* [PATCH 0/2] zcache: a new start for upstream
@ 2013-07-20 14:36 Bob Liu
2013-07-20 14:36 ` [PATCH 1/2] zcache: staging: %s/ZCACHE/ZCACHE_OLD Bob Liu
` (3 more replies)
0 siblings, 4 replies; 9+ messages in thread
From: Bob Liu @ 2013-07-20 14:36 UTC (permalink / raw)
Cc: linux-kernel, sjenning, gregkh, ngupta, minchan, konrad.wilk,
rcj, mgorman, riel, penberg, akpm, Bob Liu
We already have zswap helps reducing the swap out/in IO operations by
compressing anon pages.
It has been merged into v3.11-rc1 together with the zbud allocation layer.
However there is another kind of pages(clean file pages) suitable for
compression as well. Upstream has already merged its frontend(cleancache).
Now we are lacking of a backend of cleancache as zswap to frontswap.
Furthermore, we need to balance the number of compressed anon and file pages,
E.g. it's unfair to normal file pages if zswap pool occupies too much memory for
the storage of compressed anon pages.
Although the current version of zcache in staging tree has already done those
works mentioned above, the implementation is too complicated to be merged into
upstream.
What I'm looking for is a new way for zcache towards upstream.
The first change is no more staging tree.
Second is implemented a simple cleancache backend at first, which is based on
the zbud allocation same as zswap.
At the end, I hope we can combine the new cleancache backend with
zswap(frontswap backend), in order to have a generic in-kernel memory
compression solution in upstream.
Bob Liu (2):
zcache: staging: %s/ZCACHE/ZCACHE_OLD
mm: zcache: core functions added
drivers/staging/zcache/Kconfig | 12 +-
drivers/staging/zcache/Makefile | 4 +-
mm/Kconfig | 18 +
mm/Makefile | 1 +
mm/zcache.c | 840 +++++++++++++++++++++++++++++++++++++++
5 files changed, 867 insertions(+), 8 deletions(-)
create mode 100644 mm/zcache.c
--
1.7.10.4
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH 1/2] zcache: staging: %s/ZCACHE/ZCACHE_OLD
2013-07-20 14:36 [PATCH 0/2] zcache: a new start for upstream Bob Liu
@ 2013-07-20 14:36 ` Bob Liu
2013-07-20 15:24 ` Fwd: " Bob Liu
2013-07-20 16:42 ` Greg KH
2013-07-20 14:36 ` [PATCH 2/2] mm: zcache: core functions added Bob Liu
` (2 subsequent siblings)
3 siblings, 2 replies; 9+ messages in thread
From: Bob Liu @ 2013-07-20 14:36 UTC (permalink / raw)
Cc: linux-kernel, sjenning, gregkh, ngupta, minchan, konrad.wilk,
rcj, mgorman, riel, penberg, akpm, Bob Liu
Signed-off-by: Bob Liu <bob.liu@oracle.com>
---
drivers/staging/zcache/Kconfig | 12 ++++++------
drivers/staging/zcache/Makefile | 4 ++--
2 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/drivers/staging/zcache/Kconfig b/drivers/staging/zcache/Kconfig
index 2d7b2da..f96fb12 100644
--- a/drivers/staging/zcache/Kconfig
+++ b/drivers/staging/zcache/Kconfig
@@ -1,4 +1,4 @@
-config ZCACHE
+config ZCACHE_OLD
tristate "Dynamic compression of swap pages and clean pagecache pages"
depends on CRYPTO=y && SWAP=y && CLEANCACHE && FRONTSWAP
select CRYPTO_LZO
@@ -10,9 +10,9 @@ config ZCACHE
memory to store clean page cache pages and swap in RAM,
providing a noticeable reduction in disk I/O.
-config ZCACHE_DEBUG
+config ZCACHE_OLD_DEBUG
bool "Enable debug statistics"
- depends on DEBUG_FS && ZCACHE
+ depends on DEBUG_FS && ZCACHE_OLD
default n
help
This is used to provide an debugfs directory with counters of
@@ -20,7 +20,7 @@ config ZCACHE_DEBUG
config RAMSTER
tristate "Cross-machine RAM capacity sharing, aka peer-to-peer tmem"
- depends on CONFIGFS_FS=y && SYSFS=y && !HIGHMEM && ZCACHE
+ depends on CONFIGFS_FS=y && SYSFS=y && !HIGHMEM && ZCACHE_OLD
depends on NET
# must ensure struct page is 8-byte aligned
select HAVE_ALIGNED_STRUCT_PAGE if !64BIT
@@ -45,9 +45,9 @@ config RAMSTER_DEBUG
# __add_to_swap_cache, and implement __swap_writepage (which is swap_writepage
# without the frontswap call. When these are in-tree, the dependency on
# BROKEN can be removed
-config ZCACHE_WRITEBACK
+config ZCACHE_OLD_WRITEBACK
bool "Allow compressed swap pages to be writtenback to swap disk"
- depends on ZCACHE=y && BROKEN
+ depends on ZCACHE_OLD=y && BROKEN
default n
help
Zcache caches compressed swap pages (and other data) in RAM which
diff --git a/drivers/staging/zcache/Makefile b/drivers/staging/zcache/Makefile
index 845a5c2..34d27bd 100644
--- a/drivers/staging/zcache/Makefile
+++ b/drivers/staging/zcache/Makefile
@@ -1,8 +1,8 @@
zcache-y := zcache-main.o tmem.o zbud.o
-zcache-$(CONFIG_ZCACHE_DEBUG) += debug.o
+zcache-$(CONFIG_ZCACHE_OLD_DEBUG) += debug.o
zcache-$(CONFIG_RAMSTER_DEBUG) += ramster/debug.o
zcache-$(CONFIG_RAMSTER) += ramster/ramster.o ramster/r2net.o
zcache-$(CONFIG_RAMSTER) += ramster/nodemanager.o ramster/tcp.o
zcache-$(CONFIG_RAMSTER) += ramster/heartbeat.o ramster/masklog.o
-obj-$(CONFIG_ZCACHE) += zcache.o
+obj-$(CONFIG_ZCACHE_OLD) += zcache.o
--
1.7.10.4
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH 2/2] mm: zcache: core functions added
2013-07-20 14:36 [PATCH 0/2] zcache: a new start for upstream Bob Liu
2013-07-20 14:36 ` [PATCH 1/2] zcache: staging: %s/ZCACHE/ZCACHE_OLD Bob Liu
@ 2013-07-20 14:36 ` Bob Liu
2013-07-20 15:25 ` Fwd: " Bob Liu
2013-07-20 15:23 ` Fwd: [PATCH 0/2] zcache: a new start for upstream Bob Liu
[not found] ` <20130722150702.GB4706@variantweb.net>
3 siblings, 1 reply; 9+ messages in thread
From: Bob Liu @ 2013-07-20 14:36 UTC (permalink / raw)
Cc: linux-kernel, sjenning, gregkh, ngupta, minchan, konrad.wilk,
rcj, mgorman, riel, penberg, akpm, Bob Liu
This patch adds the cleancache backend for clean file pages compression.
Nitin Gupta have already done many works on this topic in 2010.
You can see his work from below links:
http://lwn.net/Articles/396467/
http://thread.gmane.org/gmane.linux.kernel.mm/50523
But at that time neither the allocation layer nor cleancache have been merged
into upstream.
(Most of below comments are copyed from his patch.)
Frequently accessed filesystem data is stored in memory to reduce access to
(much) slower backing disks. Under memory pressure, these pages are freed and
when needed again, they have to be read from disks again. When combined
working set of all running application exceeds amount of physical RAM, we get
extereme slowdown as reading a page from disk can take time in order of
milliseconds.
Memory compression increases effective memory size and allows more pages to
stay in RAM. Since de/compressing memory pages is several orders of magnitude
faster than disk I/O, this can provide signifant performance gains for many
workloads. Also, with multi-cores becoming common, benefits of reduced disk
I/O should easily outweigh the problem of increased CPU usage.
It is implemented as a "backend" for cleancache which provides
callbacks for events such as when a page is to be removed from the page cache
and when it is required again. We use them to implement a 'second chance'
cache for these evicted page cache pages by compressing and storing them in
memory itself.
We use zbud memory allocator which is already merged and used by zswap for the
same purpose.
A separate "pool" is created for each mount instance for a cleancache-aware
filesystem. Each incoming page is identified with <pool_id, inode_no, index>
where inode_no identifies file within the filesystem corresponding to pool_id
and index is offset of the page within this inode. Within a pool, inodes are
maintained in an rb-tree and each of its nodes points to a separate radix-tree
which maintains list of pages within that inode.
Tests were done on physical machine (not in a VM)
Only played with iozone for some simple tests.
Kernel booted with command line "single mem=1G zcache.enabled=1"
Kernel 3.10.0+ (with Seth's zswap patches)
CPU: Core-i5 4-Core
RAM: 1G
Boot into single mode
Swapoff -a to avoid I/O interference
Command for testing:
iozone -a -M -B -s 1G -y 4k -+u -R -b iozone.xls
Results:
Without zcache
random random bkwd record stride
KB reclen write rewrite read reread read write read rewrite read
1048576 4 73070 36713 75187 74916 1292 674 26724 45514 8491
1048576 8 68777 34407 71162 73407 2703 1233 27800 42417 5548
1048576 16 70030 35156 71496 71186 4462 2181 31480 42040 8737
1048576 32 68796 35442 72557 72734 6955 3615 40783 44627 10959
1048576 64 76576 35247 68685 72279 11383 6615 49913 44620 14777
1048576 128 77516 33878 72538 71231 17897 10896 64393 48613 35265
1048576 256 73465 37450 22857 22854 22845 16655 61152 49170 40571
1048576 512 68096 35303 22265 22398 36154 23952 58286 48594 39972
1048576 1024 69442 36192 22206 22541 38927 29643 60695 50483 44120
1048576 2048 69404 34891 22951 23286 40036 35984 62095 50704 43764
1048576 4096 68871 35716 23147 23272 41587 37619 66809 47613 45229
1048576 8192 66775 36409 22997 23070 39023 39674 69262 55548 49324
1048576 16384 68728 34792 23829 24022 39922 42496 65714 44732 39104
Average: 70734 35507 45529 45938 23760 19326 52700 47283 29682
With zcache
random random bkwd record stride
KB reclen write rewrite read reread read write read rewrite read
1048576 4 80330 35970 120942 115559 1491 686 29923 47864 11177
1048576 8 69553 36658 134402 105351 2978 1332 33291 45885 6331
1048576 16 79538 36719 149905 155649 5970 2305 38136 42365 14070
1048576 32 68326 37064 150126 151728 10462 4128 44693 44975 15607
1048576 64 74450 35379 147918 130771 19199 7468 54065 43630 22104
1048576 128 71655 36125 137384 139080 27495 11507 65742 47471 49833
1048576 256 78867 36030 51814 42656 41578 17829 77058 44247 54368
1048576 512 68671 35378 52359 44516 52296 25944 80121 47270 57271
1048576 1024 69495 37064 53579 56057 60121 31833 83420 46752 65267
1048576 2048 69014 35589 52216 49919 69441 37169 92552 45746 68838
1048576 4096 67338 36194 56068 56855 71569 39895 98462 49440 72496
1048576 8192 65153 35345 54983 58602 78402 43841 98809 47334 74803
1048576 16384 63579 34842 50888 54429 68070 42518 87534 45665 64967
Average: 71228 36027 93345 89321 39159 20497 67985 46050 44395
Chnage : 1% 1% 105% 94% 65% 6% 29% -3% 50%
You can see that reading side performance get improved a lot after using zcache.
Because pages are cached by zcache, we only need to decompress them instead of
reading from disk.
Signed-off-by: Bob Liu <bob.liu@oracle.com>
---
mm/Kconfig | 18 ++
mm/Makefile | 1 +
mm/zcache.c | 840 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 859 insertions(+)
create mode 100644 mm/zcache.c
diff --git a/mm/Kconfig b/mm/Kconfig
index eec97f2..2b68103 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -507,3 +507,21 @@ config ZSWAP
interactions don't cause any known issues on simple memory setups,
they have not be fully explored on the large set of potential
configurations and workloads that exist.
+
+config ZCACHE
+ bool "Compressed cache for swap and clean file pages (EXPERIMENTAL)"
+ depends on FRONTSWAP && CRYPTO && CLEANCACHE
+ select CRYPTO_LZO
+ select ZBUD
+ default n
+ help
+ A compressed cache for swap and clean file pages.
