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

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Message-ID: <20200504080308.GI22838@dhcp22.suse.cz>
Date:   Mon, 4 May 2020 10:03:08 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     Shakeel Butt <shakeelb@...gle.com>,
        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 Mon 04-05-20 15:40:18, Yafang Shao wrote:
> On Mon, May 4, 2020 at 3:35 PM Michal Hocko <mhocko@...nel.org> wrote:
> >
> > On Mon 04-05-20 15:26:52, Yafang Shao wrote:
[...]
> > > As explianed above, no eligible task is different from no task.
> > > If there are some candidates but no one is eligible, the system will panic.
> > > While if there's no task, it is definitely no OOM, because that's an
> > > improssible thing for the system.
> >
> > This is very much possible situation when all eligible tasks have been
> > already killed but they didn't really help to resolve the oom situation
> > - e.g. in kernel memory leak or unbounded shmem consumption etc...
> >
> 
> That's still an impossible thing, because many tasks are invisible to
> the oom killer.
> See oom_unkillable_task().

I do not follow, really. oom_unkillable_task only says that global init
cannot be killed and that it doesn't make any sense to kill kernel
threads as they do not own any mm normally.

-- 
Michal Hocko
SUSE Labs