linux-kernel - Re: [patch v3] mm, oom: fix unnecessary killing of additional processes

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Date:   Fri, 6 Jul 2018 07:39:00 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     David Rientjes <rientjes@...gle.com>,
        kbuild test robot <fengguang.wu@...el.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch v3] mm, oom: fix unnecessary killing of additional
 processes

On Thu 05-07-18 16:46:21, Andrew Morton wrote:
> On Thu, 21 Jun 2018 14:35:20 -0700 (PDT) David Rientjes <rientjes@...gle.com> wrote:
> 
> > The oom reaper ensures forward progress by setting MMF_OOM_SKIP itself if
> > it cannot reap an mm.  This can happen for a variety of reasons,
> > including:
> > 
> >  - the inability to grab mm->mmap_sem in a sufficient amount of time,
> > 
> >  - when the mm has blockable mmu notifiers that could cause the oom reaper
> >    to stall indefinitely,
> > 
> > but we can also add a third when the oom reaper can "reap" an mm but doing
> > so is unlikely to free any amount of memory:
> > 
> >  - when the mm's memory is mostly mlocked.
> 
> Michal has been talking about making the oom-reaper handle mlocked
> memory.  Where are we at with that?

I didn't get to mlocked memory yet because blockable mmu notifiers are
more important. And I've already posted patch for that and it is under
discussion [1]. Mlocked memory is next. 
 
[1] http://lkml.kernel.org/r/20180627074421.GF32348@dhcp22.suse.cz

Btw. I still hate this patch and making any timeout user defineable. It
is a wrong approach and my nack to this patch still applies.

-- 
Michal Hocko
SUSE Labs