+
+ It can takes pages that are in the process of being swapped out and
+ attempts to compress them into a dynamically allocated RAM-based memory pool.
+ This can result in a significant I/O reduction on swap device and,
+ in the case where decompressing from RAM is faster that swap device
+ reads, can also improve workload performance.
+
+ Besides swap pages, zcache can also compress the clean file pages into a memory pool.
+ This can reduce the refaults of reading those file pages back from disks.
diff --git a/mm/Makefile b/mm/Makefile
index f008033..a29232b 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -33,6 +33,7 @@ obj-$(CONFIG_BOUNCE) += bounce.o
obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o
obj-$(CONFIG_FRONTSWAP) += frontswap.o
obj-$(CONFIG_ZSWAP) += zswap.o
+obj-$(CONFIG_ZCACHE) += zcache.o
obj-$(CONFIG_HAS_DMA) += dmapool.o
obj-$(CONFIG_HUGETLBFS) += hugetlb.o
obj-$(CONFIG_NUMA) += mempolicy.o
diff --git a/mm/zcache.c b/mm/zcache.c
new file mode 100644
index 0000000..a2408e8
--- /dev/null
+++ b/mm/zcache.c
@@ -0,0 +1,840 @@
+/*
+ * zcache.c - zcache driver file
+ *
+ * The goal of zcache is implement a generic memory compression layer.
+ * It's a backend of both frontswap and cleancache.
+ *
+ * This file only implemented cleancache part currently.
+ * Concepts based on original zcache by Dan Magenheimer.
+ *
+ * Copyright (C) 2013 Bob Liu <bob.liu@oracle.com>
+ *
+ * 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.
+*/
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/cpu.h>
+#include <linux/highmem.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+#include <linux/atomic.h>
+#include <linux/cleancache.h>
+#include <linux/rbtree.h>
+#include <linux/radix-tree.h>
+#include <linux/swap.h>
+#include <linux/crypto.h>
+#include <linux/mempool.h>
+#include <linux/zbud.h>
+
+#include <linux/mm_types.h>
+#include <linux/page-flags.h>
+#include <linux/swapops.h>
+#include <linux/writeback.h>
+#include <linux/pagemap.h>
+
+/* Enable/disable zcache (disabled by default) */
+static bool zcache_enabled __read_mostly;
+module_param_named(enabled, zcache_enabled, bool, 0);
+
+/* Enable/disable cleancache part of zcache */
+static bool zcache_nocleancache __read_mostly;
+module_param_named(nocleancache, zcache_nocleancache, bool, 0);
+
+/* Compressor to be used by zcache */
+#define ZCACHE_COMPRESSOR_DEFAULT "lzo"
+static char *zcache_compressor = ZCACHE_COMPRESSOR_DEFAULT;
+module_param_named(compressor, zcache_compressor, charp, 0);
+
+/* The maximum percentage of memory that the compressed pool can occupy */
+static unsigned int zcache_max_pool_percent = 10;
+module_param_named(max_pool_percent,
+ zcache_max_pool_percent, uint, 0644);
+
+/* zcache cleancache part statistics */
+static u64 zcache_cleancache_pool_pages;
+static u64 zcache_cleancache_pool_limit_hit;
+static u64 zcache_cleancache_written_back_pages;
+static u64 zcache_cleancache_dup_entry;
+static u64 zcache_cleancache_reclaim_fail;
+static u64 zcache_cleancache_zbud_alloc_fail;
+static atomic_t zcache_cleancache_stored_pages = ATOMIC_INIT(0);
+
+struct zcache_cleancache_meta {
+ int ra_index;
+ int length; /* compressed page size */
+};
+
+#define MAX_ZCACHE_POOLS 32 /* arbitrary */
+
+/* Red-Black tree node. Maps inode to its page-tree */
+struct zcache_rb_entry {
+ int rb_index;
+ struct kref refcount;
+
+ struct radix_tree_root ra_root; /* maps inode index to page */
+ spinlock_t ra_lock; /* protects radix tree */
+ struct rb_node rb_node;
+};
+
+/* One zcache pool per (cleancache aware) filesystem mount instance */
+struct zcache_pool {
+ struct rb_root rb_root; /* maps inode number to page tree */
+ rwlock_t rb_lock; /* protects inode_tree */
+ struct zbud_pool *pool; /* zbud pool used */
+};
+
+/* Manage all zcache pools */
+struct _zcache {
+ struct zcache_pool *pools[MAX_ZCACHE_POOLS];
+ u32 num_pools; /* current no. of zcache pools */
+ spinlock_t pool_lock; /* protects pools[] and num_pools */
+};
+struct _zcache zcache;
+
+static struct kmem_cache *zcache_cleancache_entry_cache;
+
+/*********************************
+* compression functions
+**********************************/
+/* per-cpu compression transforms */
+static struct crypto_comp * __percpu *zcache_comp_pcpu_tfms;
+
+enum comp_op {
+ ZCACHE_COMPOP_COMPRESS,
+ ZCACHE_COMPOP_DECOMPRESS
+};
+
+static int zcache_comp_op(enum comp_op op, const u8 *src, unsigned int slen,
+ u8 *dst, unsigned int *dlen)
+{
+ struct crypto_comp *tfm;
+ int ret;
+
+ tfm = *per_cpu_ptr(zcache_comp_pcpu_tfms, get_cpu());
+ switch (op) {
+ case ZCACHE_COMPOP_COMPRESS:
+ ret = crypto_comp_compress(tfm, src, slen, dst, dlen);
+ break;
+ case ZCACHE_COMPOP_DECOMPRESS:
+ ret = crypto_comp_decompress(tfm, src, slen, dst, dlen);
+ break;
+ default:
+ ret = -EINVAL;
+ }
+
+ put_cpu();
+ return ret;
+}
+
+static int __init zcache_comp_init(void)
+{
+ if (!crypto_has_comp(zcache_compressor, 0, 0)) {
+ pr_info("%s compressor not available\n", zcache_compressor);
+ /* fall back to default compressor */
+ zcache_compressor = ZCACHE_COMPRESSOR_DEFAULT;
+ if (!crypto_has_comp(zcache_compressor, 0, 0))
+ /* can't even load the default compressor */
+ return -ENODEV;
+ }
+ pr_info("using %s compressor\n", zcache_compressor);
+
+ /* alloc percpu transforms */
+ zcache_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *);
+ if (!zcache_comp_pcpu_tfms)
+ return -ENOMEM;
+ return 0;
+}
+
+static void zcache_comp_exit(void)
+{
+ /* free percpu transforms */
+ if (zcache_comp_pcpu_tfms)
+ free_percpu(zcache_comp_pcpu_tfms);
+}
+
+/*********************************
+* per-cpu code
+**********************************/
+static DEFINE_PER_CPU(u8 *, zcache_dstmem);
+
+static int __zcache_cpu_notifier(unsigned long action, unsigned long cpu)
+{
+ struct crypto_comp *tfm;
+ u8 *dst;
+
+ switch (action) {
+ case CPU_UP_PREPARE:
+ tfm = crypto_alloc_comp(zcache_compressor, 0, 0);
+ if (IS_ERR(tfm)) {
+ pr_err("can't allocate compressor transform\n");
+ return NOTIFY_BAD;
+ }
+ *per_cpu_ptr(zcache_comp_pcpu_tfms, cpu) = tfm;
+ dst = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
+ if (!dst) {
+ pr_err("can't allocate compressor buffer\n");
+ crypto_free_comp(tfm);
+ *per_cpu_ptr(zcache_comp_pcpu_tfms, cpu) = NULL;
+ return NOTIFY_BAD;
+ }
+ per_cpu(zcache_dstmem, cpu) = dst;
+ break;
+ case CPU_DEAD:
+ case CPU_UP_CANCELED:
+ tfm = *per_cpu_ptr(zcache_comp_pcpu_tfms, cpu);
+ if (tfm) {
+ crypto_free_comp(tfm);
+ *per_cpu_ptr(zcache_comp_pcpu_tfms, cpu) = NULL;
+ }
+ dst = per_cpu(zcache_dstmem, cpu);
+ kfree(dst);
+ per_cpu(zcache_dstmem, cpu) = NULL;
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static int zcache_cpu_notifier(struct notifier_block *nb,
+ unsigned long action, void *pcpu)
+{
+ unsigned long cpu = (unsigned long)pcpu;
+ return __zcache_cpu_notifier(action, cpu);
+}
+
+static struct notifier_block zcache_cpu_notifier_block = {
+ .notifier_call = zcache_cpu_notifier
+};
+
+static int zcache_cpu_init(void)
+{
+ unsigned long cpu;
+
+ get_online_cpus();
+ for_each_online_cpu(cpu)
+ if (__zcache_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK)
+ goto cleanup;
+ register_cpu_notifier(&zcache_cpu_notifier_block);
+ put_online_cpus();
+ return 0;
+
+cleanup:
+ for_each_online_cpu(cpu)
+ __zcache_cpu_notifier(CPU_UP_CANCELED, cpu);
+ put_online_cpus();
+ return -ENOMEM;
+}
+
+/*********************************
+* helpers
+**********************************/
+static bool zcache_is_full(void)
+{
+ return (totalram_pages * zcache_max_pool_percent / 100 <
+ zcache_cleancache_pool_pages);
+}
+
+static int zcache_cleancache_entry_cache_create(void)
+{
+ zcache_cleancache_entry_cache = KMEM_CACHE(zcache_rb_entry, 0);
+ return (zcache_cleancache_entry_cache == NULL);
+}
+static void zcache_cleancache_entry_cache_destory(void)
+{
+ kmem_cache_destroy(zcache_cleancache_entry_cache);
+}
+
+static struct zcache_rb_entry *zcache_find_rb_entry(struct rb_root *root,
+ int index, struct rb_node **rb_parent, struct rb_node ***rb_link)
+{
+ struct zcache_rb_entry *entry;
+ struct rb_node **__rb_link, *__rb_parent, *rb_prev;
+
+ __rb_link = &root->rb_node;
+ rb_prev = __rb_parent = NULL;
+
+ while (*__rb_link) {
+ __rb_parent = *__rb_link;
+ entry = rb_entry(__rb_parent, struct zcache_rb_entry, rb_node);
+ if (entry->rb_index > index)
+ __rb_link = &__rb_parent->rb_left;
+ else if (entry->rb_index < index) {
+ rb_prev = __rb_parent;
+ __rb_link = &__rb_parent->rb_right;
+ } else
+ return entry;
+ }
+
+ if (rb_parent)
+ *rb_parent = __rb_parent;
+ if (rb_link)
+ *rb_link = __rb_link;
+ return NULL;
+}
+
+static struct zcache_rb_entry *zcache_find_get_rb_entry(struct zcache_pool *zpool,
+ int rb_index)
+{
+ unsigned long flags;
+ struct zcache_rb_entry *rb_entry;
+
+ read_lock_irqsave(&zpool->rb_lock, flags);
+ rb_entry = zcache_find_rb_entry(&zpool->rb_root, rb_index, 0, 0);
+ if (rb_entry)
+ kref_get(&rb_entry->refcount);
+ read_unlock_irqrestore(&zpool->rb_lock, flags);
+ return rb_entry;
+}
+
+/*
+ * kref_put callback for zcache rb_entry.
+ *
+ * The entry must have been isolated from rbtree already.
+ */
+static void zcache_rb_entry_release(struct kref *kref)
+{
+ struct zcache_rb_entry *rb_entry;
+
+ rb_entry = container_of(kref, struct zcache_rb_entry, refcount);
+ BUG_ON(rb_entry->ra_root.rnode);
+ kmem_cache_free(zcache_cleancache_entry_cache, rb_entry);
+}
+
+/*
+ * Called under zcache_rb_entry->ra_lock
+ */
+static int zcache_rb_entry_is_empty(struct zcache_rb_entry *rb_entry)
+{
+ return rb_entry->ra_root.rnode == NULL;
+}
+
+/* Remove rb_entry from rbtree */
+static void zcache_rb_entry_isolate(struct zcache_pool *zpool,
+ struct zcache_rb_entry *rb_entry, bool hold_rblock)
+{
+ unsigned long flags;
+
+ if (!hold_rblock)
+ write_lock_irqsave(&zpool->rb_lock, flags);
+ /*
+ * Someone can get reference on this node before we could
+ * acquire write lock above. We want to remove it from its
+ * inode_tree when only the caller and corresponding inode_tree
+ * holds a reference to it. This ensures that a racing zcache
+ * put will not end up adding a page to an isolated node and
+ * thereby losing that memory.
+ *
+ */
+ if (atomic_read(&rb_entry->refcount.refcount) == 2) {
+ rb_erase(&rb_entry->rb_node, &zpool->rb_root);
+ RB_CLEAR_NODE(&rb_entry->rb_node);
+ kref_put(&rb_entry->refcount, zcache_rb_entry_release);
+ }
+ if (!hold_rblock)
+ write_unlock_irqrestore(&zpool->rb_lock, flags);
+}
+
+
+static int zcache_store_handle(struct zcache_pool *zpool,
+ unsigned long handle, int rb_index, int ra_index)
+{
+ unsigned long flags;
+ struct zcache_rb_entry *rb_entry, *tmp;
+ struct rb_node **link = NULL, *parent = NULL;
+ int ret;
+ void *dup_handlep;
+
+ rb_entry = zcache_find_get_rb_entry(zpool, rb_index);
+ if (!rb_entry) {
+ /* alloc new rb_entry */
+ rb_entry = kmem_cache_alloc(zcache_cleancache_entry_cache, GFP_KERNEL);
+ if (!rb_entry)
+ return -ENOMEM;
+
+ INIT_RADIX_TREE(&rb_entry->ra_root, GFP_ATOMIC|__GFP_NOWARN);
+ spin_lock_init(&rb_entry->ra_lock);
+ rb_entry->rb_index = rb_index;
+ kref_init(&rb_entry->refcount);
+ RB_CLEAR_NODE(&rb_entry->rb_node);
+
+ /* add new entry to rb tree */
+ write_lock_irqsave(&zpool->rb_lock, flags);
+
+ tmp = zcache_find_rb_entry(&zpool->rb_root, rb_index, &parent, &link);
+ if (tmp) {
+ /* somebody else allocated new entry */
+ kmem_cache_free(zcache_cleancache_entry_cache, rb_entry);
+ rb_entry = tmp;
+ } else {
+ rb_link_node(&rb_entry->rb_node, parent, link);
+ rb_insert_color(&rb_entry->rb_node, &zpool->rb_root);
+ }
+
+ kref_get(&rb_entry->refcount);
+ write_unlock_irqrestore(&zpool->rb_lock, flags);
+ }
+
+ /* Succ get rb_entry and refcount after arrived here */
+ spin_lock_irqsave(&rb_entry->ra_lock, flags);
+ dup_handlep = radix_tree_delete(&rb_entry->ra_root, ra_index);
+ if (unlikely(dup_handlep)) {
+ WARN_ON("duplicated entry, will be replaced!\n");
+ zbud_free(zpool->pool, (unsigned long)dup_handlep);
+ atomic_dec(&zcache_cleancache_stored_pages);
+ zcache_cleancache_pool_pages = zbud_get_pool_size(zpool->pool);
+ zcache_cleancache_dup_entry++;
+ }
+ ret = radix_tree_insert(&rb_entry->ra_root, ra_index, (void *)handle);
+
+ if (unlikely(ret))
+ if (zcache_rb_entry_is_empty(rb_entry))
+ zcache_rb_entry_isolate(zpool, rb_entry, 0);
+ spin_unlock_irqrestore(&rb_entry->ra_lock, flags);
+
+ kref_put(&rb_entry->refcount, zcache_rb_entry_release);
+ return ret;
+}
+
+/* Load the handle, and delete it */
+static unsigned long *zcache_load_delete_handle(struct zcache_pool *zpool, int rb_index,
+ int ra_index)
+{
+ struct zcache_rb_entry *rb_entry;
+ void *handlep = NULL;
+ unsigned long flags;
+
+ rb_entry = zcache_find_get_rb_entry(zpool, rb_index);
+ if (!rb_entry)
+ goto out;
+
+ BUG_ON(rb_entry->rb_index != rb_index);
+
+ spin_lock_irqsave(&rb_entry->ra_lock, flags);
+ handlep = radix_tree_delete(&rb_entry->ra_root, ra_index);
+ if (zcache_rb_entry_is_empty(rb_entry))
+ /* If no more nodes in the rb_entry->radix_tree,
+ * rm rb_entry from the rbtree and drop the refcount
+ */
+ zcache_rb_entry_isolate(zpool, rb_entry, 0);
+ spin_unlock_irqrestore(&rb_entry->ra_lock, flags);
+
+ /* After arrive here, rb_entry have dropped from rbtree */
+ kref_put(&rb_entry->refcount, zcache_rb_entry_release);
+out:
+ return handlep;
+}
+
+static void zcache_cleancache_store_page(int pool_id, struct cleancache_filekey key,
+ pgoff_t index, struct page *page)
+{
+ unsigned int dlen = PAGE_SIZE, len;
+ unsigned long handle;
+ char *buf;
+ u8 *src, *dst;
+ struct zcache_cleancache_meta *zmeta;
+ int ret;
+
+ struct zcache_pool *zpool = zcache.pools[pool_id];
+
+ /* reclaim space if needed */
+ if (zcache_is_full()) {
+ /* Reclaim will be implemented in following version */
+ zcache_cleancache_pool_limit_hit++;
+ return;
+ }
+
+ /* compress */
+ dst = get_cpu_var(zcache_dstmem);
+ src = kmap_atomic(page);
+ ret = zcache_comp_op(ZCACHE_COMPOP_COMPRESS, src, PAGE_SIZE, dst, &dlen);
+ kunmap_atomic(src);
+ if (ret) {
+ pr_err("zcache_cleancache compress error ret %d\n", ret);
+ put_cpu_var(zcache_dstmem);
+ return;
+ }
+
+ /* store handle with meta data */
+ len = dlen + sizeof(struct zcache_cleancache_meta);
+ ret = zbud_alloc(zpool->pool, len, __GFP_NORETRY | __GFP_NOWARN, &handle);
+ if (ret) {
+ zcache_cleancache_zbud_alloc_fail++;
+ put_cpu_var(zcache_dstmem);
+ return;
+ }
+
+ zmeta = zbud_map(zpool->pool, handle);
+ zmeta->ra_index = index;
+ zmeta->length = dlen;
+ buf = (u8 *)(zmeta + 1);
+ memcpy(buf, dst, dlen);
+ zbud_unmap(zpool->pool, handle);
+ put_cpu_var(zcache_dstmem);
+
+ /* populate entry */
+ ret = zcache_store_handle(zpool, handle, key.u.ino, index);
+ if (ret) {
+ pr_err("%s: store handle error %d\n", __func__, ret);
+ zbud_free(zpool->pool, handle);
+ }
+
+ /* update stats */
+ atomic_inc(&zcache_cleancache_stored_pages);
+ zcache_cleancache_pool_pages = zbud_get_pool_size(zpool->pool);
+ return;
+}
+
+static int zcache_cleancache_load_page(int pool_id, struct cleancache_filekey key,
+ pgoff_t index, struct page *page)
+{
+ struct zcache_pool *zpool = zcache.pools[pool_id];
+ u8 *src, *dst;
+ unsigned int dlen;
+ int ret;
+ unsigned long *handlep;
+ struct zcache_cleancache_meta *zmeta;
+
+ handlep = zcache_load_delete_handle(zpool, key.u.ino, index);
+ if (!handlep)
+ return -1;
+
+ zmeta = (struct zcache_cleancache_meta *)zbud_map(zpool->pool, (unsigned long)handlep);
+ src = (u8 *)(zmeta + 1);
+
+ /* decompress */
+ dlen = PAGE_SIZE;
+ dst = kmap_atomic(page);
+ ret = zcache_comp_op(ZCACHE_COMPOP_DECOMPRESS, src, zmeta->length, dst, &dlen);
+ kunmap_atomic(dst);
+ zbud_unmap(zpool->pool, (unsigned long)handlep);
+ zbud_free(zpool->pool, (unsigned long)handlep);
+
+ WARN_ON(ret); /* decompress err, will fetch from real disk */
+ /* update stats */
+ atomic_dec(&zcache_cleancache_stored_pages);
+ zcache_cleancache_pool_pages = zbud_get_pool_size(zpool->pool);
+ return ret;
+}
+
+static void zcache_cleancache_flush_page(int pool_id, struct cleancache_filekey key,
+ pgoff_t index)
+{
+ struct zcache_pool *zpool = zcache.pools[pool_id];
+ unsigned long *handlep = NULL;
+
+ handlep = zcache_load_delete_handle(zpool, key.u.ino, index);
+ if (handlep) {
+ zbud_free(zpool->pool, (unsigned long)handlep);
+ atomic_dec(&zcache_cleancache_stored_pages);
+ zcache_cleancache_pool_pages = zbud_get_pool_size(zpool->pool);
+ }
+}
+
+#define FREE_BATCH 16
+static void zcache_cleancache_flush_ratree(struct zcache_pool *zpool,
+ struct zcache_rb_entry *entry)
+{
+ int count, i;
+ unsigned long index = 0;
+
+ do {
+ struct zcache_cleancache_meta *handles[FREE_BATCH];
+
+ count = radix_tree_gang_lookup(&entry->ra_root,
+ (void **)handles, index, FREE_BATCH);
+
+ for (i = 0; i < count; i++) {
+ index = handles[i]->ra_index;
+ radix_tree_delete(&entry->ra_root, index);
+ zbud_free(zpool->pool, (unsigned long)handles[i]);
+ atomic_dec(&zcache_cleancache_stored_pages);
+ zcache_cleancache_pool_pages = zbud_get_pool_size(zpool->pool);
+ }
+
+ index++;
+ } while (count == FREE_BATCH);
+}
+
+static void zcache_cleancache_flush_inode(int pool_id,
+ struct cleancache_filekey key)
+{
+ struct zcache_rb_entry *rb_entry;
+ unsigned long flags1, flags2;
+ struct zcache_pool *zpool = zcache.pools[pool_id];
+
+ /* refuse new pages added in to the same inode */
+ write_lock_irqsave(&zpool->rb_lock, flags1);
+ rb_entry = zcache_find_rb_entry(&zpool->rb_root, key.u.ino, 0, 0);
+ if (!rb_entry) {
+ write_unlock_irqrestore(&zpool->rb_lock, flags1);
+ return;
+ }
+
+ kref_get(&rb_entry->refcount);
+
+ spin_lock_irqsave(&rb_entry->ra_lock, flags2);
+ zcache_cleancache_flush_ratree(zpool, rb_entry);
+ if (zcache_rb_entry_is_empty(rb_entry))
+ zcache_rb_entry_isolate(zpool, rb_entry, 1);
+ spin_unlock_irqrestore(&rb_entry->ra_lock, flags2);
+
+ write_unlock_irqrestore(&zpool->rb_lock, flags1);
+ kref_put(&rb_entry->refcount, zcache_rb_entry_release);
+}
+
+static void zcache_destroy_pool(struct zcache_pool *zpool);
+static void zcache_cleancache_flush_fs(int pool_id)
+{
+ struct zcache_rb_entry *entry = NULL;
+ struct rb_node *node;
+ unsigned long flags1, flags2;
+ struct zcache_pool *zpool = zcache.pools[pool_id];
+
+ if (!zpool)
+ return;
+
+ /* refuse new pages added in to the same inode */
+ write_lock_irqsave(&zpool->rb_lock, flags1);
+
+ node = rb_first(&zpool->rb_root);
+ while (node) {
+ entry = rb_entry(node, struct zcache_rb_entry, rb_node);
+ node = rb_next(node);
+ if (entry) {
+ kref_get(&entry->refcount);
+ spin_lock_irqsave(&entry->ra_lock, flags2);
+ zcache_cleancache_flush_ratree(zpool, entry);
+ if (zcache_rb_entry_is_empty(entry))
+ zcache_rb_entry_isolate(zpool, entry, 1);
+ spin_unlock_irqrestore(&entry->ra_lock, flags2);
+ kref_put(&entry->refcount, zcache_rb_entry_release);
+ }
+ }
+
+ write_unlock_irqrestore(&zpool->rb_lock, flags1);
+
+ zcache_destroy_pool(zpool);
+}
+
+static int zcache_cleancache_evict_entry(struct zbud_pool *pool,
+ unsigned long handle)
+{
+ return -1;
+}
+
+static struct zbud_ops zcache_cleancache_zbud_ops = {
+ .evict = zcache_cleancache_evict_entry
+};
+
+static void zcache_destroy_pool(struct zcache_pool *zpool)
+{
+ int i;
+
+ if (!zpool)
+ return;
+
+ spin_lock(&zcache.pool_lock);
+ zcache.num_pools--;
+ for (i = 0; i < MAX_ZCACHE_POOLS; i++)
