linux-kernel - Re: [PATCH] cpufreq: intel_pstate: Change the calculation of next pstate

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Date:	Thu, 01 May 2014 11:42:05 -0700
From:	Dirk Brandewie <dirk.brandewie@...il.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Stratos Karafotis <stratosk@...aphore.gr>
CC:	dirk.brandewie@...il.com, Viresh Kumar <viresh.kumar@...aro.org>,
	Dirk Brandewie <dirk.j.brandewie@...el.com>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpufreq: intel_pstate: Change the calculation of next
 pstate

On 04/29/2014 02:52 PM, Rafael J. Wysocki wrote:
> On Tuesday, April 29, 2014 07:34:46 PM Stratos Karafotis wrote:
>> On 29/04/2014 07:58 πμ, Viresh Kumar wrote:
>>> Cc'd Dirk,
>>>
>>> On 28 April 2014 03:42, Stratos Karafotis <stratosk@...aphore.gr> wrote:
>>>> Currently the driver calculates the next pstate proportional to
>>>> core_busy factor and reverse proportional to current pstate.
>>>>
>>>> Change the above method and calculate the next pstate independently
>>>> of current pstate.
>>>
>>> We must mention why the change is required.
>>>
>>
>> Hi Viresh,
>>
>> Actually, I can't say that it's required. :)
>> I just believe that calculation of next p-state should be independent
>> from current one. In my opinion we can't scale the load across different
>> p-states, because it's not always equivalent.
>>
>> For example suppose a load of 100% because of a tight for loop in the
>> current p-state. It will be also a 100% load in any other p-state.
>> It will be wrong if we scale the load in the calculation formula
>> according to the current p-state.
>>
>> I included the test results in the change log to point out an improvement
>> because of this patch.
>>
>> I will enrich more the change log as you suggested.
>
> Please do so.
>
> Also, we need to take your patch to our power lab and see if we can reproduce
> your results in other workloads.
>
> And I'm waiting for the intel_pstate developer Dirk Brandewie to comment.

Sorry I just returned from dealing with a family emergency and am digging
out of my inbox.

I will run this patch through some tests.


>
> Thanks!
>

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