lang.hm wrote:
> On Sat, 28 Jul 2007, Daniel Hazelton wrote:
> > On Saturday 28 July 2007 04:55:58 david@lang.hm wrote:
> >> On Sat, 28 Jul 2007, Rene Herman wrote:
> >>> On 07/27/2007 09:43 PM, david@lang.hm wrote:
> >>>>  On Fri, 27 Jul 2007, Rene Herman wrote:
> >>>>>  On 07/27/2007 07:45 PM, Daniel Hazelton wrote:
> >>
> >> nobody is arguing that swap prefetch helps in the second cast.
> >
> > Actually, I made a mistake when tracking the thread and reading the code
> > for the patch and started to argue just that. But I have to admit I made
> > a mistake - the patches author has stated (as Rene was kind enough to
> > point out) that swap prefetch can't help when memory is filled.
>
> I stand corrected, thaks for speaking up and correcting your position.

If you had made the statement before I decided to speak up you would have been 
correct :)

Anyway, I try to always admit when I've made a mistake - its part of my 
philosophy. (There have been times when I haven't done it, but I'm trying to 
make that stop entirely)

> >> what people are arguing is that there are situations where it helps for
> >> the first case. on some machines and version of updatedb the nighly run
> >> of updatedb can cause both sets of problems. but the nightly updatedb
> >> run is not the only thing that can cause problems
> >
> > Solving the cache filling memory case is difficult. There have been a
> > number of discussions about it. The simplest solution, IMHO, would be to
> > place a (configurable) hard limit on the maximum size any of the kernels
> > caches can grow to. (The only solution that was discussed, however, is a
> > complex beast)
>
> limiting the size of the cache is also the wrong thing to do in many
> situations. it's only right if the cache pushes out other data you care
> about, if you are trying to do one thing as fast as you can you really do
> want the system to use all the memory it can for the cache.

After thinking about this you are partially correct. There are those sorts of 
situations where you want the system to use all the memory it can for caches. 
OTOH, if those situations could be described in some sort of simple 
heuristic, then a soft-limit that uses those heuristics to determine when to 
let the cache expand could exploit the benefits of having both a limited and 
unlimited cache. (And, potentially, if the heuristic has allowed a cache to 
expand beyond the limit then, when the heuristic no longer shows the oversize 
cache is no longer necessary it could trigger and automatic reclaim of that 
memory.)

(I'm willing to help write and test code to do this exactly. There is no 
guarantee that I'll be able to help with more than testing - I don't 
understand the parts of the code involved all that well)

DRH

-- 
Dialup is like pissing through a pipette. Slow and excruciatingly painful.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rik van Riel]

Andrew Morton wrote:

> What I think is killing us here is the blockdev pagecache: the pagecache
> which backs those directory entries and inodes.  These pages get read
> multiple times because they hold multiple directory entries and multiple
> inodes.  These multiple touches will put those pages onto the active list
> so they stick around for a long time and everything else gets evicted.
> 
> I've never been very sure about this policy for the metadata pagecache.  We
> read the filesystem objects into the dcache and icache and then we won't
> read from that page again for a long time (I expect).  But the page will
> still hang around for a long time.
> 
> It could be that we should leave those pages inactive.

Good idea for updatedb.

However, it may be a bad idea for files that are often
written to.  Turning an inode write into a read plus a
write does not sound like such a hot idea, we really
want to keep those in the cache.

I think what you need is to ignore multiple references
to the same page when they all happen in one time
interval, counting them only if they happen in multiple
time intervals.

The use-once cleanup (which takes a page flag for PG_new,
I know...) would solve that problem.

However, it would introduce the problem of having to scan
all the pages on the list before a page becomes freeable.
We would have to add some background scanning (or a separate
list for PG_new pages) to make the initial pageout run use
an acceptable amount of CPU time.

Not sure that complexity will be worth it...

-- 
Politics is the struggle between those who want to make their country
the best in the world, and those who believe it already is.  Each group
calls the other unpatriotic.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Andrew Morton]

On Sat, 28 Jul 2007 21:33:59 -0400 Rik van Riel <riel@redhat.com> wrote:

> Andrew Morton wrote:
> 
> > What I think is killing us here is the blockdev pagecache: the pagecache
> > which backs those directory entries and inodes.  These pages get read
> > multiple times because they hold multiple directory entries and multiple
> > inodes.  These multiple touches will put those pages onto the active list
> > so they stick around for a long time and everything else gets evicted.
> > 
> > I've never been very sure about this policy for the metadata pagecache.  We
> > read the filesystem objects into the dcache and icache and then we won't
> > read from that page again for a long time (I expect).  But the page will
> > still hang around for a long time.
> > 
> > It could be that we should leave those pages inactive.
> 
> Good idea for updatedb.
> 
> However, it may be a bad idea for files that are often
> written to.  Turning an inode write into a read plus a
> write does not sound like such a hot idea, we really
> want to keep those in the cache.

Remember that this problem applies to both inode blocks and to directory
blocks.  Yes, it might be useful to hold onto an inode block for a future
write (atime, mtime, usually), but not a directory block.

> I think what you need is to ignore multiple references
> to the same page when they all happen in one time
> interval, counting them only if they happen in multiple
> time intervals.

Yes, the sudden burst of accesses for adjacent inode/dirents will be a
common pattern, and it'd make heaps of sense to treat that as a single
touch.  It'd have to be done in the fs I guess, and it might be a bit hard
to do.  And it turns out that embedding the touch_buffer() all the way down
in __find_get_block() was convenient, but it's going to be tricky to
change.

For now I'm fairly inclined to just nuke the touch_buffer() on the read side
and maybe add one on the modification codepaths and see what happens.

As always, testing is the problem.

> The use-once cleanup (which takes a page flag for PG_new,
> I know...) would solve that problem.
> 
> However, it would introduce the problem of having to scan
> all the pages on the list before a page becomes freeable.
> We would have to add some background scanning (or a separate
> list for PG_new pages) to make the initial pageout run use
> an acceptable amount of CPU time.
> 
> Not sure that complexity will be worth it...
> 

I suspect that the situation we have now is so bad that pretty much
anything we do will be an improvement.  I've always wondered "ytf is there
so much blockdev pagecache?"

This machine I'm typing at:

MemTotal:      3975080 kB
MemFree:        750400 kB
Buffers:        547736 kB
Cached:        1299532 kB
SwapCached:      12772 kB
Active:        1789864 kB
Inactive:       861420 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:      3975080 kB
LowFree:        750400 kB
SwapTotal:     4875716 kB
SwapFree:      4715660 kB
Dirty:              76 kB
Writeback:           0 kB
Mapped:         638036 kB
Slab:           522724 kB
CommitLimit:   6863256 kB
Committed_AS:  1115632 kB
PageTables:      14452 kB
VmallocTotal: 34359738367 kB
VmallocUsed:     36432 kB
VmallocChunk: 34359696379 kB
HugePages_Total:     0
HugePages_Free:      0
HugePages_Rsvd:      0
Hugepagesize:     2048 kB

More that a quarter of my RAM in fs metadata!  Most of it I'll bet is on the
active list.  And the fs on which I do most of the work is mounted
noatime..

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/28/2007 01:21 PM, Alan Cox wrote:

>> It is. Prefetched pages can be dropped on the floor without additional
>> I/O.
> 
> Which is essentially free for most cases. In addition your disk access 
> may well have been in idle time (and should be for this sort of stuff)

Yes. The swap-prefetch patch ensures that the machine (well, the VM) is very 
idle before it allows itself to kick in.

> and if it was in the same chunk as something nearby was effectively free 
> anyway.
> 
> Actual physical disk ops are precious resource and anything that mostly 
> reduces the number will be a win - not to stay swap prefetch is the right
> answer but accidentally or otherwise there are good reasons it may
> happen to help.
> 
> Bigger more linear chunks of writeout/readin is much more important I 
> suspect than swap prefetching.

Yes, I believe this might be an important point. Earlier I posted a dumb 
little VM thrasher:

http://lkml.org/lkml/2007/7/25/85

Contrived thing and all, but what it does do is show exactly how bad seeking 
all over swap-space is. If you push it out before hitting enter, the time it 
takes easily grows past 10 minutes (with my 768M) versus sub-second (!) when 
it's all in to start with.

What are the tradeoffs here? What wants small chunks? Also, as far as I'm 
aware Linux does not do things like up the granularity when it notices it's 
swapping in heavily? That sounds sort of promising...

>> good overview of exactly how broken -mm can be at times. How many -mm users 
>> use it anyway? He himself said he's not convinced of usefulness having not 
> 
> I've been using it for months with no noticed problem. I turn it on
> because it might as well get tested. I've not done comparison tests so I
> can't comment on if its worth it.
> 
> Lots of -mm testers turn *everything* on because its a test kernel.

Okay.

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/28/2007 11:00 PM, david@lang.hm wrote:

>> many -mm users use it anyway? He himself said he's not convinced of 
>> usefulness having not seen it help for him (and notice that most 
>> developers are also users), turned it off due to it annoying him at 
>> some point and hasn't seen a serious investigation into potential 
>> downsides.
> 
> if that was the case then people should be responding to the request to 
> get it merged with 'but it caused problems for me when I tried it'
> 
> I haven't seen any comments like that.

So you're saying Andrew did not say that? You're jumping to the conclusion 
that I am saying that it's causing problems.

>>>  that the only significant con left is the potential to mask other
>>>  problems.
>>
>> Which is not a madeup issue, mind you. As an example, I just now tried 
>> GNU locate and saw it's a complete pig and specifically unsuitable for 
>> the low memory boxes under discussion. Upon completion, it actually 
>> frees enough memory that swap-prefetch _could_ help on some boxes, 
>> while the real issue is that they should first and foremost dump GNU 
>> locate.
> 
> I see the conclusion as being exactly the opposite.

And now you do it again :-) There is no conclusion -- just the inescapable 
observation that swap-prefetch was (or may have been) masking the problem of 
GNU locate being a program that noone in their right mind should be using.

> so there is a legitimate situation where swap-prefetch will help 
> significantly, what is the downside that prevents it from being 
> included?

People being unconvinced it helps all that much, no serious investigation 
into possible downsides and no consideration of alternatives is three I've 
personally heard.

You don't want to merge a conceptually core VM feature if you're not really 
convinced. It's not a part of the kernel you can throw a feature into like 
you could some driver saying "ah, heck, if it makes someone happy" since 
everything in the VM ends up interacting -- that in fact is actually the 
hard part of VM as far as I've seen it.

And in this situation the proposed feature is something that "papers over a 
problem" by design -- where it could certainly be that the problem is not 
solveable in another way simply due to the kernel not growing the possiblity 
to read user's minds anytime soon (which some might even like to rephrase as 
"due to no problem existing") but that this gets people a bit anxious is not 
surprising.

> I've seen it mentioned that there is still a maintainer but I missed who
> it is, but I haven't seen any concerns that can be addressed, they all 
> seem to be 'this is a core concept, people need to think about it' or 
> 'but someone may find a better answer in the future' type of things. it's
> impossible to address these concerns directly.

So do it indirectly. But please don't just say "it help some people (not me 
mind you!) so merge it and if you don't it's all just politics and we can't 
do anything about it anyway". Because that's mostly what I've been hearing.

And no, I'm not subscribed to any ck mailinglists nor do I hang around its 
IRC community which will can account for part of that. I expect though that 
the same holds for the people that actually matter in this, such as Andrew 
Morton and Nick Piggin.

-- 1: people being unconvinced it helps all that much

At least partly caused by the updatedb i/dcache red herring that infected 
this issue. Also, at the point VM  pressure has mounted high enough to cause 
enough to be swapped out to give you a bad experience, a lot of other things 
have been dropped already as well.

It's unsurprising though that it would for example help the issue of 
openoffice with a large open spreadsheet having been thrown out overnight 
meaning it's a matter of deciding whether or not this is an important enough 
issue to fix inside the VM with something like swap-prefetch.

Personally -- no opinion, I do not experience the problem (I even switch off 
the machine at night and do not run cron at all).

-- 2: no serious investigation into possible downsides

Swap-prefetch tries hard to be as free as possible and it seems to largely 
be succeeding at that. Thing that (obviously -- as in I wouldn't want to 
state it's the only possible worry anyone could have left) remains is the 
"papering over effect" it has by design that one might not care for.

-- 3: no serious consideration of possible alternatives

Tweaking existing use-oce logic is one I've heard but if we consider the 
i/dcache issue dead, I believe that one is as well. Going to userspace is 
another one. Largest theoretical potential. I myself am extremely sceptical 
about the Linux userland, and largely equate it with "smallest _practical_ 
potential" -- but that might just be me.

A larger swap granularity, possible even a self-training granularity. Up to 
now, seeks only get costlier and costlier with respect to reads with every 
generation of disk (flash would largely overcome it though) and doing more 
in one read/write _greatly_ improves throughput, maybe up to the point that 
swap-prefetch is no longer very useful. I myself don't know about the 
tradeoffs involved.

Any other alternatives?

Any 4th and higher points?

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[david]

On Sun, 29 Jul 2007, Rene Herman wrote:

> On 07/28/2007 11:00 PM, david@lang.hm wrote:
>
>> >  many -mm users use it anyway? He himself said he's not convinced of 
>> >  usefulness having not seen it help for him (and notice that most 
>> >  developers are also users), turned it off due to it annoying him at some 
>> >  point and hasn't seen a serious investigation into potential downsides.
>>
>>  if that was the case then people should be responding to the request to
>>  get it merged with 'but it caused problems for me when I tried it'
>>
>>  I haven't seen any comments like that.
>
> So you're saying Andrew did not say that? You're jumping to the conclusion 
> that I am saying that it's causing problems.

I don't remember anyone saying that it actually caused problems (including 
both you and andrew). I (and others) have been trying to learn what 
problems people believe it has in the hope that they can be addressed one 
way or another.

>> > >   that the only significant con left is the potential to mask other
>> > >   problems.
>> > 
>> >  Which is not a madeup issue, mind you. As an example, I just now tried 
>> >  GNU locate and saw it's a complete pig and specifically unsuitable for 
>> >  the low memory boxes under discussion. Upon completion, it actually 
>> >  frees enough memory that swap-prefetch _could_ help on some boxes, while 
>> >  the real issue is that they should first and foremost dump GNU locate.
>>
>>  I see the conclusion as being exactly the opposite.
>
> And now you do it again :-) There is no conclusion -- just the inescapable 
> observation that swap-prefetch was (or may have been) masking the problem of 
> GNU locate being a program that noone in their right mind should be using.

isn't your conclusion then that if people just stopped useing that version 
of updatedb the problem would be solved and there would be no need for the 
swap prefetch patch? that seemed to be what you were strongly implying (if 
not saying outright)

>>  so there is a legitimate situation where swap-prefetch will help
>>  significantly, what is the downside that prevents it from being included?
>
> People being unconvinced it helps all that much, no serious investigation 
> into possible downsides and no consideration of alternatives is three I've 
> personally heard.
>
> You don't want to merge a conceptually core VM feature if you're not really 
> convinced. It's not a part of the kernel you can throw a feature into like 
> you could some driver saying "ah, heck, if it makes someone happy" since 
> everything in the VM ends up interacting -- that in fact is actually the hard 
> part of VM as far as I've seen it.
>
> And in this situation the proposed feature is something that "papers over a 
> problem" by design -- where it could certainly be that the problem is not 
> solveable in another way simply due to the kernel not growing the possiblity 
> to read user's minds anytime soon (which some might even like to rephrase as 
> "due to no problem existing") but that this gets people a bit anxious is not 
> surprising.

people who have lots of memory and so don't use swap will never see the 
benifit of this patch. over the years many people have investigated the 
problem and tried to address it in other ways (the better version of 
updatedb is an attempt to fix it for that program as an example), but 
there is still a problem.

I agree that tinkering with the core VM code should not be done lightly, 
but this has been put through the proper process and is stalled with no 
hints on how to move forward.

>>  I've seen it mentioned that there is still a maintainer but I missed who
>>  it is, but I haven't seen any concerns that can be addressed, they all
>>  seem to be 'this is a core concept, people need to think about it' or 'but
>>  someone may find a better answer in the future' type of things. it's
>>  impossible to address these concerns directly.
>
> So do it indirectly. But please don't just say "it help some people (not me 
> mind you!) so merge it and if you don't it's all just politics and we can't 
> do anything about it anyway". Because that's mostly what I've been hearing.
>
> And no, I'm not subscribed to any ck mailinglists nor do I hang around its 
> IRC community which will can account for part of that. I expect though that 
> the same holds for the people that actually matter in this, such as Andrew 
> Morton and Nick Piggin.
>
> -- 1: people being unconvinced it helps all that much
>
> At least partly caused by the updatedb i/dcache red herring that infected 
> this issue. Also, at the point VM  pressure has mounted high enough to cause 
> enough to be swapped out to give you a bad experience, a lot of other things 
> have been dropped already as well.
>
> It's unsurprising though that it would for example help the issue of 
> openoffice with a large open spreadsheet having been thrown out overnight 
> meaning it's a matter of deciding whether or not this is an important enough 
> issue to fix inside the VM with something like swap-prefetch.
>
> Personally -- no opinion, I do not experience the problem (I even switch off 
> the machine at night and do not run cron at all).

forget the nightly cron jobs for the moment. think of this scenerio. you 
have your memory fairly full with apps that you have open (including 
firefox with many tabs), you receive a spreadsheet you need to look at, so 
you fire up openoffice to look at it. then you exit openoffice and try to 
go back to firefox (after a pause while you walk to the printer to get 
the printout of the spreadsheet), only to find that it's going to be 
sluggish becouse it got swapped out due to the preasure from openoffice.

no nightly cron job needed, just enough of a memory hog or a small enough 
amount of ram to have your working set exceed it.

> -- 2: no serious investigation into possible downsides
>
> Swap-prefetch tries hard to be as free as possible and it seems to largely be 
> succeeding at that. Thing that (obviously -- as in I wouldn't want to state 
> it's the only possible worry anyone could have left) remains is the "papering 
> over effect" it has by design that one might not care for.
>
> -- 3: no serious consideration of possible alternatives
>
> Tweaking existing use-oce logic is one I've heard but if we consider the 
> i/dcache issue dead, I believe that one is as well. Going to userspace is 
> another one. Largest theoretical potential. I myself am extremely sceptical 
> about the Linux userland, and largely equate it with "smallest _practical_ 
> potential" -- but that might just be me.
>
> A larger swap granularity, possible even a self-training granularity. Up to 
> now, seeks only get costlier and costlier with respect to reads with every 
> generation of disk (flash would largely overcome it though) and doing more in 
> one read/write _greatly_ improves throughput, maybe up to the point that 
> swap-prefetch is no longer very useful. I myself don't know about the 
> tradeoffs involved.

larger swap granularity may help, but waiting for the user to need the ram 
and have to wait for it to be read back in is always going to be worse for 
the user then pre-populating the free memory (for the case where the 
pre-population is right, for other cases it's the same). so I see this as 
a red herring

> Any other alternatives?
>
> Any 4th and higher points?

there are fully legitimate situations where this is useful, the 'papering 
over' effect is not referring to these, it's referring to other possible 
problems in the future. I see this argument as being in the same catagory 
as people wanting to remove the old, working driver for some hardware in 
favor of the new, unreliable driver for the same hardware in order to get 
more bug reports to find the holes in the new driver. that's causing users 
unessasary pain and within the last week Linus was takeing a driver author 
to task for attempting exactly that IIRC (and yes, there does come a point 
where there are no further bugs known in the new driver, and it appears to 
do everything the old driver did that you do remove the old driver, but 
you don't remove it early to help the new driver stabilize)

David Lang

> Rene.
>
>

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Paul Jackson]

Andi wrote:
> GNU sort uses a merge sort with temporary files on disk. Not sure
> how much it keeps in memory during that, but it's probably less
> than 150MB. 

If I'm reading the source code for GNU sort correctly, then the
following snippet of shell code displays how much memory it uses
for its primary buffer on typical GNU/Linux systems:

    head -2 /proc/meminfo | awk '
	NR == 1 { memtotal = $2 }
	NR == 2 { memfree = $2 }
	END     {
		   if (memfree > memtotal/8)
		       m = memfree
		   else
		       m = memtotal/8
		   print "sort size:", m/2, "kB"
	}
    '

That is, over simplifying, GNU sort looks at the first two entries
in /proc/meminfo, which for example on a machine near me happen to be:

  MemTotal:      2336472 kB
  MemFree:        110600 kB

and then uses one-half of whichever is -greater- of MemTotal/8 or
MemFree.

... However ... for the typical GNU locate updatedb run, it is sorting
the list of pathnames for almost all files on the system, which is
usually larger than fits in one of these sized buffers.   So it ends up
using quite a few of the temporary files you mention, which tends to
chew up easily freed memory.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.925.600.0401

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Alan Cox]

> Contrived thing and all, but what it does do is show exactly how bad seeking 
> all over swap-space is. If you push it out before hitting enter, the time it 
> takes easily grows past 10 minutes (with my 768M) versus sub-second (!) when 
> it's all in to start with.

Think in "operations/second" and you get a better view of the disk.

> What are the tradeoffs here? What wants small chunks? Also, as far as I'm 
> aware Linux does not do things like up the granularity when it notices it's 
> swapping in heavily? That sounds sort of promising...

Small chunks means you get better efficiency of memory use - large chunks
mean you may well page in a lot more than you needed to each time (and
cause more paging in turn). Your disk would prefer you fed it big linear
I/O's - 512KB would probably be my first guess at tuning a large box
under load for paging chunk size.

More radically if anyone wants to do real researchy type work - how about
log structured swap with a cleaner  ?

Alan

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/29/2007 01:41 PM, david@lang.hm wrote:

>> And now you do it again :-) There is no conclusion -- just the 
>> inescapable observation that swap-prefetch was (or may have been) 
>> masking the problem of GNU locate being a program that noone in their 
>> right mind should be using.
> 
> isn't your conclusion then that if people just stopped useing that 
> version of updatedb the problem would be solved and there would be no 
> need for the swap prefetch patch? that seemed to be what you were 
> strongly implying (if not saying outright)

No. What I said outright, every single time, is that swap-prefetch in itself 
seems to make sense. And specifically that even if the _direct_ problem is a 
crummy program, it _still_ makes sense generally. Every single time.

But see -- you failed to notice this because you guys are stuck in this dumb 
adversary "us against them" thing so inherent of (online) communities, where 
you sit around your own habitats patting each other on the back for extended 
periods of time and then every once a while go out clinging on to each other 
vigorously and going "boo! hiss!" at the big bad outside world.

I already got overly violent at one point in this thread so I'll leave out 
any further references to sense-deprived fanboy-culture but please, I said 
every single time that I'm not against swap-prefetch. I cannot communicate 
when I'm not being read.

> I agree that tinkering with the core VM code should not be done lightly, 
> but this has been put through the proper process and is stalled with no 
> hints on how to move forward.

It has not. Concerns that were raised (by specifically Nick Piggin) weren't 
being addressed.

> forget the nightly cron jobs for the moment. think of this scenerio. you 
> have your memory fairly full with apps that you have open (including 
> firefox with many tabs), you receive a spreadsheet you need to look at, 
> so you fire up openoffice to look at it. then you exit openoffice and try
>  to go back to firefox (after a pause while you walk to the printer to
> get the printout of the spreadsheet)

And swinging a dead rat from its tail facing east-wards while reciting 
Documentation/CodingStyle.

