Tuning Flatcar Container Linux power management

    CPU governor

    By default, