Date:   Fri, 3 Dec 2021 15:37:08 -0800
From:   Roman Gushchin <guro@fb.com>
To:     Dan Schatzberg <schatzberg.dan@gmail.com>
CC:     Johannes Weiner <hannes@cmpxchg.org>, Tejun Heo <tj@kernel.org>,
        Zefan Li <lizefan.x@bytedance.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Michal Hocko <mhocko@kernel.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Shakeel Butt <shakeelb@google.com>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Muchun Song <songmuchun@bytedance.com>,
        Alex Shi <alexs@kernel.org>,
        Wei Yang <richard.weiyang@gmail.com>,
        "open list:CONTROL GROUP (CGROUP)" <cgroups@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:CONTROL GROUP - MEMORY RESOURCE CONTROLLER (MEMCG)" 
        <linux-mm@kvack.org>
Subject: Re: [PATCH] mm: add group_oom_kill memory event
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References: <20211203162426.3375036-1-schatzberg.dan@gmail.com>
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On Fri, Dec 03, 2021 at 08:24:23AM -0800, Dan Schatzberg 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@gmail.com>

Reviewed-by: Roman Gushchin <guro@fb.com>

Thanks!