linux-kernel - Re: [PATCH 0/8] Avoiding fragmentation with subzone groupings v25

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Message-Id: <1157704232.17799.48.camel@lappy>
Date:	Fri, 08 Sep 2006 10:30:32 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Andrew Morton <akpm@...l.org>
Cc:	Mel Gorman <mel@....ul.ie>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/8] Avoiding fragmentation with subzone groupings v25

On Thu, 2006-09-07 at 17:58 -0700, Andrew Morton wrote:
> On Thu,  7 Sep 2006 20:03:42 +0100 (IST)
> Mel Gorman <mel@....ul.ie> wrote:
> 
> > When a page is allocated, the page-flags
> > are updated with a value indicating it's type of reclaimability so that it
> > is placed on the correct list on free.
> 
> We're getting awful tight on page-flags.
> 
> Would it be possible to avoid adding the flag?  Say, have a per-zone bitmap
> of size (zone->present_pages/(1<<MAX_ORDER)) bits, then do a lookup in
> there to work out whether a particular page is within a MAX_ORDER clump of
> easy-reclaimable pages?

That would not actually work, the fallback allocation path can move
blocks smaller than MAX_ORDER to another recaim type.

But yeah, page flags are getting right, perhaps Rafael can use his
recently introduced bitmaps to rid us of the swsusp flags?


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