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| author | Michal Hocko <mhocko@suse.cz> | 2012-11-17 02:14:49 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-11-17 02:33:04 +0400 |
| commit | 9a5a8f19b43430752067ecaee62fc59e11e88fa6 (patch) | |
| tree | ffa31761b0e208d8be324dc97368caf4bea87fd8 /Documentation/cgroups/memory.txt | |
| parent | 1756954c61cb5c97c618ccb366482b9c1f891d6d (diff) | |
| download | linux-9a5a8f19b43430752067ecaee62fc59e11e88fa6.tar.xz | |
memcg: oom: fix totalpages calculation for memory.swappiness==0
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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/cgroups/memory.txt')
| -rw-r--r-- | Documentation/cgroups/memory.txt | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt index c07f7b4fb88d..71c4da413444 100644 --- a/Documentation/cgroups/memory.txt +++ b/Documentation/cgroups/memory.txt @@ -466,6 +466,10 @@ Note: 5.3 swappiness Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only. +Please note that unlike the global swappiness, memcg knob set to 0 +really prevents from any swapping even if there is a swap storage +available. This might lead to memcg OOM killer if there are no file +pages to reclaim. Following cgroups' swappiness can't be changed. - root cgroup (uses /proc/sys/vm/swappiness). |