From 01fb58bcba63f8fba37581c24c99e9a515dd0335 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 22 Feb 2017 15:41:30 -0800 Subject: slab: remove synchronous synchronize_sched() from memcg cache deactivation path With kmem cgroup support enabled, kmem_caches can be created and destroyed frequently and a great number of near empty kmem_caches can accumulate if there are a lot of transient cgroups and the system is not under memory pressure. When memory reclaim starts under such conditions, it can lead to consecutive deactivation and destruction of many kmem_caches, easily hundreds of thousands on moderately large systems, exposing scalability issues in the current slab management code. This is one of the patches to address the issue. slub uses synchronize_sched() to deactivate a memcg cache. synchronize_sched() is an expensive and slow operation and doesn't scale when a huge number of caches are destroyed back-to-back. While there used to be a simple batching mechanism, the batching was too restricted to be helpful. This patch implements slab_deactivate_memcg_cache_rcu_sched() which slub can use to schedule sched RCU callback instead of performing synchronize_sched() synchronously while holding cgroup_mutex. While this adds online cpus, mems and slab_mutex operations, operating on these locks back-to-back from the same kworker, which is what's gonna happen when there are many to deactivate, isn't expensive at all and this gets rid of the scalability problem completely. Link: http://lkml.kernel.org/r/20170117235411.9408-9-tj@kernel.org Signed-off-by: Tejun Heo Reported-by: Jay Vana Acked-by: Vladimir Davydov Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/slab.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/linux/slab.h') diff --git a/include/linux/slab.h b/include/linux/slab.h index af1a5bef80f4..3c37a8c51921 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -582,6 +582,12 @@ struct memcg_cache_params { struct mem_cgroup *memcg; struct list_head children_node; struct list_head kmem_caches_node; + + void (*deact_fn)(struct kmem_cache *); + union { + struct rcu_head deact_rcu_head; + struct work_struct deact_work; + }; }; }; }; -- cgit