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authorVladimir Davydov <vdavydov@virtuozzo.com>2016-05-19 17:10:34 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-05-19 19:12:14 -0700
commit81ae6d03952c1bfb96e1a716809bd65e7cd14360 (patch)
tree3acbc338b72f21b1f8df7eaea417f135f80773ec
parent801faf0db8947e01877920e848a4d338dd7a99e7 (diff)
downloadop-kernel-dev-81ae6d03952c1bfb96e1a716809bd65e7cd14360.zip
op-kernel-dev-81ae6d03952c1bfb96e1a716809bd65e7cd14360.tar.gz
mm/slub.c: replace kick_all_cpus_sync() with synchronize_sched() in kmem_cache_shrink()
When we call __kmem_cache_shrink on memory cgroup removal, we need to synchronize kmem_cache->cpu_partial update with put_cpu_partial that might be running on other cpus. Currently, we achieve that by using kick_all_cpus_sync, which works as a system wide memory barrier. Though fast it is, this method has a flaw - it issues a lot of IPIs, which might hurt high performance or real-time workloads. To fix this, let's replace kick_all_cpus_sync with synchronize_sched. Although the latter one may take much longer to finish, it shouldn't be a problem in this particular case, because memory cgroups are destroyed asynchronously from a workqueue so that no user visible effects should be introduced. OTOH, it will save us from excessive IPIs when someone removes a cgroup. Anyway, even if using synchronize_sched turns out to take too long, we can always introduce a kind of __kmem_cache_shrink batching so that this method would only be called once per one cgroup destruction (not per each per memcg kmem cache as it is now). Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com> Reported-by: Peter Zijlstra <peterz@infradead.org> Suggested-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/slub.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/slub.c b/mm/slub.c
index 4dbb109e..ba81cf6 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3697,7 +3697,7 @@ int __kmem_cache_shrink(struct kmem_cache *s, bool deactivate)
* s->cpu_partial is checked locklessly (see put_cpu_partial),
* so we have to make sure the change is visible.
*/
- kick_all_cpus_sync();
+ synchronize_sched();
}
flush_all(s);
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