linux-ext4 - Re: buffered writeback torture program

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Message-Id: <1303408265-sup-2454@think>
Date:	Thu, 21 Apr 2011 14:00:29 -0400
From:	Chris Mason <chris.mason@...cle.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-ext4 <linux-ext4@...r.kernel.org>, xfs <xfs@....sgi.com>,
	jack <jack@...e.cz>, axboe <axboe@...nel.dk>,
	dchinner <dchinner@...hat.com>
Subject: Re: buffered writeback torture program

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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