linux-kernel - Re: [PATCH] memcg: oom: ignore oom warnings from memory.max

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Message-ID: <20200504065701.GB22838@dhcp22.suse.cz>
Date:   Mon, 4 May 2020 08:57:01 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Johannes Weiner <hannes@...xchg.org>, Roman Gushchin <guro@...com>,
        Greg Thelen <gthelen@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Cgroups <cgroups@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] memcg: oom: ignore oom warnings from memory.max

On Thu 30-04-20 13:20:10, Shakeel Butt wrote:
> On Thu, Apr 30, 2020 at 12:29 PM Johannes Weiner <hannes@...xchg.org> wrote:
> >
> > On Thu, Apr 30, 2020 at 11:27:12AM -0700, Shakeel Butt wrote:
> > > Lowering memory.max can trigger an oom-kill if the reclaim does not
> > > succeed. However if oom-killer does not find a process for killing, it
> > > dumps a lot of warnings.
> > >
> > > Deleting a memcg does not reclaim memory from it and the memory can
> > > linger till there is a memory pressure. One normal way to proactively
> > > reclaim such memory is to set memory.max to 0 just before deleting the
> > > memcg. However if some of the memcg's memory is pinned by others, this
> > > operation can trigger an oom-kill without any process and thus can log a
> > > lot un-needed warnings. So, ignore all such warnings from memory.max.
> >
> > Can't you set memory.high=0 instead? It does the reclaim portion of
> > memory.max, without the actual OOM killing that causes you problems.
> 
> Yes that would work but remote charging concerns me. Remote charging
> can still happen after the memcg is offlined and at the moment, high
> reclaim does not work for remote memcg and the usage can go till max
> or global pressure. This is most probably a misconfiguration and we
> might not receive the warnings in the log ever. Setting memory.max to
> 0 will definitely give such warnings.

Can we add a warning for the remote charging on dead memcgs?

-- 
Michal Hocko
SUSE Labs