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Re: [Xen-users] Xen hard-disk performance regression?

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Xen hard-disk performance regression?
From: Fabiano Francesconi <fabiano.francesconi@xxxxxxxxx>
Date: Sun, 11 Apr 2010 21:44:57 +0200
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On Sun, Apr 11, 2010 at 02:55:24PM +0100, Andrew Lyon wrote:
> On Sun, Apr 11, 2010 at 11:30 AM, Fabiano Francesconi
> <fabiano.francesconi@xxxxxxxxx> wrote:
> > Hello there,
> > I'm noticing a performance regression for what's matter the hard-disk I
> > pass to the domU (aquaria).
> Have you checked the performance of the disk in dom0?
> >
> > The slow-down is very noticeable even when moving small videos file
> > (~350mb).
> >
> > In the configuration file of the domU, I pass the whole disk
> > ('phy:/dev/sdb,xvdb,w') to the guest OS.
> >
> > The distribution under both systems is Gentoo/Linux, x86 arch.
> >
> > The hypervisor is always the same, in both scenarios (Linux xevelon
> > 2.6.32-xen-r1 #1 SMP Sat Apr 10 13:37:02 CEST 2010 i686 Intel(R)
> > Atom(TM) CPU 330 @ 1.60GHz GenuineIntel GNU/Linux).
> >
> > The machine is an Atom, so it's not capable of any VT technology but so
> > far it's a great machine and XEN is working just fine on it.
> >
> > I attach you few logs I've gathered.
> >
> > Thank you
> >
> > --
> > Fabiano Francesconi [GPG key: 0x81E53461]
> >
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-users
> >

Ok, confirmed. The problem is only visible when copying files so it's
not something related to the hard-disk itself.

I sincerely don't know how to dig into this but I have made some tests

I've tried copying a single avi file (350mb) from one partition to
another one. Both partition are on the same device (WDC WD10EADS-00M2B0)
and both formatted in XFS filesystem.

Running 2.6.32-xen-r1 I have the following output:

real    1m35.001s
user    0m0.016s
sys     0m0.722s

Running 2.6.29-xen-r4 I have, instead, the following output:

real    0m20.689s
user    0m0.018s
sys     0m2.047s

How can I see such a difference? Is there some known regression for XFS
filesystem? I might try to run a vanilla kernel instead of a xen-patched

Any suggestion will be very much appreciated.

Fabiano Francesconi [GPG key: 0x81E53461]

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