linux-kernel - Re: [PATCH 2/4] oom: kill younger process first

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Message-ID: <4DCD0582.2020601@jp.fujitsu.com>
Date:	Fri, 13 May 2011 19:18:42 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	CAI Qian <caiqian@...hat.com>, avagin@...il.com,
	Andrey Vagin <avagin@...nvz.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Minchan Kim <minchan.kim@...il.com>,
	David Rientjes <rientjes@...gle.com>,
	Hugh Dickins <hughd@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH 2/4] oom: kill younger process first

(2011/05/12 9:52), KAMEZAWA Hiroyuki wrote:
> On Tue, 10 May 2011 17:15:01 +0900 (JST)
> KOSAKI Motohiro<kosaki.motohiro@...fujitsu.com>  wrote:
>
>> This patch introduces do_each_thread_reverse() and
>> select_bad_process() uses it. The benefits are two,
>> 1) oom-killer can kill younger process than older if
>> they have a same oom score. Usually younger process
>> is less important. 2) younger task often have PF_EXITING
>> because shell script makes a lot of short lived processes.
>> Reverse order search can detect it faster.
>>
>> Reported-by: CAI Qian<caiqian@...hat.com>
>> Signed-off-by: KOSAKI Motohiro<kosaki.motohiro@...fujitsu.com>
>
> IIUC, for_each_thread() can be called under rcu_read_lock() but
> for_each_thread_reverse() must be under tasklist_lock.
>
> Could you add some comment ? and prev_task() should use list_entry()
> not list_entry_rcu().

Will fix. thanks.


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