The patch titled
Subject: mm/slub.c: replace kick_all_cpus_sync() with synchronize_sched() in kmem_cache_shrink()
has been added to the -mm tree. Its filename is
mm-slub-replace-kick_all_cpus_sync-with-synchronize_sched-in-kmem_cache_shrink.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-slub-replace-kick_all_cpus_sync-with-synchronize_sched-in-kmem_cache_shrink.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-slub-replace-kick_all_cpus_sync-with-synchronize_sched-in-kmem_cache_shrink.patch
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From: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxx>
Reported-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slub.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN mm/slub.c~mm-slub-replace-kick_all_cpus_sync-with-synchronize_sched-in-kmem_cache_shrink mm/slub.c
--- a/mm/slub.c~mm-slub-replace-kick_all_cpus_sync-with-synchronize_sched-in-kmem_cache_shrink
+++ a/mm/slub.c
@@ -3697,7 +3697,7 @@ int __kmem_cache_shrink(struct kmem_cach
* 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);
_
Patches currently in -mm which might be from vdavydov@xxxxxxxxxxxxx are
mm-slub-replace-kick_all_cpus_sync-with-synchronize_sched-in-kmem_cache_shrink.patch
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