linux-kernel - Re: [00/17] Large Blocksize Support V3

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Date:	Thu, 26 Apr 2007 17:32:16 -0700
From:	William Lee Irwin III <wli@...omorphy.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Nick Piggin <nickpiggin@...oo.com.au>,
	Christoph Lameter <clameter@....com>,
	linux-kernel@...r.kernel.org, Mel Gorman <mel@...net.ie>,
	David Chinner <dgc@....com>,
	Jens Axboe <jens.axboe@...cle.com>,
	Badari Pulavarty <pbadari@...il.com>,
	Maxim Levitsky <maximlevitsky@...il.com>
Subject: Re: [00/17] Large Blocksize Support V3

William Lee Irwin III <wli@...omorphy.com> writes:
>> In memory as on disk, contiguity matters a lot for performance.

On Thu, Apr 26, 2007 at 12:21:24PM -0600, Eric W. Biederman wrote:
> Not nearly so much though.  In memory you don't have seeks to avoid.
> On disks avoiding seeks is everything.

I readily concede that seeks are most costly. Yet memory contiguity
remains rather influential.

Witness the fact that I'm now being called upon a second time to
adjust the order in which mm/page_alloc.c returns pages for the
sake of implicitly establishing IO contiguity (or otherwise
determining why things are coming out backward now).


-- wli
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