memcg: make oom less frequently

In previous implementation, mem_cgroup_try_charge checked the return
value of mem_cgroup_try_to_free_pages, and just retried if some pages
had been reclaimed.
But now, try_charge(and mem_cgroup_hierarchical_reclaim called from it)
only checks whether the usage is less than the limit.

This patch tries to change the behavior as before to cause oom less
frequently.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 322625f551c2..fb62b4335fa9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -773,10 +773,10 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
          * but there might be left over accounting, even after children
          * have left.
          */
-        ret = try_to_free_mem_cgroup_pages(root_mem, gfp_mask, noswap,
+        ret += try_to_free_mem_cgroup_pages(root_mem, gfp_mask, noswap,
                                            get_swappiness(root_mem));
         if (mem_cgroup_check_under_limit(root_mem))
-                return 0;
+                return 1;       /* indicate reclaim has succeeded */
         if (!root_mem->use_hierarchy)
                 return ret;
 
@@ -787,10 +787,10 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
                         next_mem = mem_cgroup_get_next_node(root_mem);
                         continue;
                 }
-                ret = try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap,
+                ret += try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap,
                                                    get_swappiness(next_mem));
                 if (mem_cgroup_check_under_limit(root_mem))
-                        return 0;
+                        return 1;       /* indicate reclaim has succeeded */
                 next_mem = mem_cgroup_get_next_node(root_mem);
         }
         return ret;
@@ -875,6 +875,8 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
 
                 ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, gfp_mask,
                                                         noswap);
+                if (ret)
+                        continue;
 
                 /*
                  * try_to_free_mem_cgroup_pages() might not give us a full