Bug#619573: xen-linux-system-2.6.32-5-xen-amd64: cpufreq scaling in Dom0 does not work
> > I've also tried cpufreq=xen (where the hypervisor is supposed to do
> > cpufreq scaling), but that didn't work either as the xenpm command
> > didn't appear to be able to do anything.
>
> Why do you think that?
Nevermind, I just gave it another try (on the Intel box) and it does work, xenpm get-cpufreq-para actually produces the expected output now and the CPU appears to scale down.
> > cpufreq=dom0-kernel
>
> Oh, I wasn't aware that was an option. But as the note says, it only
> works if you set a 1-to-1 mapping between physical CPUs and vCPUs in
> dom0.
The 1-to-1 mapping is set using the dom0_vcpu_pin option, which is implied by the cpufreq=dom0-kernel option (taken from xen-4.0.1/xen/common/domain.c:setup_cpufreq_option):
if ( !strcmp(str, "dom0-kernel") )
{
xen_processor_pmbits &= ~XEN_PROCESSOR_PM_PX;
cpufreq_controller = FREQCTL_dom0_kernel;
opt_dom0_vcpus_pin = 1;
return;
}
The cpufreq=dom0-kernel option is what I am actually interested in because cpufreq=xen is not supported on older AMD CPUs. However, I have not been able to actually get it to work yet.
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