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authorVladimir Davydov <vdavydov.dev@gmail.com>2016-12-12 16:41:29 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-12-12 18:55:06 -0800
commit13583c3d3224508582ec03d881d0b68dd3ee8e10 (patch)
tree48ca686076bb06069656111ed4321236c1e83944 /mm/memcontrol.c
parentc62c38f6b91b87a013bccd3637c2a1850d8e590c (diff)
mm: memcontrol: use special workqueue for creating per-memcg caches
Creating a lot of cgroups at the same time might stall all worker threads with kmem cache creation works, because kmem cache creation is done with the slab_mutex held. The problem was amplified by commits 801faf0db894 ("mm/slab: lockless decision to grow cache") in case of SLAB and 81ae6d03952c ("mm/slub.c: replace kick_all_cpus_sync() with synchronize_sched() in kmem_cache_shrink()") in case of SLUB, which increased the maximal time the slab_mutex can be held. To prevent that from happening, let's use a special ordered single threaded workqueue for kmem cache creation. This shouldn't introduce any functional changes regarding how kmem caches are created, as the work function holds the global slab_mutex during its whole runtime anyway, making it impossible to run more than one work at a time. By using a single threaded workqueue, we just avoid creating a thread per each work. Ordering is required to avoid a situation when a cgroup's work is put off indefinitely because there are other cgroups to serve, in other words to guarantee fairness. Link: https://bugzilla.kernel.org/show_bug.cgi?id=172981 Link: http://lkml.kernel.org/r/20161004131417.GC1862@esperanza Signed-off-by: Vladimir Davydov <vdavydov.dev@gmail.com> Reported-by: Doug Smythies <dsmythies@telus.net> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Pekka Enberg <penberg@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c15
1 files changed, 14 insertions, 1 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0f870ba43942..91dfc7c5ce8f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2154,6 +2154,8 @@ 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 =
@@ -2185,7 +2187,7 @@ static void __memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
cw->cachep = cachep;
INIT_WORK(&cw->work, memcg_kmem_cache_create_func);
- schedule_work(&cw->work);
+ queue_work(memcg_kmem_cache_create_wq, &cw->work);
}
static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
@@ -5783,6 +5785,17 @@ static int __init mem_cgroup_init(void)
{
int cpu, node;
+#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.
+ */
+ memcg_kmem_cache_create_wq =
+ alloc_ordered_workqueue("memcg_kmem_cache_create", 0);
+ BUG_ON(!memcg_kmem_cache_create_wq);
+#endif
+
hotcpu_notifier(memcg_cpu_hotplug_callback, 0);
for_each_possible_cpu(cpu)