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Commit 89e364db authored by Vladimir Davydov's avatar Vladimir Davydov Committed by Linus Torvalds
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slub: move synchronize_sched out of slab_mutex on shrink 

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: default avatarVladimir Davydov <vdavydov.dev@gmail.com>
Reported-by: default avatarDoug Smythies <dsmythies@telus.net>
Acked-by: default avatarJoonsoo 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 13583c3d

mm/slab.c

+2 −2
Original line number Diff line number Diff line
@@ -2332,7 +2332,7 @@ static int drain_freelist(struct kmem_cache *cache, 
	return nr_freed;

}



int __kmem_cache_shrink(struct kmem_cache *cachep, bool deactivate)

int __kmem_cache_shrink(struct kmem_cache *cachep)

{

	int ret = 0;

	int node;
@@ -2352,7 +2352,7 @@ int __kmem_cache_shrink(struct kmem_cache *cachep, bool deactivate) 


int __kmem_cache_shutdown(struct kmem_cache *cachep)

{

	return __kmem_cache_shrink(cachep, false);

	return __kmem_cache_shrink(cachep);

}



void __kmem_cache_release(struct kmem_cache *cachep)

mm/slab.h

+1 −1
Original line number Diff line number Diff line
@@ -146,7 +146,7 @@ static inline unsigned long kmem_cache_flags(unsigned long object_size, 


int __kmem_cache_shutdown(struct kmem_cache *);

void __kmem_cache_release(struct kmem_cache *);

int __kmem_cache_shrink(struct kmem_cache *, bool);

int __kmem_cache_shrink(struct kmem_cache *);

void slab_kmem_cache_release(struct kmem_cache *);



struct seq_file;

mm/slab_common.c

+25 −2
Original line number Diff line number Diff line
@@ -573,6 +573,29 @@ void memcg_deactivate_kmem_caches(struct mem_cgroup *memcg) 
	get_online_cpus();

	get_online_mems();



#ifdef CONFIG_SLUB

	/*

	 * In case of SLUB, we need to disable empty slab caching to

	 * avoid pinning the offline memory cgroup by freeable kmem

	 * pages charged to it. SLAB doesn't need this, as it

	 * periodically purges unused slabs.

	 */

	mutex_lock(&slab_mutex);

	list_for_each_entry(s, &slab_caches, list) {

		c = is_root_cache(s) ? cache_from_memcg_idx(s, idx) : NULL;

		if (c) {

			c->cpu_partial = 0;

			c->min_partial = 0;

		}

	}

	mutex_unlock(&slab_mutex);

	/*

	 * kmem_cache->cpu_partial is checked locklessly (see

	 * put_cpu_partial()). Make sure the change is visible.

	 */

	synchronize_sched();

#endif



	mutex_lock(&slab_mutex);

	list_for_each_entry(s, &slab_caches, list) {

		if (!is_root_cache(s))
@@ -584,7 +607,7 @@ void memcg_deactivate_kmem_caches(struct mem_cgroup *memcg) 
		if (!c)

			continue;



		__kmem_cache_shrink(c, true);

		__kmem_cache_shrink(c);

		arr->entries[idx] = NULL;

	}

	mutex_unlock(&slab_mutex);
@@ -755,7 +778,7 @@ int kmem_cache_shrink(struct kmem_cache *cachep) 
	get_online_cpus();

	get_online_mems();

	kasan_cache_shrink(cachep);

	ret = __kmem_cache_shrink(cachep, false);

	ret = __kmem_cache_shrink(cachep);

	put_online_mems();

	put_online_cpus();

	return ret;

mm/slob.c

+1 −1
Original line number Diff line number Diff line
@@ -634,7 +634,7 @@ void __kmem_cache_release(struct kmem_cache *c) 
{

}



int __kmem_cache_shrink(struct kmem_cache *d, bool deactivate)

int __kmem_cache_shrink(struct kmem_cache *d)

{

	return 0;

}

mm/slub.c

+2 −17
Original line number Diff line number Diff line
@@ -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;