linux-kernel - Re: [PATCH] mm: add group_oom

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Date:   Fri, 3 Dec 2021 16:45:54 -0800
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Dan Schatzberg <schatzberg.dan@...il.com>
Cc:     Johannes Weiner <hannes@...xchg.org>, Roman Gushchin <guro@...com>,
        Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        Jonathan Corbet <corbet@....net>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Muchun Song <songmuchun@...edance.com>,
        Alex Shi <alexs@...nel.org>,
        Wei Yang <richard.weiyang@...il.com>,
        "open list:CONTROL GROUP (CGROUP)" <cgroups@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:CONTROL GROUP - MEMORY RESOURCE CONTROLLER (MEMCG)" 
        <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: add group_oom_kill memory event

On Fri, Dec 3, 2021 at 8:24 AM Dan Schatzberg <schatzberg.dan@...il.com> wrote:
>
> Our container agent wants to know when a container exits if it was OOM
> killed or not to report to the user. We use memory.oom.group = 1 to
> ensure that OOM kills within the container's cgroup kill
> everything. Existing memory.events are insufficient for knowing if
> this triggered:
>
> 1) Our current approach reads memory.events oom_kill and reports the
> container was killed if the value is non-zero. This is erroneous in
> some cases where containers create their children cgroups with
> memory.oom.group=1 as such OOM kills will get counted against the
> container cgroup's oom_kill counter despite not actually OOM killing
> the entire container.
>
> 2) Reading memory.events.local will fail to identify OOM kills in leaf
> cgroups (that don't set memory.oom.group) within the container cgroup.
>
> This patch adds a new oom_group_kill event when memory.oom.group
> triggers to allow userspace to cleanly identify when an entire cgroup
> is oom killed.
>
> Signed-off-by: Dan Schatzberg <schatzberg.dan@...il.com>

So, with this patch, will you be watching oom_group_kill from
memory.events or memory.events.local file for your use-case?

Reviewed-by: Shakeel Butt <shakeelb@...gle.com>