From 510ded33e075c2bd662b1efab0110f4240325fc9 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 22 Feb 2017 15:41:24 -0800 Subject: slab: implement slab_root_caches list 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. slab_caches currently lists all caches including root and memcg ones. This is the only data structure which lists the root caches and iterating root caches can only be done by walking the list while skipping over memcg caches. As there can be a huge number of memcg caches, this can become very expensive. This also can make /proc/slabinfo behave very badly. seq_file processes reads in 4k chunks and seeks to the previous Nth position on slab_caches list to resume after each chunk. With a lot of memcg cache churns on the list, reading /proc/slabinfo can become very slow and its content often ends up with duplicate and/or missing entries. This patch adds a new list slab_root_caches which lists only the root caches. When memcg is not enabled, it becomes just an alias of slab_caches. memcg specific list operations are collected into memcg_[un]link_cache(). Link: http://lkml.kernel.org/r/20170117235411.9408-7-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 | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux/slab.h') diff --git a/include/linux/slab.h b/include/linux/slab.h index a0cc7a77cda2..af1a5bef80f4 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -556,6 +556,8 @@ struct memcg_cache_array { * used to index child cachces during allocation and cleared * early during shutdown. * + * @root_caches_node: List node for slab_root_caches list. + * * @children: List of all child caches. While the child caches are also * reachable through @memcg_caches, a child cache remains on * this list until it is actually destroyed. @@ -573,6 +575,7 @@ struct memcg_cache_params { union { struct { struct memcg_cache_array __rcu *memcg_caches; + struct list_head __root_caches_node; struct list_head children; }; struct { -- cgit