From: Alexander Duyck <email@example.com> To: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org Cc: email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org Subject: [PATCH v12 0/6] mm / virtio: Provide support for unused page reporting Date: Tue, 22 Oct 2019 15:27:52 -0700 [thread overview] Message-ID: <email@example.com> (raw) This series provides an asynchronous means of reporting unused guest pages to a hypervisor so that the memory associated with those pages can be dropped and reused by other processes and/or guests. When enabled it will allocate a set of statistics to track the number of reported pages. When the nr_free for a given free_area is greater than this by the high water mark we will schedule a worker to begin allocating the non-reported memory and to provide it to the reporting interface via a scatterlist. Currently this is only in use by virtio-balloon however there is the hope that at some point in the future other hypervisors might be able to make use of it. In the virtio-balloon/QEMU implementation the hypervisor is currently using MADV_DONTNEED to indicate to the host kernel that the page is currently unused. It will be faulted back into the guest the next time the page is accessed. To track if a page is reported or not the Uptodate flag was repurposed and used as a Reported flag for Buddy pages. While we are processing the pages in a given zone we have a set of pointers we track called reported_boundary that is used to keep our processing time to a minimum. Without these we would have to iterate through all of the reported pages which would become a significant burden. I measured as much as a 20% performance degradation without using the boundary pointers. In the event of something like compaction needing to process the zone at the same time it currently resorts to resetting the boundary if it is rearranging the list. However in the future it could choose to delay processing the zone if a flag is set indicating that a zone is being actively processed. Below are the results from various benchmarks. I primarily focused on two tests. The first is the will-it-scale/page_fault2 test, and the other is a modified version of will-it-scale/page_fault1 that was enabled to use THP. I did this as it allows for better visibility into different parts of the memory subsystem. The guest is running on one node of a E5-2630 v3 CPU with 48G of RAM that I split up into two logical nodes in the guest in order to test with NUMA as well. Test page_fault1 (THP) page_fault2 Baseline 1 1256106.33 +/-0.09% 482202.67 +/-0.46% 16 8864441.67 +/-0.09% 3734692.00 +/-1.23% Patches applied 1 1257096.00 +/-0.06% 477436.00 +/-0.16% 16 8864677.33 +/-0.06% 3800037.00 +/-0.19% Patches enabled 1 1258420.00 +/-0.04% 480080.00 +/-0.07% MADV disabled 16 8753840.00 +/-1.27% 3782764.00 +/-0.37% Patches enabled 1 1267916.33 +/-0.08% 472075.67 +/-0.39% 16 8287050.33 +/-0.67% 3774500.33 +/-0.11% The results above are for a baseline with a linux-next-20191021 kernel, that kernel with this patch set applied but page reporting disabled in virtio-balloon, patches applied but the madvise disabled by direct assigning a device, and the patches applied and page reporting fully enabled. These results include the deviation seen between the average value reported here versus the high and/or low value. I observed that during the test the memory usage for the first three tests never dropped whereas with the patches fully enabled the VM would drop to using only a few GB of the host's memory when switching from memhog to page fault tests. Most of the overhead seen with this patch set fully enabled is due to the fact that accessing the reported pages will cause a page fault and the host will have to zero the page before giving it back to the guest. The overall guest size is kept fairly small to only a few GB while the test is running. This overhead is much more visible when using THP than with standard 4K pages. As such for the case where the host memory is not oversubscribed this results in a performance regression, however if the host memory were oversubscribed this patch set should result in a performance improvement