linux-kernel - Re: [v10 4/6] mm, oom: introduce memory.oom

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Date:   Wed, 4 Oct 2017 15:37:00 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Roman Gushchin <guro@...com>
Cc:     linux-mm@...ck.org, Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        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 4/6] mm, oom: introduce memory.oom_group

On Wed, Oct 04, 2017 at 04:46:36PM +0100, Roman Gushchin wrote:
> The cgroup-aware OOM killer treats leaf memory cgroups as memory
> consumption entities and performs the victim selection by comparing
> them based on their memory footprint. Then it kills the biggest task
> inside the selected memory cgroup.
> 
> But there are workloads, which are not tolerant to a such behavior.
> Killing a random task may leave the workload in a broken state.
> 
> To solve this problem, memory.oom_group knob is introduced.
> It will define, whether a memory group should be treated as an
> indivisible memory consumer, compared by total memory consumption
> with other memory consumers (leaf memory cgroups and other memory
> cgroups with memory.oom_group set), and whether all belonging tasks
> should be killed if the cgroup is selected.
> 
> If set on memcg A, it means that in case of system-wide OOM or
> memcg-wide OOM scoped to A or any ancestor cgroup, all tasks,
> belonging to the sub-tree of A will be killed. If OOM event is
> scoped to a descendant cgroup (A/B, for example), only tasks in
> that cgroup can be affected. OOM killer will never touch any tasks
> outside of the scope of the OOM event.
> 
> Also, tasks with oom_score_adj set to -1000 will not be killed.
> 
> The default value is 0.
> 
> 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

Those semantics make sense to me and the code looks good.

Acked-by: Johannes Weiner <hannes@...xchg.org>