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Date: Thu, 15 May 2008 10:42:15 -0700 (PDT)
From: Christoph Lameter <clameter@sgi.com>
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To: David Chinner <dgc@sgi.com>
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       andi@firstfloor.org, Rik van Riel <riel@redhat.com>,
       Pekka Enberg <penberg@cs.helsinki.fi>, mpm@selenic.com
Subject: Re: [patch 10/21] buffer heads: Support slab defrag
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On Mon, 12 May 2008, David Chinner wrote:

> If you are going to clean bufferheads (or pages), please clean entire
> mappings via ->writepages as it leads to far superior I/O patterns
> and a far higher aggregate rate of page cleaning.....

That brings up another issue: Lets say I use writepages on a large file 
(couple of gig). How much do you want to write back?