linux-kernel - Re: [PATCH v8] oom_kill.c: futex: Don't OOM reap the VMA containing the robust_list

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Message-ID: <YlACJMp7AFaVa/Gt@dhcp22.suse.cz>
Date:   Fri, 8 Apr 2022 11:36:36 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Nico Pache <npache@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Rafael Aquini <aquini@...hat.com>,
        Waiman Long <longman@...hat.com>, Baoquan He <bhe@...hat.com>,
        Christoph von Recklinghausen <crecklin@...hat.com>,
        Don Dutile <ddutile@...hat.com>,
        "Herton R . Krzesinski" <herton@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Ingo Molnar <mingo@...hat.com>,
        Joel Savitz <jsavitz@...hat.com>,
        Darren Hart <dvhart@...radead.org>, stable@...nel.org
Subject: Re: [PATCH v8] oom_kill.c: futex: Don't OOM reap the VMA containing
 the robust_list_head

On Fri 08-04-22 04:52:33, Nico Pache wrote:
[...]
> In a heavily contended CPU with high memory pressure the delay may also
> lead to other processes unnecessarily OOMing.

Let me just comment on this part because there is likely a confusion
inlved. Delaying the oom_reaper _cannot_ lead to additional OOM killing
because the the oom killing is throttled by existence of a preexisting
OOM victim. In other words as long as there is an alive victim no
further victims are not selected and the oom killer backs off. The
oom_repaer will hide the alive oom victim after it is processed.
The longer the delay will be the longer an oom victim can block a
further progress but it cannot really cause unnecessary OOMing.
-- 
Michal Hocko
SUSE Labs