Commit d1a05b69 authored Jul 26, 2011 by Michal Hocko Committed by Linus Torvalds Jul 26, 2011

memcg: do not try to drain per-cpu caches without pages



drain_all_stock_async tries to optimize a work to be done on the work
queue by excluding any work for the current CPU because it assumes that
the context we are called from already tried to charge from that cache
and it's failed so it must be empty already.

While the assumption is correct we can optimize it even more by checking
the current number of pages in the cache.  This will also reduce a work
on other CPUs with an empty stock.

For the current CPU we can simply call drain_local_stock rather than
deferring it to the work queue.

[kamezawa.hiroyu@jp.fujitsu.com: use drain_local_stock for current CPU optimization]
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 82f9d486

mm/memcontrol.c

+7 −6

Original line number	Diff line number	Diff line
		@@ -2180,11 +2180,8 @@ static void drain_all_stock_async(struct mem_cgroup *root_mem)
		struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu);
		struct mem_cgroup *mem;

		if (cpu == curcpu)
		continue;

		mem = stock->cached;
		if (!mem)
		if (!mem \|\| !stock->nr_pages)
		continue;
		if (mem != root_mem) {
		if (!root_mem->use_hierarchy)
		@@ -2193,9 +2190,13 @@ static void drain_all_stock_async(struct mem_cgroup *root_mem)
		if (!css_is_ancestor(&mem->css, &root_mem->css))
		continue;
		}
		if (!test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags))
		if (!test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags)) {
		if (cpu == curcpu)
		drain_local_stock(&stock->work);
		else
		schedule_work_on(cpu, &stock->work);
		}
		}
		put_online_cpus();
		mutex_unlock(&percpu_charge_mutex);
		/* We don't wait for flush_work */

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