+ if (zcache.pools[i] == zpool)
+ break;
+ zcache.pools[i] = NULL;
+ spin_unlock(&zcache.pool_lock);
+
+ if (!RB_EMPTY_ROOT(&zpool->rb_root)) {
+ WARN_ON("Memory leak detected. Freeing non-empty pool!\n");
+ }
+
+ zbud_destroy_pool(zpool->pool);
+ kfree(zpool);
+}
+
+/* return pool id */
+static int zcache_create_pool(void)
+{
+ int ret;
+ struct zcache_pool *zpool;
+
+ zpool = kzalloc(sizeof(*zpool), GFP_KERNEL);
+ if (!zpool) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ zpool->pool = zbud_create_pool(GFP_KERNEL, &zcache_cleancache_zbud_ops);
+ if (!zpool->pool) {
+ kfree(zpool);
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ spin_lock(&zcache.pool_lock);
+ if (zcache.num_pools == MAX_ZCACHE_POOLS) {
+ pr_info("Cannot create new pool (limit: %u)\n",
+ MAX_ZCACHE_POOLS);
+ zbud_destroy_pool(zpool->pool);
+ kfree(zpool);
+ ret = -EPERM;
+ goto out_unlock;
+ }
+
+ rwlock_init(&zpool->rb_lock);
+ zpool->rb_root = RB_ROOT;
+
+ /* Add to pool list */
+ for (ret = 0; ret < MAX_ZCACHE_POOLS; ret++)
+ if (!zcache.pools[ret])
+ break;
+ zcache.pools[ret] = zpool;
+ zcache.num_pools++;
+ pr_info("New pool created id:%d\n", ret);
+
+out_unlock:
+ spin_unlock(&zcache.pool_lock);
+out:
+ return ret;
+}
+
+static int zcache_cleancache_init_fs(size_t pagesize)
+{
+ int ret;
+
+ if (pagesize != PAGE_SIZE) {
+ pr_info("Unsupported page size: %zu", pagesize);
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = zcache_create_pool();
+ if (ret < 0) {
+ pr_info("Failed to create new pool\n");
+ ret = -ENOMEM;
+ goto out;
+ }
+
+out:
+ return ret;
+}
+
+static int zcache_cleancache_init_shared_fs(char *uuid, size_t pagesize)
+{
+ /* shared pools are unsupported and map to private */
+ return zcache_cleancache_init_fs(pagesize);
+}
+
+static struct cleancache_ops zcache_cleancache_ops = {
+ .put_page = zcache_cleancache_store_page,
+ .get_page = zcache_cleancache_load_page,
+ .invalidate_page = zcache_cleancache_flush_page,
+ .invalidate_inode = zcache_cleancache_flush_inode,
+ .invalidate_fs = zcache_cleancache_flush_fs,
+ .init_shared_fs = zcache_cleancache_init_shared_fs,
+ .init_fs = zcache_cleancache_init_fs
+};
+
+/*********************************
+* debugfs functions
+**********************************/
+#ifdef CONFIG_DEBUG_FS
+#include <linux/debugfs.h>
+
+static struct dentry *zcache_cleancache_debugfs_root;
+
+static int __init zcache_debugfs_init(void)
+{
+ if (!debugfs_initialized())
+ return -ENODEV;
+
+ if (!zcache_nocleancache) {
+ zcache_cleancache_debugfs_root = debugfs_create_dir("zcache_cleancache", NULL);
+ if (!zcache_cleancache_debugfs_root)
+ return -ENOMEM;
+
+ debugfs_create_u64("pool_limit_hit", S_IRUGO,
+ zcache_cleancache_debugfs_root, &zcache_cleancache_pool_limit_hit);
+ debugfs_create_u64("reclaim_fail", S_IRUGO,
+ zcache_cleancache_debugfs_root, &zcache_cleancache_reclaim_fail);
+ debugfs_create_u64("reject_alloc_fail", S_IRUGO,
+ zcache_cleancache_debugfs_root, &zcache_cleancache_zbud_alloc_fail);
+ debugfs_create_u64("written_back_pages", S_IRUGO,
+ zcache_cleancache_debugfs_root, &zcache_cleancache_written_back_pages);
+ debugfs_create_u64("duplicate_entry", S_IRUGO,
+ zcache_cleancache_debugfs_root, &zcache_cleancache_dup_entry);
+ debugfs_create_u64("pool_pages", S_IRUGO,
+ zcache_cleancache_debugfs_root, &zcache_cleancache_pool_pages);
+ debugfs_create_atomic_t("stored_pages", S_IRUGO,
+ zcache_cleancache_debugfs_root, &zcache_cleancache_stored_pages);
+ }
+ return 0;
+}
+
+static void __exit zcache_debugfs_exit(void)
+{
+ debugfs_remove_recursive(zcache_cleancache_debugfs_root);
+}
+#else
+static int __init zcache_debugfs_init(void)
+{
+ return 0;
+}
+static void __exit zcache_debugfs_exit(void)
+{
+}
+#endif
+
+/*********************************
+* module init and exit
+**********************************/
+static int __init init_zcache(void)
+{
+ if (!zcache_enabled)
+ return 0;
+
+ pr_info("loading zcache..\n");
+ if (!zcache_nocleancache)
+ if (zcache_cleancache_entry_cache_create()) {
+ pr_err("entry cache creation failed\n");
+ goto error;
+ }
+
+ if (zcache_comp_init()) {
+ pr_err("compressor initialization failed\n");
+ goto compfail;
+ }
+ if (zcache_cpu_init()) {
+ pr_err("per-cpu initialization failed\n");
+ goto pcpufail;
+ }
+
+ spin_lock_init(&zcache.pool_lock);
+ if (!zcache_nocleancache)
+ cleancache_register_ops(&zcache_cleancache_ops);
+
+ if (zcache_debugfs_init())
+ pr_warn("debugfs initialization failed\n");
+ return 0;
+pcpufail:
+ zcache_comp_exit();
+compfail:
+ zcache_cleancache_entry_cache_destory();
+error:
+ return -ENOMEM;
+}
+/* must be late so crypto has time to come up */
+late_initcall(init_zcache);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Bob Liu <bob.liu@oracle.com>");
+MODULE_DESCRIPTION("Compressed cache for clean file pages");
--
1.7.10.4
^ permalink raw reply related [flat|nested] 9+ messages in thread
* Fwd: [PATCH 0/2] zcache: a new start for upstream
2013-07-20 14:36 [PATCH 0/2] zcache: a new start for upstream Bob Liu
2013-07-20 14:36 ` [PATCH 1/2] zcache: staging: %s/ZCACHE/ZCACHE_OLD Bob Liu
2013-07-20 14:36 ` [PATCH 2/2] mm: zcache: core functions added Bob Liu
@ 2013-07-20 15:23 ` Bob Liu
[not found] ` <20130722150702.GB4706@variantweb.net>
3 siblings, 0 replies; 9+ messages in thread
From: Bob Liu @ 2013-07-20 15:23 UTC (permalink / raw)
To: linux-mm
[-- Attachment #1: Type: text/plain, Size: 2110 bytes --]
A extra space in my git script cause linux-mm missed!
-------- Original Message --------
Subject: [PATCH 0/2] zcache: a new start for upstream
Date: Sat, 20 Jul 2013 22:36:56 +0800
From: Bob Liu <lliubbo@gmail.com>
CC: linux-kernel@vger.kernel.org, sjenning@linux.vnet.ibm.com,
gregkh@linuxfoundation.org, ngupta@vflare.org, minchan@kernel.org,
konrad.wilk@oracle.com, rcj@linux.vnet.ibm.com, mgorman@suse.de,
riel@redhat.com, penberg@kernel.org, akpm@linux-foundation.org,
Bob Liu <bob.liu@oracle.com>
We already have zswap helps reducing the swap out/in IO operations by
compressing anon pages.
It has been merged into v3.11-rc1 together with the zbud allocation layer.
However there is another kind of pages(clean file pages) suitable for
compression as well. Upstream has already merged its frontend(cleancache).
Now we are lacking of a backend of cleancache as zswap to frontswap.
Furthermore, we need to balance the number of compressed anon and file
pages,
E.g. it's unfair to normal file pages if zswap pool occupies too much
memory for
the storage of compressed anon pages.
Although the current version of zcache in staging tree has already done
those
works mentioned above, the implementation is too complicated to be
merged into
upstream.
What I'm looking for is a new way for zcache towards upstream.
The first change is no more staging tree.
Second is implemented a simple cleancache backend at first, which is
based on
the zbud allocation same as zswap.
At the end, I hope we can combine the new cleancache backend with
zswap(frontswap backend), in order to have a generic in-kernel memory
compression solution in upstream.
Bob Liu (2):
zcache: staging: %s/ZCACHE/ZCACHE_OLD
mm: zcache: core functions added
drivers/staging/zcache/Kconfig | 12 +-
drivers/staging/zcache/Makefile | 4 +-
mm/Kconfig | 18 +
mm/Makefile | 1 +
mm/zcache.c | 840
+++++++++++++++++++++++++++++++++++++++
5 files changed, 867 insertions(+), 8 deletions(-)
create mode 100644 mm/zcache.c
--
1.7.10.4
--
Regards,
-Bob
[-- Attachment #2: Attached Message Part --]
[-- Type: text/plain, Size: 0 bytes --]
^ permalink raw reply [flat|nested] 9+ messages in thread
* Fwd: [PATCH 1/2] zcache: staging: %s/ZCACHE/ZCACHE_OLD
2013-07-20 14:36 ` [PATCH 1/2] zcache: staging: %s/ZCACHE/ZCACHE_OLD Bob Liu
@ 2013-07-20 15:24 ` Bob Liu
2013-07-20 16:42 ` Greg KH
1 sibling, 0 replies; 9+ messages in thread
From: Bob Liu @ 2013-07-20 15:24 UTC (permalink / raw)
To: linux-mm
[-- Attachment #1: Type: text/plain, Size: 2956 bytes --]
-------- Original Message --------
Subject: [PATCH 1/2] zcache: staging: %s/ZCACHE/ZCACHE_OLD
Date: Sat, 20 Jul 2013 22:36:57 +0800
From: Bob Liu <lliubbo@gmail.com>
CC: linux-kernel@vger.kernel.org, sjenning@linux.vnet.ibm.com,
gregkh@linuxfoundation.org, ngupta@vflare.org, minchan@kernel.org,
konrad.wilk@oracle.com, rcj@linux.vnet.ibm.com, mgorman@suse.de,
riel@redhat.com, penberg@kernel.org, akpm@linux-foundation.org,
Bob Liu <bob.liu@oracle.com>
Signed-off-by: Bob Liu <bob.liu@oracle.com>
---
drivers/staging/zcache/Kconfig | 12 ++++++------
drivers/staging/zcache/Makefile | 4 ++--
2 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/drivers/staging/zcache/Kconfig b/drivers/staging/zcache/Kconfig
index 2d7b2da..f96fb12 100644
--- a/drivers/staging/zcache/Kconfig
+++ b/drivers/staging/zcache/Kconfig
@@ -1,4 +1,4 @@
-config ZCACHE
+config ZCACHE_OLD
tristate "Dynamic compression of swap pages and clean pagecache pages"
depends on CRYPTO=y && SWAP=y && CLEANCACHE && FRONTSWAP
select CRYPTO_LZO
@@ -10,9 +10,9 @@ config ZCACHE
memory to store clean page cache pages and swap in RAM,
providing a noticeable reduction in disk I/O.
