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Date:   Thu, 5 Oct 2017 13:40:47 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Roman Gushchin <guro@...com>
Cc:     linux-mm@...ck.org, Vladimir Davydov <vdavydov.dev@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        David Rientjes <rientjes@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>, kernel-team@...com,
        cgroups@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [v10 3/6] mm, oom: cgroup-aware OOM killer

On Wed 04-10-17 16:46:35, Roman Gushchin wrote:
> Traditionally, the OOM killer is operating on a process level.
> Under oom conditions, it finds a process with the highest oom score
> and kills it.
> 
> This behavior doesn't suit well the system with many running
> containers:
> 
> 1) There is no fairness between containers. A small container with
> few large processes will be chosen over a large one with huge
> number of small processes.
> 
> 2) Containers often do not expect that some random process inside
> will be killed. In many cases much safer behavior is to kill
> all tasks in the container. Traditionally, this was implemented
> in userspace, but doing it in the kernel has some advantages,
> especially in a case of a system-wide OOM.
> 
> To address these issues, the cgroup-aware OOM killer is introduced.
> 
> Under OOM conditions, it looks for the biggest leaf memory cgroup
> and kills the biggest task belonging to it. The following patches
> will extend this functionality to consider non-leaf memory cgroups
> as well, and also provide an ability to kill all tasks belonging
> to the victim cgroup.
> 
> The root cgroup is treated as a leaf memory cgroup, so it's score
> is compared with leaf memory cgroups.
> Due to memcg statistics implementation a special algorithm
> is used for estimating it's oom_score: we define it as maximum
> oom_score of the belonging tasks.

Thanks for separating the group_oom part. This is getting in the
mergeable state. I will ack it once the suggested fixes are folded in.
There is some clean up potential on top (I find the oc->chosen_memcg
quite ugly and will post a patch on top of yours) but that can be done
later.
 
> Signed-off-by: Roman Gushchin <guro@...com>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: Vladimir Davydov <vdavydov.dev@...il.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: kernel-team@...com
> Cc: cgroups@...r.kernel.org
> Cc: linux-doc@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-mm@...ck.org
-- 
Michal Hocko
SUSE Labs

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