From: Michal Hocko <mhocko@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, David Rientjes <rientjes@google.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] memcg: oom: fix totalpages calculation for memory.swappiness==0
Date: Thu, 8 Nov 2012 09:35:55 +0100 [thread overview]
Message-ID: <20121108083454.GA30792@dhcp22.suse.cz> (raw)
In-Reply-To: <20121107145340.b45a387c.akpm@linux-foundation.org>
On Wed 07-11-12 14:53:40, Andrew Morton wrote:
> On Wed, 7 Nov 2012 23:46:40 +0100
> Michal Hocko <mhocko@suse.cz> wrote:
>
> > > Realistically, is anyone likely to hurt from this?
> >
> > The primary motivation for the fix was a real report by a customer.
>
> Describe it please and I'll copy it to the changelog.
The original issue (a wrong tasks get killed in a small group and memcg
swappiness=0) has been reported on top of our 3.0 based kernel (with
fe35004f backported). I have tried to replicate it by the test case
mentioned https://lkml.org/lkml/2012/10/10/223.
As David correctly pointed out (https://lkml.org/lkml/2012/10/10/418)
the significant role played the fact that all the processes in the group
have CAP_SYS_ADMIN but oom_score_adj has the similar effect.
Say there is 2G of swap space which is 524288 pages. If you add
CAP_SYS_ADMIN bonus then you have -15728 score for the bias. This means
that all tasks with less than 60M get the minimum score and it is tasks
ordering which determines who gets killed as a result.
To summarize it. Users of small groups (relatively to the swap size)
with CAP_SYS_ADMIN tasks resp. oom_score_adj are affected the most
others might see an unexpected oom_badness calculation.
Whether this is a workload which is representative, I don't know but
I think that it is worth fixing and pushing to stable as well.
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2012-11-08 8:36 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-10 14:11 [RFC PATCH] memcg: oom: fix totalpages calculation for swappiness==0 Michal Hocko
2012-10-10 20:50 ` David Rientjes
2012-10-11 8:50 ` Michal Hocko
2012-10-11 8:57 ` [PATCH] memcg: oom: fix totalpages calculation for memory.swappiness==0 Michal Hocko
2012-10-11 9:13 ` Michal Hocko
2012-10-11 12:20 ` Johannes Weiner
2012-10-12 13:01 ` Michal Hocko
2012-10-11 22:36 ` KOSAKI Motohiro
2012-10-12 13:01 ` Michal Hocko
2012-10-15 22:04 ` [PATCH v2] " Michal Hocko
2012-10-15 22:07 ` [PATCH] doc: describe memcg swappiness more precisely memory.swappiness==0 Michal Hocko
2012-10-16 0:51 ` Kamezawa Hiroyuki
2012-10-16 0:54 ` David Rientjes
2012-11-07 22:10 ` [PATCH v2] memcg: oom: fix totalpages calculation for memory.swappiness==0 Andrew Morton
2012-11-07 22:46 ` Michal Hocko
2012-11-07 22:53 ` Andrew Morton
2012-11-08 8:35 ` Michal Hocko [this message]
2012-10-15 9:11 ` [RFC PATCH] memcg: oom: fix totalpages calculation for swappiness==0 Kamezawa Hiroyuki
2012-10-15 9:49 ` Michal Hocko
2012-10-15 14:25 ` KOSAKI Motohiro
2012-10-15 14:47 ` Michal Hocko
2012-10-15 22:33 ` KOSAKI Motohiro
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