From mboxrd@z Thu Jan 1 00:00:00 1970 From: Carsten Schiers Subject: AW: How to use Px/Cx for power saving? Date: Wed, 14 Jan 2009 16:07:19 +0100 Message-ID: <7198961.251231945639314.JavaMail.root@uhura> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Akio Takebe , xen-devel , "Tian, Kevin" , Yu Ke List-Id: xen-devel@lists.xenproject.org Hi, cpufreq support can be either handled by xen or dom0-kernel. You have to specify cpufreq=xen or cpufreq=dom0-kernel as parameters when starting the hypervisor. Kevin Tian wrote yesterday: > It's intentional since Xen itself supports cpufreq now. To avoid > dependency on dom0's CONFIG_CPU_FREQ and also intrusive > checks on whether external control is enabled in every linux > cpufreq drivers, CPU_FREQ in dom0 is silented by default now. > It's not a neat approach, but makes sense since xen controlled > cpufreq is sure a better model. You can enable CPU_FREQ in > dom0 manually though, by removing below dependency. > (drivers/cpufreq/Kconfig) > config CPU_FREQ > bool "CPU Frequency scaling" > ----> depends on !PROCESSOR_EXTERNAL_CONTROL > However once that dependency is removed, there's no automatic > check to avoid confliction when dom0 and xen both want to > control freq change, and then you should keep an eye yourself. For AMD, pre-Family 10 CPUs you are supposed to use dom0-kernel, where you can encounter problems with TSC drifts. For other CPUs, I have no knowledge. Family 10 CPUs will have P-State invariant TSCs and will be should be supported by xen cpufreq. C-State handling is switched on by cpuidle as parameter. Note: xenpm is used to handle xen cpufreq support. In dom0-kernel, you use the dom0 tools. BR, Carsten. ----- Originalnachricht ----- Von: Akio Takebe Gesendet: Mit, 14.1.2009 15:32 An: xen-devel ; "Tian, Kevin" ; Yu Ke Betreff: [Xen-devel] How to use Px/Cx for power saving? Hi, If we want to use ACPI power saving(Cx/Px), how do we use them? I tried to turn CONFIG_xxxx of cpufreq on with linux-2.6.18-xen.hg, but I couldn't turn them on. Also xenpm said the following error. # xenpm get-cpuidle-states Xen cpuidle is not enabled! # xenpm get-cpufreq-states Xen cpufreq is not enabled! What should I do? If there are some good documents, please tell me. Best Regards, Akio Takebe _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel