On Sat, Jan 14, 2017 at 12:54:45AM -0500, Tejun Heo wrote: > 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. > > While a memcg kmem_cache is listed on its root cache's ->children > list, there is no direct way to iterate all kmem_caches which are > assocaited with a memory cgroup. The only way to iterate them is > walking all caches while filtering out caches which don't match, which > would be most of them. > > This makes memcg destruction operations O(N^2) where N is the total > number of slab caches which can be huge. This combined with the > synchronous RCU operations can tie up a CPU and affect the whole > machine for many hours when memory reclaim triggers offlining and > destruction of the stale memcgs. > > This patch adds mem_cgroup->kmem_caches list which goes through > memcg_cache_params->kmem_caches_node of all kmem_caches which are > associated with the memcg. All memcg specific iterations, including > stat file access, are updated to use the new list instead. > > Signed-off-by: Tejun Heo <t...@kernel.org> > Reported-by: Jay Vana <jsv...@fb.com> > Cc: Vladimir Davydov <vdavydov....@gmail.com> > Cc: Christoph Lameter <c...@linux.com> > Cc: Pekka Enberg <penb...@kernel.org> > Cc: David Rientjes <rient...@google.com> > Cc: Joonsoo Kim <iamjoonsoo....@lge.com> > Cc: Andrew Morton <a...@linux-foundation.org>
Acked-by: Vladimir Davydov <vdavydov....@gmail.com>
