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

["Niraj Tolia" <ntolia@xxxxxxxxx>]

On Wed, Oct 29, 2008 at 2:02 AM, Liu, Jinsong <jinsong.liu@xxxxxxxxx> wrote:
> Niraj,
>
> Any update about xen cpufreq at your platform? Does the patch work?
>

Hi Jinsong,

Yup, it does seem to work. I will let you know if I run into any other issues.

Cheers,
Niraj

> Thanks,
> Jinsong
>
> Niraj Tolia wrote:
>> On Mon, Oct 27, 2008 at 7:19 PM, Niraj Tolia <ntolia@xxxxxxxxx> wrote:
>>> On Mon, Oct 27, 2008 at 6:04 PM, Tian, Kevin <kevin.tian@xxxxxxxxx>
>>> wrote:
>>>>> From: Niraj Tolia [mailto:ntolia@xxxxxxxxx]
>>>>> Sent: Tuesday, October 28, 2008 2:01 AM
>>>>>
>>>>> On Thu, Oct 23, 2008 at 10:59 PM, Yu, Ke <ke.yu@xxxxxxxxx> wrote:
>>>>>> After discussing with Jinsong, we got the root cause. You
>>>>> are right, this is xen pm statistics logic issue. when the
>>>>> coordination type is SW_ANY, we only record the first CPU
>>>>> cpufreq change, the other 3 cores within the same dependency
>>>>> domain is ignored, so you only see one core changes every
>>>>> dependency domain.
>>>>>>
>>>>>> The attached patch fix  this issue. could you please have a
>>>>> try? If it works in your platform, we will send out for
>>>>> applying in upstream.
>>>>>
>>>>> I just applied the patch and while xenpm might be doing the right
>>>>> thing, I am not completely sure. For example, if I launch a single
>>>>> VCPU VM, pin it to a core, and launch a CPU intensive task on it,
>>>>> ALL four cores on the socket are reported to switch into P0.
>>>>> However, from what I understand about this processor (Xeon E7330),
>>>>> only two of them should. Like vanilla Linux, the other two should
>>>>> be able to operate at independent voltage/frequency settings. Once
>>>>> again, I am not sure if this is xenpm's fault or if the underlying
>>>>> frequency control code isn't able to determine what  CPUs need to
>>>>> switch frequency at the same time.
>>>>>
>>>>
>>>> Do you change any BIOS setting when comparing native Linux and
>>>> Xen? From the xen dmesg you posted last time:
>>>
>>>
>>> No, I did not change anything in the BIOS. However, when I run
>>> vanilla Linux w/ cpufreqd, cpufreq-info will only list two cores
>>> being tied together. This is with the 2.6.24-21 kernel provided with
>>> Ubuntu
>>> 8.04.1.
>>>
>>> # cpufreq-info
>>> cpufrequtils 002: cpufreq-info (C) Dominik Brodowski 2004-2006
>>> Report errors and bugs to linux@xxxxxxxx, please.
>>> analyzing CPU 0:
>>>  driver: acpi-cpufreq
>>>  CPUs which need to switch frequency at the same time: 0 4
>>>  hardware limits: 1.60 GHz - 2.40 GHz
>>>  available frequency steps: 2.40 GHz, 2.13 GHz, 1.87 GHz, 1.60 GHz
>>>  available cpufreq governors: powersave, conservative, ondemand,
>>>  userspace, performance current policy: frequency should be within
>>>                  1.60 GHz and 1.60 GHz. The governor "powersave" may
>>>                  decide which speed to use within this range.
>>>  current CPU frequency is 1.60 GHz.
>>>
>>> ...
>>>
>>
>> I just noticed that cpufreq-info only lists 8 CPUs. Turns out that
>> Ubuntu's kernels come with NR_CPUS = 8. So, you might be right. I will
>> try and recompile a vanilla kernel tomorrow to see what happens.
>>
>> Cheers,
>> Niraj
>>
>>> Cheers,
>>> NIraj
>>>
>>>> ...
>>>> (XEN)   _PSD: num_entries=5 rev=0 domain=1 coord_type=253
>>>> num_processors=4 ... (XEN)   _PSD: num_entries=5 rev=0 domain=2
>>>> coord_type=253 num_processors=4 ... (XEN)   _PSD: num_entries=5
>>>> rev=0 domain=3 coord_type=253 num_processors=4 ... You can see that
>>>> BIOS reports 4 processors in a dependent domain
>>>> with a SW_ANY coordination type. It means that any cpu within
>>>> given dependent domain changes freq, all the rest 3 cpus change too.
>>>>
>>>> Thanks,
>>>> Kevin
>>>>
>>>>
>>>
>>>
>>>
>>> --
>>> Niraj Tolia, Researcher, HP Labs
>>> http://www.hpl.hp.com/personal/Niraj_Tolia/
>
>



-- 
Niraj Tolia, Researcher, HP Labs
http://www.hpl.hp.com/personal/Niraj_Tolia/

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