[Bug 58801] New: intel_pstate/powersave - cpu frequency remains at high level if if system is idle

[Bug 58801] New: intel_pstate/powersave - cpu frequency remains at high level if if system is idle

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=58801

           Summary: intel_pstate/powersave - cpu frequency remains at high
                    level if if system is idle
           Product: Power Management
           Version: 2.5
    Kernel Version: 3.9.3 and 3.9.4
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: cpufreq
        AssignedTo: cpufreq@vger.kernel.org
        ReportedBy: c.h.l@web.de
        Regression: Yes


I have a Lenovo T520 with a Intel(R) Core(TM) i5-2450M CPU and a Sandy Bridge
chipset.

Starting from kernel version 3.9.1 I switched the CPU frequency scaling driver
from acpi-cpufreq to intel_pstate. In combination with the powersave governor
it worked like a charm. I had higher frequencies due to the turbo boost (3.1
GHz instead of 2.5 GHz) and when the system was idle the frequency was switched
to the lowest values (around 800 MHz).

With the kernel versions 3.9.3 and now even 3.9.4 the frequency remains at a
quite high frequency (3.0 or 2.9 GHz) even if the the system is completely
idle.

As I have not changed the kernel-config when I updated to the versions 3.9.3
and 3.9.4 I assume some bug was introduced in the kernel as of 3.9.3.

Please let me know if you need any further info.

Christoph

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[Bug 58801] intel_pstate/powersave - cpu frequency remains at high level if if system is idle

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=58801





--- Comment #1 from Rafael J. Wysocki <rjw@sisk.pl>  2013-05-25 09:07:20 ---
On Saturday, May 25, 2013 07:24:54 AM bugzilla-daemon@bugzilla.kernel.org
wrote:
[...]
> 
> With the kernel versions 3.9.3 and now even 3.9.4 the frequency remains at a
> quite high frequency (3.0 or 2.9 GHz) even if the the system is completely
> idle.
> 
> As I have not changed the kernel-config when I updated to the versions 3.9.3
> and 3.9.4 I assume some bug was introduced in the kernel as of 3.9.3.
> 
> Please let me know if you need any further info.

Can you possibly identify the change between 3.9.1 and 3.9.3 that introduced
the problem for you?

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Re: [Bug 58801] New: intel_pstate/powersave - cpu frequency remains at high level if if system is idle

[Rafael J. Wysocki]

On Saturday, May 25, 2013 07:24:54 AM bugzilla-daemon@bugzilla.kernel.org wrote:
[...]
> 
> With the kernel versions 3.9.3 and now even 3.9.4 the frequency remains at a
> quite high frequency (3.0 or 2.9 GHz) even if the the system is completely
> idle.
> 
> As I have not changed the kernel-config when I updated to the versions 3.9.3
> and 3.9.4 I assume some bug was introduced in the kernel as of 3.9.3.
> 
> Please let me know if you need any further info.

Can you possibly identify the change between 3.9.1 and 3.9.3 that introduced
the problem for you?

[Bug 58801] intel_pstate/powersave - cpu frequency remains at high level if if system is idle

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=58801





--- Comment #2 from Christoph Loehr <c.h.l@web.de>  2013-05-25 09:39:02 ---
At first I have to add that also kernel 3.9.2 worked. According to the
changelog of kernel 3.9.3 between 3.9.2 and 3.9.3 three commitments concerning
intel_pstate (b540137a810d0267051c538e68d4348e43a1edf3,
2aa491f8bdcac932006548b1a2b655b29c942e08 and
1abc4b20b85b42e8573957e54b193385cf48b0d6) have been added to the kernel. I
guess that one of them might be the culprit. 

As I am rather a user it's only possible for me to describe the symptoms. 

With kernel 3.9.2, when the system is idle according to cpufreg-info the
frequency of all cpu's is between 775 and 800 MHz, which is the minimum. With
kernel 3.9.3 and 3.9.4 it never goes below 2.85 GHz. In both cases intel_pstate
is the driver and powersave the governor.

Christoph

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[Bug 58801] intel_pstate/powersave - cpu frequency remains at high level if if system is idle

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=58801





--- Comment #3 from Christoph Loehr <c.h.l@web.de>  2013-05-25 14:57:21 ---
In the meantime I have made a git bisect between kernel 3.9.2 and 3.9.3 with
the following result:

5aacc8bcf0b23e20cbb205ac6fdc3ce797e1cae2 is the first bad commit
commit 5aacc8bcf0b23e20cbb205ac6fdc3ce797e1cae2
Author: Dirk Brandewie <dirk.j.brandewie@intel.com>
Date:   Tue May 7 08:20:25 2013 -0700

cpufreq / intel_pstate: remove idle time and duration from sample and
calculations

commit 1abc4b20b85b42e8573957e54b193385cf48b0d6 upstream.


In order to confirm this is the relevant commit I have compiled a 3.9.3 kernel
where I had reverted the changes provided by this commit. With this kernel
booted the frequency switching works again. 

I hope that helps.

Christoph

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[Bug 58801] intel_pstate/powersave - cpu frequency remains at high level if if system is idle

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=58801


Dirk Brandewie <dirk.brandewie@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dirk.brandewie@gmail.com




--- Comment #4 from Dirk Brandewie <dirk.brandewie@gmail.com>  2013-05-25 16:30:58 ---
Can you attach your kernel config file please.

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[Bug 58801] intel_pstate/powersave - cpu frequency remains at high level if if system is idle

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=58801





--- Comment #5 from Christoph Loehr <c.h.l@web.de>  2013-05-25 17:34:51 ---
Created an attachment (id=102571)
 --> (https://bugzilla.kernel.org/attachment.cgi?id=102571)
Kernel config 3.9.3

Here is my kernel-config.

Christoph

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[Bug 58801] intel_pstate/powersave - cpu frequency remains at high level if if system is idle

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=58801


Zhang Rui <rui.zhang@intel.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|cpufreq@vger.kernel.org     |dirk.brandewie@gmail.com




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