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Re: Filesystem writes on RAID5 too slow

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: Filesystem writes on RAID5 too slow
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 11 Dec 2013 11:27:53 +1100
Cc: Martin Boutin <martboutin@xxxxxxxxx>, "Kernel.org-Linux-RAID" <linux-raid@xxxxxxxxxxxxxxx>, Eric Sandeen <sandeen@xxxxxxxxxx>, "Kernel.org-Linux-EXT4" <linux-ext4@xxxxxxxxxxxxxxx>, xfs-oss <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20131210191803.GA31162@xxxxxxxxxxxxx>
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>
User-agent: Mutt/1.5.21 (2010-09-15)
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...

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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