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

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Date:	Wed, 30 Mar 2016 17:29:18 +0200
From:	Jörg Otte <jrg.otte@...il.com>
To:	"Rafael J. Wysocki" <rafael@...nel.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	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

2016-03-30 13:05 GMT+02:00 Rafael J. Wysocki <rafael@...nel.org>:
> On Wed, Mar 30, 2016 at 12:17 PM, Jörg Otte <jrg.otte@...il.com> wrote:
>> 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 :).
>
> Thanks for doing this.  Can you please post the revert patch you have used?
>

The patch is on top of 4.5.0-02535-g09fd671.
I'm not sure what gmail is doing with spaces and tabs,
so I attach the revert patch.


>> 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)%
>
> Please also run turbostat with and without your revert patch applied.
>

turbostat without revert
Kernel: 4.5.0-02535-g09fd671
-----------------------------
CPUID(7): No-SGX
     CPU Avg_MHz   Busy% Bzy_MHz TSC_MHz
       -      13    0.53    2514    2495
       0      14    0.55    2518    2495
       1       8    0.33    2527    2495
       2      15    0.60    2506    2495
       3      16    0.62    2509    2495

turbostat after revert of commit a4675fbc4a7a
kernel: 4.5.0-reva4675fbc4a7a-02536-g77225b1
------------------------------
CPUID(7): No-SGX
     CPU Avg_MHz   Busy% Bzy_MHz TSC_MHz
       -       4    0.35    1142    2494
       0       1    0.11    1016    2494
       1       2    0.17     961    2494
       2      10    0.82    1215    2494
       3       3    0.29    1086    2494
     CPU Avg_MHz   Busy% Bzy_MHz TSC_MHz
       -       4    0.46     885    2494
       0       1    0.12     889    2494
       1       1    0.16     885    2494
       2      10    1.15     883    2494
       3       4    0.40     891    2494

View attachment "intel_pstate_revert.patch" of type "text/x-patch" (7194 bytes)