Okay, very very sorry, that was particularly childish, but that "walking to 
the printer" is ofcourse completely constructed and this _is_ something to 
take into account. Swap-prefetch wants to be free, which (also again) it is 
doing a good job at it seems, but this also means that it waits for the VM 
to be _very_ idle before it does anything and as such, we cannot just forget 
the "nightly" scenario and pretend it's about something else entirely. As 
long as the machine's being used, swap-prefetch doesn't kick in.

Which is a good feature for swap-prefetch, but also something that needs to 
weighed alongside its other features in a discussion of alternatives, where 
for example something like a larger swap granularity would not have anything 
of the sort to take into account. If it were about walks to the printer, we 
could shelve the issue as being of too limited practical use for inclusion.

>> -- 2: no serious investigation into possible downsides
>>
>> Swap-prefetch tries hard to be as free as possible and it seems to 
>> largely be succeeding at that. Thing that (obviously -- as in I 
>> wouldn't want to state it's the only possible worry anyone could have 
>> left) remains is the "papering over effect" it has by design that one 
>> might not care for.

Arjan van de Ven made another point here about seeking away due to 
swap-prefetch (just) before the next request comes in, but that's probably a 
bit of a non-issue in practice with the "very idle" precondition.

>> -- 3: no serious consideration of possible alternatives
>>
>> Tweaking existing use-oce logic is one I've heard but if we consider 
>> the i/dcache issue dead, I believe that one is as well. Going to 
>> userspace is another one. Largest theoretical potential. I myself am 
>> extremely sceptical about the Linux userland, and largely equate it 
>> with "smallest _practical_ potential" -- but that might just be me.
>>
>> A larger swap granularity, possible even a self-training granularity. 
>> Up to now, seeks only get costlier and costlier with respect to reads 
>> with every generation of disk (flash would largely overcome it though) 
>> and doing more in one read/write _greatly_ improves throughput, maybe 
>> up to the point that swap-prefetch is no longer very useful. I myself 
>> don't know about the tradeoffs involved.
> 
> larger swap granularity may help, but waiting for the user to need the 
> ram and have to wait for it to be read back in is always going to be 
> worse for the user then pre-populating the free memory (for the case 
> where the pre-population is right, for other cases it's the same). so I 
> see this as a red herring

I saw Chris Snook make a good post here and am going to defer this part to 
that discussion:

http://lkml.org/lkml/2007/7/27/421

But no, it's not a red herring if _practically_ speaking the swapin is fast 
enough once started that people don't actually mind anymore since in that 
case you could simply do without yet more additional VM complexity (and 
kernel daemon).

> there are fully legitimate situations where this is useful, the 'papering
> over' effect is not referring to these, it's referring to other possible
> problems in the future.

No, it's not just future. Just look at the various things under discussion 
now such as improved use-once and better swapin.

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/29/2007 03:12 PM, Alan Cox wrote:

>> What are the tradeoffs here? What wants small chunks? Also, as far as
>> I'm aware Linux does not do things like up the granularity when it
>> notices it's swapping in heavily? That sounds sort of promising...
> 
> Small chunks means you get better efficiency of memory use - large chunks
> mean you may well page in a lot more than you needed to each time (and 
> cause more paging in turn). Your disk would prefer you fed it big linear
> I/O's - 512KB would probably be my first guess at tuning a large box 
> under load for paging chunk size.

That probably kills my momentary hope that I was looking at yet another good 
use of large soft-pages seeing as how 512K would be going overboard a bit 
right? :-/

> More radically if anyone wants to do real researchy type work - how about
> log structured swap with a cleaner  ?

Right over my head. Why does log-structure help anything?

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Ray Lee]

On 7/29/07, Rene Herman <rene.herman@gmail.com> wrote:
> On 07/29/2007 03:12 PM, Alan Cox wrote:
> > More radically if anyone wants to do real researchy type work - how about
> > log structured swap with a cleaner  ?
>
> Right over my head. Why does log-structure help anything?

Log structured disk layouts allow for better placement of writeout, so
that you cn eliminate most or all seeks. Seeks are the enemy when
trying to get full disk bandwidth.

google on log structured disk layout, or somesuch, for details.

Ray

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/29/2007 04:58 PM, Ray Lee wrote:

> On 7/29/07, Rene Herman <rene.herman@gmail.com> wrote:
>> On 07/29/2007 03:12 PM, Alan Cox wrote:

>>> More radically if anyone wants to do real researchy type work - how about
>>> log structured swap with a cleaner  ?

>> Right over my head. Why does log-structure help anything?
> 
> Log structured disk layouts allow for better placement of writeout, so
> that you cn eliminate most or all seeks. Seeks are the enemy when
> trying to get full disk bandwidth.
> 
> google on log structured disk layout, or somesuch, for details.

I understand what log structure is generally, but how does it help swapin?

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Ray Lee]

On 7/29/07, Rene Herman <rene.herman@gmail.com> wrote:
> On 07/29/2007 04:58 PM, Ray Lee wrote:
> > On 7/29/07, Rene Herman <rene.herman@gmail.com> wrote:
> >> Right over my head. Why does log-structure help anything?
> >
> > Log structured disk layouts allow for better placement of writeout, so
> > that you cn eliminate most or all seeks. Seeks are the enemy when
> > trying to get full disk bandwidth.
> >
> > google on log structured disk layout, or somesuch, for details.
>
> I understand what log structure is generally, but how does it help swapin?

Look at the swap out case first.

Right now, when swapping out the kernel places whatever it can
wherever it can inside the swap space. The closer you are to filling
your swap space, the more likely that those swapped out blocks will be
all over place, rather than in one nice chunk. Contrast that with a
log structured scheme, where the writeout happens to sequential spaces
on the drive instead of scattered about.

So, at some point when the system needs to fault those blocks that
back in, it now has a linear span of sectors to read instead of asking
the drive to bounce over twenty tracks for a hundred blocks.

So, it eliminates the seeks. My laptop drive can read (huh, how odd,
it got slower, need to retest in single user mode), hmm, let's go with
about 25 MB/s. If we ask for a single block from each track, though,
that'll drop to 4k * (1 second / seek time) which is about a megabyte
a second if we're lucky enough to read from consecutive tracks. Even
worse if it's not.

Seeks are the enemy any time you need to hit the drive for anything,
be it swapping or optimizing a database.

Ray

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/29/2007 05:20 PM, Ray Lee wrote:

>> I understand what log structure is generally, but how does it help swapin?
> 
> Look at the swap out case first.
> 
> Right now, when swapping out the kernel places whatever it can
> wherever it can inside the swap space. The closer you are to filling
> your swap space, the more likely that those swapped out blocks will be
> all over place, rather than in one nice chunk. Contrast that with a
> log structured scheme, where the writeout happens to sequential spaces
> on the drive instead of scattered about.

This seems to be now fixing the different problem of swap-space filling up. 
I'm quite willing to for now assume I've got plenty free.

> So, at some point when the system needs to fault those blocks that
> back in, it now has a linear span of sectors to read instead of asking
> the drive to bounce over twenty tracks for a hundred blocks.

Moreover though -- what I know about log structure is that generally it 
optimises for write (swapout) and might make read (swapin) worse due to 
fragmentation that wouldn't happen with a regular fs structure.

I guess that cleaner that Alan mentioned might be involved there -- I don't 
know how/what it would be doing.

> So, it eliminates the seeks. My laptop drive can read (huh, how odd,
> it got slower, need to retest in single user mode), hmm, let's go with
> about 25 MB/s. If we ask for a single block from each track, though,
> that'll drop to 4k * (1 second / seek time) which is about a megabyte
> a second if we're lucky enough to read from consecutive tracks. Even
> worse if it's not.
> 
> Seeks are the enemy any time you need to hit the drive for anything,
> be it swapping or optimizing a database.

I am very aware of the costs of seeks (on current magnetic media).

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Ray Lee]

On 7/29/07, Rene Herman <rene.herman@gmail.com> wrote:
> On 07/29/2007 05:20 PM, Ray Lee wrote:
> This seems to be now fixing the different problem of swap-space filling up.
> I'm quite willing to for now assume I've got plenty free.

I was trying to point out that currently, as an example, memory that
is linear in a process' space could be fragmented on disk when swapped
out. That's today.

Under a log-structured scheme, one could set it up such that something
that was linear in RAM could be swapped out linearly on the drive,
minimizing seeks on writeout, which will naturally minimize seeks on
swap in of that same data.

> > So, at some point when the system needs to fault those blocks that
> > back in, it now has a linear span of sectors to read instead of asking
> > the drive to bounce over twenty tracks for a hundred blocks.
>
> Moreover though -- what I know about log structure is that generally it
> optimises for write (swapout) and might make read (swapin) worse due to
> fragmentation that wouldn't happen with a regular fs structure.

It looks like I'm not doing a very good job of explaining this, I'm afraid.

Suffice it to say that a log structured swap would give optimization
options that we don't have today.

> I guess that cleaner that Alan mentioned might be involved there -- I don't
> know how/what it would be doing.

Then you should google on `log structured filesystem (primer OR
introduction)` and read a few of the links that pop up. You might find
it interesting.

> I am very aware of the costs of seeks (on current magnetic media).

Then perhaps you can just take it on faith -- log structured layouts
are designed to help minimize seeks, read and write.

Ray

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/29/2007 06:04 PM, Ray Lee wrote:

>> I am very aware of the costs of seeks (on current magnetic media).
> 
> Then perhaps you can just take it on faith -- log structured layouts
> are designed to help minimize seeks, read and write.

I am particularly bad at faith. Let's take that stupid program that I posted:

http://lkml.org/lkml/2007/7/25/85

You push it out before you hit enter, it's written out to swap, at whatever 
speed. How should it be layed out so that it's swapped in most efficiently 
after hitting enter? Reading bigger chunks would quite obviously help, but 
the layout?

The program is not a real-world issue and if you do not consider it a useful 
boundary condition either (okay I guess), how would log structured swap help 
if I just assume I have plenty of free swap to begin with?

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Ray Lee]

On 7/29/07, Rene Herman <rene.herman@gmail.com> wrote:
> On 07/29/2007 06:04 PM, Ray Lee wrote:
> >> I am very aware of the costs of seeks (on current magnetic media).
> >
> > Then perhaps you can just take it on faith -- log structured layouts
> > are designed to help minimize seeks, read and write.
>
> I am particularly bad at faith. Let's take that stupid program that I posted:

You only think you are :-). I'm sure there are lots of things you have
faith in. Gravity, for example :-).

> The program is not a real-world issue and if you do not consider it a useful
> boundary condition either (okay I guess), how would log structured swap help
> if I just assume I have plenty of free swap to begin with?

Is that generally the case on your systems? Every linux system I've
run, regardless of RAM, has always pushed things out to swap. And once
there's something already in swap, you now have a packing problem when
you want to swap something else out.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/29/2007 07:19 PM, Ray Lee wrote:

>> The program is not a real-world issue and if you do not consider it a useful
>> boundary condition either (okay I guess), how would log structured swap help
>> if I just assume I have plenty of free swap to begin with?
> 
> Is that generally the case on your systems? Every linux system I've
> run, regardless of RAM, has always pushed things out to swap.

For me, it is generally the case yes. We are still discussing this in the 
context of desktop machines and their problems with being slow as things 
have been swapped out and generally I expect a desktop to have plenty of 
swap which it's not regularly going to fillup significantly since then the 
machine's unworkably slow as a desktop anyway.

> And once there's something already in swap, you now have a packing
> problem when you want to swap something else out.

Once we're crammed, it gets to be a different situation yes. As far as I'm 
concerned that's for another thread though. I'm spending too much time on 
LKML as it is...

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Ray Lee]

On 7/29/07, Rene Herman <rene.herman@gmail.com> wrote:
> On 07/29/2007 07:19 PM, Ray Lee wrote:
> For me, it is generally the case yes. We are still discussing this in the
> context of desktop machines and their problems with being slow as things
> have been swapped out and generally I expect a desktop to have plenty of
> swap which it's not regularly going to fillup significantly since then the
> machine's unworkably slow as a desktop anyway.

<Shrug> Well, that doesn't match my systems. My laptop has 400MB in swap:

ray@phoenix:~$ free
             total       used       free     shared    buffers     cached
Mem:        894208     883920      10288          0       3044     163224
-/+ buffers/cache:     717652     176556
Swap:      1116476     393132     723344

> > And once there's something already in swap, you now have a packing
> > problem when you want to swap something else out.
>
> Once we're crammed, it gets to be a different situation yes. As far as I'm
> concerned that's for another thread though. I'm spending too much time on
> LKML as it is...

No, it's not even when crammed. It's just when there are holes.
mm/swapfile.c does try to cluster things, but doesn't work too hard at
it as we don't want to spend all our time looking for a perfect fit
that may not exist.

Ray

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Alan Cox]

> > Is that generally the case on your systems? Every linux system I've
> > run, regardless of RAM, has always pushed things out to swap.
> 
> For me, it is generally the case yes. We are still discussing this in the 
> context of desktop machines and their problems with being slow as things 
> have been swapped out and generally I expect a desktop to have plenty of 
> swap which it's not regularly going to fillup significantly since then the 
> machine's unworkably slow as a desktop anyway.

A simple log optimises writeout (which is latency critical) and can
otherwise stall an enitre system. In a log you can also have multiple
copies of the same page on disk easily, some stale - so you can write out
chunks of data that are not all them removed from memory, just so you get
them back more easily if you then do (and I guess you'd mark them
accordingly)

The second element is a cleaner - something to go around removing stuff
from the log that is needed when the disks are idle - and also to repack
data in nice linear chunks. So instead of using the empty disk time for
page-in you use it for packing data and optimising future paging.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman]

On 07/29/2007 07:52 PM, Ray Lee wrote:

> <Shrug> Well, that doesn't match my systems. My laptop has 400MB in swap:

Which in your case is slightly more than 1/3 of available swap space. Quite 
a lot for a desktop indeed. And if it's more than a few percent fragmented, 
please fix current swapout instead of log structuring it.

Rene.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Paul Jackson]

Ray wrote:
> a log structured scheme, where the writeout happens to sequential spaces
> on the drive instead of scattered about.

If the problem is reading stuff back in from swap quickly when
needed, then this likely helps, by reducing the seeks needed.

If the problem is reading stuff back in from swap at the *same time*
that the application is reading stuff from some user file system, and if
that user file system is on the same drive as the swap partition
(typical on laptops), then interleaving the user file system accesses
with the swap partition accesses might overwhelm all other performance
problems, due to the frequent long seeks between the two.

In that case, swap layout and swap i/o block size are secondary.
However, pre-fetching, so that swap read back is not interleaved
with application file accesses, could help dramatically.

===

Perhaps we could have a 'wake-up' command, analogous to the various sleep
and hibernate commands.  The 'wake-up' command could do whatever of the
following it knew to do, in order to optimize for an anticipated change in
usage patterns:
 1) pre-fetch swap
 2) clean (write out) dirty pages
 3) maximize free memory
 4) layout swap nicely
 5) pre-fetch a favorite set of apps

Stumble out of bed in the morning, press 'wake-up', start boiling the
water for your coffee, and in another ten minutes, one is ready to rock
and roll.

In case Andrew is so bored he read this far -- yes this wake-up sounds
like user space code, with minimal kernel changes to support any
particular lower level operation that we can't do already.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.925.600.0401

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Ray Lee]

On 7/29/07, Paul Jackson <pj@sgi.com> wrote:
> If the problem is reading stuff back in from swap at the *same time*
> that the application is reading stuff from some user file system, and if
> that user file system is on the same drive as the swap partition
> (typical on laptops), then interleaving the user file system accesses
> with the swap partition accesses might overwhelm all other performance
> problems, due to the frequent long seeks between the two.

Ah, so in a normal scenario where a working-set is getting faulted
back in, we have the swap storage as well as the file-backed stuff
that needs to be read as well. So even if swap is organized perfectly,
we're still seeking. Damn.

On the other hand, that explains another thing that swap prefetch
could be helping with -- if it preemptively faults the swap back in,
then the file-backed stuff can be faulted back more quickly, just by
the virtue of not needing to seek back and forth to swap for its
stuff. Hadn't thought of that.

That also implies that people running with swap files rather than swap
partitions will see less of an issue. I should dig out my old compact
flash card and try putting swap on that for a week.

> In that case, swap layout and swap i/o block size are secondary.
> However, pre-fetching, so that swap read back is not interleaved
> with application file accesses, could help dramatically.

<Nod>

> Perhaps we could have a 'wake-up' command, analogous to the various sleep
> and hibernate commands.
[...]
> In case Andrew is so bored he read this far -- yes this wake-up sounds
> like user space code, with minimal kernel changes to support any
> particular lower level operation that we can't do already.

He'd suggested using, uhm, ptrace_peek or somesuch for just such a
purpose. The second half of the issue is to know when and what to
target.

Ray

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Paul Jackson]

Ray wrote:
> Ah, so in a normal scenario where a working-set is getting faulted
> back in, we have the swap storage as well as the file-backed stuff
> that needs to be read as well. So even if swap is organized perfectly,
> we're still seeking. Damn.

Perhaps this applies in some cases ... perhaps.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.925.600.0401

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Ray Lee]

On 7/29/07, Paul Jackson <pj@sgi.com> wrote:
> Ray wrote:
> > Ah, so in a normal scenario where a working-set is getting faulted
> > back in, we have the swap storage as well as the file-backed stuff
> > that needs to be read as well. So even if swap is organized perfectly,
> > we're still seeking. Damn.
>
> Perhaps this applies in some cases ... perhaps.

Yeah, point taken: better data would make this a lot easier to figure
out and target fixes.

Ray

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Daniel Hazelton]

On Sunday 29 July 2007 16:00:22 Ray Lee wrote:
> On 7/29/07, Paul Jackson <pj@sgi.com> wrote:
> > If the problem is reading stuff back in from swap at the *same time*
> > that the application is reading stuff from some user file system, and if
> > that user file system is on the same drive as the swap partition
> > (typical on laptops), then interleaving the user file system accesses
> > with the swap partition accesses might overwhelm all other performance
> > problems, due to the frequent long seeks between the two.
>
> Ah, so in a normal scenario where a working-set is getting faulted
> back in, we have the swap storage as well as the file-backed stuff
> that needs to be read as well. So even if swap is organized perfectly,
> we're still seeking. Damn.

That is one reason why I try to have swap on a device dedicated just for it. 
It helps keep the system from having to seek all over the drive for data. (I 
remember that this was recommended years ago with Windows - back when you 
could tell Windows where to put the swap file)

> On the other hand, that explains another thing that swap prefetch
> could be helping with -- if it preemptively faults the swap back in,
> then the file-backed stuff can be faulted back more quickly, just by
> the virtue of not needing to seek back and forth to swap for its
> stuff. Hadn't thought of that.

For it to really help swap-prefetch would have to be more aggressive. At the 
moment (if I'm reading the code correctly) the system has to have close to 
zero for it to kick in. A tunable knob controlling how much activity is too 
much for the prefetch to kick in would help with finding a sane default. IMHO 
it should be the one that provides the most benefit with the least hit to 
performance.

> That also implies that people running with swap files rather than swap
> partitions will see less of an issue. I should dig out my old compact
> flash card and try putting swap on that for a week.

Maybe. It all depends on how much seeking is needed to track down the pages in 
the swapfile and such. What would really help make the situation even better 
would be doing the log structured swap + cleaner. The log structured swap + 
cleaner should provide a performance boost by itself - add in the prefetch 
mechanism and the benefits are even more visible.

Another way to improve performance would require making the page replacement 
mechanism more intelligent. There are bounds to what can be done in the 
kernel without negatively impacting performance, but, if I've read the code 
correctly, there might be a better way to decide which pages to evict. One 
way to do this would be to implement some mechanism that allows the system to 
choose a single group of contiguous pages (or, say, a large soft-page) over 
swapping out a single page at a time.

(some form of memory defrag would also be nice, but I can't think of a way to 
do that without massively breaking everything)

<snip>
> > In case Andrew is so bored he read this far -- yes this wake-up sounds
> > like user space code, with minimal kernel changes to support any
> > particular lower level operation that we can't do already.
>
> He'd suggested using, uhm, ptrace_peek or somesuch for just such a
> purpose. The second half of the issue is to know when and what to
> target.

The userspace suggestion that was thrown out earlier would have been as 
error-prone and problematic as FUSE. A solution like you suggest would be 
workable - its small and does a task that is best done in userspace (IMHO). 
(IIRC, the original suggestion involved merging maps2 and another patchset 
into mainline and using that, combined with PEEKTEXT to provide for a 
userspace swap daemon. Swap, IMHO, should never be handled outside the 
kernel)

What might be useful is a userspace daemon that tracks memory pressure and 
uses a concise API to trigger various levels of prefetch and/or swap 
aggressiveness.

DRH

-- 
Dialup is like pissing through a pipette. Slow and excruciatingly painful.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[david]

On Sun, 29 Jul 2007, Rene Herman wrote:

> On 07/29/2007 01:41 PM, david@lang.hm wrote:
>
>>  I agree that tinkering with the core VM code should not be done lightly,
>>  but this has been put through the proper process and is stalled with no
>>  hints on how to move forward.
>
> It has not. Concerns that were raised (by specifically Nick Piggin) weren't 
> being addressed.

I may have missed them, but what I saw from him weren't specific issues, 
but instead a nebulous 'something better may come along later'

>>  forget the nightly cron jobs for the moment. think of this scenerio. you
>>  have your memory fairly full with apps that you have open (including
>>  firefox with many tabs), you receive a spreadsheet you need to look at, so
>>  you fire up openoffice to look at it. then you exit openoffice and try
>>  to go back to firefox (after a pause while you walk to the printer to
>>  get the printout of the spreadsheet)
>
> And swinging a dead rat from its tail facing east-wards while reciting 
> Documentation/CodingStyle.
>
> Okay, very very sorry, that was particularly childish, but that "walking to 
> the printer" is ofcourse completely constructed and this _is_ something to 
> take into account.

yes it was contrived for simplicity.

the same effect would happen if instead of going back to firefox the user 
instead went to their e-mail software and read some mail. doing so should 
still make the machine idle enough to let prefetch kick in.

> Swap-prefetch wants to be free, which (also again) it is 
> doing a good job at it seems, but this also means that it waits for the VM to 
> be _very_ idle before it does anything and as such, we cannot just forget the 
> "nightly" scenario and pretend it's about something else entirely. As long as 
> the machine's being used, swap-prefetch doesn't kick in.

how long does the machine need to be idle? if someone spends 30 seconds 
reading an e-mail that's an incredibly long time for the system and I 
would think it should be enough to let the prefetch kick in.

