linux-kernel - Re: [patch -mm] oom: exclude tasks with badness score of 0 from being selected

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Message-ID: <20100402210459.GA5112@redhat.com>
Date:	Fri, 2 Apr 2010 23:04:59 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	anfei <anfei.zhou@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	nishimura@....nes.nec.co.jp,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Mel Gorman <mel@....ul.ie>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch -mm] oom: exclude tasks with badness score of 0 from
	being selected

On 04/02, David Rientjes wrote:
>
> An oom_badness() score of 0 means "never kill" according to
> Documentation/filesystems/proc.txt, so explicitly exclude it from being
> selected for kill.  These tasks have either detached their p->mm or are
> set to OOM_DISABLE.

Agreed, but

> @@ -336,6 +336,8 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
>  			continue;
>
>  		points = oom_badness(p, totalpages);
> +		if (!points)
> +			continue;
>  		if (points > *ppoints || !chosen) {

then "|| !chosen" can be killed.

with this patch  !chosen <=> !*ppoints, and since points > 0

		if (points > *ppoints) {

is enough.

Oleg.

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