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From: Chris Mason <chris.mason@oracle.com>
Subject: Re: buffered writeback torture program
In-reply-to: <20110421174120.GA7267@infradead.org>
References: <1303322378-sup-1722@think> <20110421083258.GA26784@infradead.org>
	<1303407205-sup-6141@think> <20110421174120.GA7267@infradead.org>
Date: Thu, 21 Apr 2011 14:00:29 -0400
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To: Christoph Hellwig <hch@infradead.org>
Cc: axboe <axboe@kernel.dk>, jack <jack@suse.cz>, xfs <xfs@oss.sgi.com>, dchinner <dchinner@redhat.com>, linux-fsdevel <linux-fsdevel@vger.kernel.org>, linux-ext4 <linux-ext4@vger.kernel.org>

Excerpts from Christoph Hellwig's message of 2011-04-21 13:41:21 -0400:
> On Thu, Apr 21, 2011 at 01:34:44PM -0400, Chris Mason wrote:
> > Sorry, this doesn't do it.  I think that given what a strange special
> > case this is, we're best off waiting for the IO-less throttling, and
> > maybe changing the code in xfs/ext4 to be a little more seek aware.  Or
> > maybe not, it has to get written eventually either way.
> 
> I'm not sure what you mean with seek aware.  XFS only clusters
> additional pages that are in the same extent, and in fact only does
> so for asynchrononous writeback.  Not sure how this should be more
> seek aware.
> 

How big are extents?  fiemap tells me the file has a single 8GB extent.

There's a little room for seeking inside there.

-chris

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