>> >  -- 3: no serious consideration of possible alternatives
>> > 
>> >  Tweaking existing use-oce logic is one I've heard but if we consider 
>> >  the i/dcache issue dead, I believe that one is as well. Going to 
>> >  userspace is another one. Largest theoretical potential. I myself am 
>> >  extremely sceptical about the Linux userland, and largely equate it 
>> >  with "smallest _practical_ potential" -- but that might just be me.
>> > 
>> >  A larger swap granularity, possible even a self-training 
>> >  granularity. Up to now, seeks only get costlier and costlier with 
>> >  respect to reads with every generation of disk (flash would largely 
>> >  overcome it though) and doing more in one read/write _greatly_ 
>> >  improves throughput, maybe up to the point that swap-prefetch is no 
>> >  longer very useful. I myself don't know about the tradeoffs 
>> >  involved.
>>
>>  larger swap granularity may help, but waiting for the user to need the
>>  ram and have to wait for it to be read back in is always going to be
>>  worse for the user then pre-populating the free memory (for the case
>>  where the pre-population is right, for other cases it's the same). so
>>  I see this as a red herring
>
> I saw Chris Snook make a good post here and am going to defer this part to 
> that discussion:
>
> http://lkml.org/lkml/2007/7/27/421
>
> But no, it's not a red herring if _practically_ speaking the swapin is fast 
> enough once started that people don't actually mind anymore since in that 
> case you could simply do without yet more additional VM complexity (and 
> kernel daemon).

swapin will always require disk access, and avoiding doing disk access 
while the user is waiting for it by doing it when the system isn't useing 
the disk will always be a win (possibly not as large of a win, but still a 
win) on slow laptop drives where you may only get 20MB/second of reads 
under optimal situations it doesn't take much reading to be noticed by the 
user.

>>  there are fully legitimate situations where this is useful, the 'papering
>>  over' effect is not referring to these, it's referring to other possible
>>  problems in the future.
>
> No, it's not just future. Just look at the various things under discussion 
> now such as improved use-once and better swapin.

and these thing do not conflict with prefetch, they compliment it.

improved use-once will avoid pushing things out to swap in the first 
place. this will help during normal workloads so is valuble in any case.

better swapin (I assume you are talking about things like larger swap 
granularity) will also help during normal workloads when you are thrashing 
into swap.

prefetch will help when you have pushed things out to swap and now have 
free memory and a momentarily idle system.

David Lang

Re: [ck] Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Helge Hafting]

Matthew Hawkins wrote:
> updatedb by itself doesn't really bug me, its just that on occasion
> its still running at 7am 
You should start it earlier then - assuming it doesn't
already start at the earliest opportunity?


Helge Hafting

Re: [ck] Re: -mm merge plans for 2.6.23

[Matthew Hawkins]

[-- Attachment #1: Type: text/plain, Size: 1199 bytes --]

On 7/25/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> I guess /proc/meminfo, /proc/zoneinfo, /proc/vmstat, /proc/slabinfo
> before and after the updatedb run with the latest kernel would be a
> first step. top and vmstat output during the run wouldn't hurt either.

Hi Nick,

I've attached two files with this kind of info.  Being up at the cron
hours of the morning meant I got a better picture of what my system is
doing.  Here's a short summary of what I saw in top:

beagleindexer used gobs of ram.  600M or so (I have 1G)

updatedb didn't use much ram, but while it was running kswapd kept on
frequenting the top 10 cpu hogs - it would stick around for 5 seconds
or so then disappear for no more than 10 seconds, then come back
again.  This behaviour persisted during the run.  updatedb ran third
(beagleindexer was first, then update-dlocatedb)

I'm going to do this again, this time under a CFS kernel & use Ingo's
sched_debug script to see what the scheduler is doing also.

Let me know if there's anything else you wish to see.  The running
kernel at the time was 2.6.22.1-ck.  There's no slabinfo since I'm
using slub instead (and I don't have slub debug enabled).

Cheers,

-- 
Matt

[-- Attachment #2: beaglecron.ck --]
[-- Type: application/octet-stream, Size: 4539 bytes --]

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[-- Attachment #3: updatedbcron.ck --]
[-- Type: application/octet-stream, Size: 5382 bytes --]

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CFS review

[Roman Zippel]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 11264 bytes --]

Hi,

On Sat, 14 Jul 2007, Mike Galbraith wrote:

> > On Fri, 13 Jul 2007, Mike Galbraith wrote:
> > 
> > > > The new scheduler does _a_lot_ of heavy 64 bit calculations without any 
> > > > attempt to scale that down a little...
> > > 
> > > See prio_to_weight[], prio_to_wmult[] and sysctl_sched_stat_granularity.
> > > Perhaps more can be done, but "without any attempt..." isn't accurate.
> > 
> > Calculating these values at runtime would have been completely insane, the 
> > alternative would be a crummy approximation, so using a lookup table is 
> > actually a good thing. That's not the problem.
> 
> I meant see usage.

I more meant serious attempts. At this point I'm not that much interested 
in a few localized optimizations, what I'm interested in is how can this 
optimized at the design level (e.g. how can arch information be used to 
simplify things). So I spent quite a bit of time looking through cfs and 
experimenting with some ideas. I want to put the main focus on the 
performance aspect, but there are a few other issues as well.


But first something else (especially for Ingo): I tried to be very careful 
with any claims made in this mail, but this of course doesn't exclude the 
possibility of errors, in which case I'd appreciate any corrections. Any 
explanations done in this mail don't imply that anyone needs any such 
explanations, they're done to keep things in context, so that interested 
readers have a chance to follow even if they don't have the complete 
background information. Any suggestions made don't imply that they have to 
be implemented like this, there are more an incentive for further 
discussion and I'm always interested in better solutions.


A first indication that something may not be quite right is the increase
in code size:

2.6.22:
   text    data     bss     dec     hex filename
  10150      24    3344   13518    34ce kernel/sched.o

recent git:
   text    data     bss     dec     hex filename
  14724     228    2020   16972    424c kernel/sched.o

That's i386 without stats/debug. A lot of the new code is in regularly
executed regions and it's often not exactly trivial code as cfs added
lots of heavy 64bit calculations. With the increased text comes
increased runtime memory usage, e.g. task_struct increased so that only
5 of them instead 6 fit now into 8KB.

Since sched-design-CFS.txt doesn't really go into any serious detail, so
the EEVDF paper was more helpful and after playing with the ideas a
little I noticed that the whole idea of fair scheduling can be explained
somewhat simpler and I'm a little surprised not finding it mentioned
anywhere.
So a different view on this is that the runtime of a task is simply
normalized and the virtual time (or fair_clock) is the weighted average of
these normalized runtimes. The advantage of normalization is that it
makes things comparable, once the normalized time values are equal each
task got its fair share. It's more obvious in the EEVDF paper, cfs makes
it a bit more complicated, as it uses the virtual time to calculate the
eligible runtime, but it doesn't maintain a per process virtual time
(fair_key is not quite the same).

Here we get to the first problem, cfs is not overly accurate at
maintaining a precise balance. First there a lot of rounding errors due
to constant conversion between normalized and non-normalized values and
the higher the update frequency the bigger the error. The effect of
this can be seen by running:

	while (1)
		sched_yield();

and watching the sched_debug output and watch the underrun counter go 
crazy. cfs thus needs the limiting to keep this misbehaviour under
control. The problem here is that it's not that difficult to hit one of
the many limits, which may change the behaviour and makes cfs hard to
predict how it will behave under different situations.

The next issue is scheduler granularity, here I don't quite understand
why the actual running time has no influence at all, which makes it
difficult to predict how much cpu time a process will get at a time
(even the comments only refer to the vmstat output). What is basically
used instead is the normalized time since it was enqueued and
practically it's a bit more complicated, as fair_key is not entirely a
normalized time value. If the wait_runtime value is positive, higher
prioritized tasks are given even more priority than they already get
from their larger wait_runtime value. The problem here is that this
triggers underruns and lower priority tasks get even less time.

Another issue is the sleep bonus given to sleeping tasks. A problem here
is that this can be exploited, if a job is spread over a few threads,
they can get more time relativ to other tasks, e.g. in this example
there are three tasks that run only for about 1ms every 3ms, but they
get far more time than should have gotten fairly:

 4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
 4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
 4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
 4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l

The debug output for this is also interesting:

            task   PID        tree-key         delta       waiting  switches  prio        sum-exec        sum-wait       sum-sleep    wait-overrun   wait-underrun
------------------------------------------------------------------------------------------------------------------------------------------------------------------
              lt  4544  42958653977764      -2800118       2797765     11753   120     11449444657       201615584     23750292211            9600               0
              lt  4545  42958653767067      -3010815       2759284     11747   120     11442604925       202910051     23746575676            9613               0
               l  4547  42958653330276      -3447606       1332892     32333   120      1035284848       -47628857               0               0           14247

Practically this means a few interactive tasks can steal quite a lot of
time from other tasks, which might try to get some work done. This may
be fine in Desktop environments, but I'm not sure it can be that easily
generalized. This can make cfs quite unfair, if waiting outside the
runqueue has more advantages than waiting in the runqueue.

Finally there is still the issue with the nice levels, where I still
think the massive increase overcompensates for adequate scheduling
classes, e.g. to give audio apps a fixed amount of time instead of a
relative portion.

Overall while cfs has a number of good ideas, I don't think it was
quite ready for a stable release. Maybe it's possible to fix this until
the release, but I certainly would have prefered less time pressure.
It's not just the small inaccuracies, it's also the significantly
increased complexity. In this regard I find the claim that cfs "has no
heuristics whatsoever" interesting, for that to be true I would expect a
little more accuracy, but that wouldn't be a big problem, if cfs were a
really fast and compact scheduler and here it's quite hard to argue that
cfs has been improvement in this particular area. Anyway, before Ingo
starts accussing me now of "negativism", let's look at some
possibilities how this could be improved.


To reduce the inaccuracies it's better to avoid conversion between 
normalized and real time values, so the first example program pretty much 
shows just that and demonstrate the very core of a scheduler. It maintains 
per task normalized times and uses only that to make the scheduling 
decision (it doesn't even need an explicit wait_runtime value). The nice 
thing about this how consistently it gives out time shares - unless there 
is a higher priority task, that task will get the maximum share, which 
makes the scheduling behaviour quite a bit more predictable.

The second example program is more complete (e.g. it demonstrates
adding/removing tasks) but it's based on the same basic idea. First the
floating point values are converted to fixed point values. To maintain
accuracy one has to take overflows into account, cfs currently avoids
overflows by throwing away (possibly important) information, but that
adds checks all over the place instead of dealing with them within the
design, so I consider this overflow avoidance a failed strategy - it
doesn't make anything simpler and creates problems elsewhere. Of course
the example program has its own limits, but in this case I can define
them, so that within them the scheduler will work correctly. The most
important limits are:

max normalized task time delta = max inverse weight * max cpu share
max normalized average time delta = max active tasks * max inverse weight * cpu share base

The first limit is used for comparing individual task and the second one
is used for maintaining the average.  With these limits it's possible to
choose the appropriate data types that can hold these maximum values and
then I don't really have to worry about overflows and I know the
scheduler is accurate without the need for a lot of extra checks.

The second example also adds a normalized average, but contrary to
current cfs it's not central to the design. An average is not needed to
give every task its fair share, but it can be used to make better
scheduling decisions to control _when_ a task gets its share. In this
example I provided two possibilities where it's used to schedule new
tasks, the first divides time into slices and sets a new task to the
start of that slice, the second gives the task a full time share
relative to the current average, but approximating the average (by
looking just at the min/max time) should work as well.
The average here is not a weighted average, a weighted average is a
little more complex to maintain accurately and has issues regarding
overflows, so I'm using a simple average, which is sufficient especially
since it's not a primary part of the scheduler anymore.

BTW above unfairness of sleeping tasks can be easily avoided in this
model by simply making sure that normalized time never goes backward.

The accuracy of this model makes it possible to further optimize the
code (it's really a key element, that's why I'm stressing it so much,
OTOH it's rather difficult to further optimize current cfs without
risking to make it worse).
For example the regular updates aren't really necessary, they can also
be done when necessary (i.e. when scheduling, where an update is
necessary anyway for precise accounting), the next schedule time can be
easily precalculated instead. OTOH the regular updates allow for very
cheap incremental updates, especially if one already knows that
scheduler clock has only limited resolution (because it's based on
jiffies), it becomes possible to use mostly 32bit values.

I hope the code example helps to further improve scheduler, I'm quite
aware that it doesn't implement everything, but this just means some of
the cfs design decisions need more explanation. I'm not really that
much interested in scheduler, I only want a small and fast scheduler and
that's some areas where cfs is no real improvement right now. cfs
practically obliterated my efforts I put into the ntp code to keep the
regular updates both cheap and highly precise...

bye, Roman

[-- Attachment #2: Type: TEXT/x-csrc, Size: 1247 bytes --]

#include <stdio.h>

int weight[10] = {
	20, 20, 20, 50, 20, 20, 20
};
double time[10];
double ntime[10];

#define MIN_S		1
#define MAX_S		10

#define SLICE(x)	(MAX_S / (double)weight[x])
#define MINSLICE(x)	(MIN_S / (double)weight[x])

int main(void)
{
	int i, j, l, w;
	double s, t, min, max;

	for (i = 0; i < 10; i++)
		ntime[i] = time[i] = 0;

	j = 0;
	l = 0;
	s = 0;
	while (1) {
		j = l ? 0 : 1;
		for (i = 0; i < 10; i++) {
			if (!weight[i] || i == l)
				continue;
			if (ntime[i] + MINSLICE(i) < ntime[j] + MINSLICE(j))
				j = i;
		}
		if (ntime[l] >= ntime[j] + SLICE(j) ||
		    (ntime[l] >= ntime[j] &&
		     ntime[l] >= s + SLICE(l))) {
			l = j;
			s = ntime[l];
		}
		time[l] += MIN_S;
		ntime[l] += MIN_S / (double)weight[l];

		printf("%u", l);
		for (i = 0, w = 0, t = 0; i < 10; i++) {
			if (!weight[i])
				continue;
			w += weight[i];
			t += ntime[i] * weight[i];
			printf("\t%3u/%u:%5g/%-7g", i, weight[i], time[i], ntime[i]);
		}
		t /= w;
		min = max = t;
		for (i = 0; i < 10; i++) {
			if (!weight[i])
				continue;
			if (ntime[i] < min)
				min = ntime[i];
			if (ntime[i] > max)
				max = ntime[i];
		}
		printf("\t| %g (%g)\n", t, max - min);
	}
}

[-- Attachment #3: Type: TEXT/x-csrc, Size: 4966 bytes --]

#include <stdio.h>
#include <stdlib.h>

struct task {
	unsigned int weight, weight_inv;
	int active;

	unsigned int time, time_avg;
	int time_norm, avg_fract;
} task[10]  = {
	{ .weight = 10 },
	{ .weight = 40 },
	{ .weight = 80 },
};

#define MIN_S		100
#define MAX_S		1000

#define SLICE(x)	(MAX_S * task[x].weight_inv)
#define MINSLICE(x)	(MIN_S * task[x].weight_inv)

#define WEIGTH0		40
#define WEIGTH0_INV	((1 << 16) / WEIGTH0)

unsigned int time_avg, time_norm_sum;
int avg_fract, weight_sum_inv;

static void normalize_avg(int i)
{
	if (!weight_sum_inv)
		return;
	/* assume the common case of 0/1 first, then fallback */
	if (task[i].avg_fract < 0 || task[i].avg_fract >= WEIGTH0_INV * MAX_S) {
		task[i].time_avg++;
		task[i].avg_fract -= WEIGTH0_INV * MAX_S;
		if (task[i].avg_fract < 0 || task[i].avg_fract >= WEIGTH0_INV * MAX_S) {
			task[i].time_avg += task[i].avg_fract / (WEIGTH0_INV * MAX_S);
			task[i].avg_fract %= WEIGTH0_INV * MAX_S;
		}
	}
	if (avg_fract < 0 || avg_fract >= weight_sum_inv) {
		time_avg++;
		avg_fract -= weight_sum_inv;
		if (avg_fract < 0 || avg_fract >= weight_sum_inv) {
			time_avg += avg_fract / weight_sum_inv;
			avg_fract %= weight_sum_inv;
		}
	}
}

int main(void)
{
	int i, j, l, task_cnt;
	unsigned int s;
	unsigned int time_sum, time_sum2;

	task_cnt = time_avg = 0;
	for (i = 0; i < 10; i++) {
		if (!task[i].weight)
			continue;
		task[i].active = 1;
		task_cnt++;
		task[i].weight_inv = (1 << 16) / task[i].weight;
	}
	weight_sum_inv = task_cnt * WEIGTH0_INV * MAX_S;
	printf("w: %u,%u\n", WEIGTH0_INV * MAX_S, weight_sum_inv);

	time_norm_sum = avg_fract = 0;
	l = 0;
	s = 0;
	while (1) {
		j = -1;
		for (i = 0; i < 10; i++) {
			if (i == l)
				continue;
			if (!task[i].active && task[i].weight) {
				if (!(rand() % 30)) {
					normalize_avg(i);
					task[i].active = 1;
					if (!task_cnt)
						goto done;
#if 1
					if ((int)(task[i].time_avg - time_avg) < 0) {
						task[i].time_norm -= (int)(task[i].time_avg - time_avg) * WEIGTH0_INV * MAX_S + task[i].avg_fract;
						task[i].time_avg = time_avg;
						task[i].avg_fract = 0;
					}
#else
					unsigned int new_time_avg = time_avg;
					int new_avg_fract = avg_fract / task_cnt - task[i].weight_inv * MAX_S;
					while (new_avg_fract < 0) {
						new_time_avg--;
						new_avg_fract += WEIGTH0_INV * MAX_S;
					}
					if ((int)(task[i].time_avg - new_time_avg) < 0 ||
					    ((int)(task[i].time_avg - new_time_avg) == 0 &&
					     task[i].avg_fract < new_avg_fract)) {
						task[i].time_norm += (int)(new_time_avg - task[i].time_avg) * WEIGTH0_INV * MAX_S +
							new_avg_fract - task[i].avg_fract;
						task[i].time_avg = new_time_avg;
						task[i].avg_fract = new_avg_fract;
					}
#endif
				done:
					task_cnt++;
					weight_sum_inv += WEIGTH0_INV * MAX_S;
					avg_fract += (int)(task[i].time_avg - time_avg) * WEIGTH0_INV * MAX_S + task[i].avg_fract;
					time_norm_sum += task[i].time_norm;
				}
			}
			if (!task[i].active)
				continue;
			if (j < 0 ||
			    (int)(task[i].time_norm + MINSLICE(i) - (task[j].time_norm + MINSLICE(j))) < 0)
				j = i;
		}

		if (!task[l].active) {
			if (j < 0)
				continue;
			goto do_switch;
		}

		if (!(rand() % 100)) {
			task[l].active = 0;
			task_cnt--;
			weight_sum_inv -= WEIGTH0_INV * MAX_S;
			avg_fract -= (int)(task[l].time_avg - time_avg) * WEIGTH0_INV * MAX_S + task[l].avg_fract;
			time_norm_sum -= task[l].time_norm;
			if (j < 0)
				continue;
			goto do_switch;
		}

		if (j >= 0 &&
		    ((int)(task[l].time_norm - (task[j].time_norm + SLICE(j))) >= 0 ||
		     ((int)(task[l].time_norm - task[j].time_norm) >= 0 &&
		      (int)(task[l].time_norm - (s + SLICE(l))) >= 0))) {
			int prev_time_avg;
		do_switch:
			prev_time_avg = time_avg;
			normalize_avg(l);
			if (prev_time_avg < time_avg)
				printf("-\n");
			l = j;
			s = task[l].time_norm;
		}
		task[l].time += MIN_S;
		task[l].time_norm += MINSLICE(l);
		task[l].avg_fract += MINSLICE(l);
		time_norm_sum += MINSLICE(l);
		avg_fract += MINSLICE(l);

		printf("%u", l);
		time_sum = time_sum2 = 0;
		for (i = 0; i < 10; i++) {
			if (!task[i].active) {
				if (task[i].weight)
					printf("\t%3u/%u: -\t", i, task[i].weight);
				continue;
			}
			time_sum += task[i].time_norm;
			time_sum2 += task[i].time_avg * WEIGTH0_INV * MAX_S + task[i].avg_fract;
			printf("\t%3u/%u:%5u/%-7g/%-7g", i, task[i].weight, task[i].time,
				(double)task[i].time_norm / (1 << 16),
				task[i].time_avg + (double)task[i].avg_fract / (WEIGTH0_INV * MAX_S));
		}
		if (time_sum != time_norm_sum)
			abort();
		if (time_sum2 != time_avg * weight_sum_inv + avg_fract)
			abort();
		if (time_sum != time_sum2)
			abort();
		printf("\t| %g/%g\n", (double)time_norm_sum / task_cnt / (1 << 16),
			time_avg + (double)(int)avg_fract / weight_sum_inv);
	}
}

Re: CFS review

[Ingo Molnar]

Roman,

Thanks for the testing and the feedback, it's much appreciated! :-) On
what platform did you do your tests, and what .config did you use (and
could you please send me your .config)?

Please also send me the output of this script:

  http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh

(if the output is too large send it to me privately, or bzip2 -9 it.)

Could you also please send the source code for the "l.c" and "lt.c" apps
you used for your testing so i can have a look. Thanks!

	Ingo

Re: CFS review

[Mike Galbraith]

On Wed, 2007-08-01 at 09:12 +0200, Ingo Molnar wrote:
> Roman,
> 
> Thanks for the testing and the feedback, it's much appreciated! :-) On
> what platform did you do your tests, and what .config did you use (and
> could you please send me your .config)?
> 
> Please also send me the output of this script:
> 
>   http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh
> 
> (if the output is too large send it to me privately, or bzip2 -9 it.)
> 
> Could you also please send the source code for the "l.c" and "lt.c" apps
> you used for your testing so i can have a look. Thanks!

I haven't been able to reproduce this with any combination of features,
and massive_intr tweaked to his work/sleep cycle.  I notice he's
collecting stats though, and they look funky.  Recompiling.

	-Mike

Re: CFS review

[Ingo Molnar]

* Mike Galbraith <efault@gmx.de> wrote:

> > Thanks for the testing and the feedback, it's much appreciated! :-) 
> > On what platform did you do your tests, and what .config did you use 
> > (and could you please send me your .config)?
> > 
> > Please also send me the output of this script:
> > 
> >   http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh
> > 
> > (if the output is too large send it to me privately, or bzip2 -9 
> > it.)
> > 
> > Could you also please send the source code for the "l.c" and "lt.c" 
> > apps you used for your testing so i can have a look. Thanks!
> 
> I haven't been able to reproduce this with any combination of 
> features, and massive_intr tweaked to his work/sleep cycle.  I notice 
> he's collecting stats though, and they look funky.  Recompiling.

yeah, the posted numbers look most weird, but there's a complete lack of 
any identification of test environment - so we'll need some more word 
from Roman. Perhaps this was run on some really old box that does not 
have a high-accuracy sched_clock()? The patch below should simulate that 
scenario on 32-bit x86.