-config ZCACHE_DEBUG
+config ZCACHE_OLD_DEBUG
bool "Enable debug statistics"
- depends on DEBUG_FS && ZCACHE
+ depends on DEBUG_FS && ZCACHE_OLD
default n
help
This is used to provide an debugfs directory with counters of
@@ -20,7 +20,7 @@ config ZCACHE_DEBUG
config RAMSTER
tristate "Cross-machine RAM capacity sharing, aka peer-to-peer tmem"
- depends on CONFIGFS_FS=y && SYSFS=y && !HIGHMEM && ZCACHE
+ depends on CONFIGFS_FS=y && SYSFS=y && !HIGHMEM && ZCACHE_OLD
depends on NET
# must ensure struct page is 8-byte aligned
select HAVE_ALIGNED_STRUCT_PAGE if !64BIT
@@ -45,9 +45,9 @@ config RAMSTER_DEBUG
# __add_to_swap_cache, and implement __swap_writepage (which is
swap_writepage
# without the frontswap call. When these are in-tree, the dependency on
# BROKEN can be removed
-config ZCACHE_WRITEBACK
+config ZCACHE_OLD_WRITEBACK
bool "Allow compressed swap pages to be writtenback to swap disk"
- depends on ZCACHE=y && BROKEN
+ depends on ZCACHE_OLD=y && BROKEN
default n
help
Zcache caches compressed swap pages (and other data) in RAM which
diff --git a/drivers/staging/zcache/Makefile
b/drivers/staging/zcache/Makefile
index 845a5c2..34d27bd 100644
--- a/drivers/staging/zcache/Makefile
+++ b/drivers/staging/zcache/Makefile
@@ -1,8 +1,8 @@
zcache-y := zcache-main.o tmem.o zbud.o
-zcache-$(CONFIG_ZCACHE_DEBUG) += debug.o
+zcache-$(CONFIG_ZCACHE_OLD_DEBUG) += debug.o
zcache-$(CONFIG_RAMSTER_DEBUG) += ramster/debug.o
zcache-$(CONFIG_RAMSTER) += ramster/ramster.o ramster/r2net.o
zcache-$(CONFIG_RAMSTER) += ramster/nodemanager.o ramster/tcp.o
zcache-$(CONFIG_RAMSTER) += ramster/heartbeat.o ramster/masklog.o
-obj-$(CONFIG_ZCACHE) += zcache.o
+obj-$(CONFIG_ZCACHE_OLD) += zcache.o
--
1.7.10.4
--
Regards,
-Bob
[-- Attachment #2: Attached Message Part --]
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* Fwd: [PATCH 2/2] mm: zcache: core functions added
2013-07-20 14:36 ` [PATCH 2/2] mm: zcache: core functions added Bob Liu
@ 2013-07-20 15:25 ` Bob Liu
0 siblings, 0 replies; 9+ messages in thread
From: Bob Liu @ 2013-07-20 15:25 UTC (permalink / raw)
To: linux-mm
-------- Original Message --------
Subject: [PATCH 2/2] mm: zcache: core functions added
Date: Sat, 20 Jul 2013 22:36:58 +0800
From: Bob Liu <lliubbo@gmail.com>
CC: linux-kernel@vger.kernel.org, sjenning@linux.vnet.ibm.com,
gregkh@linuxfoundation.org, ngupta@vflare.org, minchan@kernel.org,
konrad.wilk@oracle.com, rcj@linux.vnet.ibm.com, mgorman@suse.de,
riel@redhat.com, penberg@kernel.org, akpm@linux-foundation.org,
Bob Liu <bob.liu@oracle.com>
This patch adds the cleancache backend for clean file pages compression.
Nitin Gupta have already done many works on this topic in 2010.
You can see his work from below links:
http://lwn.net/Articles/396467/
http://thread.gmane.org/gmane.linux.kernel.mm/50523
But at that time neither the allocation layer nor cleancache have been
merged
into upstream.
(Most of below comments are copyed from his patch.)
Frequently accessed filesystem data is stored in memory to reduce access to
(much) slower backing disks. Under memory pressure, these pages are
freed and
when needed again, they have to be read from disks again. When combined
working set of all running application exceeds amount of physical RAM,
we get
extereme slowdown as reading a page from disk can take time in order of
milliseconds.
Memory compression increases effective memory size and allows more pages to
stay in RAM. Since de/compressing memory pages is several orders of
magnitude
faster than disk I/O, this can provide signifant performance gains for many
workloads. Also, with multi-cores becoming common, benefits of reduced disk
I/O should easily outweigh the problem of increased CPU usage.
It is implemented as a "backend" for cleancache which provides
callbacks for events such as when a page is to be removed from the page
cache
and when it is required again. We use them to implement a 'second chance'
cache for these evicted page cache pages by compressing and storing them in
memory itself.
We use zbud memory allocator which is already merged and used by zswap
for the
same purpose.
A separate "pool" is created for each mount instance for a cleancache-aware
filesystem. Each incoming page is identified with <pool_id, inode_no, index>
where inode_no identifies file within the filesystem corresponding to
pool_id
and index is offset of the page within this inode. Within a pool, inodes are
maintained in an rb-tree and each of its nodes points to a separate
radix-tree
which maintains list of pages within that inode.
Tests were done on physical machine (not in a VM)
Only played with iozone for some simple tests.
Kernel booted with command line "single mem=1G zcache.enabled=1"
Kernel 3.10.0+ (with Seth's zswap patches)
CPU: Core-i5 4-Core
RAM: 1G
Boot into single mode
Swapoff -a to avoid I/O interference
Command for testing:
iozone -a -M -B -s 1G -y 4k -+u -R -b iozone.xls
Results:
Without zcache
random
random bkwd record stride
KB reclen write rewrite read reread read
write read rewrite read
1048576 4 73070 36713 75187 74916 1292
674 26724 45514 8491
1048576 8 68777 34407 71162 73407 2703
1233 27800 42417 5548
1048576 16 70030 35156 71496 71186 4462
2181 31480 42040 8737
1048576 32 68796 35442 72557 72734 6955
3615 40783 44627 10959
1048576 64 76576 35247 68685 72279 11383
6615 49913 44620 14777
1048576 128 77516 33878 72538 71231 17897
10896 64393 48613 35265
1048576 256 73465 37450 22857 22854 22845
16655 61152 49170 40571
1048576 512 68096 35303 22265 22398 36154
23952 58286 48594 39972
1048576 1024 69442 36192 22206 22541 38927
29643 60695 50483 44120
1048576 2048 69404 34891 22951 23286 40036
35984 62095 50704 43764
1048576 4096 68871 35716 23147 23272 41587
37619 66809 47613 45229
1048576 8192 66775 36409 22997 23070 39023
39674 69262 55548 49324
1048576 16384 68728 34792 23829 24022 39922
42496 65714 44732 39104
Average: 70734 35507 45529 45938 23760 19326 52700
47283 29682
With zcache
random
random bkwd record stride
KB reclen write rewrite read reread read
write read rewrite read
1048576 4 80330 35970 120942 115559 1491
686 29923 47864 11177
1048576 8 69553 36658 134402 105351 2978
1332 33291 45885 6331
1048576 16 79538 36719 149905 155649 5970
2305 38136 42365 14070
1048576 32 68326 37064 150126 151728 10462
4128 44693 44975 15607
1048576 64 74450 35379 147918 130771 19199
7468 54065 43630 22104
1048576 128 71655 36125 137384 139080 27495
11507 65742 47471 49833
1048576 256 78867 36030 51814 42656 41578
17829 77058 44247 54368
1048576 512 68671 35378 52359 44516 52296
25944 80121 47270 57271
1048576 1024 69495 37064 53579 56057 60121
31833 83420 46752 65267
1048576 2048 69014 35589 52216 49919 69441
37169 92552 45746 68838
1048576 4096 67338 36194 56068 56855 71569
39895 98462 49440 72496
1048576 8192 65153 35345 54983 58602 78402
43841 98809 47334 74803
1048576 16384 63579 34842 50888 54429 68070
42518 87534 45665 64967
Average: 71228 36027 93345 89321 39159
20497 67985 46050 44395
Chnage : 1% 1% 105% 94% 65%
6% 29% -3% 50%
You can see that reading side performance get improved a lot after using
zcache.
Because pages are cached by zcache, we only need to decompress them
instead of
reading from disk.
Signed-off-by: Bob Liu <bob.liu@oracle.com>
---
mm/Kconfig | 18 ++
mm/Makefile | 1 +
mm/zcache.c | 840
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 859 insertions(+)
create mode 100644 mm/zcache.c
diff --git a/mm/Kconfig b/mm/Kconfig
index eec97f2..2b68103 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -507,3 +507,21 @@ config ZSWAP
interactions don't cause any known issues on simple memory setups,
they have not be fully explored on the large set of potential
configurations and workloads that exist.
+
+config ZCACHE
+ bool "Compressed cache for swap and clean file pages (EXPERIMENTAL)"
+ depends on FRONTSWAP && CRYPTO && CLEANCACHE
+ select CRYPTO_LZO
+ select ZBUD
+ default n
+ help
+ A compressed cache for swap and clean file pages.
+
+ It can takes pages that are in the process of being swapped out and
+ attempts to compress them into a dynamically allocated RAM-based
memory pool.
+ This can result in a significant I/O reduction on swap device and,
+ in the case where decompressing from RAM is faster that swap device
+ reads, can also improve workload performance.
+
+ Besides swap pages, zcache can also compress the clean file pages
into a memory pool.
+ This can reduce the refaults of reading those file pages back from
disks.
diff --git a/mm/Makefile b/mm/Makefile
index f008033..a29232b 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -33,6 +33,7 @@ obj-$(CONFIG_BOUNCE) += bounce.o
obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o
obj-$(CONFIG_FRONTSWAP) += frontswap.o
obj-$(CONFIG_ZSWAP) += zswap.o
+obj-$(CONFIG_ZCACHE) += zcache.o
obj-$(CONFIG_HAS_DMA) += dmapool.o
obj-$(CONFIG_HUGETLBFS) += hugetlb.o
obj-$(CONFIG_NUMA) += mempolicy.o
diff --git a/mm/zcache.c b/mm/zcache.c
new file mode 100644
index 0000000..a2408e8
--- /dev/null
+++ b/mm/zcache.c
@@ -0,0 +1,840 @@
+/*
+ * zcache.c - zcache driver file
+ *
+ * The goal of zcache is implement a generic memory compression layer.
+ * It's a backend of both frontswap and cleancache.
+ *
+ * This file only implemented cleancache part currently.
+ * Concepts based on original zcache by Dan Magenheimer.
+ *
+ * Copyright (C) 2013 Bob Liu <bob.liu@oracle.com>
+ *
+ * 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.
