Re: [Xen-devel] [james-xen@xxxxxxxxxxxxxx: [Xen-users] Xen 4.2.0 - CPU Frequency Scaling]

[James Dingwall <james@xxxxxxxxxxxxxx>]

On 2012-10-01 17:33, Konrad Rzeszutek Wilk wrote:
> On Sun, Sep 30, 2012 at 12:13 PM, James Dingwall 
> <james@xxxxxxxxxxxxxx> wrote:
> > Hi,
> >
> > I didn't get any response on xen-users for this issue but so I'm 
> > hoping
> > -devel can help.
> Lets see if we can help you.
Thank you:)

> > I have had problems using cpu frequency scaling since the
> > xen-acpi-processor code was added to the mainline kernel source.  I
> > wasn't sure if the problem I was seeing was related to the old 
> > version
> > (4.1.2) of Xen that I was using but now I'm on 4.2.0 and it still 
> > exists
> > I thought I would check if I have a misconfiguration or if I have
> > discovered a problem.  My system is a dual AMD Opteron(tm) Processor
> > 2423 HE on kernel 3.4.8.
> >
> > The xen command line is:
> >  console=vga,com2 com2=115200,8n1 dom0_mem=max:2048M 
> > dom0_max_vcpus=2
> > dom0_vcpus_pin
> Do you nee the dom0_max_vcpus=2? If they are not present does the
> problem persist?
> > The CPU scaling information reported by xenpm is below.  The problem
> > is that only cpuid 1 can be managed separately, all the others are
> What exactly are you trying to manage? As in what are you doing?
What I was trying to achieve was 2 vcpus assigned and pinned to dom0 
with the remaining available for domUs.  I wanted to set the scaling 
governor as performance for the dom0 vcpus and ondemand for domUs.
It was an obvious test to change dom0_max_vcpus and I should have done 
it before. On removing the parameter so that all cpus were seen in dom0 
I could control the power state of them all independently.  Reinstating 
the parameter with value of n showed that cpu 1 - (n-1) could be 
controlled independently while cpus 0 and n-11 were grouped together.
> > bundled together and cannot be handled independently which used to 
> > be
> > possible with the old xen kernel.  If further information would be
> > useful please let me know.
I did have a look at xen-acpi-processor.c but it is a bit beyond me and 
perhaps not even the right place to start.
Thanks,
James

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