	Ingo

Index: linux/arch/i386/kernel/tsc.c
===================================================================
--- linux.orig/arch/i386/kernel/tsc.c
+++ linux/arch/i386/kernel/tsc.c
@@ -110,7 +110,7 @@ unsigned long long native_sched_clock(vo
 	 *   very important for it to be as fast as the platform
 	 *   can achive it. )
 	 */
-	if (unlikely(!tsc_enabled && !tsc_unstable))
+//	if (unlikely(!tsc_enabled && !tsc_unstable))
 		/* No locking but a rare wrong value is not a big deal: */
 		return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
 

Re: CFS review

[Mike Galbraith]

On Wed, 2007-08-01 at 09:30 +0200, Ingo Molnar wrote:
> * Mike Galbraith <efault@gmx.de> wrote:

> > I haven't been able to reproduce this with any combination of 
> > features, and massive_intr tweaked to his work/sleep cycle.  I notice 
> > he's collecting stats though, and they look funky.  Recompiling.
> 
> yeah, the posted numbers look most weird, but there's a complete lack of 
> any identification of test environment - so we'll need some more word 
> >from Roman. Perhaps this was run on some really old box that does not 
> have a high-accuracy sched_clock()? The patch below should simulate that 
> scenario on 32-bit x86.
> 
> 	Ingo
> 
> Index: linux/arch/i386/kernel/tsc.c
> ===================================================================
> --- linux.orig/arch/i386/kernel/tsc.c
> +++ linux/arch/i386/kernel/tsc.c
> @@ -110,7 +110,7 @@ unsigned long long native_sched_clock(vo
>  	 *   very important for it to be as fast as the platform
>  	 *   can achive it. )
>  	 */
> -	if (unlikely(!tsc_enabled && !tsc_unstable))
> +//	if (unlikely(!tsc_enabled && !tsc_unstable))
>  		/* No locking but a rare wrong value is not a big deal: */
>  		return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
>  

Ah, thanks.  I noticed that clocksource= went away.  I'll test with
stats, with and without jiffies resolution.

	-Mike

Re: CFS review

[Mike Galbraith]

On Wed, 2007-08-01 at 09:36 +0200, Mike Galbraith wrote:
> On Wed, 2007-08-01 at 09:30 +0200, Ingo Molnar wrote:
>  
> > yeah, the posted numbers look most weird, but there's a complete lack of 
> > any identification of test environment - so we'll need some more word 
> > >from Roman. Perhaps this was run on some really old box that does not 
> > have a high-accuracy sched_clock()? The patch below should simulate that 
> > scenario on 32-bit x86.
> > 
> > 	Ingo
> > 
> > Index: linux/arch/i386/kernel/tsc.c
> > ===================================================================
> > --- linux.orig/arch/i386/kernel/tsc.c
> > +++ linux/arch/i386/kernel/tsc.c
> > @@ -110,7 +110,7 @@ unsigned long long native_sched_clock(vo
> >  	 *   very important for it to be as fast as the platform
> >  	 *   can achive it. )
> >  	 */
> > -	if (unlikely(!tsc_enabled && !tsc_unstable))
> > +//	if (unlikely(!tsc_enabled && !tsc_unstable))
> >  		/* No locking but a rare wrong value is not a big deal: */
> >  		return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
> >  
> 
> Ah, thanks.  I noticed that clocksource= went away.  I'll test with
> stats, with and without jiffies resolution.

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  P COMMAND
6465 root      20   0  1432  356  296 R   30  0.0   1:02.55 1 chew
6462 root      20   0  1576  216  140 R   23  0.0   0:50.29 1 massive_intr_x
6463 root      20   0  1576  216  140 R   23  0.0   0:50.23 1 massive_intr_x
6464 root      20   0  1576  216  140 R   23  0.0   0:50.28 1 massive_intr_x

Well, jiffies resolution clock did upset fairness a bit with a right at
jiffies resolution burn time, but not nearly as bad as on Roman's box,
and not in favor of the sleepers.  With the longer burn time of stock
massive_intr.c (8ms burn, 1ms sleep), lower resolution clock didn't
upset it.

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  P COMMAND
6511 root      20   0  1572  220  140 R   25  0.0   1:00.11 1 massive_intr
6512 root      20   0  1572  220  140 R   25  0.0   1:00.14 1 massive_intr
6514 root      20   0  1432  356  296 R   25  0.0   1:00.31 1 chew
6513 root      20   0  1572  220  140 R   24  0.0   1:00.14 1 massive_intr

	-Mike

Re: CFS review

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> [...] e.g. in this example there are three tasks that run only for 
> about 1ms every 3ms, but they get far more time than should have 
> gotten fairly:
> 
>  4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
>  4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
>  4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
>  4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l

Mike and me have managed to reproduce similarly looking 'top' output, 
but it takes some effort: we had to deliberately run a non-TSC 
sched_clock(), CONFIG_HZ=100, !CONFIG_NO_HZ and !CONFIG_HIGH_RES_TIMERS.

in that case 'top' accounting symptoms similar to the above are not due 
to the scheduler starvation you suspected, but due the effect of a 
low-resolution scheduler clock and a tightly coupled timer/scheduler 
tick to it. I tried the very same workload on 2.6.22 (with the same 
.config) and i saw similarly anomalous 'top' output. (Not only can one 
create really anomalous CPU usage, one can completely hide tasks from 
'top' output.)

if your test-box has a high-resolution sched_clock() [easily possible] 
then please send us the lt.c and l.c code so that we can have a look.

	Ingo

Re: CFS review

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> [...] the increase in code size:
> 
> 2.6.22:
>    text    data     bss     dec     hex filename
>   10150      24    3344   13518    34ce kernel/sched.o
> 
> recent git:
>    text    data     bss     dec     hex filename
>   14724     228    2020   16972    424c kernel/sched.o
> 
> That's i386 without stats/debug. [...]

that's without CONFIG_SMP, right? :-) On SMP they are about net break 
even:

     text    data     bss     dec     hex filename
    26535    4173      24   30732    780c kernel/sched.o-2.6.22
    28378    2574      16   30968    78f8 kernel/sched.o-2.6.23-git

(plus a further ~1.5K per CPU data reduction which is not visible here) 

btw., here's the general change in size of a generic vmlinux from .22 to 
.23-git, using the same .config:

     text    data     bss     dec     hex filename
  5256628  520760 1331200 7108588  6c77ec vmlinux.22
  5306918  535844 1327104 7169866  6d674a vmlinux.23-git

+50K. (this was on UP)

In any case, there's still some debugging code in the scheduler (beyond 
SCHED_DEBUG), i'll work some more on reducing it.

	Ingo

Re: CFS review

[Roman Zippel]

Hi,

On Wed, 1 Aug 2007, Ingo Molnar wrote:

> > [...] e.g. in this example there are three tasks that run only for 
> > about 1ms every 3ms, but they get far more time than should have 
> > gotten fairly:
> > 
> >  4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
> >  4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
> >  4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
> >  4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l
> 
> Mike and me have managed to reproduce similarly looking 'top' output, 
> but it takes some effort: we had to deliberately run a non-TSC 
> sched_clock(), CONFIG_HZ=100, !CONFIG_NO_HZ and !CONFIG_HIGH_RES_TIMERS.

I used my old laptop for these tests, where tsc is indeed disabled due to 
instability. Otherwise the kernel was configured with CONFIG_HZ=1000.

> in that case 'top' accounting symptoms similar to the above are not due 
> to the scheduler starvation you suspected, but due the effect of a 
> low-resolution scheduler clock and a tightly coupled timer/scheduler 
> tick to it.

Well, it magnifies the rounding problems in CFS.
I mainly wanted to test a little the behaviour of CFS and I thought a saw 
patch which enabled the use of TSC in these cases, so I didn't check 
sched_clock().

Anyway, I want to point out that this wasn't the main focus of what I 
wrote.

bye, Roman

Re: CFS review

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> On Wed, 1 Aug 2007, Ingo Molnar wrote:
> 
> > > [...] e.g. in this example there are three tasks that run only for 
> > > about 1ms every 3ms, but they get far more time than should have 
> > > gotten fairly:
> > > 
> > >  4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
> > >  4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
> > >  4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
> > >  4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l
> > 
> > Mike and me have managed to reproduce similarly looking 'top' output, 
> > but it takes some effort: we had to deliberately run a non-TSC 
> > sched_clock(), CONFIG_HZ=100, !CONFIG_NO_HZ and !CONFIG_HIGH_RES_TIMERS.
> 
> I used my old laptop for these tests, where tsc is indeed disabled due 
> to instability. Otherwise the kernel was configured with 
> CONFIG_HZ=1000.

please send all the debug info and source code we asked for - thanks!

	Ingo

Re: CFS review

[Roman Zippel]

Hi,

On Wed, 1 Aug 2007, Ingo Molnar wrote:

> * Roman Zippel <zippel@linux-m68k.org> wrote:
> 
> > [...] the increase in code size:
> > 
> > 2.6.22:
> >    text    data     bss     dec     hex filename
> >   10150      24    3344   13518    34ce kernel/sched.o
> > 
> > recent git:
> >    text    data     bss     dec     hex filename
> >   14724     228    2020   16972    424c kernel/sched.o
> > 
> > That's i386 without stats/debug. [...]
> 
> that's without CONFIG_SMP, right? :-) On SMP they are about net break 
> even:
> 
>      text    data     bss     dec     hex filename
>     26535    4173      24   30732    780c kernel/sched.o-2.6.22
>     28378    2574      16   30968    78f8 kernel/sched.o-2.6.23-git

That's still quite an increase in some rather important code paths and 
it's not just the code size, but also code complexity which is important 
- a major point I tried to address in my review.

> (plus a further ~1.5K per CPU data reduction which is not visible here) 

That's why I mentioned the increased runtime memory usage...

bye, Roman

Re: CFS review

[Roman Zippel]

Hi,

On Wed, 1 Aug 2007, Ingo Molnar wrote:

> Please also send me the output of this script:
> 
>   http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh

Send privately.

> Could you also please send the source code for the "l.c" and "lt.c" apps
> you used for your testing so i can have a look. Thanks!

l.c is a simple busy loop (well, with the option to start many of them).
This is lt.c, what it does is to run a bit less than a jiffie, so it 
needs a low resolution clock to trigger the problem:

#include <stdio.h>
#include <signal.h>
#include <time.h>
#include <sys/time.h>

#define NSEC 1000000000
#define USEC 1000000

#define PERIOD	(NSEC/1000)

int i;

void worker(int sig)
{
	struct timeval tv;
	long long t0, t;

	gettimeofday(&tv, 0);
	//printf("%u,%lu\n", i, tv.tv_usec);
	t0 = (long long)tv.tv_sec * 1000000 + tv.tv_usec + PERIOD / 1000 - 50;
	do {
		gettimeofday(&tv, 0);
		t = (long long)tv.tv_sec * 1000000 + tv.tv_usec;
	} while (t < t0);
	
}

int main(int ac, char **av)
{
	int cnt;
	timer_t timer;
	struct itimerspec its;
	struct sigaction sa;

	cnt = i = atoi(av[1]);

	sa.sa_handler = worker;
	sa.sa_flags = 0;
	sigemptyset(&sa.sa_mask);

	sigaction(SIGALRM, &sa, 0);

	clock_gettime(CLOCK_MONOTONIC, &its.it_value);
	its.it_interval.tv_sec = 0;
	its.it_interval.tv_nsec = PERIOD * cnt;

	while (--i > 0 && fork() > 0)
		;

	its.it_value.tv_nsec += i * PERIOD;
	if (its.it_value.tv_nsec > NSEC) {
		its.it_value.tv_sec++;
		its.it_value.tv_nsec -= NSEC;
	}

	timer_create(CLOCK_MONOTONIC, 0, &timer);
	timer_settime(timer, TIMER_ABSTIME, &its, 0);

	printf("%u,%lu\n", i, its.it_interval.tv_nsec);

	while (1) 
		pause();
	return 0;
}

Re: CFS review

[Andi Kleen]

Roman Zippel <zippel@linux-m68k.org> writes:

> especially if one already knows that
> scheduler clock has only limited resolution (because it's based on
> jiffies), it becomes possible to use mostly 32bit values.

jiffies based sched_clock should be soon very rare. It's probably
not worth optimizing for it.

-Andi

Re: CFS review

[Roman Zippel]

Hi,

On Wed, 1 Aug 2007, Andi Kleen wrote:

> > especially if one already knows that
> > scheduler clock has only limited resolution (because it's based on
> > jiffies), it becomes possible to use mostly 32bit values.
> 
> jiffies based sched_clock should be soon very rare. It's probably
> not worth optimizing for it.

I'm not so sure about that. sched_clock() has to be fast, so many archs 
may want to continue to use jiffies. As soon as one does that one can also 
save a lot of computational overhead by using 32bit instead of 64bit.
The question is then how easy that is possible.

bye, Roman

Re: CFS review

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> > in that case 'top' accounting symptoms similar to the above are not 
> > due to the scheduler starvation you suspected, but due the effect of 
> > a low-resolution scheduler clock and a tightly coupled 
> > timer/scheduler tick to it.
> 
> Well, it magnifies the rounding problems in CFS.

why do you say that? 2.6.22 behaves similarly with a low-res 
sched_clock(). This has nothing to do with 'rounding problems'!

i tried your fl.c and if sched_clock() is high-resolution it's scheduled 
_perfectly_ by CFS:

   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
  5906 mingo     20   0  1576  244  196 R 71.2  0.0   0:30.11 l
  5909 mingo     20   0  1844  344  260 S  9.6  0.0   0:04.02 lt
  5907 mingo     20   0  1844  508  424 S  9.5  0.0   0:04.01 lt
  5908 mingo     20   0  1844  344  260 S  9.5  0.0   0:04.02 lt

if sched_clock() is low-resolution then indeed the 'lt' tasks will 
"hide":

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 2366 mingo     20   0  1576  248  196 R 99.9  0.0   0:07.95 loop_silent
    1 root      20   0  2132  636  548 S  0.0  0.0   0:04.64 init

but that's nothing new. CFS cannot conjure up time measurement methods 
that do not exist. If you have a low-res clock and if you create an app 
that syncs precisely to the tick of that clock via timers that run off 
that exact tick then there's nothing the scheduler can do about it. It 
is false to charachterise this as 'sleeper starvation' or 'rounding 
error' like you did. No amount of rounding logic can create a 
high-resolution clock out of thin air.

	Ingo

Re: CFS review

[Arjan van de Ven]

> but that's nothing new. CFS cannot conjure up time measurement methods 
> that do not exist. If you have a low-res clock and if you create an app 
> that syncs precisely to the tick of that clock via timers that run off 
> that exact tick then there's nothing the scheduler can do about it. It 
> is false to charachterise this as 'sleeper starvation' or 'rounding 
> error' like you did. No amount of rounding logic can create a 
> high-resolution clock out of thin air.


CFS is only as fair as your clock is good.

Re: CFS review

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> > jiffies based sched_clock should be soon very rare. It's probably 
> > not worth optimizing for it.
> 
> I'm not so sure about that. sched_clock() has to be fast, so many 
> archs may want to continue to use jiffies. [...]

i think Andi was talking about the vast majority of the systems out 
there. For example, check out the arch demography of current Fedora 
installs (according to the Smolt opt-in UUID based user metrics):

   http://smolt.fedoraproject.org/

   i686:     74743
   x86_64:   18599
   i386:      1208
   ppc:        527
   ppc64:      396
   sparc64:     14
   ---------------
   Total:    95488

even pure i386 (kernels, not systems) is a only 1.2% of all installs. By 
the time the CFS kernel gets into a distro (a few months at minimum, 
typically a year) this percentage will go down further. And embedded 
doesnt really care about task-statistics corner cases [ (it likely 
doesnt have 'top' installed - likely doesnt even have /proc mounted or 
even built in ;-) ].

of course CFS should not do _worse_ stats than what we had before, and 
should not break or massively misbehave. Also, anything sane we can do 
for low-resolution arches we should do (and we already do quite a bit - 
the while wmult stuff is to avoid expensive divisions) - and i regularly 
booted CFS with a low-resolution clock to make sure it works. So i'm not 
trying to duck anything, we've just got to keep our design priorities 
right :-)

	Ingo

Re: CFS review

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> 	while (1)
> 		sched_yield();

sched_yield() is being reworked at the moment. But in general we want 
apps to move away to sane locking constructs ASAP. There's some movement 
in the 3D space at least.

	Ingo

Re: CFS review

[Peter Zijlstra]

Hi Roman,

Took me most of today trying to figure out WTH you did in fs2.c, more
math and fundamental explanations would have been good. So please bear
with me as I try to recap this thing. (No, your code was very much _not_
obvious, a few comments and broken out functions would have made a world
of a difference)


So, for each task we keep normalised time

 normalised time := time/weight

using Bresenham's algorithm we can do this prefectly (up until a renice
- where you'd get errors)

        avg_frac += weight_inv
        
        weight_inv = X / weight
        
        avg = avg_frac / weight0_inv
        
        weight0_inv = X / weight0
        
        avg = avg_frac / (X / weight0) 
            = (X / weight) / (X / weight0) 
            = X / weight * weight0 / X 
            = weight0 / weight
        

So avg ends up being in units of [weight0/weight].

Then, in order to allow sleeping, we need to have a global clock to sync
with. Its this global clock that gave me headaches to reconstruct.

We're looking for a time like this:

  rq_time := sum(time)/sum(weight)

And you commented that the /sum(weight) part is where CFS obtained its
accumulating rounding error? (I'm inclined to believe the error will
statistically be 0, but I'll readily accept otherwise if you can show a
practical 'exploit')

Its not obvious how to do this using modulo logic like Bresenham because
that would involve using a gcm of all possible weights.

What you ended up with is quite interesting if correct.

	sum_avg_frac += weight_inv_{i}

however by virtue of the scheduler minimising:

  avg_{i} - avg_{j} | i != j

this gets a factor of:

  weight_{i}/sum_{j}^{N}(weight_{j})

 ( seems correct, needs more analysis though, this is very much a
   statistical step based on the previous constraint. this might
   very well introduce some errors )

resulting in:

        sum_avg_frac += sum_{i}^{N}(weight_inv_{i} *
        weight_{i}/sum_{j}^{N}(weight_{j}))
        
        weight_inv = X / weight
        
        sum_avg = sum_avg_frac / sum(weight0_inv)
                = sum_avg_frac / N*weight0_inv
        
        weight0_inv = X / weight0
        
        sum_avg = sum_avg_frac / N*weight0_inv
                = sum_{i}^{N}(weight_inv_{i} *
        weight_{i}/sum_{j}^{N}(weight_{j})) / N*weight0_inv
                = sum_{i}^{N}(X/weight_{i} *
        weight_{i}/sum_{j}^{N}(weight_{j})) / N*(X/weight0)
                = N*X / sum_{j}(weight_{j}) * weight0/N*X
                = weight0 / sum_{j}(weight_{j})

Exactly the unit we were looking for [weight0/sum(weight)]

 ( the extra weight0 matching the one we had in the per task normalised
   time )

I'm not sure all this is less complex than CFS, I'd be inclined to say
it is more so.

Also, I think you have an accumulating error on wakeup where you sync
with the global clock but fully discard the fraction.

Anyway, as said a more detailed explanation and certainly a proof of
your math would be nice. Is this something along the lines of what you
intended to convey?

If so, in the future please use more understandable language, we were
taught math for a reason :-)

Regards,
Peter

Re: CFS review

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> > Please also send me the output of this script:
> > 
> >   http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh
> 
> Send privately.

thanks. Just to make sure, while you said that your TSC was off on that 
laptop, the bootup log of yours suggests a working TSC:

  Time: tsc clocksource has been installed.

and still your fl.c testcases produces the top output that you've 
reported in your first mail? If so then this could be a regression. Or 
did you turn off the tsc manually via notsc? (or was it with a different 
.config or on a different machine)? Please help us figure this out 
exactly, we dont want a real regression go unnoticed.

If you can reproduce that problem with a working TSC then please 
generate a second cfs-debug-info.sh snapshot _while_ your fl+l workload 
is running and send that to me (i'll reply back to it publicly). Thanks,

	Ingo

Re: CFS review

[Roman Zippel]

Hi,

On Wed, 1 Aug 2007, Ingo Molnar wrote:

> > > in that case 'top' accounting symptoms similar to the above are not 
> > > due to the scheduler starvation you suspected, but due the effect of 
> > > a low-resolution scheduler clock and a tightly coupled 
> > > timer/scheduler tick to it.
> > 
> > Well, it magnifies the rounding problems in CFS.
> 
> why do you say that? 2.6.22 behaves similarly with a low-res 
> sched_clock(). This has nothing to do with 'rounding problems'!
> 
> i tried your fl.c and if sched_clock() is high-resolution it's scheduled 
> _perfectly_ by CFS:
> 
>    PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>   5906 mingo     20   0  1576  244  196 R 71.2  0.0   0:30.11 l
>   5909 mingo     20   0  1844  344  260 S  9.6  0.0   0:04.02 lt
>   5907 mingo     20   0  1844  508  424 S  9.5  0.0   0:04.01 lt
>   5908 mingo     20   0  1844  344  260 S  9.5  0.0   0:04.02 lt
> 
> if sched_clock() is low-resolution then indeed the 'lt' tasks will 
> "hide":
> 
>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>  2366 mingo     20   0  1576  248  196 R 99.9  0.0   0:07.95 loop_silent
>     1 root      20   0  2132  636  548 S  0.0  0.0   0:04.64 init
> 
> but that's nothing new. CFS cannot conjure up time measurement methods 
> that do not exist. If you have a low-res clock and if you create an app 
> that syncs precisely to the tick of that clock via timers that run off 
> that exact tick then there's nothing the scheduler can do about it. It 
> is false to charachterise this as 'sleeper starvation' or 'rounding 
> error' like you did. No amount of rounding logic can create a 
> high-resolution clock out of thin air.

Please calm down. You apparantly already get worked up about one of the 
secondary problems. I didn't say 'sleeper starvation' or 'rounding 
error', these are your words and it's your perception of what I said.

sched_clock() can have a low resolution, which can be a problem for the 
scheduler. This is all this program demonstrates. If and how this problem 
should be solved is a completely different issue, about which I haven't 
said anything yet and since it's not that important right now I'll leave 
it at that for now.

bye, Roman

Re: CFS review

[Andi Kleen]

On Wed, Aug 01, 2007 at 04:36:24PM +0200, Ingo Molnar wrote:
> 
> * Roman Zippel <zippel@linux-m68k.org> wrote:
> 
> > > jiffies based sched_clock should be soon very rare. It's probably 
> > > not worth optimizing for it.
> > 
> > I'm not so sure about that. sched_clock() has to be fast, so many 
> > archs may want to continue to use jiffies. [...]
> 
> i think Andi was talking about the vast majority of the systems out 
> there. For example, check out the arch demography of current Fedora 
> installs (according to the Smolt opt-in UUID based user metrics):

I meant that in many cases where the TSC is considered unreliable
today it'll be possible to use it anyways at least for sched_clock()
(and possibly even gtod()) 

The exception would be system which really have none, but there
should be very few of those.

-Andi

Re: CFS review

[Linus Torvalds]

On Wed, 1 Aug 2007, Andi Kleen wrote:

> Ingo Molnar <mingo@elte.hu> writes:
> 
> > thanks. Just to make sure, while you said that your TSC was off on that 
> > laptop, the bootup log of yours suggests a working TSC:
> > 
> >   Time: tsc clocksource has been installed.
> 
> Standard kernels often disable the TSC later after running a bit 
> with it (e.g. on any cpufreq change without p state invariant TSC) 

I assume that what Roman hit was that he had explicitly disabled the TSC 
because of TSC instability with the "notsc" kernel command line. Which 
disabled is *entirely*.

