From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Date: Thu, 15 Jan 2009 21:51:14 +0000 (-0800)
Subject: memcg: make oom less frequently
X-Git-Tag: v2.6.29-rc2~29
X-Git-Url: http://www.pilppa.org/gitweb/gitweb.cgi?p=linux-2.6-omap-h63xx.git;a=commitdiff_plain;h=4d1c627389c8ba6d9e703208567ffcdbd356f682

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>
---

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 322625f551c..fb62b4335fa 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