linux-kernel - Re: [v3.10-rc] intel

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Date:	Wed, 29 May 2013 11:25:10 +0200
From:	Jörg Otte <jrg.otte@...il.com>
To:	Dirk Brandewie <dirk.brandewie@...il.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	rafael.j.wysocki@...el.com
Subject: Re: [v3.10-rc] intel_pstate question

2013/5/28 Dirk Brandewie <dirk.brandewie@...il.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
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