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Re: [Xen-devel] Paravirtualised drivers for fully virtualised domains

To: Steven Smith <sos22-xen@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Paravirtualised drivers for fully virtualised domains
From: Steve Dobbelstein <steved@xxxxxxxxxx>
Date: Wed, 9 Aug 2006 13:05:34 -0500
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Steven Smith <sos22-xen@xxxxxxxxxxxxx> wrote on 08/08/2006 04:42:15 AM:

> I just put a new version of the PV-on-HVM patches up at
> http://www.cl.cam.ac.uk/~sos22/pv-on-hvm/rev8 .  These are against
> 10968:51c227428166 and are otherwise largely unchanged from the
> previous versions.
> Steven.

I have been running some informal performance tests on the rev8 patches.
Thought I'd share my finding thus far.

I am finding that disk performance (sequential/random read/write) with the
PV xen-vbd driver in an HVM domain is pretty much equal to that of a PV
domain.  Cool.  Not surprising, but cool nonetheless.

At the moment I'm having trouble running a network test (netperf) of the PV
xen-vnif driver within our testing framework.  I'll post those findings
when I get some reliable numbers.  Testing on the rev2 version of the
patches showed pretty much equal network performance between running on a
PV driver in an HVM domain and a PV domain.

I am noticing two odd behaviors with the rev8 patches, though.

1. When I try to create a PV domain, the domain hangs on bootup displaying
repeated messages to the console:
netfront: Bad rx response id 1.
netfront: Bad rx response id 0.
netfront: Bad rx response id 1.
netfront: Bad rx response id 0.

I had to reboot from an unpatched changeset 10968 build to get the
performance numbers for a PV domain.  (Hence, I am not comparing numbers
from the exact same code base, which is one reason why the tests are

I haven't dug into the cause of this problem yet.

2. When I destroy the HVM domain it stays in the zombie state.
dib:~ # xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      768     1 r-----  2328.4
Zombie-hvm1                        1      768     1 -----d  1502.6

I'm not sure how to debug this one.  Any pointers would be helpful.

Steve D.

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