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Date: Thu, 7 Sep 2006 17:58:48 -0700
From: Andrew Morton <akpm@osdl.org>
To: Mel Gorman <mel@csn.ul.ie>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/8] Avoiding fragmentation with subzone groupings v25
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On Thu,  7 Sep 2006 20:03:42 +0100 (IST)
Mel Gorman <mel@csn.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?