linux-kernel - Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates.

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Date:	Thu, 7 Jan 2016 11:28:15 -0500
From:	Johannes Weiner <hannes@...xchg.org>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	mhocko@...nel.org, akpm@...ux-foundation.org, mgorman@...e.de,
	rientjes@...gle.com, torvalds@...ux-foundation.org,
	oleg@...hat.com, hughd@...gle.com, andrea@...nel.org,
	riel@...hat.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates.

On Tue, Dec 29, 2015 at 10:58:22PM +0900, Tetsuo Handa wrote:
> >From 8bb9e36891a803e82c589ef78077838026ce0f7d Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Date: Tue, 29 Dec 2015 22:20:58 +0900
> Subject: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates.
> 
> The OOM reaper kernel thread can reclaim OOM victim's memory before the victim
> terminates. But since oom_kill_process() tries to kill children of the memory
> hog process first, the OOM reaper can not reclaim enough memory for terminating
> the victim if the victim is consuming little memory. The result is OOM livelock
> as usual, for timeout based next OOM victim selection is not implemented.

What we should be doing is have the OOM reaper clear TIF_MEMDIE after
it's done. There is no reason to wait for and prioritize the exit of a
task that doesn't even have memory anymore. Once a task's memory has
been reaped, subsequent OOM invocations should evaluate anew the most
desirable OOM victim.
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