[Devel] [PATCH RHEL7 COMMIT] ms/mm: add SHRINK_EMPTY shrinker methods return value
Konstantin Khorenko
khorenko at virtuozzo.com
Wed Sep 5 12:37:15 MSK 2018
The commit is pushed to "branch-rh7-3.10.0-862.11.6.vz7.71.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-862.11.6.vz7.71.8
------>
commit 20206759adaacb5166e5474ebc959f6961700c4f
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date: Wed Sep 5 12:37:15 2018 +0300
ms/mm: add SHRINK_EMPTY shrinker methods return value
ms commit 9b996468cfdb
We need to distinguish the situations when shrinker has very small
amount of objects (see vfs_pressure_ratio() called from
super_cache_count()), and when it has no objects at all. Currently, in
the both of these cases, shrinker::count_objects() returns 0.
The patch introduces new SHRINK_EMPTY return value, which will be used
for "no objects at all" case. It's is a refactoring mostly, as
SHRINK_EMPTY is replaced by 0 by all callers of do_shrink_slab() in this
patch, and all the magic will happen in further.
Link: http://lkml.kernel.org/r/153063069574.1818.11037751256699341813.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
Acked-by: Vladimir Davydov <vdavydov.dev at gmail.com>
Tested-by: Shakeel Butt <shakeelb at google.com>
Cc: Al Viro <viro at zeniv.linux.org.uk>
Cc: Andrey Ryabinin <aryabinin at virtuozzo.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Cc: Guenter Roeck <linux at roeck-us.net>
Cc: "Huang, Ying" <ying.huang at intel.com>
Cc: Johannes Weiner <hannes at cmpxchg.org>
Cc: Josef Bacik <jbacik at fb.com>
Cc: Li RongQing <lirongqing at baidu.com>
Cc: Matthew Wilcox <willy at infradead.org>
Cc: Matthias Kaehlcke <mka at chromium.org>
Cc: Mel Gorman <mgorman at techsingularity.net>
Cc: Michal Hocko <mhocko at kernel.org>
Cc: Minchan Kim <minchan at kernel.org>
Cc: Philippe Ombredanne <pombredanne at nexb.com>
Cc: Roman Gushchin <guro at fb.com>
Cc: Sahitya Tummala <stummala at codeaurora.org>
Cc: Stephen Rothwell <sfr at canb.auug.org.au>
Cc: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Waiman Long <longman at redhat.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
=====================
Patchset description:
Port "Improve shrink_slab() scalability" patchset
https://jira.sw.ru/browse/PSBM-88027
This is backport of the patchset improving the performance
of overcommited containers with many memcgs and mounts.
The original set is in Linus' tree, and came into 4.19-rc1.
Kirill Tkhai (12):
mm: assign id to every memcg-aware shrinker
mm/memcontrol.c: move up for_each_mem_cgroup{, _tree} defines
mm, memcg: assign memcg-aware shrinkers bitmap to memcg
fs: propagate shrinker::id to list_lru
mm/list_lru.c: add memcg argument to list_lru_from_kmem()
mm/list_lru: pass dst_memcg argument to memcg_drain_list_lru_node()
mm/list_lru.c: pass lru argument to memcg_drain_list_lru_node()
mm/list_lru.c: set bit in memcg shrinker bitmap on first list_lru item appearance
mm/memcontrol.c: export mem_cgroup_is_root()
mm/vmscan.c: iterate only over charged shrinkers during memcg shrink_slab()
mm: add SHRINK_EMPTY shrinker methods return value
mm/vmscan.c: clear shrinker bit if there are no objects related to memcg
Vladimir Davydov (1):
mm/vmscan.c: generalize shrink_slab() calls in shrink_node()
---
fs/super.c | 3 +++
include/linux/shrinker.h | 7 +++++--
mm/vmscan.c | 12 +++++++++---
3 files changed, 17 insertions(+), 5 deletions(-)
diff --git a/fs/super.c b/fs/super.c
index 162ca145940f..f825c142bf97 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -156,6 +156,9 @@ static unsigned long super_cache_count(struct shrinker *shrink,
total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc);
total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc);
+ if (!total_objects)
+ return SHRINK_EMPTY;
+
total_objects = vfs_pressure_ratio(total_objects);
return total_objects;
}
diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index a8bbeaa3c66e..f6938dc6c068 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -28,12 +28,15 @@ struct shrink_control {
};
#define SHRINK_STOP (~0UL)
+#define SHRINK_EMPTY (~0UL - 1)
/*
* A callback you can register to apply pressure to ageable caches.
*
* @count_objects should return the number of freeable items in the cache. If
- * there are no objects to free or the number of freeable items cannot be
- * determined, it should return 0. No deadlock checks should be done during the
+ * there are no objects to free, it should return SHRINK_EMPTY, while 0 is
+ * returned in cases of the number of freeable items cannot be determined
+ * or shrinker should skip this cache for this time (e.g., their number
+ * is below shrinkable limit). No deadlock checks should be done during the
* count callback - the shrinker relies on aggregating scan counts that couldn't
* be executed due to potential deadlocks to be run at a later call when the
* deadlock condition is no longer pending.
diff --git a/mm/vmscan.c b/mm/vmscan.c
index bd2d62dabdd9..da28fc98f0a0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -350,8 +350,8 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
: SHRINK_BATCH;
max_pass = shrinker->count_objects(shrinker, shrinkctl);
- if (max_pass == 0)
- return 0;
+ if (max_pass == 0 || max_pass == SHRINK_EMPTY)
+ return max_pass;
/*
* copy the current shrinker scan count into a local variable
@@ -464,6 +464,8 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
}
ret = do_shrink_slab(&sc, shrinker, priority);
+ if (ret == SHRINK_EMPTY)
+ ret = 0;
freed += ret;
if (rwsem_is_contended(&shrinker_rwsem)) {
@@ -513,6 +515,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
{
struct shrinker *shrinker;
unsigned long freed = 0;
+ int ret;
if (unlikely(test_tsk_thread_flag(current, TIF_MEMDIE)))
return 0;
@@ -542,7 +545,10 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
sc.nid = 0;
- freed += do_shrink_slab(&sc, shrinker, priority);
+ ret = do_shrink_slab(&sc, shrinker, priority);
+ if (ret == SHRINK_EMPTY)
+ ret = 0;
+ freed += ret;
}
up_read(&shrinker_rwsem);
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