+*/
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/cpu.h>
+#include <linux/highmem.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+#include <linux/atomic.h>
+#include <linux/cleancache.h>
+#include <linux/rbtree.h>
+#include <linux/radix-tree.h>
+#include <linux/swap.h>
+#include <linux/crypto.h>
+#include <linux/mempool.h>
+#include <linux/zbud.h>
+
+#include <linux/mm_types.h>
+#include <linux/page-flags.h>
+#include <linux/swapops.h>
+#include <linux/writeback.h>
+#include <linux/pagemap.h>
+
+/* Enable/disable zcache (disabled by default) */
+static bool zcache_enabled __read_mostly;
+module_param_named(enabled, zcache_enabled, bool, 0);
+
+/* Enable/disable cleancache part of zcache */
+static bool zcache_nocleancache __read_mostly;
+module_param_named(nocleancache, zcache_nocleancache, bool, 0);
+
+/* Compressor to be used by zcache */
+#define ZCACHE_COMPRESSOR_DEFAULT "lzo"
+static char *zcache_compressor = ZCACHE_COMPRESSOR_DEFAULT;
+module_param_named(compressor, zcache_compressor, charp, 0);
+
+/* The maximum percentage of memory that the compressed pool can occupy */
+static unsigned int zcache_max_pool_percent = 10;
+module_param_named(max_pool_percent,
+ zcache_max_pool_percent, uint, 0644);
+
+/* zcache cleancache part statistics */
+static u64 zcache_cleancache_pool_pages;
+static u64 zcache_cleancache_pool_limit_hit;
+static u64 zcache_cleancache_written_back_pages;
+static u64 zcache_cleancache_dup_entry;
+static u64 zcache_cleancache_reclaim_fail;
+static u64 zcache_cleancache_zbud_alloc_fail;
+static atomic_t zcache_cleancache_stored_pages = ATOMIC_INIT(0);
+
+struct zcache_cleancache_meta {
+ int ra_index;
+ int length; /* compressed page size */
+};
+
+#define MAX_ZCACHE_POOLS 32 /* arbitrary */
+
+/* Red-Black tree node. Maps inode to its page-tree */
+struct zcache_rb_entry {
+ int rb_index;
+ struct kref refcount;
+
+ struct radix_tree_root ra_root; /* maps inode index to page */
+ spinlock_t ra_lock; /* protects radix tree */
+ struct rb_node rb_node;
+};
+
+/* One zcache pool per (cleancache aware) filesystem mount instance */
+struct zcache_pool {
+ struct rb_root rb_root; /* maps inode number to page tree */
+ rwlock_t rb_lock; /* protects inode_tree */
+ struct zbud_pool *pool; /* zbud pool used */
+};
+
+/* Manage all zcache pools */
+struct _zcache {
+ struct zcache_pool *pools[MAX_ZCACHE_POOLS];
+ u32 num_pools; /* current no. of zcache pools */
+ spinlock_t pool_lock; /* protects pools[] and num_pools */
+};
+struct _zcache zcache;
+
+static struct kmem_cache *zcache_cleancache_entry_cache;
+
+/*********************************
+* compression functions
+**********************************/
+/* per-cpu compression transforms */
+static struct crypto_comp * __percpu *zcache_comp_pcpu_tfms;
+
+enum comp_op {
+ ZCACHE_COMPOP_COMPRESS,
+ ZCACHE_COMPOP_DECOMPRESS
+};
+
+static int zcache_comp_op(enum comp_op op, const u8 *src, unsigned int
slen,
+ u8 *dst, unsigned int *dlen)
+{
+ struct crypto_comp *tfm;
+ int ret;
+
+ tfm = *per_cpu_ptr(zcache_comp_pcpu_tfms, get_cpu());
+ switch (op) {
+ case ZCACHE_COMPOP_COMPRESS:
+ ret = crypto_comp_compress(tfm, src, slen, dst, dlen);
+ break;
+ case ZCACHE_COMPOP_DECOMPRESS:
+ ret = crypto_comp_decompress(tfm, src, slen, dst, dlen);
+ break;
+ default:
+ ret = -EINVAL;
+ }
+
+ put_cpu();
+ return ret;
+}
+
+static int __init zcache_comp_init(void)
+{
+ if (!crypto_has_comp(zcache_compressor, 0, 0)) {
+ pr_info("%s compressor not available\n", zcache_compressor);
+ /* fall back to default compressor */
+ zcache_compressor = ZCACHE_COMPRESSOR_DEFAULT;
+ if (!crypto_has_comp(zcache_compressor, 0, 0))
+ /* can't even load the default compressor */
+ return -ENODEV;
+ }
+ pr_info("using %s compressor\n", zcache_compressor);
+
+ /* alloc percpu transforms */
+ zcache_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *);
+ if (!zcache_comp_pcpu_tfms)
+ return -ENOMEM;
+ return 0;
+}
+
+static void zcache_comp_exit(void)
+{
+ /* free percpu transforms */
+ if (zcache_comp_pcpu_tfms)
+ free_percpu(zcache_comp_pcpu_tfms);
+}
+
+/*********************************
+* per-cpu code
+**********************************/
+static DEFINE_PER_CPU(u8 *, zcache_dstmem);
+
+static int __zcache_cpu_notifier(unsigned long action, unsigned long cpu)
+{
+ struct crypto_comp *tfm;
+ u8 *dst;
+
+ switch (action) {
+ case CPU_UP_PREPARE:
+ tfm = crypto_alloc_comp(zcache_compressor, 0, 0);
+ if (IS_ERR(tfm)) {
+ pr_err("can't allocate compressor transform\n");
+ return NOTIFY_BAD;
+ }
+ *per_cpu_ptr(zcache_comp_pcpu_tfms, cpu) = tfm;
+ dst = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
+ if (!dst) {
+ pr_err("can't allocate compressor buffer\n");
+ crypto_free_comp(tfm);
+ *per_cpu_ptr(zcache_comp_pcpu_tfms, cpu) = NULL;
+ return NOTIFY_BAD;
+ }
+ per_cpu(zcache_dstmem, cpu) = dst;
+ break;
+ case CPU_DEAD:
+ case CPU_UP_CANCELED:
+ tfm = *per_cpu_ptr(zcache_comp_pcpu_tfms, cpu);
+ if (tfm) {
+ crypto_free_comp(tfm);
+ *per_cpu_ptr(zcache_comp_pcpu_tfms, cpu) = NULL;
+ }
+ dst = per_cpu(zcache_dstmem, cpu);
+ kfree(dst);
+ per_cpu(zcache_dstmem, cpu) = NULL;
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static int zcache_cpu_notifier(struct notifier_block *nb,
+ unsigned long action, void *pcpu)
+{
+ unsigned long cpu = (unsigned long)pcpu;
+ return __zcache_cpu_notifier(action, cpu);
+}
+
+static struct notifier_block zcache_cpu_notifier_block = {
+ .notifier_call = zcache_cpu_notifier
+};
+
+static int zcache_cpu_init(void)
+{
+ unsigned long cpu;
+
+ get_online_cpus();
+ for_each_online_cpu(cpu)
+ if (__zcache_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK)
+ goto cleanup;
+ register_cpu_notifier(&zcache_cpu_notifier_block);
+ put_online_cpus();
+ return 0;
+
+cleanup:
+ for_each_online_cpu(cpu)
+ __zcache_cpu_notifier(CPU_UP_CANCELED, cpu);
+ put_online_cpus();
+ return -ENOMEM;
+}
+
+/*********************************
+* helpers
+**********************************/
+static bool zcache_is_full(void)
+{
+ return (totalram_pages * zcache_max_pool_percent / 100 <
+ zcache_cleancache_pool_pages);
+}
+
+static int zcache_cleancache_entry_cache_create(void)
+{
+ zcache_cleancache_entry_cache = KMEM_CACHE(zcache_rb_entry, 0);
+ return (zcache_cleancache_entry_cache == NULL);
+}
+static void zcache_cleancache_entry_cache_destory(void)
+{
+ kmem_cache_destroy(zcache_cleancache_entry_cache);
+}
+
+static struct zcache_rb_entry *zcache_find_rb_entry(struct rb_root *root,
+ int index, struct rb_node **rb_parent, struct rb_node ***rb_link)
+{
+ struct zcache_rb_entry *entry;
+ struct rb_node **__rb_link, *__rb_parent, *rb_prev;
+
+ __rb_link = &root->rb_node;
+ rb_prev = __rb_parent = NULL;
+
+ while (*__rb_link) {
+ __rb_parent = *__rb_link;
+ entry = rb_entry(__rb_parent, struct zcache_rb_entry, rb_node);
+ if (entry->rb_index > index)
+ __rb_link = &__rb_parent->rb_left;
+ else if (entry->rb_index < index) {
+ rb_prev = __rb_parent;
+ __rb_link = &__rb_parent->rb_right;
+ } else
+ return entry;
+ }
+
+ if (rb_parent)
+ *rb_parent = __rb_parent;
+ if (rb_link)
+ *rb_link = __rb_link;
+ return NULL;
+}
+
+static struct zcache_rb_entry *zcache_find_get_rb_entry(struct
zcache_pool *zpool,
+ int rb_index)
+{
+ unsigned long flags;
+ struct zcache_rb_entry *rb_entry;
+
+ read_lock_irqsave(&zpool->rb_lock, flags);
+ rb_entry = zcache_find_rb_entry(&zpool->rb_root, rb_index, 0, 0);
+ if (rb_entry)
+ kref_get(&rb_entry->refcount);
+ read_unlock_irqrestore(&zpool->rb_lock, flags);
+ return rb_entry;
+}
+
+/*
+ * kref_put callback for zcache rb_entry.
+ *
+ * The entry must have been isolated from rbtree already.
+ */
+static void zcache_rb_entry_release(struct kref *kref)
+{
+ struct zcache_rb_entry *rb_entry;
+
+ rb_entry = container_of(kref, struct zcache_rb_entry, refcount);
+ BUG_ON(rb_entry->ra_root.rnode);
+ kmem_cache_free(zcache_cleancache_entry_cache, rb_entry);
+}
+
+/*
+ * Called under zcache_rb_entry->ra_lock
+ */
+static int zcache_rb_entry_is_empty(struct zcache_rb_entry *rb_entry)
+{
+ return rb_entry->ra_root.rnode == NULL;
+}
+
+/* Remove rb_entry from rbtree */
+static void zcache_rb_entry_isolate(struct zcache_pool *zpool,
+ struct zcache_rb_entry *rb_entry, bool hold_rblock)
+{
+ unsigned long flags;
+
+ if (!hold_rblock)
+ write_lock_irqsave(&zpool->rb_lock, flags);
+ /*
+ * Someone can get reference on this node before we could
+ * acquire write lock above. We want to remove it from its
+ * inode_tree when only the caller and corresponding inode_tree
+ * holds a reference to it. This ensures that a racing zcache
+ * put will not end up adding a page to an isolated node and
+ * thereby losing that memory.