That *used* to be the right thing to do, since the gettimeofday() logic 
originally didn't know about TSC instability, and it just resulted in 
somewhat flaky timekeeping.

These days, of course, we should notice it on our own, and just switch 
away from the TSC as a reliable clock-source, but still allow it to be 
used for the cases where absolute accuracy is not a big issue.

So I suspect that Roman - by virtue of being an old-timer - ends up having 
a workaround for an old problem that isn't needed, and that in turn ends 
up meaning that his scheduler clock also ends up using the really not very 
good timer tick..

			Linus

Re: CFS review

[Andi Kleen]

Ingo Molnar <mingo@elte.hu> writes:

> thanks. Just to make sure, while you said that your TSC was off on that 
> laptop, the bootup log of yours suggests a working TSC:
> 
>   Time: tsc clocksource has been installed.

Standard kernels often disable the TSC later after running a bit 
with it (e.g. on any cpufreq change without p state invariant TSC) 

-Andi

Re: CFS review

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> > i tried your fl.c and if sched_clock() is high-resolution it's scheduled 
> > _perfectly_ by CFS:
> > 
> >    PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
> >   5906 mingo     20   0  1576  244  196 R 71.2  0.0   0:30.11 l
> >   5909 mingo     20   0  1844  344  260 S  9.6  0.0   0:04.02 lt
> >   5907 mingo     20   0  1844  508  424 S  9.5  0.0   0:04.01 lt
> >   5908 mingo     20   0  1844  344  260 S  9.5  0.0   0:04.02 lt
> > 
> > if sched_clock() is low-resolution then indeed the 'lt' tasks will 
> > "hide":
> > 
> >   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
> >  2366 mingo     20   0  1576  248  196 R 99.9  0.0   0:07.95 loop_silent
> >     1 root      20   0  2132  636  548 S  0.0  0.0   0:04.64 init
> > 
> > but that's nothing new. CFS cannot conjure up time measurement 
> > methods that do not exist. If you have a low-res clock and if you 
> > create an app that syncs precisely to the tick of that clock via 
> > timers that run off that exact tick then there's nothing the 
> > scheduler can do about it. It is false to charachterise this as 
> > 'sleeper starvation' or 'rounding error' like you did. No amount of 
> > rounding logic can create a high-resolution clock out of thin air.
> 
> [...] I didn't say 'sleeper starvation' or 'rounding error', these are 
> your words and it's your perception of what I said.

Oh dear :-) It was indeed my preception that yesterday you said:

| A problem here is that this can be exploited, if a job is spread over 
|                        ^^^^^^^^^^^^^^^^^^^^^
| a few threads, they can get more time relativ to other tasks, e.g. in 
|                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| this example there are three tasks that run only for about 1ms every 
| 3ms, but they get far more time than should have gotten fairly:
|          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
| 4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
| 4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
| 4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
| 4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l

 [ http://lkml.org/lkml/2007/7/31/668 ]

( the underlined portion, in other words, is called 'starvation'.)

And again today, i clearly perceived you to say:

| > in that case 'top' accounting symptoms similar to the above are not 
| > due to the scheduler starvation you suspected, but due the effect of 
| > a low-resolution scheduler clock and a tightly coupled 
| > timer/scheduler tick to it.
|
| Well, it magnifies the rounding problems in CFS.

 [ http://lkml.org/lkml/2007/8/1/153 ]

But you are right, that must be my perception alone, you couldnt 
possibly have said any of that =B-)

Or are you perhaps one of those who claims that saying something 
analogous to sleeper starvation does not equal to talking about 'sleeper 
starvation' and saying something about 'rounding problems in CFS' does 
in no way mean you were talking about rounding errors? :-)

	Ingo

Re: CFS review

[Andi Kleen]

> I assume that what Roman hit was that he had explicitly disabled the TSC 
> because of TSC instability with the "notsc" kernel command line. Which 
> disabled is *entirely*.

It might just have been cpufreq. That nearly hits everybody with cpufreq
unless you have a pstate invariant TSC; and that's pretty much
always the case on older laptops.

It used to not be that drastic, but since i386 switched to the
generic clock frame work it is like that :/

> These days, of course, we should notice it on our own, and just switch 
> away from the TSC as a reliable clock-source, but still allow it to be 
> used for the cases where absolute accuracy is not a big issue.

The rewritten sched_clock() i still have queued does just that. I planned
to submit it for .23, but then during later in deepth testing
on my machine park I found a show stopper that I couldn't fix on time.
Hopefully for .24

-Andi

Re: CFS review

[Ingo Molnar]

* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Wed, 1 Aug 2007, Andi Kleen wrote:
> 
> > Ingo Molnar <mingo@elte.hu> writes:
> > 
> > > thanks. Just to make sure, while you said that your TSC was off on that 
> > > laptop, the bootup log of yours suggests a working TSC:
> > > 
> > >   Time: tsc clocksource has been installed.
> > 
> > Standard kernels often disable the TSC later after running a bit 
> > with it (e.g. on any cpufreq change without p state invariant TSC) 
> 
> I assume that what Roman hit was that he had explicitly disabled the 
> TSC because of TSC instability with the "notsc" kernel command line. 
> Which disabled is *entirely*.

but that does not appear to be the case, the debug info i got from Roman 
includes the following boot options:

  Kernel command line: auto BOOT_IMAGE=2.6.23-rc1-git9 ro root=306

there's no "notsc" option there.

Andi's theory cannot be true either, Roman's debug info also shows this 
/proc/<PID>/sched data:

  clock-delta              :                  95

that means that sched_clock() is in high-res mode, the TSC is alive and 
kicking and a sched_clock() call took 95 nanoseconds.

Roman, could you please help us with this mystery?

	Ingo

Re: CFS review

[Roman Zippel]

Hi,

On Wed, 1 Aug 2007, Ingo Molnar wrote:

> Andi's theory cannot be true either, Roman's debug info also shows this 
> /proc/<PID>/sched data:
> 
>   clock-delta              :                  95
> 
> that means that sched_clock() is in high-res mode, the TSC is alive and 
> kicking and a sched_clock() call took 95 nanoseconds.
> 
> Roman, could you please help us with this mystery?

Actually, Andi is right. What I sent you was generated directly after 
boot, as I had to reboot for the right kernel, so a little later appeared 
this:

Aug  1 14:54:30 spit kernel: eth0: link up, 100Mbps, full-duplex, lpa 0x45E1
Aug  1 15:09:56 spit kernel: Clocksource tsc unstable (delta = 656747233 ns)
Aug  1 15:09:56 spit kernel: Time: pit clocksource has been installed.

bye, Roman

Re: CFS review

[Roman Zippel]

Hi,

On Wed, 1 Aug 2007, Ingo Molnar wrote:

> > [...] I didn't say 'sleeper starvation' or 'rounding error', these are 
> > your words and it's your perception of what I said.
> 
> Oh dear :-) It was indeed my preception that yesterday you said:

*sigh* and here you go off again nitpicking on a minor issue just to prove 
your point...
When I wrote the earlier stuff I hadn't realized it was resolution 
related, so things have to be put into proper context and you make it 
yourself a little easy by equating them.
Yippi, you found another small error I made, can we drop this now? Please?

bye, Roman

Re: CFS review

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> Hi,
> 
> On Wed, 1 Aug 2007, Ingo Molnar wrote:
> 
> > Andi's theory cannot be true either, Roman's debug info also shows this 
> > /proc/<PID>/sched data:
> > 
> >   clock-delta              :                  95
> > 
> > that means that sched_clock() is in high-res mode, the TSC is alive and 
> > kicking and a sched_clock() call took 95 nanoseconds.
> > 
> > Roman, could you please help us with this mystery?
> 
> Actually, Andi is right. What I sent you was generated directly after 
> boot, as I had to reboot for the right kernel, so a little later 
> appeared this:
> 
> Aug  1 14:54:30 spit kernel: eth0: link up, 100Mbps, full-duplex, lpa 0x45E1
> Aug  1 15:09:56 spit kernel: Clocksource tsc unstable (delta = 656747233 ns)
> Aug  1 15:09:56 spit kernel: Time: pit clocksource has been installed.

just to make sure, how does 'top' output of the l + "lt 3" testcase look 
like now on your laptop? Yesterday it was this:

 4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
 4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
 4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
 4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l

and i'm still wondering how that output was possible.

	Ingo

Re: CFS review

[Linus Torvalds]

On Wed, 1 Aug 2007, Roman Zippel wrote:
> 
> I'm not so sure about that. sched_clock() has to be fast, so many archs 
> may want to continue to use jiffies. As soon as one does that one can also 
> save a lot of computational overhead by using 32bit instead of 64bit.
> The question is then how easy that is possible.

I have to say, it would be interesting to try to use 32-bit arithmetic.

I also think it's likely a mistake to do a nanosecond resolution. That's 
part of what forces us to 64 bits, and it's just not even an *interesting* 
resolution.

It would be better, I suspect, to make the scheduler clock totally 
distinct from the other clock sources (many architectures have per-cpu 
cycle counters), and *not* try to even necessarily force it to be a 
"time-based" one.

So I think it would be entirely appropriate to

 - do something that *approximates* microseconds.

   Using microseconds instead of nanoseconds would likely allow us to do 
   32-bit arithmetic in more areas, without any real overflow.

   And quite frankly, even on fast CPU's, the scheduler is almost 
   certainly not going to be able to take any advantage of the nanosecond 
   resolution. Just about anything takes a microsecond - including IO. I 
   don't think nanoseconds are worth the ten extra bits they need, if we 
   could do microseconds in 32 bits.

   And the "approximates" thing would be about the fact that we don't 
   actually care about "absolute" microseconds as much as something that 
   is in the "roughly a microsecond" area. So if we say "it doesn't have 
   to be microseconds, but it should be within a factor of two of a ms", 
   we could avoid all the expensive divisions (even if they turn into 
   multiplications with reciprocals), and just let people *shift* the CPU 
   counter instead.

   In fact, we could just say that we don't even care about CPU counters 
   that shift frequency - so what? It gets a bit further off the "ideal 
   microsecond", but the scheduler just cares about _relative_ times 
   between tasks (and that the total latency is within some reasonable 
   value), it doesn't really care about absolute time.

Hmm?

It would still be true that something that is purely based on timer ticks 
will always be liable to have rounding errors that will inevitably mean 
that you don't get good fairness - tuning threads to run less than a timer 
tick at a time would effectively "hide" them from the scheduler 
accounting. However, in the end, I think that's pretty much unavoidable. 
We should make sure that things mostly *work* for that situation, but I 
think it's ok to say that the *quality* of the fairness will obviously 
suffer (and possibly a lot in the extreme cases).

			Linus

Re: CFS review

[Willy Tarreau]

On Wed, Aug 01, 2007 at 07:17:51PM -0700, Linus Torvalds wrote:
> 
> 
> On Wed, 1 Aug 2007, Roman Zippel wrote:
> > 
> > I'm not so sure about that. sched_clock() has to be fast, so many archs 
> > may want to continue to use jiffies. As soon as one does that one can also 
> > save a lot of computational overhead by using 32bit instead of 64bit.
> > The question is then how easy that is possible.
> 
> I have to say, it would be interesting to try to use 32-bit arithmetic.
> 
> I also think it's likely a mistake to do a nanosecond resolution. That's 
> part of what forces us to 64 bits, and it's just not even an *interesting* 
> resolution.

I would add that I have been bothered by the 64-bit arithmetics when
trying to see what could be improved in the code. In fact, it's very
hard to optimize anything when you have arithmetics on integers larger
than the CPU's, and gcc is known not to emit very good code in this
situation (I remember it could not play with registers renaming, etc...).

However, I undertand why Ingo chose to use 64 bits. It has the advantage
that the numbers never wrap within 584 years. I'm well aware that it's
very difficult to keep tasks ordered according to a key which can wrap.

But if we consider that we don't need to be more precise than the return
value from gettimeofday() that all applications use, we see that a bunch
of microseconds is enough. 32 bits at the microsecond level wraps around
every hour. We may accept to recompute all keys every hour. It's not that
dramatic. The problem is how to detect that we will need to.

I remember a trick used by Tim Schmielau in his jiffies64 patch for 2.4.
He kept a copy of the highest bit of the lower word in the lowest bit of
the higher word, and considered that the lower one could not wrap before
we could check it. I liked this approach, which could be translated here
in something like the following :

Have all keys use 32-bit resolution, and monitor the 32nd bit. All tasks
must have the same value in this bit, otherwise we consider that their
keys have wrapped. The "current" value of this bit is copied somewhere.
When we walk the tree and find a task with a key which does not have its
32nd bit equal to the current value, it means that this key has wrapped,
so we have to use this information in our arithmetics.

When all keys have their 32nd bit different from the "current" value,
then we switch this value to reflect the new 32nd bit, and everything is
in sync again. The only requirement is that no key wraps around before
the "current" value is switched. This implies that no couple of tasks
could have their keys distant by more than 31 bits (35 minutes), which
seems reasonable. If we can recompute all tasks' keys when all of them
have wrapped, then we do not have to store the "current" bit value
anymore, and consider that it is always zero instead (I don't know if
the code permits this).

It is possible that using the 32nd bit to detect the wrapping may impose
us to perform some computations on 33 bits. If this is the case, then it
would be fine if we reduced the range to 31 bits, with all tasks distant
from at most 30 bits (17 minutes).

Also, I remember that the key is signed. I've never experimented with the
tricks above on signed values, but we might be able to define something
like this for the higher bits :

  00 = positive, no wrap
  01 = positive, wrapped
  10 = negative, wrapped
  11 = negative, no wrap

I have no code to show, I just wanted to expose this idea. I know that if
Ingo likes it, he will beat everyone at implementing it ;-)

> 			Linus

Willy

Re: CFS review

[Willy Tarreau]

On Thu, Aug 02, 2007 at 12:43:29PM +0200, Andi Kleen wrote:
> > However, I undertand why Ingo chose to use 64 bits. It has the advantage
> > that the numbers never wrap within 584 years. I'm well aware that it's
> > very difficult to keep tasks ordered according to a key which can wrap.
> 
> If you define an appropiate window and use some macros for the comparisons
> it shouldn't be a big problem.

It should not, but the hardest thing is often to keep values sorted within a
window. When you store your values in a tree according to a key, it's not
always easy to do find the first one relative to a sliding offset.

> > But if we consider that we don't need to be more precise than the return
> > value from gettimeofday() that all applications use,
> 
> gettimeofday() has too strict requirements, that make it unnecessarily slow
> for this task.

maybe we would use (TSC >> (x bits)) when TSC is available, or jiffies in other
cases. I believe that people not interested in high time accuracies are not
much interested in perfect fairness either. However, we should do the best to
avoid any form of starvation, otherwise we jump back to the problem with the
current scheduler.

> > every hour. We may accept to recompute all keys every hour.
> 
> You don't need to recompute keys; just use careful comparisons using
> subtractions and a window. TCPs have done that for decades. 
> 
> > Have all keys use 32-bit resolution, and monitor the 32nd bit. All tasks
> 
> If you're worried about wrapping in one hour why is wrapping in two
> hours not a problem? 

I've not said I was worried about that (or maybe I explained myself poorly).
Even if it was once a minute, it would not bother me. I wanted to explain
that if the solution requires to do it that often, it should be acceptable.

> I have one request though. If anybody adds anything complicated
> for this please make it optional so that 64bit platforms are not 
> burdened by it.

Fair enough. But the solution is not there yet. Maybe once it's there, it
will be better than current design for all platforms and the only difference
will be the accuracy due to optional use of the TSC.

> -Andi

Willy

Re: CFS review

[Andi Kleen]

Willy Tarreau <w@1wt.eu> writes:

>(I remember it could not play with registers renaming, etc...).

This has changed in recent gccs. It doesn't force register pairs anymore.
Given the code is still not that good, but some of the worst sins are gone

> However, I undertand why Ingo chose to use 64 bits. It has the advantage
> that the numbers never wrap within 584 years. I'm well aware that it's
> very difficult to keep tasks ordered according to a key which can wrap.

If you define an appropiate window and use some macros for the comparisons
it shouldn't be a big problem.

> But if we consider that we don't need to be more precise than the return
> value from gettimeofday() that all applications use,

gettimeofday() has too strict requirements, that make it unnecessarily slow
for this task.

> every hour. We may accept to recompute all keys every hour.

You don't need to recompute keys; just use careful comparisons using
subtractions and a window. TCPs have done that for decades. 

> Have all keys use 32-bit resolution, and monitor the 32nd bit. All tasks

If you're worried about wrapping in one hour why is wrapping in two
hours not a problem? 

I have one request though. If anybody adds anything complicated
for this please make it optional so that 64bit platforms are not 
burdened by it.

-Andi

Re: CFS review

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> [...] With the increased text comes increased runtime memory usage, 
> e.g. task_struct increased so that only 5 of them instead 6 fit now 
> into 8KB.

yeah, thanks for the reminder, this is on my todo list. As i suspect you 
noticed it too, much of the task_struct size increase is not fundamental 
and not related to 64-bit math at all - it's simply debug and 
instrumentation overhead.

Look at the following table (i386, nodebug):

                         size 
                         ----
    pre-CFS              1328
        CFS              1472
        CFS+patch        1376 

the very small patch below gets rid of 96 bytes. And that's only the
beginning.

	Ingo

-------------------------------------------------->
---
 include/linux/sched.h |   21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

Index: linux/include/linux/sched.h
===================================================================
--- linux.orig/include/linux/sched.h
+++ linux/include/linux/sched.h
@@ -905,23 +905,28 @@ struct sched_entity {
 	struct rb_node		run_node;
 	unsigned int		on_rq;
 
+	u64			exec_start;
+	u64			sum_exec_runtime;
 	u64			wait_start_fair;
+	u64			sleep_start_fair;
+
+#ifdef CONFIG_SCHEDSTATS
 	u64			wait_start;
-	u64			exec_start;
+	u64			wait_max;
+	s64			sum_wait_runtime;
+
 	u64			sleep_start;
-	u64			sleep_start_fair;
-	u64			block_start;
 	u64			sleep_max;
+	s64			sum_sleep_runtime;
+
+	u64			block_start;
 	u64			block_max;
 	u64			exec_max;
-	u64			wait_max;
-	u64			last_ran;
 
-	u64			sum_exec_runtime;
-	s64			sum_wait_runtime;
-	s64			sum_sleep_runtime;
 	unsigned long		wait_runtime_overruns;
 	unsigned long		wait_runtime_underruns;
+#endif
+
 #ifdef CONFIG_FAIR_GROUP_SCHED
 	struct sched_entity	*parent;
 	/* rq on which this entity is (to be) queued: */

Re: CFS review

[Ingo Molnar]

* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> It would be better, I suspect, to make the scheduler clock totally 
> distinct from the other clock sources (many architectures have per-cpu 
> cycle counters), and *not* try to even necessarily force it to be a 
> "time-based" one.

yeah. Note that i largely detached sched_clock() from the GTOD 
clocksources already in CFS, so part of this is already implemented and 
the intention is clear. For example, when the following happens:

   Marking TSC unstable due to: possible TSC halt in C2.
   Clocksource tsc unstable (delta = -71630388 ns)

sched_clock() does _not_ stop using the TSC. It is very careful with the 
TSC value, it checks against wraps, jumping, etc. (the whole rq_clock() 
wrapper around sched_clock()), but still tries to use the highest 
resolution time source possible, even if that time source is not good 
enough for GTOD's purposes anymore. So the scheduler clock is already 
largely detached from other clocksources in the system.

> It would still be true that something that is purely based on timer 
> ticks will always be liable to have rounding errors that will 
> inevitably mean that you don't get good fairness - tuning threads to 
> run less than a timer tick at a time would effectively "hide" them 
> from the scheduler accounting. However, in the end, I think that's 
> pretty much unavoidable.

Note that there is a relatively easy way of reducing the effects of such 
intentional coupling: turn on CONFIG_HIGH_RES_TIMERS. That decouples the 
scheduler tick from the jiffy tick and works against such 'exploits' - 
_even_ if the scheduler clock is otherwise low resolution. Also enable 
CONFIG_NO_HZ and the whole thing (of when the scheduler tick kicks in) 
becomes very hard to predict.

[ So while in a low-res clock situation scheduling will always be less 
  precise, with hres-timers and dynticks we have a natural 'random 
  sampler' mechanism so that no task can couple to the scheduler tick - 
  accidentally or even intentionally.

  The only 'unavoidable coupling' scenario is when the hardware has only 
  a single, low-resolution time sampling method. (that is pretty rare 
  though, even in the ultra-embedded space. If a box has two independent 
  hw clocks, even if they are low resolution, the timer tick can be
  decoupled from the scheduler tick.) ]

> I have to say, it would be interesting to try to use 32-bit 
> arithmetic.

yeah. We tried to do as much of that as possible, please read on below 
for (many) more details. There's no short summary i'm afraid :-/

Most importantly, CFS _already_ includes a number of measures that act 
against too frequent math. So even though you can see 64-bit math code 
in it, it's only rarely called if your clock has a low resolution - and 
that happens all automatically! (see below the details of this buffered 
delta math)

I have not seen Roman notice and mention any of these important details 
(perhaps because he was concentrating on finding faults in CFS - which a 
reviewer should do), but those measures are still very important for a 
complete, balanced picture, especially if one focuses on overhead on 
small boxes where the clock is low-resolution.

As Peter has said it in his detailed review of Roman's suggested 
algorithm, our main focus is on keeping total complexity down - and we 
are (of course) fundamentally open to changing the math behind CFS, we 
ourselves tweaked it numerous times, it's not cast into stone in any 
way, shape or form.

> I also think it's likely a mistake to do a nanosecond resolution. 
> That's part of what forces us to 64 bits, and it's just not even an 
> *interesting* resolution.

yes, very much not interesting, and we did not pick nanoseconds because 
we find anything "interesting" in that timescale. Firstly, before i go 
into the thinking behind nanoseconds, microseconds indeed have 
advantages too, so the choice was not easy, see the arguments in favor 
of microseconds below at: [*].

There are two fundamental reasons for nanoseconds:

 1) they _automatically_ act as a 'carry-over' for fractional math and
    thus reduce rounding errors. As Roman has noticed we dont care much
    about math rounding errors in the algorithm: _exactly_ because we
    *dont have to* care about rounding errors: we've got extra 10
    "uninteresting" bits in the time variables to offset the effects of 
    rounding errors and to carry over fractionals.

    ( Sidenote: in fact we had some simple extra anti-rounding-error 
      code in CFS and removed it because it made no measurable 
      difference. So even in the current structure there's additional 
      design reserves that we could tap before having to go to another 
      math model. All we need is a testcase that demonstrates rounding 
      errors. Roman's testcase was _not_ a demonstration of math 
      rounding errors, it was about clock granularity! )

 2) i tried microseconds resolution once (it's easy) but on fast hw it 
    already showed visible accounting/rounding artifacts in 
    high-frequency scheduling workloads, which, if hw gets just a little 
    bit faster, will become pain.

