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

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Message-ID: <20180709123524.GK22049@dhcp22.suse.cz>
Date:   Mon, 9 Jul 2018 14:35:24 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        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 Fri 06-07-18 17:05:39, David Rientjes wrote:
[...]
> Blockable mmu notifiers and mlocked memory is not the extent of the 
> problem, if a process has a lot of virtual memory we must wait until 
> free_pgtables() completes in exit_mmap() to prevent unnecessary oom 
> killing.  For implementations such as tcmalloc, which does not release 
> virtual memory, this is important because, well, it releases this only at 
> exit_mmap().  Of course we cannot do that with only the protection of 
> mm->mmap_sem for read.

And how exactly a timeout helps to prevent from "unnecessary killing" in
that case?
-- 
Michal Hocko
SUSE Labs