+ *
+ */
+ if (atomic_read(&rb_entry->refcount.refcount) == 2) {
+ rb_erase(&rb_entry->rb_node, &zpool->rb_root);
+ RB_CLEAR_NODE(&rb_entry->rb_node);
+ kref_put(&rb_entry->refcount, zcache_rb_entry_release);
+ }
+ if (!hold_rblock)
+ write_unlock_irqrestore(&zpool->rb_lock, flags);
+}
+
+
+static int zcache_store_handle(struct zcache_pool *zpool,
+ unsigned long handle, int rb_index, int ra_index)
+{
+ unsigned long flags;
+ struct zcache_rb_entry *rb_entry, *tmp;
+ struct rb_node **link = NULL, *parent = NULL;
+ int ret;
+ void *dup_handlep;
+
+ rb_entry = zcache_find_get_rb_entry(zpool, rb_index);
+ if (!rb_entry) {
+ /* alloc new rb_entry */
+ rb_entry = kmem_cache_alloc(zcache_cleancache_entry_cache, GFP_KERNEL);
+ if (!rb_entry)
+ return -ENOMEM;
+
+ INIT_RADIX_TREE(&rb_entry->ra_root, GFP_ATOMIC|__GFP_NOWARN);
+ spin_lock_init(&rb_entry->ra_lock);
+ rb_entry->rb_index = rb_index;
+ kref_init(&rb_entry->refcount);
+ RB_CLEAR_NODE(&rb_entry->rb_node);
+
+ /* add new entry to rb tree */
+ write_lock_irqsave(&zpool->rb_lock, flags);
+
+ tmp = zcache_find_rb_entry(&zpool->rb_root, rb_index, &parent, &link);
+ if (tmp) {
+ /* somebody else allocated new entry */
+ kmem_cache_free(zcache_cleancache_entry_cache, rb_entry);
+ rb_entry = tmp;
+ } else {
+ rb_link_node(&rb_entry->rb_node, parent, link);
+ rb_insert_color(&rb_entry->rb_node, &zpool->rb_root);
+ }
+
+ kref_get(&rb_entry->refcount);
+ write_unlock_irqrestore(&zpool->rb_lock, flags);
+ }
+
+ /* Succ get rb_entry and refcount after arrived here */
+ spin_lock_irqsave(&rb_entry->ra_lock, flags);
+ dup_handlep = radix_tree_delete(&rb_entry->ra_root, ra_index);
+ if (unlikely(dup_handlep)) {
+ WARN_ON("duplicated entry, will be replaced!\n");
+ zbud_free(zpool->pool, (unsigned long)dup_handlep);
+ atomic_dec(&zcache_cleancache_stored_pages);
+ zcache_cleancache_pool_pages = zbud_get_pool_size(zpool->pool);
+ zcache_cleancache_dup_entry++;
+ }
+ ret = radix_tree_insert(&rb_entry->ra_root, ra_index, (void *)handle);
+
+ if (unlikely(ret))
+ if (zcache_rb_entry_is_empty(rb_entry))
+ zcache_rb_entry_isolate(zpool, rb_entry, 0);
+ spin_unlock_irqrestore(&rb_entry->ra_lock, flags);
+
+ kref_put(&rb_entry->refcount, zcache_rb_entry_release);
+ return ret;
+}
+
+/* Load the handle, and delete it */
+static unsigned long *zcache_load_delete_handle(struct zcache_pool
*zpool, int rb_index,
+ int ra_index)
+{
+ struct zcache_rb_entry *rb_entry;
+ void *handlep = NULL;
+ unsigned long flags;
+
+ rb_entry = zcache_find_get_rb_entry(zpool, rb_index);
+ if (!rb_entry)
+ goto out;
+
+ BUG_ON(rb_entry->rb_index != rb_index);
+
+ spin_lock_irqsave(&rb_entry->ra_lock, flags);
+ handlep = radix_tree_delete(&rb_entry->ra_root, ra_index);
+ if (zcache_rb_entry_is_empty(rb_entry))
+ /* If no more nodes in the rb_entry->radix_tree,
+ * rm rb_entry from the rbtree and drop the refcount
+ */
+ zcache_rb_entry_isolate(zpool, rb_entry, 0);
+ spin_unlock_irqrestore(&rb_entry->ra_lock, flags);
+
+ /* After arrive here, rb_entry have dropped from rbtree */
+ kref_put(&rb_entry->refcount, zcache_rb_entry_release);
+out:
+ return handlep;
+}
+
+static void zcache_cleancache_store_page(int pool_id, struct
cleancache_filekey key,
+ pgoff_t index, struct page *page)
+{
+ unsigned int dlen = PAGE_SIZE, len;
+ unsigned long handle;
+ char *buf;
+ u8 *src, *dst;
+ struct zcache_cleancache_meta *zmeta;
+ int ret;
+
+ struct zcache_pool *zpool = zcache.pools[pool_id];
+
+ /* reclaim space if needed */
+ if (zcache_is_full()) {
+ /* Reclaim will be implemented in following version */
+ zcache_cleancache_pool_limit_hit++;
+ return;
+ }
+
+ /* compress */
+ dst = get_cpu_var(zcache_dstmem);
+ src = kmap_atomic(page);
+ ret = zcache_comp_op(ZCACHE_COMPOP_COMPRESS, src, PAGE_SIZE, dst, &dlen);
+ kunmap_atomic(src);
+ if (ret) {
+ pr_err("zcache_cleancache compress error ret %d\n", ret);
+ put_cpu_var(zcache_dstmem);
+ return;
+ }
+
+ /* store handle with meta data */
+ len = dlen + sizeof(struct zcache_cleancache_meta);
+ ret = zbud_alloc(zpool->pool, len, __GFP_NORETRY | __GFP_NOWARN, &handle);
+ if (ret) {
+ zcache_cleancache_zbud_alloc_fail++;
+ put_cpu_var(zcache_dstmem);
+ return;
+ }
+
+ zmeta = zbud_map(zpool->pool, handle);
+ zmeta->ra_index = index;
+ zmeta->length = dlen;
+ buf = (u8 *)(zmeta + 1);
+ memcpy(buf, dst, dlen);
+ zbud_unmap(zpool->pool, handle);
+ put_cpu_var(zcache_dstmem);
+
+ /* populate entry */
+ ret = zcache_store_handle(zpool, handle, key.u.ino, index);
+ if (ret) {
+ pr_err("%s: store handle error %d\n", __func__, ret);
+ zbud_free(zpool->pool, handle);
+ }
+
+ /* update stats */
+ atomic_inc(&zcache_cleancache_stored_pages);
+ zcache_cleancache_pool_pages = zbud_get_pool_size(zpool->pool);
+ return;
+}
+
+static int zcache_cleancache_load_page(int pool_id, struct
cleancache_filekey key,
+ pgoff_t index, struct page *page)
+{
+ struct zcache_pool *zpool = zcache.pools[pool_id];
+ u8 *src, *dst;
+ unsigned int dlen;
+ int ret;
+ unsigned long *handlep;
+ struct zcache_cleancache_meta *zmeta;
+
+ handlep = zcache_load_delete_handle(zpool, key.u.ino, index);
+ if (!handlep)
+ return -1;
+
+ zmeta = (struct zcache_cleancache_meta *)zbud_map(zpool->pool,
(unsigned long)handlep);
+ src = (u8 *)(zmeta + 1);
+
+ /* decompress */
+ dlen = PAGE_SIZE;
+ dst = kmap_atomic(page);
+ ret = zcache_comp_op(ZCACHE_COMPOP_DECOMPRESS, src, zmeta->length,
dst, &dlen);
+ kunmap_atomic(dst);
+ zbud_unmap(zpool->pool, (unsigned long)handlep);
+ zbud_free(zpool->pool, (unsigned long)handlep);
+
+ WARN_ON(ret); /* decompress err, will fetch from real disk */
+ /* update stats */
+ atomic_dec(&zcache_cleancache_stored_pages);
+ zcache_cleancache_pool_pages = zbud_get_pool_size(zpool->pool);
+ return ret;
+}
+
+static void zcache_cleancache_flush_page(int pool_id, struct
cleancache_filekey key,
+ pgoff_t index)
+{
+ struct zcache_pool *zpool = zcache.pools[pool_id];
+ unsigned long *handlep = NULL;
+
+ handlep = zcache_load_delete_handle(zpool, key.u.ino, index);
+ if (handlep) {
+ zbud_free(zpool->pool, (unsigned long)handlep);
+ atomic_dec(&zcache_cleancache_stored_pages);
+ zcache_cleancache_pool_pages = zbud_get_pool_size(zpool->pool);
+ }
+}
+
+#define FREE_BATCH 16
+static void zcache_cleancache_flush_ratree(struct zcache_pool *zpool,
+ struct zcache_rb_entry *entry)
+{
+ int count, i;
+ unsigned long index = 0;
+
+ do {
+ struct zcache_cleancache_meta *handles[FREE_BATCH];
+
+ count = radix_tree_gang_lookup(&entry->ra_root,
+ (void **)handles, index, FREE_BATCH);
+
+ for (i = 0; i < count; i++) {
+ index = handles[i]->ra_index;
+ radix_tree_delete(&entry->ra_root, index);
+ zbud_free(zpool->pool, (unsigned long)handles[i]);
+ atomic_dec(&zcache_cleancache_stored_pages);
+ zcache_cleancache_pool_pages = zbud_get_pool_size(zpool->pool);
+ }
+
+ index++;
+ } while (count == FREE_BATCH);
+}
+
+static void zcache_cleancache_flush_inode(int pool_id,
+ struct cleancache_filekey key)
+{
+ struct zcache_rb_entry *rb_entry;
+ unsigned long flags1, flags2;
+ struct zcache_pool *zpool = zcache.pools[pool_id];
+
+ /* refuse new pages added in to the same inode */
+ write_lock_irqsave(&zpool->rb_lock, flags1);
+ rb_entry = zcache_find_rb_entry(&zpool->rb_root, key.u.ino, 0, 0);
+ if (!rb_entry) {
+ write_unlock_irqrestore(&zpool->rb_lock, flags1);
+ return;
+ }
+
+ kref_get(&rb_entry->refcount);
+
+ spin_lock_irqsave(&rb_entry->ra_lock, flags2);
+ zcache_cleancache_flush_ratree(zpool, rb_entry);
+ if (zcache_rb_entry_is_empty(rb_entry))
+ zcache_rb_entry_isolate(zpool, rb_entry, 1);
+ spin_unlock_irqrestore(&rb_entry->ra_lock, flags2);
+
+ write_unlock_irqrestore(&zpool->rb_lock, flags1);
+ kref_put(&rb_entry->refcount, zcache_rb_entry_release);
+}
+
+static void zcache_destroy_pool(struct zcache_pool *zpool);
+static void zcache_cleancache_flush_fs(int pool_id)
+{
+ struct zcache_rb_entry *entry = NULL;
+ struct rb_node *node;
+ unsigned long flags1, flags2;
+ struct zcache_pool *zpool = zcache.pools[pool_id];
+
+ if (!zpool)
+ return;
+
+ /* refuse new pages added in to the same inode */
+ write_lock_irqsave(&zpool->rb_lock, flags1);
+
+ node = rb_first(&zpool->rb_root);
+ while (node) {
+ entry = rb_entry(node, struct zcache_rb_entry, rb_node);
+ node = rb_next(node);
+ if (entry) {
+ kref_get(&entry->refcount);
+ spin_lock_irqsave(&entry->ra_lock, flags2);
+ zcache_cleancache_flush_ratree(zpool, entry);
+ if (zcache_rb_entry_is_empty(entry))
+ zcache_rb_entry_isolate(zpool, entry, 1);
+ spin_unlock_irqrestore(&entry->ra_lock, flags2);
+ kref_put(&entry->refcount, zcache_rb_entry_release);
+ }
+ }
+
+ write_unlock_irqrestore(&zpool->rb_lock, flags1);
+
+ zcache_destroy_pool(zpool);
+}
+
+static int zcache_cleancache_evict_entry(struct zbud_pool *pool,
+ unsigned long handle)
+{
+ return -1;
+}
+
+static struct zbud_ops zcache_cleancache_zbud_ops = {
+ .evict = zcache_cleancache_evict_entry
+};
+
+static void zcache_destroy_pool(struct zcache_pool *zpool)
+{
+ int i;
+
+ if (!zpool)
+ return;
+
+ spin_lock(&zcache.pool_lock);
+ zcache.num_pools--;
+ for (i = 0; i < MAX_ZCACHE_POOLS; i++)
+ if (zcache.pools[i] == zpool)
+ break;
+ zcache.pools[i] = NULL;
+ spin_unlock(&zcache.pool_lock);
+
+ if (!RB_EMPTY_ROOT(&zpool->rb_root)) {
+ WARN_ON("Memory leak detected. Freeing non-empty pool!\n");
+ }
+
+ zbud_destroy_pool(zpool->pool);
+ kfree(zpool);
+}
+
+/* return pool id */
+static int zcache_create_pool(void)
+{
+ int ret;
+ struct zcache_pool *zpool;
+
+ zpool = kzalloc(sizeof(*zpool), GFP_KERNEL);
+ if (!zpool) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ zpool->pool = zbud_create_pool(GFP_KERNEL, &zcache_cleancache_zbud_ops);
+ if (!zpool->pool) {
+ kfree(zpool);
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ spin_lock(&zcache.pool_lock);
+ if (zcache.num_pools == MAX_ZCACHE_POOLS) {
+ pr_info("Cannot create new pool (limit: %u)\n",
+ MAX_ZCACHE_POOLS);
+ zbud_destroy_pool(zpool->pool);
+ kfree(zpool);
+ ret = -EPERM;
+ goto out_unlock;
+ }
+
+ rwlock_init(&zpool->rb_lock);
+ zpool->rb_root = RB_ROOT;
+
+ /* Add to pool list */
+ for (ret = 0; ret < MAX_ZCACHE_POOLS; ret++)
+ if (!zcache.pools[ret])
+ break;
+ zcache.pools[ret] = zpool;
+ zcache.num_pools++;
+ pr_info("New pool created id:%d\n", ret);
+
+out_unlock:
+ spin_unlock(&zcache.pool_lock);
+out:
+ return ret;
+}
+
+static int zcache_cleancache_init_fs(size_t pagesize)
+{
+ int ret;
+
+ if (pagesize != PAGE_SIZE) {
+ pr_info("Unsupported page size: %zu", pagesize);
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = zcache_create_pool();
+ if (ret < 0) {
+ pr_info("Failed to create new pool\n");
+ ret = -ENOMEM;
+ goto out;
+ }
+
+out:
+ return ret;
+}
+
+static int zcache_cleancache_init_shared_fs(char *uuid, size_t pagesize)
+{
+ /* shared pools are unsupported and map to private */
+ return zcache_cleancache_init_fs(pagesize);
+}
+
+static struct cleancache_ops zcache_cleancache_ops = {
+ .put_page = zcache_cleancache_store_page,
+ .get_page = zcache_cleancache_load_page,
+ .invalidate_page = zcache_cleancache_flush_page,
+ .invalidate_inode = zcache_cleancache_flush_inode,
+ .invalidate_fs = zcache_cleancache_flush_fs,
+ .init_shared_fs = zcache_cleancache_init_shared_fs,
+ .init_fs = zcache_cleancache_init_fs
+};
+
+/*********************************
+* debugfs functions
+**********************************/
+#ifdef CONFIG_DEBUG_FS
+#include <linux/debugfs.h>
+
+static struct dentry *zcache_cleancache_debugfs_root;
+
+static int __init zcache_debugfs_init(void)
+{
+ if (!debugfs_initialized())
+ return -ENODEV;
+
