linux-kernel - Re: [PATCH 3/5] oom: create oom autogroup

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Date:	Wed, 23 Mar 2011 08:21:12 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>, linux-mm <linux-mm@...ck.org>,
	Andrey Vagin <avagin@...nvz.org>,
	Hugh Dickins <hughd@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Mike Galbraith <efault@....de>
Subject: Re: [PATCH 3/5] oom: create oom autogroup

On Tue, Mar 22, 2011 at 8:08 PM, KOSAKI Motohiro
<kosaki.motohiro@...fujitsu.com> wrote:
> When plenty processes (eg fork bomb) are running, the TIF_MEMDIE task
> never exit, at least, human feel it's never. therefore kernel become
> hang-up.
>
> "perf sched" tell us a hint.
>
>  ------------------------------------------------------------------------------
>  Task                  |   Runtime ms  | Average delay ms | Maximum delay ms |
>  ------------------------------------------------------------------------------
>  python:1754           |      0.197 ms | avg: 1731.727 ms | max: 3433.805 ms |
>  python:1843           |      0.489 ms | avg: 1707.433 ms | max: 3622.955 ms |
>  python:1715           |      0.220 ms | avg: 1707.125 ms | max: 3623.246 ms |
>  python:1818           |      2.127 ms | avg: 1527.331 ms | max: 3622.553 ms |
>  ...
>  ...
>
> Processes flood makes crazy scheduler delay. and then the victim process
> can't run enough. Grr. Should we do?
>
> Fortunately, we already have anti process flood framework, autogroup!
> This patch reuse this framework and avoid kernel live lock.

That's cool idea but I have a concern.

You remove boosting priority in [2/5] and move victim tasks into autogroup.
If I understand autogroup right, victim process and threads in the
process take less schedule chance than now.

Could it make unnecessary killing of other tasks?
I am not sure. Just out of curiosity.

Thanks for nice work, Kosaki.
-- 
Kind regards,
Minchan Kim
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