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Date: Fri, 26 Feb 2016 14:49:20 +0100
From: Michal Hocko <mhocko@kernel.org>
To: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: "'Hugh Dickins'" <hughd@google.com>,
        "'Andrew Morton'" <akpm@linux-foundation.org>,
        "'Linus Torvalds'" <torvalds@linux-foundation.org>,
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        linux-mm@kvack.org, "'LKML'" <linux-kernel@vger.kernel.org>,
        "'Sergey Senozhatsky'" <sergey.senozhatsky.work@gmail.com>
Subject: Re: [PATCH 0/3] OOM detection rework v4
Message-ID: <20160226134920.GA18200@dhcp22.suse.cz>
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On Fri 26-02-16 18:27:16, Hillf Danton wrote:
> >> 
> > > --- 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
> > 
> Then in another direction, below is what I can do.
> 
> thanks
> Hillf
> --- a/mm/page_alloc.c	Thu Feb 25 15:43:18 2016
> +++ b/mm/page_alloc.c	Fri Feb 26 18:14:59 2016
> @@ -3366,8 +3366,11 @@ retry:
>  		no_progress_loops++;
>  
>  	if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags,
> -				 did_some_progress > 0, no_progress_loops))
> +				 did_some_progress > 0, no_progress_loops)) {
> +		/* Burn more cycles if any zone seems to satisfy our request */
> +		no_progress_loops /= 2;

No, I do not think this makes any sense. If we need more retry loops
then we can do it by increasing MAX_RECLAIM_RETRIES.

>  		goto retry;
> +	}
>  
>  	/* Reclaim has failed us, start killing things */
>  	page = __alloc_pages_may_oom(gfp_mask, order, ac, &did_some_progress);

-- 
Michal Hocko
SUSE Labs