linux-kernel - Re: [PATCH 9/9] oom: give the dying task a higher priority

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Message-Id: <20100617084943.FB45.A69D9226@jp.fujitsu.com>
Date:	Thu, 17 Jun 2010 10:51:35 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	"Luis Claudio R. Goncalves" <lclaudio@...g.org>
Cc:	kosaki.motohiro@...fujitsu.com,
	Minchan Kim <minchan.kim@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH 9/9] oom: give the dying task a higher priority

> On Thu, Jun 17, 2010 at 12:31:20AM +0900, Minchan Kim wrote:
> | >         /*
> | >          * We give our sacrificial lamb high priority and access to
> | >          * all the memory it needs. That way it should be able to
> | >          * exit() and clear out its resources quickly...
> | >          */
> | >  	p->rt.time_slice = HZ;
> | >  	set_tsk_thread_flag(p, TIF_MEMDIE);
> ...
> | > +	if (rt_task(p)) {
> | > +		p->rt.time_slice = HZ;
> | > +		return;
> 
> I am not sure the code above will have any real effect for an RT task.
> Kosaki-san, was this change motivated by test results or was it just a code
> cleanup? I ask that out of curiosity.

just cleanup.
ok, I remove this dubious code.

> 
> | I have a question from long time ago. 
> | If we change rt.time_slice _without_ setscheduler, is it effective?
> | I mean scheduler pick up the task faster than other normal task?
> 
> $ git log --pretty=oneline -Stime_slice mm/oom_kill.c
> 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Linux-2.6.12-rc2
> 
> This code ("time_slice = HZ;") is around for quite a while and
> probably comes from a time where having a big time slice was enough to be
> sure you would be the next on the line. I would say sched_setscheduler is
> indeed necessary.

ok


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