Re: SpeedStep in DomUs?

[Jean-Yves Migeon <jeanyves.migeon%free.fr@localhost>]

On 11.07.2010 13:24, Stefan Groà wrote:
> Ok, thanks for the Tip. That didn't work that easy, and i think i found
> the reason here: http://wiki.xensource.com/xenwiki/xenpm They say:
> "Domain0 based cpufreq has one limitations, i.e. domain0 VCPU number
> must be the same as the number of physical CPUs, and the domain0 VCPU
> must be pinned to physical CPU"
> I didn't try to set that, because the same page talks about
> frequency-control with xen, and i thought that should be more robust, so
> i tryed to set up that first.
> But that doesn't seem to work for me too, although i enabled support for
> deep c-states in the bios, and also support for est (Enhanced Speed
> Step). I attached some Info: output of "xm dmesg" and of "xenpm
> get-cpufreq-states". Can anyone help me on that?

Power management by Xen requires to parse ACPI in dom0, and pass that
information to hypervisor. Unfortunately, AFAICT, we do not have proper
ACPI support within dom0.

> And the second question is: If i can't get the xen-throttling, how do i
> setup my dom0 to meet the requirenments of the limitation? (that's
> really a newbie-question, what files to edit how? Till now i don't have
> a setup-file for dom0 - is it boot-options?)

In a multi CPU setup, you would have to pin the VCPU to its associated
physical CPU. Then use machdep.powernow.frequency.target or
machdep.est.frequency.target, through sysctl:

# sysctl -d machdep.est.frequency.available # to get all available freq
# sysctl -d machdep.est.frequency.target=<frequency> # to set the freq

To test rapidly if it worked correctly, you can try "openssl speed".

In an automated fashion, there is sysutils/estd, although I never tested
it with Xen.

Cheers,

-- 
Jean-Yves Migeon
jeanyves.migeon%free.fr@localhost