linux-ext4 - Re: Filesystem writes on RAID5 too slow

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Message-ID: <20131211002753.GD10988@dastard>
Date:	Wed, 11 Dec 2013 11:27:53 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Martin Boutin <martboutin@...il.com>,
	"Kernel.org-Linux-RAID" <linux-raid@...r.kernel.org>,
	Eric Sandeen <sandeen@...hat.com>,
	"Kernel.org-Linux-EXT4" <linux-ext4@...r.kernel.org>,
	xfs-oss <xfs@....sgi.com>
Subject: Re: Filesystem writes on RAID5 too slow

On Tue, Dec 10, 2013 at 11:18:03AM -0800, Christoph Hellwig wrote:
> > xfs: align initial file allocations correctly.
> > 
> > From: Dave Chinner <dchinner@...hat.com>
> > 
> > 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@...morbit.com
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