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.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Reported-by: Jay Vana <jsvana@xxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 1 +
mm/memcontrol.c | 16 ++++++++--------
mm/slab_common.c | 2 +-
3 files changed, 10 insertions(+), 9 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 4de925c..67f3303 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -810,6 +810,7 @@ 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);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a2b20f7f..8757403 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 */
/**
@@ -2145,8 +2147,6 @@ 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 =
@@ -2178,7 +2178,7 @@ 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,
@@ -5780,12 +5780,12 @@ 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,
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 32610d1..5e6a98c 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -656,7 +656,7 @@ 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);
}
/**
--
2.9.3
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