[v3.10-rc] intel_pstate question

[v3.10-rc] intel_pstate question

[Jörg Otte]

Hi,

the sysfs-interface of intel_pstate is different to that of the acpi driver:
- intel_pstate shows current cpu-frequency in "cpuinfo_cur_freq" whereas
  the acpi counterpart uses "scaling_cur_freq".
- moreover cpuinfo_cur_freq is readable by root only, whereas
  scaling_cur_freq is world readable.

  A monitoring tool must take care of theese differences.
  Is this intentional?

Thanks, Jörg

Please CC me in answeres, I'm not subscribed.

Re: [v3.10-rc] intel_pstate question

[Dirk Brandewie]

Hi Jörg,

On 05/28/2013 08:02 AM, Jörg Otte wrote:
> Hi,
>
> the sysfs-interface of intel_pstate is different to that of the acpi driver:
> - intel_pstate shows current cpu-frequency in "cpuinfo_cur_freq" whereas
>    the acpi counterpart uses "scaling_cur_freq".
> - moreover cpuinfo_cur_freq is readable by root only, whereas
>    scaling_cur_freq is world readable.
>
>    A monitoring tool must take care of theese differences.
>    Is this intentional?
>

This is a side effect of the interface that intel_pstate presents to the cpufreq
core.

cpuinfo_cur_freq reports the value returned from the scaling driver.

scaling_cur_freq reports the current frequency in the governors policy structure.

intel_pstate has an internal governor so the core does not try to interpret
the policy structure.

I don't know why cpuinfo_cur_info is read-only root maybe Rafael knows the history.


> Thanks, Jörg
>
> Please CC me in answeres, I'm not subscribed.
>

Re: [v3.10-rc] intel_pstate question

[Jörg Otte]

2013/5/28 Dirk Brandewie <dirk.brandewie@gmail.com>:
> Hi Jörg,
>
>
> On 05/28/2013 08:02 AM, Jörg Otte wrote:
>>
>> Hi,
>>
>> the sysfs-interface of intel_pstate is different to that of the acpi
>> driver:
>> - intel_pstate shows current cpu-frequency in "cpuinfo_cur_freq" whereas
>>    the acpi counterpart uses "scaling_cur_freq".
>> - moreover cpuinfo_cur_freq is readable by root only, whereas
>>    scaling_cur_freq is world readable.
>>
>>    A monitoring tool must take care of theese differences.
>>    Is this intentional?
>>
>
> This is a side effect of the interface that intel_pstate presents to the
> cpufreq
> core.
>
> cpuinfo_cur_freq reports the value returned from the scaling driver.
>
> scaling_cur_freq reports the current frequency in the governors policy
> structure.
>
> intel_pstate has an internal governor so the core does not try to interpret
> the policy structure.
>
> I don't know why cpuinfo_cur_info is read-only root maybe Rafael knows the
> history.
>
Thank you Dirk, for the information!

Just another question: Now that processor 3a is supported, I am giving
pstate driver a try on my notebook. This is the first time I see frequencies
between above 2.5 and up to 3.1 GHz. With cpufreq driver I never saw that
frequencies.
So I think pstate driver uses turbo mode if appropriate (in contrast to
cpufreq). is this correct?

Thanks, Jörg