linux-kernel - Re: OOM Killer don't works at all if the system have >gigabytes memory (was Re: [PATCH] mm: check zone->all_unreclaimable in all

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Date:	Thu, 12 May 2011 09:13:54 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	CAI Qian <caiqian@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.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, Hugh Dickins <hughd@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: OOM Killer don't works at all if the system have >gigabytes
 memory (was Re: [PATCH] mm: check zone->all_unreclaimable in all_unreclaimable())

On Thu, May 12, 2011 at 5:34 AM, David Rientjes <rientjes@...gle.com> wrote:
> On Tue, 10 May 2011, CAI Qian wrote:
>
>> Sure, I saw there were some discussion going on between you and David
>> about your patches. Does it make more sense for me to test those after
>> you have settled down technical arguments?
>>
>
> Something like the following (untested) patch should fix the issue by
> simply increasing the range of a task's badness from 0-1000 to 0-10000.
>
> There are other things to fix like the tasklist dump output and
> documentation, but this shows how easy it is to increase the resolution of
> the scoring.  (This patch also includes a change to only give root

It does make sense.
I think raising resolution should be a easy way to fix the problem.

> processes a 1% bonus for every 30% of memory they use as proposed
> earlier.)

I didn't follow earlier your suggestion.
But it's not formal patch so I expect if you send formal patch to
merge, you would write down the rationale.

>
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -160,7 +160,7 @@ unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem,
>         */
>        if (p->flags & PF_OOM_ORIGIN) {
>                task_unlock(p);
> -               return 1000;
> +               return 10000;
>        }
>
>        /*
> @@ -177,32 +177,32 @@ unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem,
>        points = get_mm_rss(p->mm) + p->mm->nr_ptes;
>        points += get_mm_counter(p->mm, MM_SWAPENTS);
>
> -       points *= 1000;
> +       points *= 10000;
>        points /= totalpages;
>        task_unlock(p);
>
>        /*
> -        * Root processes get 3% bonus, just like the __vm_enough_memory()
> -        * implementation used by LSMs.
> +        * Root processes get 1% bonus per 30% memory used for a total of 3%
> +        * possible just like LSMs.
>         */
>        if (has_capability_noaudit(p, CAP_SYS_ADMIN))
> -               points -= 30;
> +               points -= 100 * (points / 3000);
>
>        /*
>         * /proc/pid/oom_score_adj ranges from -1000 to +1000 such that it may
>         * either completely disable oom killing or always prefer a certain
>         * task.
>         */
> -       points += p->signal->oom_score_adj;
> +       points += p->signal->oom_score_adj * 10;
>
>        /*
>         * Never return 0 for an eligible task that may be killed since it's
> -        * possible that no single user task uses more than 0.1% of memory and
> +        * possible that no single user task uses more than 0.01% of memory and
>         * no single admin tasks uses more than 3.0%.
>         */
>        if (points <= 0)
>                return 1;
> -       return (points < 1000) ? points : 1000;
> +       return (points < 10000) ? points : 10000;
>  }
>
>  /*
> @@ -314,7 +314,7 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
>                         */
>                        if (p == current) {
>                                chosen = p;
> -                               *ppoints = 1000;
> +                               *ppoints = 10000;

Scattering constant value isn't good.
You are proving it now.
I think you did it since this is not a formal patch.
I expect you will define new value (ex, OOM_INTERNAL_MAX_SCORE or whatever)


-- 
Kind regards,
Minchan Kim
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