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Re: Filesystem writes on RAID5 too slow

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: Filesystem writes on RAID5 too slow
From: Ben Myers <bpm@xxxxxxx>
Date: Wed, 11 Dec 2013 13:09:45 -0600
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>, Martin Boutin <martboutin@xxxxxxxxx>, "Kernel.org-Linux-RAID" <linux-raid@xxxxxxxxxxxxxxx>, xfs-oss <xfs@xxxxxxxxxxx>, "Kernel.org-Linux-EXT4" <linux-ext4@xxxxxxxxxxxxxxx>, Eric Sandeen <sandeen@xxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20131211002753.GD10988@dastard>
References: <CACtJ3HZxp6xEjY_wOucCcqX4scNzEGuiAsovQYObJS9whtYJsQ@xxxxxxxxxxxxxx> <528A5C45.4080906@xxxxxxxxxx> <20131119005740.GY6188@dastard> <CACtJ3Ha3C7JNi5VZRnNMn+-okNheygmbj=j9AnUMvfzfZjNwug@xxxxxxxxxxxxxx> <20131121092606.GU11434@dastard> <CACtJ3HZAsOtmLArMWraygfQxpGymtZjr+a_reXv8o6LJzoMbvw@xxxxxxxxxxxxxx> <CACtJ3Ha5P2Heu4qiEEk6c4g+tKyR=RrD-4E-Cqj+bP8YDjKQ6w@xxxxxxxxxxxxxx> <20131121234116.GD6502@dastard> <20131210191803.GA31162@xxxxxxxxxxxxx> <20131211002753.GD10988@dastard>
User-agent: Mutt/1.5.20 (2009-06-14)
Hi,

On Wed, Dec 11, 2013 at 11:27:53AM +1100, Dave Chinner wrote:
> On Tue, Dec 10, 2013 at 11:18:03AM -0800, Christoph Hellwig wrote:
> > > xfs: align initial file allocations correctly.
> > > 
> > > From: Dave Chinner <dchinner@xxxxxxxxxx>
> > > 
> > > The function xfs_bmap_isaeof() is used to indicate that an
> > > allocation is occurring at or past the end of file, and as such
> > > should be aligned to the underlying storage geometry if possible.
> > > 
> > > Commit 27a3f8f ("xfs: introduce xfs_bmap_last_extent") changed the
> > > behaviour of this function for empty files - it turned off
> > > allocation alignment for this case accidentally. Hence large initial
> > > allocations from direct IO are not getting correctly aligned to the
> > > underlying geometry, and that is cause write performance to drop in
> > > alignment sensitive configurations.
> > > 
> > > Fix it by considering allocation into empty files as requiring
> > > aligned allocation again.
> > 
> > Seems like this one didn't get picked up yet?
> 
> I'm about to resend all my outstanding patches...

Sorry I didn't see that one.  If you stick the keyword 'patch' in the subject I
tend to do a bit better.

Regards,
        Ben

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