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RE: [Xen-users] Xen-4.0 and GPLPV Driver - Slow Write perf

To: "Stephane ROZET" <stban1983@xxxxxxxx>, <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-users] Xen-4.0 and GPLPV Driver - Slow Write perf
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Sat, 19 Feb 2011 00:44:04 +1100
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Thread-topic: [Xen-users] Xen-4.0 and GPLPV Driver - Slow Write perf
> Hi,
> I'm using 3 servers with XEN and 2 San. Twice have Xen3.2 and Windows
VM are
> OK with GPLPV drivers. One server have Xen-4.0 and I have a problem
> Windows VM:
> Windows VM have very poor write disk performance (3 MB/s) with GPLPV
driver (I
> tried 0.9 and 0.11 versions). Read perf are ok (~200MB/s).
> Without GPLPV driver, it's more credible, but I'm not using the best
of my VM
> without GPLPV...
> Xen host is Debian 6, with kernel 2.6.32-5. I'm using AOE, with
AOEtools in
> version 32 and aoe driver in version 76.
> What can I do for that ?

How are you testing performance? If the performance testing tool issues
overlapping writes or unaligned writes then performance will suffer
badly. If you are using the _debug version of the drivers then the
logging done for overlapped writes might kill performance too.

If you are using the _debug version of GPLPV, please send me a copy of
your /var/log/xen/qemu-dm-<domU name>.log file after doing performance

Do you have a local disk you can test with to rule out any strange
interaction with AoE?

What is cpu load in Dom0 and DomU when writing?

Can you test a Linux DomU and make sure the problem is definitely
related to GPLPV?

Also what is network performance like for your Windows DomU?



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