linux-kernel - Re: [PATCH 0/3] OOM detection rework v4

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Date:	Fri, 26 Feb 2016 10:24:07 +0100
From:	Michal Hocko <mhocko@...nel.org>
To:	Hillf Danton <hillf.zj@...baba-inc.com>
Cc:	'Hugh Dickins' <hughd@...gle.com>,
	'Andrew Morton' <akpm@...ux-foundation.org>,
	'Linus Torvalds' <torvalds@...ux-foundation.org>,
	'Johannes Weiner' <hannes@...xchg.org>,
	'Mel Gorman' <mgorman@...e.de>,
	'David Rientjes' <rientjes@...gle.com>,
	'Tetsuo Handa' <penguin-kernel@...ove.sakura.ne.jp>,
	'KAMEZAWA Hiroyuki' <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm@...ck.org, 'LKML' <linux-kernel@...r.kernel.org>,
	'Sergey Senozhatsky' <sergey.senozhatsky.work@...il.com>
Subject: Re: [PATCH 0/3] OOM detection rework v4

On Fri 26-02-16 15:54:19, Hillf Danton wrote:
> > 
> > It didn't really help, I'm afraid: it reduces the actual number of OOM
> > kills which occur before the job is terminated, but doesn't stop the
> > job from being terminated very soon.
> > 
> > I also tried Hillf's patch (separately) too, but as you expected,
> > it didn't seem to make any difference.
> > 
> Perhaps non-costly means NOFAIL as shown by folding the two

nofail only means that the page allocator doesn't return with NULL.
OOM killer is still not put aside...

> patches into one. Can it make any sense?
> 
> thanks
> Hillf
> --- a/mm/page_alloc.c	Thu Feb 25 15:43:18 2016
> +++ b/mm/page_alloc.c	Fri Feb 26 15:18:55 2016
> @@ -3113,6 +3113,8 @@ should_reclaim_retry(gfp_t gfp_mask, uns
>  	struct zone *zone;
>  	struct zoneref *z;
>  
> +	if (order <= PAGE_ALLOC_COSTLY_ORDER)
> +		return true;

This is defeating the whole purpose of the rework - to behave
deterministically. You have just disabled the oom killer completely.
This is not the way to go

-- 
Michal Hocko
SUSE Labs