    ( Sidenote: if a workload is rescheduling once every few 
      microseconds, then it very much matters to the balance of things 
      whether there's a fundamental +- 1 microsecond skew on who gets 
      accounted what. In fact the placement of sched_clock() call within 
      schedule() is already visible in practice in some testcases, 
      whether the runqueue-spinlock acquire spinning time is accounted 
      to the 'previous' or the 'next' task - despite that time being 
      sub-microsecond on average. Going to microseconds makes this too 
      coarse. )

I.e. microseconds are on the limit today on fast hardware, and 
nanoseconds give us an automatic buffer against rounding errors.

On _slow_ hardware, with a low-resolution clock, i very much agree that 
we should not do too frequent math, and there are already four 
independent measures that we did in CFS to keep the math overhead down:

Firstly, CFS fundamentally "buffers the math" via deltas, _everywhere_ 
in the fastpath:

        if (unlikely(curr->delta_exec > sysctl_sched_stat_granularity)) {
                __update_curr(cfs_rq, curr, now);
                curr->delta_exec = 0;
        }

I.e. we only call the math routines if there was any delta. The beauty 
is that this "math buffering" works _automatically_ if there is a 
low-resolution sched_clock() present, because with a low-resolution 
clock a delta is only observed if a tick happens. I.e. in a 
high-frequency scheduling workload (the only place where scheduler 
overhead would be noticeable) all the CFS math is in a rare _slowpath_, 
that gets triggered only every 10 msecs or so! (if HZ=1000)

I.e. we didnt have to go down the (very painful) path of ktime_t 
split-model math and we didnt have to introduce a variable precision 
model for "scheduler time" either, because the delta math itself 
automatically buffers on slow boxes.

Secondly, note that all the key fastpath variables are already 32-bit 
(on 32-bit platforms):

        long                    wait_runtime;
        unsigned long           delta_fair_run;
        unsigned long           delta_fair_sleep;
        unsigned long           delta_exec;

The _timestamps_ are still 64-bit, but most of the actual math goes on 
in 32-bit delta variables. That's one of the advantages of doing deltas 
instead of absolute values.

Thirdly, if even this amount of buffering is not enough for an 
architecture, CFS also includes the sched_stat_granularity_ns tunable 
that allows the further reduction of the sampling frequency (and the 
frequency of us having to do the math) - so if the math overhead is a 
problem an architecture can set it.

Fourthly, in CFS there is a _single_ 64-bit division, and even for that 
division, the actual values passed to it are typically in a 32-bit 
range. Hence we've introduced the following optimization:

  static u64 div64_likely32(u64 divident, unsigned long divisor)
  {
  #if BITS_PER_LONG == 32
          if (likely(divident <= 0xffffffffULL))
                  return (u32)divident / divisor;
          do_div(divident, divisor);

          return divident;
  #else
          return divident / divisor;
  #endif
  }

Which, if the divident is in 32-bit range, does a 32-bit division.

About math related rounding errors mentioned by Roman (not to be 
confused with clock granularity rounding), in our analysis and in our 
experience rounding errors of the math were never an issue in CFS, due 
to the extra buffering that nanosecs gives - i tweaked it a bit around 
CFSv10 but it was unprovable to have any effect. That's one of the 
advantages of working with nanoseconds: the fundamental time unit 
includes about 10 "low bits" that can carry over much of the error and 
reduce rounding artifacts. And even that math rounding errors we believe 
centers around 0.

In Roman's variant of CFS's algorithm the variables are 32-bit, but the 
error is rolled forward in separate fract_* (fractional) 32-bit 
variables, so we still have 32+32==64 bit of stuff to handle. So we 
think that in the end such a 32+32 scheme would be more complex (and 
anyone who took a look at fs2.c would i think agree - it took Peter a 
day to decypher the math!) - but we'll be happy to be surprised with 
patches of course :-)

	Ingo

[*] the main advantage of microseconds would be that we could use "u32"
    throughout to carry around the "now" variable (timestamp). That 
    property of microseconds _is_ tempting and would reduce the 
    task_struct footprint as well. But if we did that it would have
    ripple effects: we'd have to resort to (pretty complex and 
    non-obvious) math to act against rounding errors. We'd either have 
    to carry the rounding error with us in separate 32-bit variables (in 
    essence creating 32+32 bit 64-bit variable), or we'd have to shift 
    up the microseconds by say ... 10 binary positions ... in essence 
    bringing us back into the same nanoseconds range. And then the 
    wraparound problem of microseconds - 72 hours is not _that_ 
    unrealistic to trigger intentionally, so we have to do _something_
    about it to inhibit infinite starvation. We experimented
    around with all this and the overwhelming conclusion (so far) was 
    that trying to reduce timestamps back to 32 bits is just not worth 
    it. _Deltas_ should, can and _are_ 32-bit values already, even in 
    the nanosecond model. So all the buffering and delta logic gives us
    most of the 32-bit advantages already, without the disadvantages of
    microseconds.

Re: CFS review

[Roman Zippel]

Hi,

On Wed, 1 Aug 2007, Peter Zijlstra wrote:

> Took me most of today trying to figure out WTH you did in fs2.c, more
> math and fundamental explanations would have been good. So please bear
> with me as I try to recap this thing. (No, your code was very much _not_
> obvious, a few comments and broken out functions would have made a world
> of a difference)

Thanks for the effort though. :)
I know I'm not the best explaining these things, so I really appreciate 
the questions, so I know what to concentrate on.

> So, for each task we keep normalised time
> 
>  normalised time := time/weight
> 
> using Bresenham's algorithm we can do this prefectly (up until a renice
> - where you'd get errors)
> 
>         avg_frac += weight_inv
>         
>         weight_inv = X / weight
>         
>         avg = avg_frac / weight0_inv
>         
>         weight0_inv = X / weight0
>         
>         avg = avg_frac / (X / weight0) 
>             = (X / weight) / (X / weight0) 
>             = X / weight * weight0 / X 
>             = weight0 / weight
>         
> 
> So avg ends up being in units of [weight0/weight].
> 
> Then, in order to allow sleeping, we need to have a global clock to sync
> with. Its this global clock that gave me headaches to reconstruct.
> 
> We're looking for a time like this:
> 
>   rq_time := sum(time)/sum(weight)
> 
> And you commented that the /sum(weight) part is where CFS obtained its
> accumulating rounding error? (I'm inclined to believe the error will
> statistically be 0, but I'll readily accept otherwise if you can show a
> practical 'exploit')
> 
> Its not obvious how to do this using modulo logic like Bresenham because
> that would involve using a gcm of all possible weights.

I think I've sent you off into the wrong direction somehow. Sorry. :)

Let's ignore the average for a second, normalized time is maintained as:

	normalized time := time * (2^16 / weight)

The important point is that I keep the value in full resolution of 2^-16 
vsec units (vsec for virtual second or sec/weight, where every tasks gets 
weight seconds for every virtual second, to keep things simpler I also 
omit the nano prefix from the units for a moment). Compared to that CFS 
maintains a global normalized value in 1 vsec units.
Since I don't round the value down I avoid the accumulating error, this 
means that 

	time_norm += time_delta1 * (2^16 / weight)
	time_norm += time_delta2 * (2^16 / weight)

is the same as

	time_norm += (time_delta1 + time_delta2) * (2^16 / weight)

CFS for example does this

	delta_mine = calc_delta_mine(delta_exec, curr->load.weight, lw);

in above terms this means

	time = time_delta * weight * (2^16 / weight_sum) / 2^16

The last shift now rounds the value down and if one does that 1000 times 
per second, the resolution of the value that is finally accounted to 
wait_runtime is also reduced appropriately.

The other rounding problem is based on that this term

	x * prio_to_weight[i] * prio_to_wmult[i] / 2^32

doesn't produce x for most values in that tables (the same applies to the 
weight sum), so if we have chains, where the values are converted from one 
scale to the other, a rounding error is produced. In CFS this happens now 
because wait_runtime is maintained in nanoseconds and fair_clock is a 
normalized value.

The problem here isn't that these errors might have a statistical 
relevance, as they are usually completely overshadowed by measurement 
errors anyway. The problem is that these errors exist at all, this means 
they have to be compensated somehow, so that they don't accumulate over 
time and then become significant. This also has to be seen in the context 
of the overflow checks. All this adds a number of variables to the system 
which considerably increases complexity and makes a thorough analysis 
quite challenging.

So to get back to the average, if you look for this

	rq_time := sum(time)/sum(weight)

you won't find it like this, this basically produces a weighted average 
and I agree this can't really be maintained via the modulo logic (at least 
AFAICT), so I'm using a simple average instead, so if we have:

	time_norm = time/weight

we can write your rq_time like this:

	weighted_avg = sum_{i}^{N}(time_norm_{i}*weight_{i})/sum_{i}^{N}(weight_{i})

this is the formula for a weighted average, so we can aproximate the value 
using a simple average instead:

	avg = sum_{i}^{N}(time_norm_{i})/N

This sum is now what I maintain at runtime incrementally:

	time_{i} = sum_{j}^{S}(time_{j})

	time_norm_{i} = time_{i}/weight_{i}
	              = sum_{j}^{S}(time_{j})/weight_{i}
	              = sum_{j}^{S}(time_{j}/weight_{i})

If I add this up and add weigth0 I get:

	avg*N*weigth0 = sum_{i}^{N}(time_norm_{i})*weight0

and now I have also the needed modulo factors.

The average probably could be further simplified by using a different 
approximation. The question is how perfect this average has to be. The 
average is only used to control when a task gets its share, currently 
higher priority tasks are already given a bit more preference or a sleep 
bonus is added.

In CFS the average already isn't perfect due to above rounding problems, 
otherwise the sum of all updated wait_runtime should be 0 and if a task 
with a wait_runtime value different from 0 is added, fair_clock would have 
to change too to keep the balance.

So unless someone has a brilliant idea, I guess we have to settle for the 
approximation of a perfect scheduler. :) My approach is insofar different 
that I at least maintain an accurate fair share and approximate based on 
this the scheduling decision. This has IMO the advantage that the 
scheduler function can be easily exchanged, one can do it the quick and 
dirty way or one can put in the extra effort to get it closer to 
perfection. Either way every task will get its fair share.

The scheduling function I used is rather simple:

	if (j >= 0 &&
	    ((int)(task[l].time_norm - (task[j].time_norm + SLICE(j))) >= 0 ||
	     ((int)(task[l].time_norm - task[j].time_norm) >= 0 &&
	      (int)(task[l].time_norm - (s + SLICE(l))) >= 0))) {

So a new task is selected if there is a higher priority task or if the 
task has used up its share (unless the other task has lower priority and 
already got its share). It would be interesting to use a dynamic (per 
task) time slice here, which should make it possible to control the 
burstiness that has been mentioned.

> I'm not sure all this is less complex than CFS, I'd be inclined to say
> it is more so.

The complexity is different, IMO the basic complexity to maintain the fair 
share is less and I can add arbitrary complexity to improve scheduling on 
top of it. Most of it comes now from maintaining the accurate average, it 
depends now on how the scheduling is finally done what other optimizations 
are possible.

> Also, I think you have an accumulating error on wakeup where you sync
> with the global clock but fully discard the fraction.

I hope not, otherwise the checks at the end should have triggered. :)
The per task requirement is

	time_norm = time_avg * weight0 + avg_fract

I don't simply discard it, it's accounted to time_norm and then synced to 
the global average.

bye, Roman

Re: CFS review

[Daniel Phillips]

Hi Linus,

On Wednesday 01 August 2007 19:17, Linus Torvalds wrote:
>    And the "approximates" thing would be about the fact that we don't
>    actually care about "absolute" microseconds as much as something
> that is in the "roughly a microsecond" area. So if we say "it doesn't
> have to be microseconds, but it should be within a factor of two of a
> ms", we could avoid all the expensive divisions (even if they turn
> into multiplications with reciprocals), and just let people *shift*
> the CPU counter instead.

On that theme, expressing the subsecond part of high precision time in 
decimal instead of left-aligned binary always was an insane idea.  
Applications end up with silly numbers of multiplies and divides 
(likely as not incorrect) whereas they would often just need a simple 
shift as you say, if the tv struct had been defined sanely from the 
start.  As a bonus, whenever precision gets bumped up, the new bits 
appear on the right in formerly zero locations on the right, meaning 
little if any code needs to change.  What we have in the incumbent libc 
timeofday scheme is the moral equivalent of BCD.

Of course libc is unlikely ever to repent, but we can at least put off 
converting into the awkward decimal format until the last possible 
instant.  In other words, I do not see why xtime is expressed as a tv 
instead of simple 32.32 fixed point.  Perhaps somebody can elucidate 
me?

Regards,

Daniel

Re: CFS review

[Roman Zippel]

Hi,

On Thu, 2 Aug 2007, Ingo Molnar wrote:

> Most importantly, CFS _already_ includes a number of measures that act 
> against too frequent math. So even though you can see 64-bit math code 
> in it, it's only rarely called if your clock has a low resolution - and 
> that happens all automatically! (see below the details of this buffered 
> delta math)
> 
> I have not seen Roman notice and mention any of these important details 
> (perhaps because he was concentrating on finding faults in CFS - which a 
> reviewer should do), but those measures are still very important for a 
> complete, balanced picture, especially if one focuses on overhead on 
> small boxes where the clock is low-resolution.
> 
> As Peter has said it in his detailed review of Roman's suggested 
> algorithm, our main focus is on keeping total complexity down - and we 
> are (of course) fundamentally open to changing the math behind CFS, we 
> ourselves tweaked it numerous times, it's not cast into stone in any 
> way, shape or form.

You're comparing apples with oranges, I explicitely said:

"At this point I'm not that much interested in a few localized 
optimizations, what I'm interested in is how can this optimized at the 
design level"

IMO it's very important to keep computational and algorithmic complexity 
separately, I want to concentrate on the latter, so unless you can _prove_ 
that a similiar set of optimizations is impossible within my example, I'm 
going to ignore them for now. CFS has already gone through several 
versions of optimization and tuning, expecting the same from my design 
prototype is a little confusing...

I want to analyze the foundation CFS is based on, in the review I 
mentioned a number of other issues and design related questions. If you 
need more time, that's fine, but I'd appreciate more background 
information related to that and not that you only jump on the more trivial 
issues.

> In Roman's variant of CFS's algorithm the variables are 32-bit, but the 
> error is rolled forward in separate fract_* (fractional) 32-bit 
> variables, so we still have 32+32==64 bit of stuff to handle. So we 
> think that in the end such a 32+32 scheme would be more complex (and 
> anyone who took a look at fs2.c would i think agree - it took Peter a 
> day to decypher the math!)

Come on, Ingo, you can do better than that, I did mention in my review 
some of the requirements for the data types.
I'm amazed how you can get to that judgement so quickly, could you please 
substantiate that a little more?

I admit that the lack of source comments is an open invitation for further 
questions and Peter did exactly this and his comments were great - I'm 
hoping for more like that. You OTOH jump to conclusions based on a partial 
understanding what I'm actually trying to do.
Ingo, how about you provide some of the mathematical prove CFS is based 
on? Can you prove that the rounding errors are irrelevant? Can you prove 
that all the limit checks can have no adverse effect? I tried that and I'm 
not entirely convinced of that, but maybe it's just me, so I'd love to see 
someone else's attempt at this.
A major goal of my design is it to be able to define the limits within the 
scheduler is working correctly, so I know which information is relevant 
and what can be approximated.

bye, Roman

Re: CFS review

[Roman Zippel]

Hi,

On Wed, 1 Aug 2007, Linus Torvalds wrote:

> So I think it would be entirely appropriate to
> 
>  - do something that *approximates* microseconds.
> 
>    Using microseconds instead of nanoseconds would likely allow us to do 
>    32-bit arithmetic in more areas, without any real overflow.

The basic problem is that one needs a number of bits (at least 16) for 
normalization, which limits the time range one can work with. This means 
that 32 bit leaves only room for 1 millisecond resolution, the remainder 
could maybe saved and reused later.
So AFAICT using micro- or nanosecond resolution doesn't make much 
computational difference.

bye, Roman

Re: CFS review

[Matt Mackall]

On Wed, Aug 01, 2007 at 01:22:29PM +0200, Ingo Molnar wrote:
> 
> * Roman Zippel <zippel@linux-m68k.org> wrote:
> 
> > [...] e.g. in this example there are three tasks that run only for 
> > about 1ms every 3ms, but they get far more time than should have 
> > gotten fairly:
> > 
> >  4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
> >  4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
> >  4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
> >  4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l
> 
> Mike and me have managed to reproduce similarly looking 'top' output, 
> but it takes some effort: we had to deliberately run a non-TSC 
> sched_clock(), CONFIG_HZ=100, !CONFIG_NO_HZ and !CONFIG_HIGH_RES_TIMERS.

..which is pretty much the state of play for lots of non-x86 hardware.

-- 
Mathematics is the supreme nostalgia of our time.

Re: CFS review

[Arjan van de Ven]

On Thu, 2007-08-02 at 22:04 -0500, Matt Mackall wrote:
> On Wed, Aug 01, 2007 at 01:22:29PM +0200, Ingo Molnar wrote:
> > 
> > * Roman Zippel <zippel@linux-m68k.org> wrote:
> > 
> > > [...] e.g. in this example there are three tasks that run only for 
> > > about 1ms every 3ms, but they get far more time than should have 
> > > gotten fairly:
> > > 
> > >  4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
> > >  4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
> > >  4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
> > >  4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l
> > 
> > Mike and me have managed to reproduce similarly looking 'top' output, 
> > but it takes some effort: we had to deliberately run a non-TSC 
> > sched_clock(), CONFIG_HZ=100, !CONFIG_NO_HZ and !CONFIG_HIGH_RES_TIMERS.
> 
> ..which is pretty much the state of play for lots of non-x86 hardware.

question is if it's significantly worse than before. With a 100 or
1000Hz timer, you can't expect perfect fairness just due to the
extremely rough measurement of time spent...

Re: CFS review

[Willy Tarreau]

On Thu, Aug 02, 2007 at 08:57:47PM -0700, Arjan van de Ven wrote:
> On Thu, 2007-08-02 at 22:04 -0500, Matt Mackall wrote:
> > On Wed, Aug 01, 2007 at 01:22:29PM +0200, Ingo Molnar wrote:
> > > 
> > > * Roman Zippel <zippel@linux-m68k.org> wrote:
> > > 
> > > > [...] e.g. in this example there are three tasks that run only for 
> > > > about 1ms every 3ms, but they get far more time than should have 
> > > > gotten fairly:
> > > > 
> > > >  4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
> > > >  4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
> > > >  4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
> > > >  4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l
> > > 
> > > Mike and me have managed to reproduce similarly looking 'top' output, 
> > > but it takes some effort: we had to deliberately run a non-TSC 
> > > sched_clock(), CONFIG_HZ=100, !CONFIG_NO_HZ and !CONFIG_HIGH_RES_TIMERS.
> > 
> > ..which is pretty much the state of play for lots of non-x86 hardware.
> 
> question is if it's significantly worse than before. With a 100 or
> 1000Hz timer, you can't expect perfect fairness just due to the
> extremely rough measurement of time spent...

Well, at least we're able to *measure* that task 'l' used 3.3% and
that tasks 'lt' used 32%. If we're able to measure it, then that's
already fine enough to be able to adjust future timeslices credits.
Granted it may be rough for small periods (a few jiffies), but it
should be fair for larger periods. Or at least it should *report*
some fair distribution.

Willy

Re: CFS review

[Arjan van de Ven]

On Fri, 2007-08-03 at 06:18 +0200, Willy Tarreau wrote:
> On Thu, Aug 02, 2007 at 08:57:47PM -0700, Arjan van de Ven wrote:
> > On Thu, 2007-08-02 at 22:04 -0500, Matt Mackall wrote:
> > > On Wed, Aug 01, 2007 at 01:22:29PM +0200, Ingo Molnar wrote:
> > > > 
> > > > * Roman Zippel <zippel@linux-m68k.org> wrote:
> > > > 
> > > > > [...] e.g. in this example there are three tasks that run only for 
> > > > > about 1ms every 3ms, but they get far more time than should have 
> > > > > gotten fairly:
> > > > > 
> > > > >  4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
> > > > >  4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
> > > > >  4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
> > > > >  4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l
> > > > 
> > > > Mike and me have managed to reproduce similarly looking 'top' output, 
> > > > but it takes some effort: we had to deliberately run a non-TSC 
> > > > sched_clock(), CONFIG_HZ=100, !CONFIG_NO_HZ and !CONFIG_HIGH_RES_TIMERS.
> > > 
> > > ..which is pretty much the state of play for lots of non-x86 hardware.
> > 
> > question is if it's significantly worse than before. With a 100 or
> > 1000Hz timer, you can't expect perfect fairness just due to the
> > extremely rough measurement of time spent...
> 
> Well, at least we're able to *measure* that task 'l' used 3.3% and
> that tasks 'lt' used 32%.

It's not measured if you use jiffies level stuff. It's at best sampled!

>  If we're able to measure it, then that's
> already fine enough to be able to adjust future timeslices credits.
> Granted it may be rough for small periods (a few jiffies), but it
> should be fair for larger periods. Or at least it should *report*

but the testcase here uses a LOT shorter time than jiffies... not "a few
jiffies".

-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org

Re: CFS review

[Matt Mackall]

On Thu, Aug 02, 2007 at 08:57:47PM -0700, Arjan van de Ven wrote:
> On Thu, 2007-08-02 at 22:04 -0500, Matt Mackall wrote:
> > On Wed, Aug 01, 2007 at 01:22:29PM +0200, Ingo Molnar wrote:
> > > 
> > > * Roman Zippel <zippel@linux-m68k.org> wrote:
> > > 
> > > > [...] e.g. in this example there are three tasks that run only for 
> > > > about 1ms every 3ms, but they get far more time than should have 
> > > > gotten fairly:
> > > > 
> > > >  4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
> > > >  4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
> > > >  4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
> > > >  4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l
> > > 
> > > Mike and me have managed to reproduce similarly looking 'top' output, 
> > > but it takes some effort: we had to deliberately run a non-TSC 
> > > sched_clock(), CONFIG_HZ=100, !CONFIG_NO_HZ and !CONFIG_HIGH_RES_TIMERS.
> > 
> > ..which is pretty much the state of play for lots of non-x86 hardware.
> 
> question is if it's significantly worse than before. With a 100 or
> 1000Hz timer, you can't expect perfect fairness just due to the
> extremely rough measurement of time spent...

Indeed. I'm just pointing out that not having TSC, fast HZ, no-HZ
mode, or high-res timers should not be treated as an unusual
circumstance. That's a PC-centric view.

-- 
Mathematics is the supreme nostalgia of our time.