+ if (!zcache_nocleancache) {
+ zcache_cleancache_debugfs_root =
debugfs_create_dir("zcache_cleancache", NULL);
+ if (!zcache_cleancache_debugfs_root)
+ return -ENOMEM;
+
+ debugfs_create_u64("pool_limit_hit", S_IRUGO,
+ zcache_cleancache_debugfs_root, &zcache_cleancache_pool_limit_hit);
+ debugfs_create_u64("reclaim_fail", S_IRUGO,
+ zcache_cleancache_debugfs_root, &zcache_cleancache_reclaim_fail);
+ debugfs_create_u64("reject_alloc_fail", S_IRUGO,
+ zcache_cleancache_debugfs_root, &zcache_cleancache_zbud_alloc_fail);
+ debugfs_create_u64("written_back_pages", S_IRUGO,
+ zcache_cleancache_debugfs_root, &zcache_cleancache_written_back_pages);
+ debugfs_create_u64("duplicate_entry", S_IRUGO,
+ zcache_cleancache_debugfs_root, &zcache_cleancache_dup_entry);
+ debugfs_create_u64("pool_pages", S_IRUGO,
+ zcache_cleancache_debugfs_root, &zcache_cleancache_pool_pages);
+ debugfs_create_atomic_t("stored_pages", S_IRUGO,
+ zcache_cleancache_debugfs_root, &zcache_cleancache_stored_pages);
+ }
+ return 0;
+}
+
+static void __exit zcache_debugfs_exit(void)
+{
+ debugfs_remove_recursive(zcache_cleancache_debugfs_root);
+}
+#else
+static int __init zcache_debugfs_init(void)
+{
+ return 0;
+}
+static void __exit zcache_debugfs_exit(void)
+{
+}
+#endif
+
+/*********************************
+* module init and exit
+**********************************/
+static int __init init_zcache(void)
+{
+ if (!zcache_enabled)
+ return 0;
+
+ pr_info("loading zcache..\n");
+ if (!zcache_nocleancache)
+ if (zcache_cleancache_entry_cache_create()) {
+ pr_err("entry cache creation failed\n");
+ goto error;
+ }
+
+ if (zcache_comp_init()) {
+ pr_err("compressor initialization failed\n");
+ goto compfail;
+ }
+ if (zcache_cpu_init()) {
+ pr_err("per-cpu initialization failed\n");
+ goto pcpufail;
+ }
+
+ spin_lock_init(&zcache.pool_lock);
+ if (!zcache_nocleancache)
+ cleancache_register_ops(&zcache_cleancache_ops);
+
+ if (zcache_debugfs_init())
+ pr_warn("debugfs initialization failed\n");
+ return 0;
+pcpufail:
+ zcache_comp_exit();
+compfail:
+ zcache_cleancache_entry_cache_destory();
+error:
+ return -ENOMEM;
+}
+/* must be late so crypto has time to come up */
+late_initcall(init_zcache);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Bob Liu <bob.liu@oracle.com>");
+MODULE_DESCRIPTION("Compressed cache for clean file pages");
--
1.7.10.4
--
Regards,
-Bob
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH 1/2] zcache: staging: %s/ZCACHE/ZCACHE_OLD
2013-07-20 14:36 ` [PATCH 1/2] zcache: staging: %s/ZCACHE/ZCACHE_OLD Bob Liu
2013-07-20 15:24 ` Fwd: " Bob Liu
@ 2013-07-20 16:42 ` Greg KH
1 sibling, 0 replies; 9+ messages in thread
From: Greg KH @ 2013-07-20 16:42 UTC (permalink / raw)
To: Bob Liu
Cc: linux-kernel, sjenning, ngupta, minchan, konrad.wilk, rcj,
mgorman, riel, penberg, akpm, Bob Liu
On Sat, Jul 20, 2013 at 10:36:57PM +0800, Bob Liu wrote:
> Signed-off-by: Bob Liu <bob.liu@oracle.com>
> ---
> drivers/staging/zcache/Kconfig | 12 ++++++------
> drivers/staging/zcache/Makefile | 4 ++--
> 2 files changed, 8 insertions(+), 8 deletions(-)
If you are going to give up on the code, why not just delete it? No
need to keep it around anymore, right?
thanks
greg k-h
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 0/2] zcache: a new start for upstream
[not found] ` <20130722150702.GB4706@variantweb.net>
@ 2013-07-24 13:52 ` Bob Liu
0 siblings, 0 replies; 9+ messages in thread
From: Bob Liu @ 2013-07-24 13:52 UTC (permalink / raw)
To: Seth Jennings
Cc: Linux-Kernel, Greg Kroah-Hartman, Nitin Gupta, Minchan Kim,
Konrad Rzeszutek Wilk, Robert Jennings, Mel Gorman, Rik van Riel,
Pekka Enberg, Andrew Morton, Bob Liu, Linux-MM
Hi Seth,
On Mon, Jul 22, 2013 at 11:07 PM, Seth Jennings
<sjenning@linux.vnet.ibm.com> wrote:
> Sorry for the dup Bob, last reply only went to linux-mm
>
> On Sat, Jul 20, 2013 at 10:36:56PM +0800, Bob Liu wrote:
>> We already have zswap helps reducing the swap out/in IO operations by
>> compressing anon pages.
>> It has been merged into v3.11-rc1 together with the zbud allocation layer.
>>
>> However there is another kind of pages(clean file pages) suitable for
>> compression as well. Upstream has already merged its frontend(cleancache).
>> Now we are lacking of a backend of cleancache as zswap to frontswap.
>>
>> Furthermore, we need to balance the number of compressed anon and file pages,
>> E.g. it's unfair to normal file pages if zswap pool occupies too much memory for
>> the storage of compressed anon pages.
>>
>> Although the current version of zcache in staging tree has already done those
>> works mentioned above, the implementation is too complicated to be merged into
>> upstream.
>>
>> What I'm looking for is a new way for zcache towards upstream.
>> The first change is no more staging tree.
>> Second is implemented a simple cleancache backend at first, which is based on
>> the zbud allocation same as zswap.
>
> I like the approach of distilling zcache down to only page cache compression
> as a start.
>
Thank you for your review!
> However, there is still the unresolved issue of the streaming read regression.
> If the workload does streaming reads (i.e. reads from a set much larger than
> RAM and does no rereads), zcache will regress that workload because it will
> be compressing pages that will quickly be tossed out of the second chance
> cache too.
>
> This is a difficult problem when it comes to page cache compression: how
> to know whether a page will be used again. In the case of zswap, the
> page is persistent in memory and therefore MUST be maintained. With
> page cache compression, that isn't that case. There is the option to
> just toss it and reread from disk.
Probably we can add checking whether the file page used to at the active list!
Only putting reclaimed file pages which are from active list to cleancache!
Of course this way can't fix this problem totally, but I think we can
get a higher hit rate!
>
> The assumption is that keeping as many cached pages as possible, regardless
> of the overhead to do so, is always a win. But this is not always true.
>
>>
>> At the end, I hope we can combine the new cleancache backend with
>> zswap(frontswap backend), in order to have a generic in-kernel memory
>> compression solution in upstream.
>
> I don't see a need to combine them since, afaict, you'd really never use them
> at the same time as zswap (anon memory pressure in general) shreds the page
> cache and would aggressively shrink zcache to the point of uselessness.
>
Make sense, but is there any way to share the compression functions
and per-cpu functions?
>>
>> Bob Liu (2):
>> zcache: staging: %s/ZCACHE/ZCACHE_OLD
>> mm: zcache: core functions added
>>
>> drivers/staging/zcache/Kconfig | 12 +-
>> drivers/staging/zcache/Makefile | 4 +-
>> mm/Kconfig | 18 +
>> mm/Makefile | 1 +
>> mm/zcache.c | 840 +++++++++++++++++++++++++++++++++++++++
>> 5 files changed, 867 insertions(+), 8 deletions(-)
>> create mode 100644 mm/zcache.c
>
> No code?
>
> Seth
--
Regards,
--Bob
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 0/2] zcache: a new start for upstream
@ 2013-07-24 13:52 ` Bob Liu
0 siblings, 0 replies; 9+ messages in thread
From: Bob Liu @ 2013-07-24 13:52 UTC (permalink / raw)
To: Seth Jennings
Cc: Linux-Kernel, Greg Kroah-Hartman, Nitin Gupta, Minchan Kim,
Konrad Rzeszutek Wilk, Robert Jennings, Mel Gorman, Rik van Riel,
Pekka Enberg, Andrew Morton, Bob Liu, Linux-MM
Hi Seth,
On Mon, Jul 22, 2013 at 11:07 PM, Seth Jennings
<sjenning@linux.vnet.ibm.com> wrote:
> Sorry for the dup Bob, last reply only went to linux-mm
>
> On Sat, Jul 20, 2013 at 10:36:56PM +0800, Bob Liu wrote:
>> We already have zswap helps reducing the swap out/in IO operations by
>> compressing anon pages.
>> It has been merged into v3.11-rc1 together with the zbud allocation layer.
>>
>> However there is another kind of pages(clean file pages) suitable for
>> compression as well. Upstream has already merged its frontend(cleancache).
>> Now we are lacking of a backend of cleancache as zswap to frontswap.
>>
>> Furthermore, we need to balance the number of compressed anon and file pages,
>> E.g. it's unfair to normal file pages if zswap pool occupies too much memory for
>> the storage of compressed anon pages.
>>
>> Although the current version of zcache in staging tree has already done those
>> works mentioned above, the implementation is too complicated to be merged into
>> upstream.
>>
>> What I'm looking for is a new way for zcache towards upstream.
>> The first change is no more staging tree.
>> Second is implemented a simple cleancache backend at first, which is based on
>> the zbud allocation same as zswap.
>
> I like the approach of distilling zcache down to only page cache compression
> as a start.
>
Thank you for your review!
> However, there is still the unresolved issue of the streaming read regression.
> If the workload does streaming reads (i.e. reads from a set much larger than
> RAM and does no rereads), zcache will regress that workload because it will
> be compressing pages that will quickly be tossed out of the second chance
> cache too.
>
> This is a difficult problem when it comes to page cache compression: how
> to know whether a page will be used again. In the case of zswap, the
> page is persistent in memory and therefore MUST be maintained. With
> page cache compression, that isn't that case. There is the option to
> just toss it and reread from disk.
Probably we can add checking whether the file page used to at the active list!
Only putting reclaimed file pages which are from active list to cleancache!
Of course this way can't fix this problem totally, but I think we can
get a higher hit rate!
>
> The assumption is that keeping as many cached pages as possible, regardless
> of the overhead to do so, is always a win. But this is not always true.
>
>>
>> At the end, I hope we can combine the new cleancache backend with
>> zswap(frontswap backend), in order to have a generic in-kernel memory
>> compression solution in upstream.
>
> I don't see a need to combine them since, afaict, you'd really never use them
> at the same time as zswap (anon memory pressure in general) shreds the page
> cache and would aggressively shrink zcache to the point of uselessness.
>
Make sense, but is there any way to share the compression functions
and per-cpu functions?
>>
>> Bob Liu (2):
>> zcache: staging: %s/ZCACHE/ZCACHE_OLD
>> mm: zcache: core functions added
>>
>> drivers/staging/zcache/Kconfig | 12 +-
>> drivers/staging/zcache/Makefile | 4 +-
>> mm/Kconfig | 18 +
>> mm/Makefile | 1 +
>> mm/zcache.c | 840 +++++++++++++++++++++++++++++++++++++++
>> 5 files changed, 867 insertions(+), 8 deletions(-)
>> create mode 100644 mm/zcache.c
>
> No code?
>
> Seth
--
Regards,
--Bob
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
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^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2013-07-24 13:52 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-07-20 14:36 [PATCH 0/2] zcache: a new start for upstream Bob Liu
2013-07-20 14:36 ` [PATCH 1/2] zcache: staging: %s/ZCACHE/ZCACHE_OLD Bob Liu
2013-07-20 15:24 ` Fwd: " Bob Liu
2013-07-20 16:42 ` Greg KH
2013-07-20 14:36 ` [PATCH 2/2] mm: zcache: core functions added Bob Liu
2013-07-20 15:25 ` Fwd: " Bob Liu
2013-07-20 15:23 ` Fwd: [PATCH 0/2] zcache: a new start for upstream Bob Liu
[not found] ` <20130722150702.GB4706@variantweb.net>
2013-07-24 13:52 ` Bob Liu
2013-07-24 13:52 ` Bob Liu
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