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3.2.2. CPUfreq Setup

Before selecting and configuring a CPUfreq governor, you need to add the appropriate CPUfreq driver first.

Procedure 3.1. How to Add a CPUfreq Driver

  1. Use the following command to view which CPUfreq drivers are available for your system: 
    ls /lib/modules/[kernel version]/kernel/arch/[architecture]/kernel/cpu/cpufreq/
  2. Use modprobe to add the appropriate CPUfreq driver. 
    modprobe [CPUfreq driver]
    When using the above command, be sure to remove the .ko filename suffix.

    Important

    When choosing an appropriate CPUfreq driver, always choose acpi-cpufreq over p4-clockmod. While using the p4-clockmod driver reduces the clock frequency of a CPU, it does not reduce the voltage. acpi-cpufreq, on the other hand, reduces voltage along with CPU clock frequency, allowing less power consumption and heat output for each unit reduction in performance.
  3. Once the CPUfreq driver is set up, you can view which governor the system is currently using with: 
    cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
You can also view which governors are available for use for a specific CPU using: 
cat /sys/devices/system/cpu/[cpu ID]/cpufreq/scaling_available_governors
Some CPUfreq governors may not be available for you to use. In this case, use modprobe to add the necessary kernel modules that enable the specific CPUfreq governor you wish to use. These kernel modules are available in /lib/modules/[kernel version]/kernel/drivers/cpufreq/.

Procedure 3.2. Enabling a CPUfreq Governor

  1. If a specific governor is not listed as available for your CPU, use modprobe to enable the governor you wish to use. For example, if the ondemand governor is not available for your CPU, use the following command: 
    modprobe cpufreq_ondemand
  2. Once a governor is listed as available for your CPU, you can enable it using: 
    echo [governor] /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor