memcg: hierarchy avoid unnecessary reclaim

If hierarchy is not used, no tree-walk is necessary.

Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 964a70035e8f..9b4993ee46b3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -606,6 +606,8 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
         ret = try_to_free_mem_cgroup_pages(root_mem, gfp_mask, noswap);
         if (mem_cgroup_check_under_limit(root_mem))
                 return 0;
+        if (!root_mem->use_hierarchy)
+                return ret;
 
         next_mem = mem_cgroup_get_first_node(root_mem);