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authorMichal Hocko <mhocko@suse.cz>2012-11-16 14:14:49 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-11-26 11:37:45 -0800
commite5c4ee6a081ec04e8ba54b00a4385391ab77e2f8 (patch)
treedc0fca050cef42f6f670ef441a8db2b5085b9b85 /mm
parent9098e8785685bd245027447b5628fa872babd3b8 (diff)
downloadlinux-linaro-stable-e5c4ee6a081ec04e8ba54b00a4385391ab77e2f8.tar.gz
memcg: oom: fix totalpages calculation for memory.swappiness==0
commit 9a5a8f19b43430752067ecaee62fc59e11e88fa6 upstream. oom_badness() takes a totalpages argument which says how many pages are available and it uses it as a base for the score calculation. The value is calculated by mem_cgroup_get_limit which considers both limit and total_swap_pages (resp. memsw portion of it). This is usually correct but since fe35004fbf9e ("mm: avoid swapping out with swappiness==0") we do not swap when swappiness is 0 which means that we cannot really use up all the totalpages pages. This in turn confuses oom score calculation if the memcg limit is much smaller than the available swap because the used memory (capped by the limit) is negligible comparing to totalpages so the resulting score is too small if adj!=0 (typically task with CAP_SYS_ADMIN or non zero oom_score_adj). A wrong process might be selected as result. The problem can be worked around by checking mem_cgroup_swappiness==0 and not considering swap at all in such a case. Signed-off-by: Michal Hocko <mhocko@suse.cz> Acked-by: David Rientjes <rientjes@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memcontrol.c21
1 files changed, 15 insertions, 6 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7685d4a0b3ce..81c275b3afed 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1489,17 +1489,26 @@ static int mem_cgroup_count_children(struct mem_cgroup *memcg)
u64 mem_cgroup_get_limit(struct mem_cgroup *memcg)
{
u64 limit;
- u64 memsw;
limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
- limit += total_swap_pages << PAGE_SHIFT;
- memsw = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
/*
- * If memsw is finite and limits the amount of swap space available
- * to this memcg, return that limit.
+ * Do not consider swap space if we cannot swap due to swappiness
*/
- return min(limit, memsw);
+ if (mem_cgroup_swappiness(memcg)) {
+ u64 memsw;
+
+ limit += total_swap_pages << PAGE_SHIFT;
+ memsw = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
+
+ /*
+ * If memsw is finite and limits the amount of swap space
+ * available to this memcg, return that limit.
+ */
+ limit = min(limit, memsw);
+ }
+
+ return limit;
}
static unsigned long mem_cgroup_reclaim(struct mem_cgroup *memcg,