linux-kernel - Re: [RFC PATCH] mm, oom: allow oom reaper to race with exit

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Message-ID: <20170627120317.GL28072@dhcp22.suse.cz>
Date:   Tue, 27 Jun 2017 14:03:17 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:     linux-mm@...ck.org, rientjes@...gle.com, oleg@...hat.com,
        andrea@...nel.org, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] mm, oom: allow oom reaper to race with exit_mmap

On Tue 27-06-17 20:39:28, Tetsuo Handa wrote:
> Michal Hocko wrote:
> > > I wonder why you prefer timeout based approach. Your patch will after all
> > > set MMF_OOM_SKIP if operations between down_write() and up_write() took
> > > more than one second.
> > 
> > if we reach down_write then we have unmapped the address space in
> > exit_mmap and oom reaper cannot do much more.
> 
> So, by the time down_write() is called, majority of memory is already released, isn't it?

In most cases yes. To be put it in other words. By the time exit_mmap
takes down_write there is nothing more oom reaper could reclaim.

-- 
Michal Hocko
SUSE Labs