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

On 2012-10-01 17:33, Konrad Rzeszutek Wilk wrote:
On Sun, Sep 30, 2012 at 12:13 PM, James Dingwall <james@xxxxxxxxxxxxxx> wrote:

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

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.


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