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SubjectRe: Poor interactive performance with I/O loads with fsync()ing
On Sun, Apr 11, 2010 at 08:16:09PM +0200, Thomas Gleixner wrote:
> On Sun, 11 Apr 2010, Avi Kivity wrote:
> > On 04/09/2010 05:56 PM, Ben Gamari wrote:
> > > On Mon, 29 Mar 2010 00:08:58 +0200, Andi Kleen<> wrote:
> > > > Ben Gamari<> writes:
> > > > ext4/XFS/JFS/btrfs should be better in this regard
> > > >
> > > I am using btrfs, so yes, I was expecting things to be better.
> > > Unfortunately,
> > > the improvement seems to be non-existent under high IO/fsync load.
> >
> > btrfs is known to perform poorly under fsync.
> XFS does not do much better. Just moved my VM images back to ext for
> that reason.

Numbers? Workload description? Mount options? I hate it when all I
hear is "XFS sucked, so I went back to extN" reports without any
more details - it's hard to improve anything without any details
of the problems.

Also worth remembering is that XFS defaults to slow-but-safe
options, but ext3 defaults to fast-and-I-don't-give-a-damn-about-
data-safety, so there's a world of difference between the
filesystem defaults....

And FWIW, I run all my VMs on XFS using default mkfs and mount options,
and I can't say that I've noticed any performance problems at all
despite hammering the IO subsystems all the time. The only thing
I've ever done is occasionally run xfs_fsr across permanent qcow2
VM images to defrag them as the grow slowly over time...


Dave Chinner

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