Unable to use multiple CPUs inside an HVM

[David Levinger]

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

[Alroger L. Gomes F.]

I have noticed that too.

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
>  
-- 
Alroger Luiz Gomes Filho
SDEV - Smart Developments
http://www.sdev.com
http://cafe-ti.blog.br

So little time, so many systems . . .

[Andrew Cathrow]

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
>  
>  
>  --
>  Fedora-xen mailing list
>  Fedora-xen(a)redhat.com
>  https://www.redhat.com/mailman/listinfo/fedora-xen

[David Levinger]

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:[e-mail]] 
Sent: Sunday, April 20, 2008 11:12 AM
To: David Levinger
Cc: fedora-xen(a)redhat.com
Subject: Re: [Fedora-xen] 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

 
--
Fedora-xen mailing list
Fedora-xen(a)redhat.com
https://www.redhat.com/mailman/listinfo/fedora-xen

[David Levinger]

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(a)redhat.com [mailto:[e-mail]]
On Behalf Of David Levinger
Sent: Monday, April 21, 2008 4:06 PM
To: acathrow(a)redhat.com
Cc: fedora-xen(a)redhat.com
Subject: RE: [Fedora-xen] 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:[e-mail]] 
Sent: Sunday, April 20, 2008 11:12 AM
To: David Levinger
Cc: fedora-xen(a)redhat.com
Subject: Re: [Fedora-xen] 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

 
--
Fedora-xen mailing list
Fedora-xen(a)redhat.com
https://www.redhat.com/mailman/listinfo/fedora-xen

[Richard W.M. Jones]

On Tue, Apr 22, 2008 at 10:03:08AM -0700, David Levinger wrote:
>  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? 
Use virt-top.  It's able to tell you which physical CPUs are being
utilized.

You can also try using virsh vcpupin to pin virtual CPUs to physical
CPUs in case there's some contention (but use virt-top first to find
out).

Rich.

-- 
Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://et.redhat.com/~rjones/virt-top