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RE: AW: [Xen-devel] How to use Px/Cx for power saving?

To: 'Akio Takebe' <takebe_akio@xxxxxxxxxxxxxx>
Subject: RE: AW: [Xen-devel] How to use Px/Cx for power saving?
From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Date: Thu, 15 Jan 2009 10:40:02 +0800
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Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Carsten Schiers <carsten@xxxxxxxxxx>, "Yu, Ke" <ke.yu@xxxxxxxxx>
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Thread-topic: AW: [Xen-devel] How to use Px/Cx for power saving?
>From: Akio Takebe [mailto:takebe_akio@xxxxxxxxxxxxxx] 
>Sent: Thursday, January 15, 2009 10:05 AM
>
>> 'cpufreq=dom0-kernel' can be always used to allow dom0 control 
>> freq directly. In such case, Xen itself exits the game, and then you
>> have to follow below trick to enable CONFIG_CPU_FREQ in dom0
>> kernel.
>>
>If dom0_max_vcpus < total_phys_cpus, dom0 control only his cpus.
>So other cpus don't enter px/cx state, right?
>And you recommend cpufreq=xen?

Yes, I'm recommending cpufreq=xen which is more efficient and
clearer method. For cpufreq=dom0-kernel, such implication exists
to have dom0 vcpus pinned to corresponding physical cpus with
same number. Unless your platform couldn't work with acpi-cpufreq
driver on native linux, you should always spin on cpufreq=xen. 

Thanks,
Kevin
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