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memcg/sl[au]b: shrink dead caches 

This means that when we destroy a memcg cache that happened to be empty,
those caches may take a lot of time to go away: removing the memcg
reference won't destroy them - because there are pending references, and
the empty pages will stay there, until a shrinker is called upon for any
reason.

In this patch, we will call kmem_cache_shrink() for all dead caches that
cannot be destroyed because of remaining pages.  After shrinking, it is
possible that it could be freed.  If this is not the case, we'll schedule
a lazy worker to keep trying.

Signed-off-by: Glauber Costa <glommer@parallels.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Frederic Weisbecker <fweisbec@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: JoonSoo Kim <js1304@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Rik van Riel <riel@redhat.com>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Tejun Heo <tj@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:
Glauber Costa 2012-12-18 14:22:59 -08:00 committed by Linus Torvalds
parent 7cf2798240
commit 2293315293
1 changed files with 43 additions and 3 deletions
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46
mm/memcontrol.c
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@ -3080,7 +3080,27 @@ static void kmem_cache_destroy_work_func(struct work_struct *w)
cachep = memcg_params_to_cache(p);
if (!atomic_read(&cachep->memcg_params->nr_pages))
/*
* If we get down to 0 after shrink, we could delete right away.
* However, memcg_release_pages() already puts us back in the workqueue
* in that case. If we proceed deleting, we'll get a dangling
* reference, and removing the object from the workqueue in that case
* is unnecessary complication. We are not a fast path.
*
* Note that this case is fundamentally different from racing with
* shrink_slab(): if memcg_cgroup_destroy_cache() is called in
* kmem_cache_shrink, not only we would be reinserting a dead cache
* into the queue, but doing so from inside the worker racing to
* destroy it.
*
* So if we aren't down to zero, we'll just schedule a worker and try
* again
*/
if (atomic_read(&cachep->memcg_params->nr_pages) != 0) {
kmem_cache_shrink(cachep);
if (atomic_read(&cachep->memcg_params->nr_pages) == 0)
return;
} else
kmem_cache_destroy(cachep);
}
@ -3089,6 +3109,26 @@ void mem_cgroup_destroy_cache(struct kmem_cache *cachep)
if (!cachep->memcg_params->dead)
return;
/*
* There are many ways in which we can get here.
*
* We can get to a memory-pressure situation while the delayed work is
* still pending to run. The vmscan shrinkers can then release all
* cache memory and get us to destruction. If this is the case, we'll
* be executed twice, which is a bug (the second time will execute over
* bogus data). In this case, cancelling the work should be fine.
*
* But we can also get here from the worker itself, if
* kmem_cache_shrink is enough to shake all the remaining objects and
* get the page count to 0. In this case, we'll deadlock if we try to
* cancel the work (the worker runs with an internal lock held, which
* is the same lock we would hold for cancel_work_sync().)
*
* Since we can't possibly know who got us here, just refrain from
* running if there is already work pending
*/
if (work_pending(&cachep->memcg_params->destroy))
return;
/*
* We have to defer the actual destroying to a workqueue, because
* we might currently be in a context that cannot sleep.
@ -3217,7 +3257,7 @@ void kmem_cache_destroy_memcg_children(struct kmem_cache *s)
* set, so flip it down to guarantee we are in control.
*/
c->memcg_params->dead = false;
cancel_delayed_work_sync(&c->memcg_params->destroy);
cancel_work_sync(&c->memcg_params->destroy);
kmem_cache_destroy(c);
}
mutex_unlock(&set_limit_mutex);
@ -3242,7 +3282,7 @@ static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
cachep = memcg_params_to_cache(params);
cachep->memcg_params->dead = true;
INIT_WORK(&cachep->memcg_params->destroy,
kmem_cache_destroy_work_func);
kmem_cache_destroy_work_func);
schedule_work(&cachep->memcg_params->destroy);
}
mutex_unlock(&memcg->slab_caches_mutex);