Problem: Possible regression in intel_pstate on 3.12

[Joakim Hernberg]

First of all excuses to the people in the CC: if they have received
this multiple times, as I haven't managed to get this mail to appear on
the lkml.  Hopefully it will work this time, and was just me
using multiple TO:'s instead of CC:.

When I'm running KDE on linux 3.12 (archlinux) my intel i7-2600k seems
to no longer reduce the cpu multiplier and thus runs hotter than under
linux 3.11.  i7z shows the cpu as being close to idle and using C0 to
C6 states.

On "Linux version 3.12.3-1-ARCH (tobias@T-POWA-LX) (gcc version 4.8.2
(GCC) ) #1 SMP PREEMPT Wed Dec 4 21:45:42 CET 2013"

Output of # cpupower frequency-list when booted to the command prompt:

analyzing CPU 0:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 0.97 ms.
  hardware limits: 1.60 GHz - 5.90 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 1.60 GHz and 5.90 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency is 1.69 GHz (asserted by call to hardware).
  boost state support:
    Supported: yes
    Active: yes
    25500 MHz max turbo 4 active cores
    25500 MHz max turbo 3 active cores
    25500 MHz max turbo 2 active cores
    25500 MHz max turbo 1 active cores

When booted into KDE and system more or less idle:

analyzing CPU 0:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 0.97 ms.
  hardware limits: 1.60 GHz - 5.90 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 1.60 GHz and 5.90 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency is 4.30 GHz (asserted by call to hardware).
  boost state support:
    Supported: yes
    Active: yes
    25500 MHz max turbo 4 active cores
    25500 MHz max turbo 3 active cores
    25500 MHz max turbo 2 active cores
    25500 MHz max turbo 1 active cores

Output of top while in KDE:

top - 14:21:13 up 9 min, 16 users,  load average: 0.48, 0.88, 0.59
Tasks: 205 total,   1 running, 204 sleeping,   0 stopped,   0 zombie
%Cpu(s):  1.2 us,  0.4 sy,  0.0 ni, 98.1 id,  0.3 wa,  0.0 hi,  0.0
si,  0.0 st KiB Mem:  15366248 total,  2435540 used, 12930708 free,
71804 buffers KiB Swap:  4193276 total,        0 used,  4193276 free,
1135904 cached



On "Linux version 3.11.6-1-ARCH
(nobody@var-lib-archbuild-extra-x86_64-thomas) (gcc version 4.8.1
20130725 (prerelease) (GCC) ) #1 SMP PREEMPT Fri Oct 18 23:22:36 CEST
2013"

Output of cpupower frequency-list while in KDE:

analyzing CPU 0:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 0.97 ms.
  hardware limits: 1.60 GHz - 5.90 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 1.60 GHz and 5.90 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency is 1.94 GHz (asserted by call to hardware).
  boost state support:
    Supported: yes
    Active: yes
    25500 MHz max turbo 4 active cores
    25500 MHz max turbo 3 active cores
    25500 MHz max turbo 2 active cores
    25500 MHz max turbo 1 active cores

I'm attaching the config files of both kernels in case it's simply a
configuration pebcak.

-- 

   Joakim

Attachment: config.3.11
Description: Binary data

Attachment: config.3.12
Description: Binary data