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wsha

Member

Registered: 2015-07-22

Posts: 19

Can't set cpu frequency to maximum frequency

I am having trouble setting the CPU frequency to its hardware maximum. I am using an Intel i5 (lscpu gives "Model name:            Intel(R) Core(TM) i5-4210U CPU"). I booted with "intel_pstate=disable". The output of cpupower frequency-info is

analyzing CPU 0:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 10.0 us.
  hardware limits: 768 MHz - 2.40 GHz
  available frequency steps: 2.40 GHz, 2.40 GHz, 2.30 GHz, 2.20 GHz, 2.00 GHz, 1.90 GHz, 1.70 GHz, 1.60 GHz, 1.50 GHz, 1.40 GHz, 1.30 GHz, 1.20 GHz, 1.10 GHz, 900 MHz, 800 MHz, 768 MHz
  available cpufreq governors: userspace, ondemand, performance
  current policy: frequency should be within 1.30 GHz and 1.70 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency is 1.70 GHz.
  boost state support:
    Supported: yes
    Active: yes

Using cpupower frequency-set, I can set the minumum frequency to anything between 768 MHz and 1.7 GHz, I can set the current frequency to anything between the minimum and maximum values of the "current policy", and I can set the governor. Also, I can set the maximum to anything 1.7 GHz or lower. However, if I try to set the maximum frequency above 1.7 GHz, it gets rounded down to 1.7 GHz (that's what is returned by cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq) without an error. What could be setting this limit?

I am trying to compile ATLAS and I can't get past the CPU Throttling check because of this.

Gusar

Member

Registered: 2009-08-25

Posts: 3,607

Re: Can't set cpu frequency to maximum frequency

No matter what you set the freq to, if the heat goes up, the CPU *will* get throttled.

And the reason you can't go beyond 1.7GHz is very simple - that's the base frequency of your CPU. Anything beyond is turbo mode, up to 2.7GHz if one core is in use, up to 2.4GHz if both cores are in use. So don't try to manage the freq yourself, just let intel_pstate do its job.

It should be possible to compile stuff at 1.7GHz, anything above only when thermal conditions allow it, usually only for short periods of time.

Last edited by Gusar (2015-09-11 09:21:57)

wsha

Member

Registered: 2015-07-22

Posts: 19

Re: Can't set cpu frequency to maximum frequency

Thanks, so I guess I have to patch the source to skip the CPU Throttling check because the developers of ATLAS removed the option to skip it. The check checks that `scaling_cur_freq` and `cpuinfo_max_freq` are equal during the configure step, which I guess is impossible on my system. Perhaps I should raise this point with the developers.