linux-kernel - Re: [PATCH 3/3] mm,vmscan: Reclaim order-0 and compact instead of lumpy reclaim when under light pressure

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Date:	Sun, 14 Nov 2010 15:02:03 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	kosaki.motohiro@...fujitsu.com,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] mm,vmscan: Reclaim order-0 and compact instead of lumpy reclaim when under light pressure

> On Thu, Nov 11, 2010 at 07:07:04PM +0000, Mel Gorman wrote:
> > +	if (COMPACTION_BUILD)
> > +		sc->lumpy_reclaim_mode = LUMPY_MODE_COMPACTION;
> > +	else
> > +		sc->lumpy_reclaim_mode = LUMPY_MODE_CONTIGRECLAIM;
> >  
> 
> Gack, I posted the slightly wrong version. This version prevents lumpy
> reclaim ever being used. The figures I posted were for a patch where
> this condition looked like
> 
>         if (COMPACTION_BUILD && priority > DEF_PRIORITY - 2)
>                 sc->lumpy_reclaim_mode = LUMPY_MODE_COMPACTION;
>         else
>                 sc->lumpy_reclaim_mode = LUMPY_MODE_CONTIGRECLAIM;

Can you please tell us your opinition which is better 1) automatically turn lumby on
by priority (this approach) 2) introduce GFP_LUMPY (andrea proposed). I'm not
sure which is better, then I'd like to hear both pros/cons concern.

Thanks.


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