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slub: move synchronize_sched out of slab_mutex on shrink

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synchronize_sched() is a heavy operation and calling it per each cache
owned by a memory cgroup being destroyed may take quite some time.  What
is worse, it's currently called under the slab_mutex, stalling all works
doing cache creation/destruction.

Actually, there isn't much point in calling synchronize_sched() for each
cache - it's enough to call it just once - after setting cpu_partial for
all caches and before shrinking them.  This way, we can also move it out
of the slab_mutex, which we have to hold for iterating over the slab
cache list.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=172991
Link: http://lkml.kernel.org/r/0a10d71ecae3db00fb4421bcd3f82bcc911f4be4.1475329751.git.vdavydov.dev@gmail.com
Signed-off-by: Vladimir Davydov <vdavydov.dev@gmail.com>
Reported-by: Doug Smythies <dsmythies@telus.net>
Acked-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vladimir Davydov
2016-12-12 16:41:32 -08:00
committed by Linus Torvalds
parent 13583c3d32
commit 89e364db71
5 changed files with 31 additions and 23 deletions
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19
mm/slub.c
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@@ -3883,7 +3883,7 @@ EXPORT_SYMBOL(kfree);
* being allocated from last increasing the chance that the last objects
* are freed in them.
*/
int __kmem_cache_shrink(struct kmem_cache *s, bool deactivate)
int __kmem_cache_shrink(struct kmem_cache *s)
{
int node;
int i;
@@ -3895,21 +3895,6 @@ int __kmem_cache_shrink(struct kmem_cache *s, bool deactivate)
unsigned long flags;
int ret = 0;
if (deactivate) {
/*
* Disable empty slabs caching. Used to avoid pinning offline
* memory cgroups by kmem pages that can be freed.
*/
s->cpu_partial = 0;
s->min_partial = 0;
/*
* s->cpu_partial is checked locklessly (see put_cpu_partial),
* so we have to make sure the change is visible.
*/
synchronize_sched();
}
flush_all(s);
for_each_kmem_cache_node(s, node, n) {
INIT_LIST_HEAD(&discard);
@@ -3966,7 +3951,7 @@ static int slab_mem_going_offline_callback(void *arg)
mutex_lock(&slab_mutex);
list_for_each_entry(s, &slab_caches, list)
__kmem_cache_shrink(s, false);
__kmem_cache_shrink(s);
mutex_unlock(&slab_mutex);
return 0;