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

  • To: "Yu, Ke" <ke.yu@xxxxxxxxx>, Niraj Tolia <ntolia@xxxxxxxxx>, Xen Developers <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
  • Date: Fri, 24 Oct 2008 10:43:20 +0800
  • Accept-language: en-US
  • Acceptlanguage: en-US
  • Cc:
  • Delivery-date: Fri, 24 Oct 2008 06:03:32 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Ack0G+ElTDzhsimQSweeKVbX7d4NiwAARfkgAFlMETA=
  • Thread-topic: [Xen-devel] Problems with enabling hypervisor C and P-state control

Niraj, any update on Ke's suggestion?


>From: Yu, Ke
>Sent: Wednesday, October 22, 2008 4:17 PM
>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
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-devel
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