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Lucas Aimaretto
Asked: 2018-08-29 15:52:46 +0800 CST

Power Management governor changes alone from powersave to performance

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So, I'm having some overheating problems with an HP Envy 15 that are driving me nuts. See this and this for reference.

Anyway, I did an Ubuntu 18.04 fresh install. Also installed tlp and cpufrequtils. So, if I do tlp stat -p ...

+++ Processor
CPU model      = Intel(R) Core(TM) i7-4510U CPU @ 2.00GHz

[....]

/sys/devices/system/cpu/cpu3/cpufreq/scaling_driver    = intel_pstate
/sys/devices/system/cpu/cpu3/cpufreq/scaling_governor  = performance
/sys/devices/system/cpu/cpu3/cpufreq/scaling_available_governors = performance powersave
/sys/devices/system/cpu/cpu3/cpufreq/scaling_min_freq  =  3100000 [kHz]
/sys/devices/system/cpu/cpu3/cpufreq/scaling_max_freq  =  3100000 [kHz]

/sys/devices/system/cpu/intel_pstate/min_perf_pct      =  25 [%]
/sys/devices/system/cpu/intel_pstate/max_perf_pct      = 100 [%]
/sys/devices/system/cpu/intel_pstate/no_turbo          =   0
/sys/devices/system/cpu/intel_pstate/turbo_pct         =  50 [%]
/sys/devices/system/cpu/intel_pstate/num_pstates       =  24

Now, since I want to use a powersave governor, as per this, I get to use it.

+++ Processor
CPU model      = Intel(R) Core(TM) i7-4510U CPU @ 2.00GHz

[....]

/sys/devices/system/cpu/cpu3/cpufreq/scaling_driver    = intel_pstate
/sys/devices/system/cpu/cpu3/cpufreq/scaling_governor  = powersave
/sys/devices/system/cpu/cpu3/cpufreq/scaling_available_governors = performance powersave
/sys/devices/system/cpu/cpu3/cpufreq/scaling_min_freq  =  3100000 [kHz]
/sys/devices/system/cpu/cpu3/cpufreq/scaling_max_freq  =  3100000 [kHz]

/sys/devices/system/cpu/intel_pstate/min_perf_pct      =  25 [%]
/sys/devices/system/cpu/intel_pstate/max_perf_pct      = 100 [%]
/sys/devices/system/cpu/intel_pstate/no_turbo          =   0
/sys/devices/system/cpu/intel_pstate/turbo_pct         =  50 [%]
/sys/devices/system/cpu/intel_pstate/num_pstates       =  24

So far, so good.

Two things do call my attention:

  1. If I do start using my laptopt again, don't know why, but from time to time, the tlp stat -p shows again that the scaling_governor=performance.
  2. Why are scaling_min_freq and scaling_max_freq equal? I'd like to reduce both of them to see if I can somehow control the overheating problem that I'm facing.

How can I avoid the performance governor? How can I tune the min and max scaling?

thanks!

Lucas

power-management cpu overheating 18.04 tlp

2 Answers

  1. Force to powersave speed governor

    You are using sudo tlp stat -p to find out when the speed governor is set at performance mode. When this happens reset it to powersave with this command:

    $ echo "powersave" | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
powersave

    Run tlp statistics again and ensure minimum frequency is normalized and no longer set at maximum frequency.

    Keep running tlp to find out how often the governor is being reset to performance mode.

    Keep searching for the program that is reseting the speed governor.

    As a last resort you could:

    1. Setup a sleeping procedure to reset to powersave every x seconds.
    2. Setup a procedure that monitors the speed governor every second and reset it when it changes.
    • 3

  2. This answer is for your second question:

    Why are scaling_min_freq and scaling_max_freq equal? I'd like to reduce both of them to see if I can somehow control the overheating problem that I'm facing.

    I don't know how they got set to the same, but something must have done it. To limit your maximum CPU frequency, when using the intel_pstate CPU frequency scaling driver, one way is (to 70% for example):

    $ echo 70 | sudo tee /sys/devices/system/cpu/intel_pstate/max_perf_pct

    Example:

    doug@s15:~/temp$ grep . /sys/devices/system/cpu/intel_pstate/*
/sys/devices/system/cpu/intel_pstate/max_perf_pct:100
/sys/devices/system/cpu/intel_pstate/min_perf_pct:42
/sys/devices/system/cpu/intel_pstate/no_turbo:0
/sys/devices/system/cpu/intel_pstate/num_pstates:23
/sys/devices/system/cpu/intel_pstate/status:active
/sys/devices/system/cpu/intel_pstate/turbo_pct:18
doug@s15:~/temp$ echo 70 | sudo tee /sys/devices/system/cpu/intel_pstate/max_perf_pct
70
doug@s15:~/temp$ grep . /sys/devices/system/cpu/intel_pstate/*
/sys/devices/system/cpu/intel_pstate/max_perf_pct:70
/sys/devices/system/cpu/intel_pstate/min_perf_pct:42
/sys/devices/system/cpu/intel_pstate/no_turbo:0
/sys/devices/system/cpu/intel_pstate/num_pstates:23
/sys/devices/system/cpu/intel_pstate/status:active
/sys/devices/system/cpu/intel_pstate/turbo_pct:18
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