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

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Date:	Mon, 31 May 2010 15:09:41 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.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, May 31, 2010 at 2:54 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@...fujitsu.com> wrote:
> 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.

Yes.

I see the code.
oom_kill_process is called by

1. mem_cgroup_out_of_memory
2. __out_of_memory
3. out_of_memory


(1,2) calls select_bad_process which select victim task in processes
by do_each_process.
But 3 isn't In case of  CONSTRAINT_MEMORY_POLICY, it kills current.
In only the case, couldn't we pass task of process, not one of thread?

>
> Thanks,
> -Kame
>
>



-- 
Kind regards,
Minchan Kim
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