as swapping memory from the host can be avoided. There is currently an alternative patch set that has been under work for some time however the v12 version of that patch set could not be tested as it triggered a kernel panic when I attempted to test it. It requires multiple modifications to get up and running with performance comparable to this patch set. A follow-on set has yet to be posted. As such I have not included results from that patch set, and I would appreciate it if we could keep this patch set the focus of any discussion on this thread. For info on earlier versions you will need to follow the links provided with the respective versions. : https://firstname.lastname@example.org/ Changes from v10: https://email@example.com/ Rebased on "Add linux-next specific files for 20190930" Added page_is_reported() macro to prevent unneeded testing of PageReported bit Fixed several spots where comments referred to older aeration naming Set upper limit for phdev->capacity to page reporting high water mark Updated virtio page poison detection logic to also cover init_on_free Tweaked page_reporting_notify_free to reduce code size Removed dead code in non-reporting path Changes from v11: https://firstname.lastname@example.org/ Removed unnecessary whitespace change from patch 2 Minor tweak to get_unreported_page to avoid excess writes to boundary Rewrote cover page to lay out additional performance info. --- Alexander Duyck (6): mm: Adjust shuffle code to allow for future coalescing mm: Use zone and order instead of free area in free_list manipulators mm: Introduce Reported pages mm: Add device side and notifier for unused page reporting virtio-balloon: Pull page poisoning config out of free page hinting virtio-balloon: Add support for providing unused page reports to host drivers/virtio/Kconfig | 1 drivers/virtio/virtio_balloon.c | 88 ++++++++- include/linux/mmzone.h | 60 ++---- include/linux/page-flags.h | 11 + include/linux/page_reporting.h | 31 +++ include/uapi/linux/virtio_balloon.h | 1 mm/Kconfig | 11 + mm/Makefile | 1 mm/compaction.c | 5 mm/memory_hotplug.c | 2 mm/page_alloc.c | 194 +++++++++++++++---- mm/page_reporting.c | 353 +++++++++++++++++++++++++++++++++++ mm/page_reporting.h | 225 ++++++++++++++++++++++ mm/shuffle.c | 12 + mm/shuffle.h | 6 + 15 files changed, 899 insertions(+), 102 deletions(-) create mode 100644 include/linux/page_reporting.h create mode 100644 mm/page_reporting.c create mode 100644 mm/page_reporting.h --
next reply other threads:[~2019-10-22 22:27 UTC|newest] Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-10-22 22:27 Alexander Duyck [this message] 2019-10-22 22:27 ` [PATCH v12 1/6] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck 2019-10-22 22:28 ` [PATCH v12 2/6] mm: Use zone and order instead of free area in free_list manipulators Alexander Duyck 2019-10-23 8:26 ` David Hildenbrand 2019-10-23 15:16 ` Alexander Duyck 2019-10-24 9:32 ` David Hildenbrand 2019-10-24 15:19 ` Alexander Duyck 2019-10-22 22:28 ` [PATCH v12 3/6] mm: Introduce Reported pages Alexander Duyck 2019-10-22 23:03 ` Andrew Morton 2019-10-22 23:25 ` Alexander Duyck 2019-10-22 22:28 ` [PATCH v12 4/6] mm: Add device side and notifier for unused page reporting Alexander Duyck 2019-10-22 22:28 ` [PATCH v12 5/6] virtio-balloon: Pull page poisoning config out of free page hinting Alexander Duyck 2019-10-22 22:28 ` [PATCH v12 6/6] virtio-balloon: Add support for providing unused page reports to host Alexander Duyck 2019-10-22 22:29 ` [PATCH v12 QEMU 1/3] virtio-ballon: Implement support for page poison tracking feature Alexander Duyck 2019-10-22 22:29 ` [PATCH v12 QEMU 2/3] virtio-balloon: Add bit to notify guest of unused page reporting Alexander Duyck 2019-10-22 22:29 ` [PATCH v12 QEMU 3/3] virtio-balloon: Provide a interface for " Alexander Duyck 2019-10-22 23:01 ` [PATCH v12 0/6] mm / virtio: Provide support " Andrew Morton 2019-10-22 23:43 ` Alexander Duyck 2019-10-23 11:19 ` Nitesh Narayan Lal 2019-10-23 11:35 ` Nitesh Narayan Lal 2019-10-23 22:24 ` Alexander Duyck 2019-10-28 14:34 ` Nitesh Narayan Lal 2019-10-28 15:24 ` Alexander Duyck
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