slab: use memcg_kmem_cache_wq for slab destruction operations

If there's contention on slab_mutex, queueing the per-cache destruction
work item on the system_wq can unnecessarily create and tie up a lot of
kworkers.

Rename memcg_kmem_cache_create_wq to memcg_kmem_cache_wq and make it
global and use that workqueue for the destruction work items too.  While
at it, convert the workqueue from an unbound workqueue to a per-cpu one
with concurrency limited to 1.  It's generally preferable to use per-cpu
workqueues and concurrency limit of 1 is safe enough.

This is suggested by Joonsoo Kim.

Link: http://lkml.kernel.org/r/20170117235411.9408-11-tj@kernel.org
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Jay Vana <jsvana@fb.com>
Acked-by: Vladimir Davydov <vdavydov@tarantool.org>
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>

1 files changed, 1 insertions, 1 deletions

diff --git a/mm/slab_common.c b/mm/slab_common.c
index c549296c7981..23ff74e61838 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -659,7 +659,7 @@ static void kmemcg_deactivate_rcufn(struct rcu_head *head)
 	 * initialized eariler.
 	 */
 	INIT_WORK(&s->memcg_params.deact_work, kmemcg_deactivate_workfn);
-	schedule_work(&s->memcg_params.deact_work);
+	queue_work(memcg_kmem_cache_wq, &s->memcg_params.deact_work);
 }
 
 /**