[SOLVED] Can't set cpu scaling governors with intel_pstate

tbdc · 2014-12-27 11:40:34

Hello,

I am having difficultly setting cpu scaling governors. I have two kernels installed, the standard arch kernel:

[doug@archibald ~]$ uname -r
3.17.6-1-ARCH

and have recently compiled from the AUR the linux-rt kernel:

[doug@archibald ~]$ uname -r
3.14.25-rt22-1-rt

I have a sandybridge cpu and am using the default intel_pstate driver. When booting into the standard kernel I have no trouble switching between the two available scaling governors performance and powersave.

On the standard kernel:

[doug@archibald ~]$ sudo cpupower frequency-info
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: 800 MHz - 2.30 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 800 MHz and 2.30 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency is 1.49 GHz (asserted by call to hardware).
  boost state support:
    Supported: yes
    Active: yes
    2000 MHz max turbo 4 active cores
    2000 MHz max turbo 3 active cores
    2000 MHz max turbo 2 active cores
    2300 MHz max turbo 1 active cores

changing govenor yields no error:

[doug@archibald ~]$ sudo cpupower frequency-set -g performance
Setting cpu: 0
Setting cpu: 1
Setting cpu: 2
Setting cpu: 3

The problem arises when booting into realtime kernel. When using realtime kernel for the purposes of recording audio ect. I want the cpu to be scaled according to the performance governor, which is loaded by default

However, the fans are running permanently on my laptop, so when wanting to do non audio work I want to switch to the powersave governor which gives the following error:

Output from frequency info:

[doug@archibald ~]$ sudo cpupower frequency-info
[sudo] password for doug: 
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: 800 MHz - 2.30 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 800 MHz and 2.30 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency is 1.81 GHz (asserted by call to hardware).
  boost state support:
    Supported: yes
    Active: yes
    2000 MHz max turbo 4 active cores
    2000 MHz max turbo 3 active cores
    2000 MHz max turbo 2 active cores
    2300 MHz max turbo 1 active cores

Error when attempting to change govenor:

[doug@archibald ~]$ sudo cpupower frequency-set -g powersave
Setting cpu: 0
Error setting new values. Common errors:
- Do you have proper administration rights? (super-user?)
- Is the governor you requested available and modprobed?
- Trying to set an invalid policy?
- Trying to set a specific frequency, but userspace governor is not available,
   for example because of hardware which cannot be set to a specific frequency
   or because the userspace governor isn't loaded?

manually loading the cpufreq_performance and cpufreq_powersave modules has no effect:

[doug@archibald ~]$ sudo modprobe cpufreq_powersave
[doug@archibald ~]$ sudo cpupower frequency-set -g powersave
Setting cpu: 0
Error setting new values. Common errors:
- Do you have proper administration rights? (super-user?)
- Is the governor you requested available and modprobed?
- Trying to set an invalid policy?
- Trying to set a specific frequency, but userspace governor is not available,
   for example because of hardware which cannot be set to a specific frequency
   or because the userspace governor isn't loaded?
[doug@archibald ~]$ lsmod | grep powersave
cpufreq_powersave       1442  0

It may be worth mentioning that this problem seems to have appeared out of nowhere, last night I had no difficulty in changing the cpu govenor but this morning cpupower had magically disappeared so needed installing and then the above errors where found.

Last edited by tbdc (2014-12-28 12:25:52)

tbdc · 2014-12-28 12:24:43

Downgrading to the linux-rt-lts fixed the issue with not being able to change the cpu scaling governor, see:
http://www.spinics.net/lists/linux-rt-u … 12173.html

This didn't stop the fans from being on constantly, this was a separate issue that was fixed by disabling my discrete graphics card with bbswitch
https://github.com/Bumblebee-Project/bbswitch.

graysky · 2014-12-28 14:01:07

I believe you shouldn't use cpupower on an ivy. The pstates driver is recommended.

Arch Linux

#1 2014-12-27 11:40:34

[SOLVED] Can't set cpu scaling governors with intel_pstate

#2 2014-12-28 12:24:43

Re: [SOLVED] Can't set cpu scaling governors with intel_pstate

#3 2014-12-28 14:01:07

Re: [SOLVED] Can't set cpu scaling governors with intel_pstate

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