Ubuntu – CPU governor changes automatically to “performance” under load

cpugovernorperformancexubuntu

I have a Lenovo T570 with Xubuntu 18.04 LTS. My current issue is that my cpu speed stepping is kind of going nuts and does what ever it thinks its best.

Sample: when I run my IDE and cpu load increases during build time, the governor changes automatically. I caught the moment during compiling my project with the following call:

martin@martin-ThinkPad-T570:~$ while cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor; do sleep 1; done
powersave
powersave
performance
performance

cpufreq-info tells me this:

martin@martin-ThinkPad-T570:~$ cpufreq-info 
cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009
Report errors and bugs to cpufreq@vger.kernel.org, please.
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: 4294.55 ms.
  hardware limits: 400 MHz - 3.50 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 3.50 GHz and 3.50 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency is 3.25 GHz.
analyzing CPU 1:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 1
  CPUs which need to have their frequency coordinated by software: 1
  maximum transition latency: 4294.55 ms.
  hardware limits: 400 MHz - 3.50 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 3.50 GHz and 3.50 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency is 3.36 GHz.
analyzing CPU 2:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 2
  CPUs which need to have their frequency coordinated by software: 2
  maximum transition latency: 4294.55 ms.
  hardware limits: 400 MHz - 3.50 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 3.50 GHz and 3.50 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency is 3.26 GHz.
analyzing CPU 3:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 3
  CPUs which need to have their frequency coordinated by software: 3
  maximum transition latency: 4294.55 ms.
  hardware limits: 400 MHz - 3.50 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 3.50 GHz and 3.50 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency is 3.36 GHz.

Please take a look at

current policy: frequency should be within 3.50 GHz and 3.50 GHz.
The governor "performance" may decide which speed to use

Afterwards to go back to powersave I use my little script:

martin@martin-ThinkPad-T570:~$ cat cpu_freq_save.sh 
#!/bin/bash
sudo cpufreq-set -g powersave -c 0 --min 400MHz
sudo cpufreq-set -g powersave -c 1 --min 400MHz
sudo cpufreq-set -g powersave -c 2 --min 400MHz
sudo cpufreq-set -g powersave -c 3 --min 400MHz

Which resets the min frequency and the governor but as soon as I compile again with my IDE every time the governor and the min frequency changes again.

Any idea how I can disable that automatic change?

PS: If you need more details, just tell me where to find them and I will provide them

Best Answer

cpufreqd is a frequency management daemon installed with:

sudo apt install cpufreqd

A configuration file cpufreqd.conf is used to change frequencies. There are two sections where you can see it changing governor to "performance":

[Profile]
name=hi_boost
minfreq=0%
maxfreq=100%
policy=performance

# full power when AC
[Rule]
name=AC_on
ac=on                   # (on/off)
profile=hi_boost

It's harder to figure out when it changes to "powersave" unless the battery charger is unplugged.

Since kernel 3.4 cpufreq is built into the kernel and loaded automatically. It includes frequency management daemon called thermald. As such there isn't much a need for cpufreqd anymore and it may have conflicted on your system.

For even greater customization under battery power the tlp package is commonly used these days.

Related Solutions

Ubuntu – How to set governors for Intel to work as old good ondemand

For compatible processors, by default Ubuntu now uses the intel_pstate CPU frequency governor, whereas it used to use the acpi_cpufreq CPU frequncy governor.

The intel_pstate drive does not have ondemand mode, but its powersave mode should be the equivalent of the acpi_cpufreq ondemand mode. Your system should default to powersave mode about 1 minute after boot, and via the /etc/init.d/ondemand script. In the recent past, that script was not properly dealing with the intel_pstate case, but it should have been fixed for all use cases by now. Reference.

To answer your actual questions:

A.) The master min and max frequencies are stored as percentage numbers.
cat /sys/devices/system/cpu/intel_pstate/min_perf_pct
cat /sys/devices/system/cpu/intel_pstate/max_perf_pct
The interpretation of those numbers is a function of the turbo enabled or disabled flag, and in my opinion there is an inconsistency in the definitions.
cat /sys/devices/system/cpu/intel_pstate/no_turbo

Example from my i7-2600K: min freq 1.6GHz; max non-turbo 3.4GHz; max turbo 3.8GHz.
Therefore as percentages:
Turbo off: max = 100%, min = 47.1%
Turbo on: max = 100%, min = 42.1%

$ cat /sys/devices/system/cpu/intel_pstate/no_turbo
0
$ cat /sys/devices/system/cpu/intel_pstate/min_perf_pct
42
$ cat /sys/devices/system/cpu/intel_pstate/max_perf_pct
100

and

$ cat /sys/devices/system/cpu/intel_pstate/no_turbo
1
$ cat /sys/devices/system/cpu/intel_pstate/max_perf_pct
100
$ cat /sys/devices/system/cpu/intel_pstate/min_perf_pct
42

B.) The intel-pstate powersave mode should be the equivalent of the acpi-cpufreq ondemand mode.

C.) There is something wrong, resulting in your grief. There have been other reports similar to yours. Myself, I do not know the root issue, but there have also been reports of incompatibilities with cpufrequtils. I do not know if they are true or not, as I don't use any such things. I only use the most primitive level of controls with the intel-pstate driver.

Ubuntu – how to make cpugovernor intel_pstate stable

It is not possible for your processor to always be at your max turbo rate of 3200MHz all the time. If you have many cores active at once, then the max frequency will be only 2.6Ghz, and that limit is fundamental within the processor itself (see also your i7z screenshot - Max Turbo Multiplier line). However you can easily pretty much have all CPUs always at 2.6 GHz by setting the min and max percent numbers accordingly. However, note that you will still observe sometimes less frequency, as the processor can back off by itself under very low load conditions. Even easier would be to set turbo to off and performance mode, effectively makes all CPU run at 2.4 GHz all the time (but again, the processor itself can back off under extremely low load).

Example for setting 2.6Ghz (if I did my math properly):

echo "81" | sudo tee /sys/devices/system/cpu/intel_pstate/max_perf_pct
echo "81" | sudo tee /sys/devices/system/cpu/intel_pstate/min_perf_pct

Example for the non-turbo method:

echo "1" | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
$ cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
powersave
powersave
powersave
powersave
powersave
powersave
powersave
powersave
$ sudo su
# for file in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor; do echo "performance" > $file; done
# exit
exit
$ cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
performance
performance
performance
performance
performance
performance
performance
performance

Best Answer

Related Solutions

Ubuntu – How to set governors for Intel to work as old good ondemand

Ubuntu – how to make cpugovernor intel_pstate stable

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