From mboxrd@z Thu Jan  1 00:00:00 1970
From: Akio Takebe <takebe_akio@jp.fujitsu.com>
Subject: Re: AW: How to use Px/Cx for power saving?
Date: Thu, 15 Jan 2009 11:04:42 +0900
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To: "Tian, Kevin" <kevin.tian@intel.com>
Cc: xen-devel <xen-devel@lists.xensource.com>, Carsten Schiers <carsten@schiers.de>, "Yu, Ke" <ke.yu@intel.com>
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Hi, Kevin

Thank you for your infomation.

Tian, Kevin wrote:
> Which version are you using? In latest Xen unstable, Xen controlled 
> cpufreq is always enabled with userspace governor as the default. 
> In such case, you could use xenpm to manually change frequency 
> (xenpm set-scaling-speed). Then "xenpm set-scaling-governor"
> can be used to choose a new governor like ondemand in the fly.
> Before 18950, cpufreq is by default disabled, and you have to add
> 'cpufreq=xen' in grub to activate xen controlled cpufreq logic. In 
> either case, CONFIG_CPU_FREQ in dom0 is not required.
> 
Oh, I used cset:18942.

> '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?

> For cpuidle, you need a similar boot option 'cpuidle' in xen cmdline
> which is off by default. We have plan to allow in-the-fly on/off from
> xenpm too.
> 
Thanks.

> One of our engineer is working on document side, including all
> relevant options and xenpm usage. We tempt to place it on Xen
> wiki first, and will let you know for comments. :-)
> 
Great! It will be very helpful.

Best Regards,

Akio Takebe