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[Xen-users] Setting CPU (core) frequency from dom0

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Setting CPU (core) frequency from dom0
From: Alberto Munoz <amunoz0221@xxxxxxxxxxx>
Date: Wed, 19 Nov 2008 10:50:12 -0800
Delivery-date: Wed, 19 Nov 2008 10:50:55 -0800
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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,

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