Re: [james-xen@dingwall.me.uk: [Xen-users] Xen 4.2.0 - CPU Frequency Scaling]

[James Dingwall <james@dingwall.me.uk>]

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