linux-kernel - Re: [patch] mm, oom: prevent additional oom kills before memory is freed

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Message-ID: <alpine.DEB.2.10.1706151459530.64172@chino.kir.corp.google.com>
Date:   Thu, 15 Jun 2017 15:03:17 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Michal Hocko <mhocko@...nel.org>
cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [patch] mm, oom: prevent additional oom kills before memory is
 freed

On Thu, 15 Jun 2017, Michal Hocko wrote:

> > Yes, quite a bit in testing.
> > 
> > One oom kill shows the system to be oom:
> > 
> > [22999.488705] Node 0 Normal free:90484kB min:90500kB ...
> > [22999.488711] Node 1 Normal free:91536kB min:91948kB ...
> > 
> > followed up by one or more unnecessary oom kills showing the oom killer 
> > racing with memory freeing of the victim:
> > 
> > [22999.510329] Node 0 Normal free:229588kB min:90500kB ...
> > [22999.510334] Node 1 Normal free:600036kB min:91948kB ...
> > 
> > The patch is absolutely required for us to prevent continuous oom killing 
> > of processes after a single process has been oom killed and its memory is 
> > in the process of being freed.
> 
> OK, could you play with the patch/idea suggested in
> http://lkml.kernel.org/r/20170615122031.GL1486@dhcp22.suse.cz?
> 

I cannot, I am trying to unblock a stable kernel release to my production 
that is obviously fixed with this patch and cannot experiment with 
uncompiled and untested patches that introduce otherwise unnecessary 
locking into the __mmput() path and is based on speculation rather than 
hard data that __mmput() for some reason stalls for the oom victim's mm.  
I was hoping that this fix could make it in time for 4.12 since 4.12 kills 
1-4 processes unnecessarily for each oom condition and then can review any 
tested solution you may propose at a later time.