Linux Power Management – How to Get Current CPUPower Governor

linuxpower-management

I want to get the current CPUPower governor.

When I type cpupower frequency-info I get a lot of information. I just want to get the governor, just like "ondemand" with no more information, to use its value in a program.

Best Answer

The current governor can be obtained as follows:

cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

Note that cpu* will give you the scaling governor of all your cores and not just e.g. cpu0.

This solution might be system dependent, though. I'm not 100% sure this is portable.

Related Solutions

Fedora Kernel – How to Get Ondemand Governor

This is related to a new driver introduced in Fedora 20 that does not need more than those two governors. See this thread CPU Governors - where is ONDEMAND? for details.

To have the missing governors, you should boot with the kernel parameter intel_pstate=disable.

To do so, in the GRUB boot screen, choose "edit boot commandline" and add this to the line which starts with kernel. You can also add it permanently to the grub config file.

Note that normally you should not need others governors than those proposed by the new driver which does its job perfectly.

Linux Kernel – Setting CPU Governor to On Demand or Conservative

Assuming your governor is the intel_pstate (default for Intel Sandy Bridge and Ivy Bridge CPUs as of kernel 3.9). This issue is not specific to Arch, but all distros using the new Intel pstate driver for managing CPU frequency/power management. Arch linux CPU frequency scaling.

Theodore Ts'o wrote his explanation on Google+:

intel_pstate can be disabled at boot-time with kernel arg intel_pstate=disable
The problem with the ondemand governor is that it doesn't know the specific capabilities of the CPU
Executing some tasks with higher frequency will consume less power than would a lower frequency taking more time e.g. arithmetic stuff, but not true for all tasks e.g. loading something from memory
The intel_pstate driver knows the details of the how the CPU works and it does a better job than the generic ACPI solution
intel_pstate offers only two governors, powersave and performance. Intel claims that the intel_pstate "powersave" is faster than the generic acpi governor with "performance"

To change back to the ACPI driver, reboot and set the kernel arg intel_pstate=disable
Then execute modprobe acpi-cpufreq and you should have the ondemand governor available.

You can make the changes permanent by editing /etc/default/grub and adding

GRUB_CMDLINE_LINUX_DEFAULT="intel_pstate=disable"

And then updating grub.cfg ala grub-mkconfig -o /boot/grub/grub.cfg

Follow the instructions for Arch kernel module loading and add the acpi-cpufreq module.

Best Answer

Related Solutions

Fedora Kernel – How to Get Ondemand Governor

Linux Kernel – Setting CPU Governor to On Demand or Conservative

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