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RE: [Xen-devel] Problems with enabling hypervisor C and P-state control

  • To: Niraj Tolia <ntolia@xxxxxxxxx>, Xen Developers <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Yu, Ke" <ke.yu@xxxxxxxxx>
  • Date: Wed, 22 Oct 2008 16:16:55 +0800
  • Accept-language: en-US
  • Acceptlanguage: en-US
  • Cc:
  • Delivery-date: Wed, 22 Oct 2008 01:17:25 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Ack0G+ElTDzhsimQSweeKVbX7d4NiwAARfkg
  • Thread-topic: [Xen-devel] Problems with enabling hypervisor C and P-state control

You can simply add xen grub option "cpufreq=xen cpuidle" to enable C and P 
state, like the following:
kernel /boot/xen.gz dom0_mem=256M console=com1 cpufreq=xen cpuidle.

For the xen-unstable and linux-2.6.18-xen.hg compilation, you don't need to 
change anything, C and P support is compiled by default, and there is no 
conflict between them

If you still can not see P state info by xenpm, could you please check your 
BIOS to see if the Px is enabled? Or can you add loglvl=info in xen command 
line and send out the xen boot log, so that we can further analysis how Px BIOS 
info is parsed by Xen?

Best Regards

Niraj Tolia wrote:
> Hi,
> Is there any documentation on enabling hypervisor support for both C
> and P-state control?
> On xen-unstable and linux-2.6.18-xen.hg, if I enable cpuidle=1 on the
> xen command line and then run xenpm, I will get output for C-states
> (shown below) but it complains that "Xen cpufreq is not enabled!"
> cpu id               : 0
> total C-states       : 2
> idle time(ms)        : 73264
> C0                   : transition [00000000000000000000]
>                        residency  [00000000000000000000 ms]
> C1                   : transition [00000000000000025505]
>                        residency  [00000000000000000000 ms]
> (repeats for all cores)
> However, CPU_FREQ depends on PROCESSOR_EXTERNAL_CONTROL being set to
> 'n'. There doesn't seem to be a way to enable/disable
> CONFIG_PROCESSOR_EXTERNAL_CONTROL from menuconfig. I therefore
> manually twiddled that bits in .config and enabled CPU_FREQ and
> CPU_FREQ_TABLE (plus the performance governor). If I don't specify the
> cpufreq option on the dom0 kernel command line, xenpm doesn't give me
> C-state information anymore (output below) and will repeat the same
> warning about cpufreq not being enabled.
> cpu id               : 0
> total C-states       : 0
> idle time(ms)        : 0
> (repeats for all cores)
> If I then add cpufreq=xen to the kernel command line, xenpm's output
> does not change. Any ideas on what I might be doing wrong? This is on
> a quad-core Xeon (E7330).
> Cheers,
> Niraj
> _______________________________________________
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> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel

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