linux-kernel - Re: [PATCH 11/12] vmscan: Write out dirty pages in batch

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Message-ID: <20100615232009.GT6590@dastard>
Date:	Wed, 16 Jun 2010 09:20:09 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Evgeniy Polyakov <zbr@...emap.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
	Chris Mason <chris.mason@...cle.com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Christoph Hellwig <hch@...radead.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 11/12] vmscan: Write out dirty pages in batch

On Tue, Jun 15, 2010 at 08:55:38PM +1000, Nick Piggin wrote:
> On Tue, Jun 15, 2010 at 02:28:22PM +0400, Evgeniy Polyakov wrote:
> > On Tue, Jun 15, 2010 at 04:36:43PM +1000, Dave Chinner (david@...morbit.com) wrote:
> > Per-mapping sorting will not do anything good in this case, even if
> > files were previously created in a good facion being placed closely and
> > so on, and only block layer will find a correlation between adjacent
> > blocks in different files. But with existing queue management it has
> > quite a small opportunity, and that's what I think Andrew is arguing
> > about.
> 
> The solution is not to sort pages on their way to be submitted either,
> really.
> 
> What I do in fsblock is to maintain a block-nr sorted tree of dirty
> blocks. This works nicely because fsblock dirty state is properly
> synchronized with page dirty state.

How does this work with delayed allocation where there is no block
number associated with the page until writeback calls the allocation
routine?

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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