Commit 17cc4dfe authored by Tejun Heo's avatar Tejun Heo Committed by Linus Torvalds
Browse files

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

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.


Signed-off-by: default avatarTejun Heo <>
Reported-by: default avatarJay Vana <>
Acked-by: default avatarVladimir Davydov <>
Cc: Christoph Lameter <>
Cc: Pekka Enberg <>
Cc: David Rientjes <>
Cc: Joonsoo Kim <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 50862ce7
......@@ -830,6 +830,7 @@ void memcg_kmem_uncharge(struct page *page, int order);
#if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)
extern struct static_key_false memcg_kmem_enabled_key;
extern struct workqueue_struct *memcg_kmem_cache_wq;
extern int memcg_nr_cache_ids;
void memcg_get_cache_ids(void);
......@@ -317,6 +317,8 @@ void memcg_put_cache_ids(void)
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)
* 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);
memcg_kmem_cache_wq = alloc_workqueue("memcg_kmem_cache", 0, 1);
cpuhp_setup_state_nocalls(CPUHP_MM_MEMCQ_DEAD, "mm/memctrl:dead", NULL,
......@@ -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);
queue_work(memcg_kmem_cache_wq, &s->memcg_params.deact_work);
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