RE: Unable to use multiple CPUs inside an HVM

"David Levinger" <davidl@xxxxxxxxxxxxxxxxxxx> · Tue, 22 Apr 2008 10:03:08 -0700 (PDT)

Title: Unable to use multiple CPUs inside an HVM

To add a couple more data points to this,
if I look in virt-manager it shows at 97-99% CPU usage, but if I look at the
virsh vcpuinfo domain then it shows that only one processor seems to be doing
anything at a time…

IE one will show blocked and the other
running, or one will show offline and the other running and sometimes running
and “no state”. Considering the rather poor performance I’m
assuming that I’m really only utilizing one at a time… Any
thoughts?

d

From:
fedora-xen-bounces@xxxxxxxxxx [mailto:fedora-xen-bounces@xxxxxxxxxx] On Behalf Of David Levinger

Sent: Monday, April 21, 2008 4:06
PM

To: acathrow@xxxxxxxxxx

Cc: fedora-xen@xxxxxxxxxx

Subject: RE:  Unable
to use multiple CPUs inside an HVM

You were 100% correct Andrew.  The
problem was with how I configured XP, though I seriously thought I knew
better.  I sysprepped my image and redid it with the
“multi-processor” hal and voila I now see and utilize both
cores.  The odd part, however, is that the time required to complete a
processor intensive operation seems to remain almost the same.  Instead of
using 50% of the available host CPU it now using 100% but estimates only a tem
minute savings in processing time… Whaaaaat?

I still feel like I’m missing
something rather important, but at least both CPUs are now available for use.

d

From: Andrew Cathrow
[mailto:acathrow@xxxxxxxxxx] 

Sent: Sunday, April 20, 2008 11:12
AM

To: David Levinger

Cc: fedora-xen@xxxxxxxxxx

Subject: Re:  Unable
to use multiple CPUs inside an HVM

When Windows installed
selects the HAL library appropriate the the hardware. If you install on a
single CPU system then the uniprocessor HAL is installed.

If you then add a second vcpu to the guest then the windows HAL won't see it. 

You'll need to replace Window's hal. See links below for some background. I
don't think there is a Microsoft *supported* way to do this but I've done this
a number of times without issue on XP and 2000, but I've not tried this on
2003, 2008 or Vista

http://support.microsoft.com/kb/309283/en-us

http://support.microsoft.com/default.aspx?scid=kb;EN-US;237556

On Sat, 2008-04-19 at 10:40 -0700, David Levinger wrote:

Hey Guys,

I have a
fully virtualized XP guest that is set to have 2 VCPUs and in the guest I see 2
CPUs but when it is under heavy load it only utilizes 1 of the physical cores.

Both xm and
virsh show that the guest only has 1 CPU, but my config file and the guest show
it should have 2.

What am I
missing? How can I get this guest to have access to both cores?

Thanks!

David

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