CODEWITHSUNDEEP
clinuxapicpu
sunmat
sunmat

Reputation: 7248

Dynamic voltage and frequency scaling API

Does an API (in C) exist on Linux to allow a process to dynamically change the voltage or the frequency of the core it runs on?

Upvotes: 1

Views: 951

Answers (3)

Kroka
Kroka

Reputation: 475

CPU Dynamic Voltage-Frequency Scaling Example:

# See availables operation performance points
cat /sys/class/devices/system/cpu/cpu0/scaling_available_frequencies
384000 460800 600000 672000 768000 864000 960000 1248000 1344000 1478400 1555200

# See current core frequency
cat /sys/devices/system/cpu/cpu0/scaling_cur_freq
384000

# See current core voltage
cat /sys/class/regulator/regulator.3/microvolts
785000

# Change CPU speed to 1248000 MHz
echo 1248000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
echo 1248000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq

cat /sys/devices/system/cpu/cpu0/scaling_cur_freq
1248000

cat /sys/class/regulator/regulator.3/microvolts
980000

Upvotes: 0

Osman Sarood
Osman Sarood

Reputation: 121

You can change the frequency voltage pair by writing to: /sys/devices/system/cpu/cpu%d/cpufreq/scaling_setspeed file. There is a file for each hardware thread. However, you can only change the frequency for the entire chip (all the cores). You can find the available frequencies from: /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies

If you do not have this folder, check if your processor has Enhanced Intel SpeedStep® Technology available. If it has, go to the BIOS and enable it and you will see the folder. One more thing, you might need to enable/install the cpufreq module.

Hope it helps someone since the original position is old.

Upvotes: 0

Genís
Genís

Reputation: 1508

There might be such a library, but even if it doesn't, you can always open the files under /sys/devices/system/cpu that configure the behavior of the CPU.
Take a look to the files under /sys/devices/system/cpu/cpuX/cpufreq .

Upvotes: 1

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