Re: CFS review

[Willy Tarreau]

On Thu, Aug 02, 2007 at 09:31:19PM -0700, Arjan van de Ven wrote:
> On Fri, 2007-08-03 at 06:18 +0200, Willy Tarreau wrote:
> > On Thu, Aug 02, 2007 at 08:57:47PM -0700, Arjan van de Ven wrote:
> > > On Thu, 2007-08-02 at 22:04 -0500, Matt Mackall wrote:
> > > > On Wed, Aug 01, 2007 at 01:22:29PM +0200, Ingo Molnar wrote:
> > > > > 
> > > > > * Roman Zippel <zippel@linux-m68k.org> wrote:
> > > > > 
> > > > > > [...] e.g. in this example there are three tasks that run only for 
> > > > > > about 1ms every 3ms, but they get far more time than should have 
> > > > > > gotten fairly:
> > > > > > 
> > > > > >  4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
> > > > > >  4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
> > > > > >  4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
> > > > > >  4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l
> > > > > 
> > > > > Mike and me have managed to reproduce similarly looking 'top' output, 
> > > > > but it takes some effort: we had to deliberately run a non-TSC 
> > > > > sched_clock(), CONFIG_HZ=100, !CONFIG_NO_HZ and !CONFIG_HIGH_RES_TIMERS.
> > > > 
> > > > ..which is pretty much the state of play for lots of non-x86 hardware.
> > > 
> > > question is if it's significantly worse than before. With a 100 or
> > > 1000Hz timer, you can't expect perfect fairness just due to the
> > > extremely rough measurement of time spent...
> > 
> > Well, at least we're able to *measure* that task 'l' used 3.3% and
> > that tasks 'lt' used 32%.
> 
> It's not measured if you use jiffies level stuff. It's at best sampled!

But if we rely on the same sampling method, at least we will report
something consistent with what happens. And sampling is often the
correct method to get finer resolution on a macroscopic scale.

I mean, we're telling users that we include the "completely fair scheduler"
in 2.6.23, a scheduler which will ensure that all tasks get a fair share of
CPU time. A user starts top and sees 33%+32%+32+3% for 4 tasks while he
would have expected to see 25%+25%+25%+25%. You can try to explain users
that it's the fairest distribution, but they will have a hard time believing
it, especially when they measure the time spent on CPU with the "time"
command. OK this is all sampling, but we should try to avoid relying on
different sources of data for computation and reporting. Time and Top
should report something close to 4*25% for comparable tasks. And if not,
because of some sampling problem, maybe the scheduler cannot be that fair
in some situations, but either it should make use of the sampling time
and top use, or top and time should rely on the view of the scheduler.

I'll try to quickly hack up a program which makes use of rdtsc from
userspace to precisely measure user-space time, and disable TSC use
from the kernel to see how the values diverge.

Regards,
Willy

Re: CFS review

[Ingo Molnar]

* Matt Mackall <mpm@selenic.com> wrote:

> > question is if it's significantly worse than before. With a 100 or 
> > 1000Hz timer, you can't expect perfect fairness just due to the 
> > extremely rough measurement of time spent...
> 
> Indeed. I'm just pointing out that not having TSC, fast HZ, no-HZ 
> mode, or high-res timers should not be treated as an unusual 
> circumstance. That's a PC-centric view.

actually, you dont need high-res or fast HZ or TSC to reduce those timer 
artifacts: all you need is _two_ (low-res, slow) hw clocks.

Most platforms do have that (even the really really cheap ones), but 
arches do not set up the scheduler tick one of them and the timer tick 
to the other, and to skew the periodic-timer programming setup a bit (by 
nature of physics they are usually already skewed a bit) so that the 
scheduler tick and timer tick are not coupled. This whole thing is not a 
big deal on embedded anyway. (you dont get students log in to the 
toaster or to the fridge to run timer exploits, do you? :-)

	Ingo

Re: CFS review

[Andi Kleen]

Matt Mackall <mpm@selenic.com> writes:
> 
> Indeed. I'm just pointing out that not having TSC, fast HZ, no-HZ
> mode, or high-res timers should not be treated as an unusual
> circumstance. That's a PC-centric view.

The question is if it would be that hard to add TSC equivalent
sched_clock() support to more systems. At least a lot of CPUs I have
ever looked at had some kind of fast clock available. Perhaps it's
more laziness of the developers or cut'n'paste that these are not as
widely used as they should be?

-Andi

Re: [ck] Re: -mm merge plans for 2.6.23

[Nick Piggin]

Matthew Hawkins wrote:
> On 7/25/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> 
>>I guess /proc/meminfo, /proc/zoneinfo, /proc/vmstat, /proc/slabinfo
>>before and after the updatedb run with the latest kernel would be a
>>first step. top and vmstat output during the run wouldn't hurt either.
> 
> 
> Hi Nick,
> 
> I've attached two files with this kind of info.  Being up at the cron
> hours of the morning meant I got a better picture of what my system is
> doing.  Here's a short summary of what I saw in top:
> 
> beagleindexer used gobs of ram.  600M or so (I have 1G)

Hmm OK, beagleindexer. I thought beagle didn't need frequent reindexing
because of inotify? Oh well...


> updatedb didn't use much ram, but while it was running kswapd kept on
> frequenting the top 10 cpu hogs - it would stick around for 5 seconds
> or so then disappear for no more than 10 seconds, then come back
> again.  This behaviour persisted during the run.  updatedb ran third
> (beagleindexer was first, then update-dlocatedb)

Kswapd will use CPU when memory is low, even if there is no swapping.

Your "buffers" grew by 600% (from 50MB to 350MB), and slab also grew
by a few thousand entries. This is not just a problem when it pushes
out swap, it will also harm filebacked working set.

This (which Ray's traces also show) is a bit of a problem. As Andrew
noticed, use-once isn't working well for buffer cache, and it doesn't
really for dentry and inode cache either (although those don't seem
to be as much of a problem on your workload).

Andrew has done a little test patch for this in -mm, but it probably
wants more work and testing. If you can test the -mm kernel and see
if things are improved, that would help.

-- 
SUSE Labs, Novell Inc.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Nick Piggin]

david@lang.hm wrote:
> On Sun, 29 Jul 2007, Rene Herman wrote:
> 
>> On 07/29/2007 01:41 PM, david@lang.hm wrote:
>>
>>>  I agree that tinkering with the core VM code should not be done 
>>> lightly,
>>>  but this has been put through the proper process and is stalled with no
>>>  hints on how to move forward.
>>
>>
>> It has not. Concerns that were raised (by specifically Nick Piggin) 
>> weren't being addressed.
> 
> 
> I may have missed them, but what I saw from him weren't specific issues, 
> but instead a nebulous 'something better may come along later'

Something better, ie. the problems with page reclaim being fixed.
Why is that nebulous?

-- 
SUSE Labs, Novell Inc.

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[david]

On Mon, 6 Aug 2007, Nick Piggin wrote:

> david@lang.hm wrote:
>>  On Sun, 29 Jul 2007, Rene Herman wrote:
>> 
>> >  On 07/29/2007 01:41 PM, david@lang.hm wrote:
>> > 
>> > >  I agree that tinkering with the core VM code should not be done 
>> > >  lightly,
>> > >   but this has been put through the proper process and is stalled with 
>> > >   no
>> > >   hints on how to move forward.
>> > 
>> > 
>> >  It has not. Concerns that were raised (by specifically Nick Piggin) 
>> >  weren't being addressed.
>>
>>
>>  I may have missed them, but what I saw from him weren't specific issues,
>>  but instead a nebulous 'something better may come along later'
>
> Something better, ie. the problems with page reclaim being fixed.
> Why is that nebulous?

becouse that doesn't begin to address all the benifits.

the approach of fixing page reclaim and updatedb is pretending that if you 
only do everything right pages won't get pushed to swap in the first 
place, and therefor swap prefetch won't be needed.

this completely ignores the use case where the swapping was exactly the 
right thing to do, but memory has been freed up from a program exiting so 
that you couldnow fill that empty ram with data that was swapped out.

David Lang

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Nick Piggin]

--- david@lang.hm wrote:

> On Mon, 6 Aug 2007, Nick Piggin wrote:
> 
> > david@lang.hm wrote:
> >>  On Sun, 29 Jul 2007, Rene Herman wrote:
> >> 
> >> >  On 07/29/2007 01:41 PM, david@lang.hm wrote:
> >> > 
> >> > >  I agree that tinkering with the core VM code
> should not be done 
> >> > >  lightly,
> >> > >   but this has been put through the proper
> process and is stalled with 
> >> > >   no
> >> > >   hints on how to move forward.
> >> > 
> >> > 
> >> >  It has not. Concerns that were raised (by
> specifically Nick Piggin) 
> >> >  weren't being addressed.
> >>
> >>
> >>  I may have missed them, but what I saw from him
> weren't specific issues,
> >>  but instead a nebulous 'something better may
> come along later'
> >
> > Something better, ie. the problems with page
> reclaim being fixed.
> > Why is that nebulous?
> 
> becouse that doesn't begin to address all the
> benifits.

What do you mean "address the benefits"? What I want
to address is the page reclaim problems.


> the approach of fixing page reclaim and updatedb is
> pretending that if you 
> only do everything right pages won't get pushed to
> swap in the first 
> place, and therefor swap prefetch won't be needed.

You should read what I wrote.

Anyway, the fact of the matter is that there are still
fairly significant problems with page reclaim in this
workload which I would like to see fixed.

I personally still think some of the low hanging fruit
*might* be better fixed before swap prefetch gets
merged, but I've repeatedly said I'm sick of getting
dragged back into the whole debate so I'm happy with
whatever Andrew decides to do with it.

I think it is sad to turn it off for laptops, if it
really makes the "desktop" experience so much better.
Surely for _most_ workloads we should be able to
manage 1-2GB of RAM reasonably well.

 
> this completely ignores the use case where the
> swapping was exactly the 
> right thing to do, but memory has been freed up from
> a program exiting so 
> that you couldnow fill that empty ram with data that
> was swapped out.

Yeah. However, merging patches (especially when
changing heuristics, especially in page reclaim) is
not about just thinking up a use-case that it works
well for and telling people that they're putting their
heads in the sand if they say anything against it.
Read this thread and you'll find other examples of
patches that have been around for as long or longer
and also have some good use-cases and also have not
been merged.



      ____________________________________________________________________________________
Yahoo!7 Mail has just got even bigger and better with unlimited storage on all webmail accounts. 
http://au.docs.yahoo.com/mail/unlimitedstorage.html

Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Paolo Ciarrocchi]

On 8/6/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
[...]
> > this completely ignores the use case where the
> > swapping was exactly the
> > right thing to do, but memory has been freed up from
> > a program exiting so
> > that you couldnow fill that empty ram with data that
> > was swapped out.
>
> Yeah. However, merging patches (especially when
> changing heuristics, especially in page reclaim) is
> not about just thinking up a use-case that it works
> well for and telling people that they're putting their
> heads in the sand if they say anything against it.
> Read this thread and you'll find other examples of
> patches that have been around for as long or longer
> and also have some good use-cases and also have not
> been merged.

What do you think Andrew?
Swap prefetch is not the panacea, it's not going to solve all the
problems but it seems to improve the "desktop experience" and it has
been discussed and reviewed a lot (it's has even been discussed more
than it should have be).

Are you going to push upstream the patch?

Ciao,
-- 
Paolo
http://paolo.ciarrocchi.googlepages.com/

Re: CFS review

[Roman Zippel]

Hi,

On Wed, 1 Aug 2007, Ingo Molnar wrote:

> just to make sure, how does 'top' output of the l + "lt 3" testcase look 
> like now on your laptop? Yesterday it was this:
> 
>  4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
>  4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
>  4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
>  4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l
> 
> and i'm still wondering how that output was possible.

I disabled the jiffies logic and the result is still the same, so this 
problem isn't related to resolution at all.
I traced it a little and what's happing is that the busy loop really only 
gets little time, it only runs inbetween the timer tasks. When the timer 
task is woken up __enqueue_sleeper() updates sleeper_bonus and a little 
later when the busy loop is preempted __update_curr() is called a last 
time and it's fully hit by the sleeper_bonus. So the timer tasks use less 
time than they actually get and thus produce overflows, the busy loop OTOH 
is punished and underflows.
So it seems my initial suspicion was right and this logic is dodgy, what 
is it actually supposed to do? Why is some random task accounted with the 
sleeper_bonus?

bye, Roman

PS: Can I still expect answer about all the other stuff?

Re: CFS review

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> >  4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
> >  4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
> >  4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
> >  4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l
> > 
> > and i'm still wondering how that output was possible.
> 
> I disabled the jiffies logic and the result is still the same, so this 
> problem isn't related to resolution at all.

how did you disable the jiffies logic? Also, could you please send me 
the cfs-debug-info.sh:

  http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh

captured _while_ the above workload is running. This is the third time 
i've asked for that :-)

to establish that the basic sched_clock() behavior is sound on that box, 
could you please also run this tool:

   http://people.redhat.com/mingo/cfs-scheduler/tools/tsc-dump.c

please run it both while the system is idle, and while there's a CPU hog 
running:

  while :; do :; done &

and send me that output too? (it's 2x 60 lines only) Thanks!

	Ingo

Re: CFS review

[Mike Galbraith]

On Fri, 2007-08-10 at 01:14 +0200, Roman Zippel wrote:
> Hi,

Greetings,

> On Wed, 1 Aug 2007, Ingo Molnar wrote:
> 
> > just to make sure, how does 'top' output of the l + "lt 3" testcase look 
> > like now on your laptop? Yesterday it was this:
> > 
> >  4544 roman     20   0  1796  520  432 S 32.1  0.4   0:21.08 lt
> >  4545 roman     20   0  1796  344  256 R 32.1  0.3   0:21.07 lt
> >  4546 roman     20   0  1796  344  256 R 31.7  0.3   0:21.07 lt
> >  4547 roman     20   0  1532  272  216 R  3.3  0.2   0:01.94 l
> > 
> > and i'm still wondering how that output was possible.
> 
> I disabled the jiffies logic and the result is still the same, so this 
> problem isn't related to resolution at all.
> I traced it a little and what's happing is that the busy loop really only 
> gets little time, it only runs inbetween the timer tasks. When the timer 
> task is woken up __enqueue_sleeper() updates sleeper_bonus and a little 
> later when the busy loop is preempted __update_curr() is called a last 
> time and it's fully hit by the sleeper_bonus. So the timer tasks use less 
> time than they actually get and thus produce overflows, the busy loop OTOH 
> is punished and underflows.

I still can't reproduce this here.  Can you please send your .config, so
I can try again with a config as close to yours as possible?

	-Mike

Re: CFS review

[Roman Zippel]

Hi,

On Fri, 10 Aug 2007, Ingo Molnar wrote:

> > I disabled the jiffies logic and the result is still the same, so this 
> > problem isn't related to resolution at all.
> 
> how did you disable the jiffies logic?

I commented it out.

> Also, could you please send me 
> the cfs-debug-info.sh:
> 
>   http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh
> 
> captured _while_ the above workload is running. This is the third time 
> i've asked for that :-)

Is there any reason to believe my analysis is wrong?
So far you haven't answered a single question about the CFS design...

Anyway, I give you something better - the raw trace data for 2ms:

1186747669.274790012: update_curr 0xc7fb06f0,479587,319708,21288884188,159880,7360532
1186747669.274790375: dequeue_entity 0xc7fb06f0,21280402988,159880
1186747669.274792580: sched 2848,2846,0xc7432cb0,-7520413
1186747669.274820987: update_curr 0xc7432ce0,29302,-130577,21288913490,1,-7680293
1186747669.274821269: dequeue_entity 0xc7432ce0,21296077409,1
1186747669.274821930: enqueue_entity 0xc7432ce0,21296593783,1
1186747669.274826979: update_curr 0xc7432ce0,5707,5707,21288919197,1,-7680294
1186747669.274827724: enqueue_entity 0xc7432180,21280919197,639451
1186747669.274829948: update_curr 0xc7432ce0,1553,-318172,21288920750,319726,-8000000
1186747669.274831878: sched 2846,2847,0xc7432150,8000000
1186747669.275789883: update_curr 0xc7432180,479797,319935,21289400547,159864,7360339
1186747669.275790295: dequeue_entity 0xc7432180,21280919197,159864
1186747669.275792439: sched 2847,2846,0xc7432cb0,-7520203
1186747669.275820819: update_curr 0xc7432ce0,29238,-130625,21289429785,1,-7680067
1186747669.275821109: dequeue_entity 0xc7432ce0,21296593783,1
1186747669.275821763: enqueue_entity 0xc7432ce0,21297109852,1
1186747669.275826887: update_curr 0xc7432ce0,5772,5772,21289435557,1,-7680068
1186747669.275827652: enqueue_entity 0xc7fb0ca0,21281435557,639881
1186747669.275829826: update_curr 0xc7432ce0,1549,-318391,21289437106,319941,-8000000
1186747669.275831584: sched 2846,2849,0xc7fb0c70,8000000

About the values:

update_curr: sched_entity, delta_fair, delta_mine, fair_clock, sleeper_bonus, wait_runtime
	(final values at the end of __update_curr)
{en,de}queue_entity: sched_entity, fair_key, sleeper_bonus
	(at the start of __enqueue_entity/__dequeue_entity)
sched: prev_pid,pid,current,wait_runtime
	(at the end of scheduling, note that current has a small structure 
	offset to sched_entity)

It starts with a timer task going to sleep, the busy loop runs for a few 
usec until the timer tick, the next timer task is woken up (sleeper_bonus 
is increased). Before switching the tasks, current task is updated and 
it's punished with the sleeper_bonus.

These tests are done without the recent updates, but they don't seem to
change the basic logic. AFAICT the change to __update_curr() only makes it 
more unpredictable, which task is punished with the sleeper_bonus.

So again, what is this logic _supposed_ to do?

bye, Roman

Re: CFS review

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> > Also, could you please send me 
> > the cfs-debug-info.sh:
> > 
> >   http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh
> > 
> > captured _while_ the above workload is running. This is the third time 
> > i've asked for that :-)
> 
> Is there any reason to believe my analysis is wrong?

please first give me the debug data captured with the script above 
(while the workload is running) - so that i can see the full picture 
about what's happening. Thanks,

	Ingo

Re: CFS review

[Mike Galbraith]

I guess I'm going to have to give up on trying to reproduce this... my
3GHz P4 is just not getting there from here.  Last attempt, compiled UP,
HZ=1000 dynticks, full preempt and highres timers fwiw.

6392 root      20   0  1696  332  248 R 25.5  0.0   3:00.14 0 lt
6393 root      20   0  1696  332  248 R 24.9  0.0   3:00.15 0 lt
6391 root      20   0  1696  488  404 R 24.7  0.0   3:00.20 0 lt
6394 root      20   0  2888 1232 1028 R 24.5  0.1   2:58.58 0 sh

	-Mike

Re: CFS review

[Michael Chang]

On 8/10/07, Roman Zippel <zippel@linux-m68k.org> wrote:
> Is there any reason to believe my analysis is wrong?

Not yet, but if you give Ingo what he wants (as opposed to what you're
giving him) it'll be easier for him to answer what's going wrong, and
perhaps "fix" the problem to boot.

(The scripts gives info about CPU characteristics, interrupts,
modules, etc. -- you know, all those "unknown" variables.)

And perhaps a patch to show what parts you commented out, too, so one
can tell if anything got broken (unintentionally).

-- 
Michael Chang

Please avoid sending me Word or PowerPoint attachments. Send me ODT,
RTF, or HTML instead.
See http://www.gnu.org/philosophy/no-word-attachments.html
Thank you.

Re: CFS review

[Roman Zippel]

Hi,

On Fri, 10 Aug 2007, Mike Galbraith wrote:

> I guess I'm going to have to give up on trying to reproduce this... my
> 3GHz P4 is just not getting there from here.  Last attempt, compiled UP,
> HZ=1000 dynticks, full preempt and highres timers fwiw.
> 
> 6392 root      20   0  1696  332  248 R 25.5  0.0   3:00.14 0 lt
> 6393 root      20   0  1696  332  248 R 24.9  0.0   3:00.15 0 lt
> 6391 root      20   0  1696  488  404 R 24.7  0.0   3:00.20 0 lt
> 6394 root      20   0  2888 1232 1028 R 24.5  0.1   2:58.58 0 sh

Except for UP and HZ=1000, everything else is pretty much turned off.
If you use a very recent kernel, the problem may not be visible like this 
anymore.
It may be a bit easier to reproduce, if you change the end time t0 in lt.c 
a little. Also try to start the busy loop first.

bye, Roman

Re: CFS review

[Roman Zippel]

Hi,

On Fri, 10 Aug 2007, Michael Chang wrote:

> On 8/10/07, Roman Zippel <zippel@linux-m68k.org> wrote:
> > Is there any reason to believe my analysis is wrong?
> 
> Not yet, but if you give Ingo what he wants (as opposed to what you're
> giving him) it'll be easier for him to answer what's going wrong, and
> perhaps "fix" the problem to boot.
> 
> (The scripts gives info about CPU characteristics, interrupts,
> modules, etc. -- you know, all those "unknown" variables.)

He already has most of this information and the trace shows _exactly_ 
what's going on. All this information should be more than enough to allow 
an initial judgement whether my analysis is correct.
Also none of this information is needed to explain the CFS logic a little 
more, which I'm still waiting for...

bye, Roman

Re: CFS review

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> > Not yet, but if you give Ingo what he wants (as opposed to what 
> > you're giving him) it'll be easier for him to answer what's going 
> > wrong, and perhaps "fix" the problem to boot.
> > 
> > (The scripts gives info about CPU characteristics, interrupts, 
> > modules, etc. -- you know, all those "unknown" variables.)
> 
> He already has most of this information and the trace shows _exactly_ 
> what's going on. [...]

i'll need the other bits of information too to have a complete picture 
about what's going on while your test is running - to maximize the 
chances of me being able to fix it. I'm a bit perplexed (and a bit 
worried) about this - you've spent _far_ more effort to _not send_ that 
script output (captured while the workload is running) than it would 
have taken to do it :-/ If you'd like me to fix bugs then please just 
send it (in private mail if you want) - or give me an ssh login to that 
box - whichever variant you prefer. Thanks,

	Ingo

Re: CFS review

[Willy Tarreau]

On Fri, Aug 10, 2007 at 07:25:57PM +0200, Roman Zippel wrote:
> Hi,
> 
> On Fri, 10 Aug 2007, Michael Chang wrote:
> 
> > On 8/10/07, Roman Zippel <zippel@linux-m68k.org> wrote:
> > > Is there any reason to believe my analysis is wrong?
> > 
> > Not yet, but if you give Ingo what he wants (as opposed to what you're
> > giving him) it'll be easier for him to answer what's going wrong, and
> > perhaps "fix" the problem to boot.
> > 
> > (The scripts gives info about CPU characteristics, interrupts,
> > modules, etc. -- you know, all those "unknown" variables.)
> 
> He already has most of this information and the trace shows _exactly_ 
> what's going on. All this information should be more than enough to allow 
> an initial judgement whether my analysis is correct.
> Also none of this information is needed to explain the CFS logic a little 
> more, which I'm still waiting for...

Roman,

fortunately all bug reporters are not like you. It's amazing how long
you can resist sending a simple bug report to a developer! Maybe you
consider that you need to fix the bug by yourself after you understand
the code, but if you systematically refuse to return the small information
Ingo asks you, we will have to wait for some more cooperative users to be
hit by the same bug when 2.6.23 is released, which is stupid.

I thought you could at least understand that one developer who is used
to read traces from the same tool every day will be far faster at decoding
a trace from the same tool than trying to figure out what your self-maid
dump means.

It's the exact same reason I ask for pcap files when people send me
outputs of tcpdumps without the information I *need*.

I you definitely do not want to cooperate, stop asking for a personal
explanation, and go figure by yourself how the code works. BTW, in the
trace you "kindly offered" in exchange for the cfs-debug-info dump,
you show several useful variables, but nothing says where they are
captured. And as you can see, they're changing. That's a fantastic
trace for a developer, really...

