On Sat, Jan 14, 2017 at 12:54:48AM -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. > > 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. > > Signed-off-by: Tejun Heo <[email protected]> > Reported-by: Jay Vana <[email protected]> > Cc: Vladimir Davydov <[email protected]> > Cc: Christoph Lameter <[email protected]> > Cc: Pekka Enberg <[email protected]> > Cc: David Rientjes <[email protected]> > Cc: Joonsoo Kim <[email protected]> > Cc: Andrew Morton <[email protected]>
I don't think there's much point in having the infrastructure for this in slab_common.c, as only SLUB needs it, but it isn't a show stopper. Acked-by: Vladimir Davydov <[email protected]>
