linux-kernel - Re: [RFC] oom-kill: give the dying task a higher priority

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Message-Id: <20100531145415.5e53f837.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Mon, 31 May 2010 14:54:15 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	balbir@...ux.vnet.ibm.com, Oleg Nesterov <oleg@...hat.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	David Rientjes <rientjes@...gle.com>,
	Mel Gorman <mel@....ul.ie>, williams@...hat.com
Subject: Re: [RFC] oom-kill: give the dying task a higher priority

On Mon, 31 May 2010 14:46:05 +0900
Minchan Kim <minchan.kim@...il.com> wrote:

> On Mon, May 31, 2010 at 2:04 PM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@...fujitsu.com> wrote:
> > On Mon, 31 May 2010 14:01:03 +0900
> > Minchan Kim <minchan.kim@...il.com> wrote:
> >
> >> Hi, Kame.
> >>
> >> On Mon, May 31, 2010 at 9:21 AM, KAMEZAWA Hiroyuki
> >> <kamezawa.hiroyu@...fujitsu.com> wrote:
> >> > On Fri, 28 May 2010 13:48:26 -0300
> >> > "Luis Claudio R. Goncalves" <lclaudio@...g.org> wrote:
> >> >>
> >> >> oom-killer: give the dying task rt priority (v3)
> >> >>
> >> >> Give the dying task RT priority so that it can be scheduled quickly and die,
> >> >> freeing needed memory.
> >> >>
> >> >> Signed-off-by: Luis Claudio R. Gonçalves <lgoncalv@...hat.com>
> >> >>
> >> >> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> >> >> index 84bbba2..2b0204f 100644
> >> >> --- a/mm/oom_kill.c
> >> >> +++ b/mm/oom_kill.c
> >> >> @@ -266,6 +266,8 @@ static struct task_struct *select_bad_process(unsigned long *ppoints)
> >> >>   */
> >> >>  static void __oom_kill_task(struct task_struct *p, int verbose)
> >> >>  {
> >> >> +     struct sched_param param;
> >> >> +
> >> >>       if (is_global_init(p)) {
> >> >>               WARN_ON(1);
> >> >>               printk(KERN_WARNING "tried to kill init!\n");
> >> >> @@ -288,6 +290,8 @@ static void __oom_kill_task(struct task_struct *p, int verbose)
> >> >>        * exit() and clear out its resources quickly...
> >> >>        */
> >> >>       p->time_slice = HZ;
> >> >> +     param.sched_priority = MAX_RT_PRIO-10;
> >> >> +     sched_setscheduler(p, SCHED_FIFO, &param);
> >> >>       set_tsk_thread_flag(p, TIF_MEMDIE);
> >> >>
> >> >
> >> > BTW, how about the other threads which share mm_struct ?
> >>
> >> Could you elaborate your intention? :)
> >>
> >
> > IIUC, the purpose of rising priority is to accerate dying thread to exit()
> > for freeing memory AFAP. But to free memory, exit, all threads which share
> > mm_struct should exit, too. I'm sorry if I miss something.
> 
> How do we kill only some thread and what's the benefit of it?
> I think when if some thread receives  KILL signal, the process include
> the thread will be killed.
> 
yes, so, if you want a _process_ die quickly, you have to acceralte the whole
threads on a process. Acceralating a thread in a process is not big help.

Thanks,
-Kame

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