linux-kernel - Re: [intel-pstate driver regression] processor frequency very high even if in idle

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Date:	Wed, 30 Mar 2016 12:17:32 +0200
From:	Jörg Otte <jrg.otte@...il.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [intel-pstate driver regression] processor frequency very high
 even if in idle

2016-03-29 23:34 GMT+02:00 Rafael J. Wysocki <rjw@...ysocki.net>:
> On Tuesday, March 29, 2016 07:32:27 PM Jörg Otte wrote:
>> 2016-03-29 19:24 GMT+02:00 Jörg Otte <jrg.otte@...il.com>:
>> > in v4.5 and earlier intel-pstate downscaled idle processors (load
>> > 0.1-0.2%) to minumum frequency, in my case 800MHz.
>> >
>> > Now in v4.6-rc1 the characteristic has dramatically changed. If in
>> > idle the processor frequency is more or less a few MHz around 2500Mhz.
>> > This is the maximum non turbo frequency.
>> >
>> > No difference between powersafe or performance governor.
>> >
>> > I currently use acpi_cpufreq which works as usual.
>> >
>> > Processor:
>> > Intel(R) Core(TM) i5-4200M CPU @ 2.50GHz (family: 0x6, model: 0x3c,
>> > stepping: 0x3)
>> >
>> > Last known good kernel is: 4.5.0-01127-g9256d5a
>> > First known bad kernel is: 4.5.0-02535-g09fd671
>> >
>> > There is
>> > commit 277edba Merge tag 'pm+acpi-4.6-rc1-1' of
>> > git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
>> > in between, which brought a few changes in intel_pstate.
>
> Can you please check commit a4675fbc4a7a (cpufreq: intel_pstate: Replace timers
> with utilization update callbacks)?
>
Yes , this solved the problem for me.
I had to resolve some conflicts myself when reverting that
commit. Hard work :).

Here is a 10-seconds trace of the used frequencies when
in "desktop-idle":

driver          cpu0 cpu1 cpu2 cpu3
-------------------------------------
intel_pstate (  800  928  941 1200) MHz   load:( 0.2)%
intel_pstate (  800  928 1181 1800) MHz   load:( 0.0)%
intel_pstate ( 1675 1576 1347  800) MHz   load:( 0.0)%
intel_pstate ( 1198 1576  842  800) MHz   load:( 0.5)%
intel_pstate (  800 1181 1113 1600) MHz   load:( 0.0)%
intel_pstate (  808 1181  805  800) MHz   load:( 0.5)%
intel_pstate (  844 1191  900 1082) MHz   load:( 0.3)%
intel_pstate (  816 1191  800  800) MHz   load:( 0.0)%
intel_pstate (  800  905  892 1082) MHz   load:( 0.2)%
intel_pstate (  945  905 1340  800) MHz   load:( 0.3)%


Thanks, Jörg