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RE: [Xen-users] Setting CPU (core) frequency from dom0
Your description is basically correct. Do you want to
control cpu frequency from dom0 user level, or just try cpufreq governor in
dom0? For the former, we're currently adding more flexibility to xen
cpufreq (such as user space governor) and control options to xenpm (such as
manually changing freq), which is expected to reach xen upstream soon. For the
latter, it's suboptimal with limitations which is why xen cpufreq is develeoped.
You may manually disable PROCESSOR_EXTERNAL_CONTROL in drivers/acpi/Kconfig
to rebuild dom0 kernel for mode A.
Thanks,
Kevin
Hello everyone,
I am running some experiments that require
changing the frequency of a CPU in a SunFire machine (32-core quad socket AMD
Barcelona).
For what I have found (bits and pieces but not a
comprehensive description), there are two meachisms for controlling core (most
probably socket) frequency in Xen:
A- The older (xen-3.2.1) mechnism
through dom0 (option cpufreq=dom0-kernel), which for what I gather uses a
module in dom0 (cpufreqd?) that allows one to set cpu frequency.
B- The
newer (xen-3.3), which has moved the governor to the hypervisor (option
cpufreq=xen), which other than a utility to read processor P and C states
(xenpm) does not (yet) allow user (dom0) control of CPU frequency.
My
first question is whetherot what I have written above is accurate. My second
question is where can I find detailed information on how to set up my system
to make use of A above and be able to set cpu frequency "manually" from Dom0
(assuming that is still possible in Xen 3.3).
I am running the latest
testing version of Xen 3.3 (about a week old).
Any information would be
greatly appreciated.
Thank
you,
Alberto
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