Please try to be a little bit more transparent if you really want the
bugs fixed, and don't behave as if you wanted this bug to survive
till -final.

Thanks,
Willy

Re: CFS review

[Roman Zippel]

Hi,

On Fri, 10 Aug 2007, Willy Tarreau wrote:

> fortunately all bug reporters are not like you. It's amazing how long
> you can resist sending a simple bug report to a developer!

I'm more amazed how long Ingo can resist providing some explanations (not 
just about this problem).
It's not like I haven't given him anything, he already has the test 
programs, he already knows the system configuration.
Well, I've sent him the stuff now...

> Maybe you
> consider that you need to fix the bug by yourself after you understand
> the code,

Fixing the bug requires some knowledge what the code is intended to do.

> Please try to be a little bit more transparent if you really want the
> bugs fixed, and don't behave as if you wanted this bug to survive
> till -final.

Could you please ask Ingo the same? I'm simply trying to get some 
transparancy into the CFS design. Without further information it's 
difficult to tell, whether something is supposed to work this way or it's 
a bug.

In this case it's quite possible that due to a recent change my testcase 
doesn't work anymore. Should I consider the problem fixed or did it just 
go into hiding? Without more information it's difficult to verify this 
independently.

bye, Roman

Re: CFS review

[Ingo Molnar]

* Roman Zippel <zippel@linux-m68k.org> wrote:

> Well, I've sent him the stuff now...

received it - thanks alot, looking at it!

> It's not like I haven't given him anything, he already has the test 
> programs, he already knows the system configuration.

one more small thing: could you please send your exact .config (Mike 
asked for that too, and i too on two prior occasions). Sometimes 
unexpected little details in the .config make a difference, we are not 
asking you that because we are second-guessing you in any way, the 
reason is simple: i frequently boot _the very .config that others use_, 
and see surprising reproducability of bugs that i couldnt trigger 
before. It's standard procedure to just pick up the .config of others to 
eliminate a whole bunch of degrees of freedom for a bug to hide behind - 
and your "it's a pretty standard config" description doesnt really 
achieve that. It probably wont make a real difference, but it's really 
easy for you to send and it's still very useful when one tries to 
eliminate possibilities and when one wants to concentrate on the 
remaining possibilities alone. Thanks again,

	Ingo

Re: CFS review

[Roman Zippel]

Hi,

On Fri, 10 Aug 2007, Ingo Molnar wrote:

> achieve that. It probably wont make a real difference, but it's really 
> easy for you to send and it's still very useful when one tries to 
> eliminate possibilities and when one wants to concentrate on the 
> remaining possibilities alone.

The thing I'm afraid about CFS is its possible unpredictability, which 
would make it hard to reproduce problems and we may end up with users with 
unexplainable weird problems. That's the main reason I'm trying so hard to 
push for a design discussion.

Just to give an idea here are two more examples of irregular behaviour, 
which are hopefully easier to reproduce.

1. Two simple busy loops, one of them is reniced to 15, according to my 
calculations the reniced task should get about 3.4% (1/(1.25^15+1)), but I 
get this:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 4433 roman     20   0  1532  300  244 R 99.2  0.2   5:05.51 l
 4434 roman     35  15  1532   72   16 R  0.7  0.1   0:10.62 l

OTOH upto nice level 12 I get what I expect.

2. If I start 20 busy loops, initially I see in top that every task gets 
5% and time increments equally (as it should):

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 4492 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4491 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4490 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4489 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4488 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4487 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4486 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4485 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4484 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4483 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4482 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4481 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4480 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4479 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4478 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4477 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4476 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4475 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4474 roman     20   0  1532   68   16 R  5.0  0.1   0:02.86 l
 4473 roman     20   0  1532  296  244 R  5.0  0.2   0:02.86 l

But if I renice all of them to -15, the time every task gets is rather 
random:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 4492 roman      5 -15  1532   68   16 R  1.0  0.1   0:07.95 l
 4491 roman      5 -15  1532   68   16 R  4.3  0.1   0:07.62 l
 4490 roman      5 -15  1532   68   16 R  3.3  0.1   0:07.50 l
 4489 roman      5 -15  1532   68   16 R  7.6  0.1   0:07.80 l
 4488 roman      5 -15  1532   68   16 R  9.6  0.1   0:08.31 l
 4487 roman      5 -15  1532   68   16 R  3.3  0.1   0:07.59 l
 4486 roman      5 -15  1532   68   16 R  6.6  0.1   0:07.08 l
 4485 roman      5 -15  1532   68   16 R 10.0  0.1   0:07.31 l
 4484 roman      5 -15  1532   68   16 R  8.0  0.1   0:07.30 l
 4483 roman      5 -15  1532   68   16 R  7.0  0.1   0:07.34 l
 4482 roman      5 -15  1532   68   16 R  1.0  0.1   0:05.84 l
 4481 roman      5 -15  1532   68   16 R  1.0  0.1   0:07.16 l
 4480 roman      5 -15  1532   68   16 R  3.3  0.1   0:07.00 l
 4479 roman      5 -15  1532   68   16 R  1.0  0.1   0:06.66 l
 4478 roman      5 -15  1532   68   16 R  8.6  0.1   0:06.96 l
 4477 roman      5 -15  1532   68   16 R  8.6  0.1   0:07.63 l
 4476 roman      5 -15  1532   68   16 R  9.6  0.1   0:07.38 l
 4475 roman      5 -15  1532   68   16 R  1.3  0.1   0:07.09 l
 4474 roman      5 -15  1532   68   16 R  2.3  0.1   0:07.97 l
 4473 roman      5 -15  1532  296  244 R  1.0  0.2   0:07.73 l

bye, Roman

Re: CFS review

[Ingo Molnar]

* Ingo Molnar <mingo@elte.hu> wrote:

> * Roman Zippel <zippel@linux-m68k.org> wrote:
> 
> > Well, I've sent him the stuff now...
> 
> received it - thanks alot, looking at it!

everything looks good in your debug output and the TSC dump data, except 
for the wait_runtime values, they are quite out of balance - and that 
balance cannot be explained with jiffies granularity or with any sort of 
sched_clock() artifact. So this clearly looks like a CFS regression that 
should be fixed.

the only relevant thing that comes to mind at the moment is that last 
week Peter noticed a buggy aspect of sleeper bonuses (in that we do not 
rate-limit their output, hence we 'waste' them instead of redistributing 
them), and i've got the small patch below in my queue to fix that - 
could you give it a try?

this is just a blind stab into the dark - i couldnt see any real impact 
from that patch in various workloads (and it's not upstream yet), so it 
might not make a big difference. The trace you did (could you send the 
source for that?) seems to implicate sleeper bonuses though.

if this patch doesnt help, could you check the general theory whether 
it's related to sleeper-fairness, via turning it off:

   echo 30 > /proc/sys/kernel/sched_features

does the bug go away if you do that? If sleeper bonuses are showing too 
many artifacts then we could turn it off for final .23.

	Ingo

--------------------->
Subject: sched: fix sleeper bonus
From: Ingo Molnar <mingo@elte.hu>

Peter Ziljstra noticed that the sleeper bonus deduction code was not 
properly rate-limited: a task that scheduled more frequently would get a 
disproportionately large deduction. So limit the deduction to delta_exec 
and limit production to runtime_limit.

Not-Yet-Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 kernel/sched_fair.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

Index: linux/kernel/sched_fair.c
===================================================================
--- linux.orig/kernel/sched_fair.c
+++ linux/kernel/sched_fair.c
@@ -75,7 +75,7 @@ enum {
 
 unsigned int sysctl_sched_features __read_mostly =
 		SCHED_FEAT_FAIR_SLEEPERS	*1 |
-		SCHED_FEAT_SLEEPER_AVG		*1 |
+		SCHED_FEAT_SLEEPER_AVG		*0 |
 		SCHED_FEAT_SLEEPER_LOAD_AVG	*1 |
 		SCHED_FEAT_PRECISE_CPU_LOAD	*1 |
 		SCHED_FEAT_START_DEBIT		*1 |
@@ -304,11 +304,9 @@ __update_curr(struct cfs_rq *cfs_rq, str
 	delta_mine = calc_delta_mine(delta_exec, curr->load.weight, lw);
 
 	if (cfs_rq->sleeper_bonus > sysctl_sched_granularity) {
-		delta = calc_delta_mine(cfs_rq->sleeper_bonus,
-					curr->load.weight, lw);
-		if (unlikely(delta > cfs_rq->sleeper_bonus))
-			delta = cfs_rq->sleeper_bonus;
-
+		delta = min(cfs_rq->sleeper_bonus, (u64)delta_exec);
+		delta = calc_delta_mine(delta, curr->load.weight, lw);
+		delta = min((u64)delta, cfs_rq->sleeper_bonus);
 		cfs_rq->sleeper_bonus -= delta;
 		delta_mine -= delta;
 	}
@@ -521,6 +519,8 @@ static void __enqueue_sleeper(struct cfs
 	 * Track the amount of bonus we've given to sleepers:
 	 */
 	cfs_rq->sleeper_bonus += delta_fair;
+	if (unlikely(cfs_rq->sleeper_bonus > sysctl_sched_runtime_limit))
+		cfs_rq->sleeper_bonus = sysctl_sched_runtime_limit;
 
 	schedstat_add(cfs_rq, wait_runtime, se->wait_runtime);
 }

Re: CFS review

[Willy Tarreau]

On Fri, Aug 10, 2007 at 11:15:55PM +0200, Roman Zippel wrote:
> Hi,
> 
> On Fri, 10 Aug 2007, Willy Tarreau wrote:
> 
> > fortunately all bug reporters are not like you. It's amazing how long
> > you can resist sending a simple bug report to a developer!
> 
> I'm more amazed how long Ingo can resist providing some explanations (not 
> just about this problem).

It's a matter of time balance. It takes a short time to send the output
of a script, and it takes a very long time to explain how things work.
I often encounter the same situation with haproxy. People ask me to
explain them in detail how this or that would apply to their context, and
it's often easier for me to provide them with a 5-lines patch to add the
feature they need, than to spend half an hour explaining why and how it
would badly behave.

> It's not like I haven't given him anything, he already has the test 
> programs, he already knows the system configuration.
> Well, I've sent him the stuff now...

fine, thanks.

> > Maybe you
> > consider that you need to fix the bug by yourself after you understand
> > the code,
> 
> Fixing the bug requires some knowledge what the code is intended to do.
> 
> > Please try to be a little bit more transparent if you really want the
> > bugs fixed, and don't behave as if you wanted this bug to survive
> > till -final.
> 
> Could you please ask Ingo the same? I'm simply trying to get some 
> transparancy into the CFS design. Without further information it's 
> difficult to tell, whether something is supposed to work this way or it's 
> a bug.

I know that Ingo tends to reply to a question with another question. But
as I said, imagine if he has to explain the same things to each person
who asks him for it. I think that a more constructive approach would be
to point what is missing/unclear/inexact in the doc so that he adds some
paragraphs for you and everyone else. If you need this information to debug,
most likely other people will need it too.

> In this case it's quite possible that due to a recent change my testcase 
> doesn't work anymore. Should I consider the problem fixed or did it just 
> go into hiding? Without more information it's difficult to verify this 
> independently.

generally, problems that appear only on one person's side and which suddenly
disappear are either caused by some random buggy patch left in the tree (not
your case it seems), or by an obscure bug of the feature being tested which
will resurface from time to time as long as it's not identified.

Willy

Re: CFS review

[Willy Tarreau]

On Sat, Aug 11, 2007 at 12:50:08AM +0200, Roman Zippel wrote:
> Hi,
> 
> On Fri, 10 Aug 2007, Ingo Molnar wrote:
> 
> > achieve that. It probably wont make a real difference, but it's really 
> > easy for you to send and it's still very useful when one tries to 
> > eliminate possibilities and when one wants to concentrate on the 
> > remaining possibilities alone.
> 
> The thing I'm afraid about CFS is its possible unpredictability, which 
> would make it hard to reproduce problems and we may end up with users with 
> unexplainable weird problems. That's the main reason I'm trying so hard to 
> push for a design discussion.

You may be interested by looking at the very early CFS versions. The design
was much more naive and understandable. After that, a lot of tricks have
been added to take into account a lot of uses and corner cases, which may
not help in understanding it globally.

> Just to give an idea here are two more examples of irregular behaviour, 
> which are hopefully easier to reproduce.
> 
> 1. Two simple busy loops, one of them is reniced to 15, according to my 
> calculations the reniced task should get about 3.4% (1/(1.25^15+1)), but I 
> get this:
> 
>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>  4433 roman     20   0  1532  300  244 R 99.2  0.2   5:05.51 l
>  4434 roman     35  15  1532   72   16 R  0.7  0.1   0:10.62 l

Could this be caused by typos in some tables like you have found in wmult ?

> OTOH upto nice level 12 I get what I expect.
> 
> 2. If I start 20 busy loops, initially I see in top that every task gets 
> 5% and time increments equally (as it should):
(...)

> But if I renice all of them to -15, the time every task gets is rather 
> random:
> 
>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>  4492 roman      5 -15  1532   68   16 R  1.0  0.1   0:07.95 l
>  4491 roman      5 -15  1532   68   16 R  4.3  0.1   0:07.62 l
>  4490 roman      5 -15  1532   68   16 R  3.3  0.1   0:07.50 l
>  4489 roman      5 -15  1532   68   16 R  7.6  0.1   0:07.80 l
>  4488 roman      5 -15  1532   68   16 R  9.6  0.1   0:08.31 l
>  4487 roman      5 -15  1532   68   16 R  3.3  0.1   0:07.59 l
>  4486 roman      5 -15  1532   68   16 R  6.6  0.1   0:07.08 l
>  4485 roman      5 -15  1532   68   16 R 10.0  0.1   0:07.31 l
>  4484 roman      5 -15  1532   68   16 R  8.0  0.1   0:07.30 l
>  4483 roman      5 -15  1532   68   16 R  7.0  0.1   0:07.34 l
>  4482 roman      5 -15  1532   68   16 R  1.0  0.1   0:05.84 l
>  4481 roman      5 -15  1532   68   16 R  1.0  0.1   0:07.16 l
>  4480 roman      5 -15  1532   68   16 R  3.3  0.1   0:07.00 l
>  4479 roman      5 -15  1532   68   16 R  1.0  0.1   0:06.66 l
>  4478 roman      5 -15  1532   68   16 R  8.6  0.1   0:06.96 l
>  4477 roman      5 -15  1532   68   16 R  8.6  0.1   0:07.63 l
>  4476 roman      5 -15  1532   68   16 R  9.6  0.1   0:07.38 l
>  4475 roman      5 -15  1532   68   16 R  1.3  0.1   0:07.09 l
>  4474 roman      5 -15  1532   68   16 R  2.3  0.1   0:07.97 l
>  4473 roman      5 -15  1532  296  244 R  1.0  0.2   0:07.73 l

Do you see this only at -15, or starting with -15 and below ?

Willy

Re: CFS review

[Ingo Molnar]

* Willy Tarreau <w@1wt.eu> wrote:

> > 1. Two simple busy loops, one of them is reniced to 15, according to 
> > my calculations the reniced task should get about 3.4% 
> > (1/(1.25^15+1)), but I get this:
> > 
> >   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
> >  4433 roman     20   0  1532  300  244 R 99.2  0.2   5:05.51 l
> >  4434 roman     35  15  1532   72   16 R  0.7  0.1   0:10.62 l
> 
> Could this be caused by typos in some tables like you have found in 
> wmult ?

note that the typo was not in the weight table but in the inverse weight 
table which didnt really affect CPU utilization (that's why we didnt 
notice the typo sooner). Regarding the above problem with nice +15 being 
beefier than intended i'd suggest to re-test with a doubled 
/proc/sys/kernel/sched_runtime_limit value, or with:

  echo 30 > /proc/sys/kernel/sched_features

(which turns off sleeper fairness)

> >  4477 roman      5 -15  1532   68   16 R  8.6  0.1   0:07.63 l
> >  4476 roman      5 -15  1532   68   16 R  9.6  0.1   0:07.38 l
> >  4475 roman      5 -15  1532   68   16 R  1.3  0.1   0:07.09 l
> >  4474 roman      5 -15  1532   68   16 R  2.3  0.1   0:07.97 l
> >  4473 roman      5 -15  1532  296  244 R  1.0  0.2   0:07.73 l
> 
> Do you see this only at -15, or starting with -15 and below ?

i think this was scheduling jitter caused by the larger granularity of 
negatively reniced tasks. This got improved recently, with latest -git i 
get:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 3108 root       5 -15  1576  248  196 R  5.0  0.0   0:07.26 loop_silent
 3109 root       5 -15  1576  248  196 R  5.0  0.0   0:07.26 loop_silent
 3110 root       5 -15  1576  248  196 R  5.0  0.0   0:07.26 loop_silent
 3111 root       5 -15  1576  244  196 R  5.0  0.0   0:07.26 loop_silent
 3112 root       5 -15  1576  248  196 R  5.0  0.0   0:07.26 loop_silent
 3113 root       5 -15  1576  248  196 R  5.0  0.0   0:07.26 loop_silent

that's picture-perfect CPU time distribution. But, and that's fair to 
say, i never ran such an artificial workload of 20x nice -15 infinite 
loops (!) before, and boy does interactivity suck (as expected) ;)

	Ingo

Re: CFS review

[Roman Zippel]

Hi,

On Sat, 11 Aug 2007, Ingo Molnar wrote:

> the only relevant thing that comes to mind at the moment is that last 
> week Peter noticed a buggy aspect of sleeper bonuses (in that we do not 
> rate-limit their output, hence we 'waste' them instead of redistributing 
> them), and i've got the small patch below in my queue to fix that - 
> could you give it a try?

It doesn't make much of a difference. OTOH if I disabled the sleeper code 
completely in __update_curr(), I get this:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 3139 roman     20   0  1796  344  256 R 21.7  0.3   0:02.68 lt
 3138 roman     20   0  1796  344  256 R 21.7  0.3   0:02.68 lt
 3137 roman     20   0  1796  520  432 R 21.7  0.4   0:02.68 lt
 3136 roman     20   0  1532  268  216 R 34.5  0.2   0:06.82 l

Disabling this code completely via sched_features makes only a minor 
difference:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 3139 roman     20   0  1796  344  256 R 20.4  0.3   0:09.94 lt
 3138 roman     20   0  1796  344  256 R 20.4  0.3   0:09.94 lt
 3137 roman     20   0  1796  520  432 R 20.4  0.4   0:09.94 lt
 3136 roman     20   0  1532  268  216 R 39.1  0.2   0:19.20 l

> this is just a blind stab into the dark - i couldnt see any real impact 
> from that patch in various workloads (and it's not upstream yet), so it 
> might not make a big difference.

Can we please skip to the point, where you try to explain the intention a 
little more?
If I had to guess that this is supposed to keep the runtime balance, then 
it would be better to use wait_runtime to adjust fair_clock, from where it 
would be evenly distributed to all tasks (but this had to be done during 
enqueue and dequeue). OTOH this also had then a consequence for the wait 
queue, as fair_clock is used to calculate fair_key.
IMHO current wait_runtime should have some influence in calculating the 
sleep bonus, so that wait_runtime doesn't constantly overflow for tasks 
which only run occasionally.

bye, Roman

Re: CFS review

[Mike Galbraith]

On Tue, 2007-08-21 at 00:19 +0200, Roman Zippel wrote: 
> Hi,
> 
> On Sat, 11 Aug 2007, Ingo Molnar wrote:
> 
> > the only relevant thing that comes to mind at the moment is that last 
> > week Peter noticed a buggy aspect of sleeper bonuses (in that we do not 
> > rate-limit their output, hence we 'waste' them instead of redistributing 
> > them), and i've got the small patch below in my queue to fix that - 
> > could you give it a try?
> 
> It doesn't make much of a difference.

I thought this was history.  With your config, I was finally able to
reproduce the anomaly (only with your proggy though), and Ingo's patch
does indeed fix it here.

Freshly reproduced anomaly and patch verification, running 2.6.23-rc3
with your config, both with and without Ingo's patch reverted:

6561 root      20   0  1696  492  404 S 32.0  0.0   0:30.83 0 lt
6562 root      20   0  1696  336  248 R 32.0  0.0   0:30.79 0 lt
6563 root      20   0  1696  336  248 R 32.0  0.0   0:30.80 0 lt
6564 root      20   0  2888 1236 1028 R  4.6  0.1   0:05.26 0 sh

6507 root      20   0  2888 1236 1028 R 25.8  0.1   0:30.75 0 sh
6504 root      20   0  1696  492  404 R 24.4  0.0   0:29.26 0 lt
6505 root      20   0  1696  336  248 R 24.4  0.0   0:29.26 0 lt
6506 root      20   0  1696  336  248 R 24.4  0.0   0:29.25 0 lt

	-Mike

Re: CFS review

[Ingo Molnar]

* Mike Galbraith <efault@gmx.de> wrote:

> > It doesn't make much of a difference.
> 
> I thought this was history.  With your config, I was finally able to 
> reproduce the anomaly (only with your proggy though), and Ingo's patch 
> does indeed fix it here.
> 
> Freshly reproduced anomaly and patch verification, running 2.6.23-rc3 
> with your config, both with and without Ingo's patch reverted:
> 
> 6561 root      20   0  1696  492  404 S 32.0  0.0   0:30.83 0 lt
> 6562 root      20   0  1696  336  248 R 32.0  0.0   0:30.79 0 lt
> 6563 root      20   0  1696  336  248 R 32.0  0.0   0:30.80 0 lt
> 6564 root      20   0  2888 1236 1028 R  4.6  0.1   0:05.26 0 sh
> 
> 6507 root      20   0  2888 1236 1028 R 25.8  0.1   0:30.75 0 sh
> 6504 root      20   0  1696  492  404 R 24.4  0.0   0:29.26 0 lt
> 6505 root      20   0  1696  336  248 R 24.4  0.0   0:29.26 0 lt
> 6506 root      20   0  1696  336  248 R 24.4  0.0   0:29.25 0 lt

oh, great! I'm glad we didnt discard this as a pure sched_clock 
resolution artifact.

Roman, a quick & easy request: please send the usual cfs-debug-info.sh 
output captured while your testcase is running. (Preferably try .23-rc3 
or later as Mike did, which has the most recent scheduler code, it 
includes the patch i sent to you already.) I'll reply to your 
sleeper-fairness questions separately, but in any case we need to figure 
out what's happening on your box - if you can still reproduce it with 
.23-rc3. Thanks,

	Ingo

Re: CFS review

[Roman Zippel]

Hi,

On Tue, 21 Aug 2007, Mike Galbraith wrote:

> I thought this was history.  With your config, I was finally able to
> reproduce the anomaly (only with your proggy though), and Ingo's patch
> does indeed fix it here.
> 
> Freshly reproduced anomaly and patch verification, running 2.6.23-rc3
> with your config, both with and without Ingo's patch reverted:

I did update to 2.6.23-rc3-git1 first, but I ended up reverting the patch, 
as I didn't notice it had been applied already. Sorry about that.
With this patch the underflows are gone, but there are still the 
overflows, so the questions from the last mail still remain.

bye, Roman