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>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 834d641..1fd6aff 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -317,6 +317,8 @@ void memcg_put_cache_ids(void)
DEFINE_STATIC_KEY_FALSE(memcg_kmem_enabled_key);
EXPORT_SYMBOL(memcg_kmem_enabled_key);
+struct workqueue_struct *memcg_kmem_cache_wq;
+
#endif /* !CONFIG_SLOB */
/**
@@ -2143,8 +2145,6 @@ struct memcg_kmem_cache_create_work {
struct work_struct work;
};
-static struct workqueue_struct *memcg_kmem_cache_create_wq;
-
static void memcg_kmem_cache_create_func(struct work_struct *w)
{
struct memcg_kmem_cache_create_work *cw =
@@ -2176,7 +2176,7 @@ static void __memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
cw->cachep = cachep;
INIT_WORK(&cw->work, memcg_kmem_cache_create_func);
- queue_work(memcg_kmem_cache_create_wq, &cw->work);
+ queue_work(memcg_kmem_cache_wq, &cw->work);
}
static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
@@ -5778,12 +5778,12 @@ static int __init mem_cgroup_init(void)
#ifndef CONFIG_SLOB
/*
* Kmem cache creation is mostly done with the slab_mutex held,
- * so use a special workqueue to avoid stalling all worker
- * threads in case lots of cgroups are created simultaneously.
+ * so use a workqueue with limited concurrency to avoid stalling
+ * all worker threads in case lots of cgroups are created and
+ * destroyed simultaneously.
*/
- memcg_kmem_cache_create_wq =
- alloc_ordered_workqueue("memcg_kmem_cache_create", 0);
- BUG_ON(!memcg_kmem_cache_create_wq);
+ memcg_kmem_cache_wq = alloc_workqueue("memcg_kmem_cache", 0, 1);
+ BUG_ON(!memcg_kmem_cache_wq);
#endif
cpuhp_setup_state_nocalls(CPUHP_MM_MEMCQ_DEAD, "mm/memctrl:dead", NULL,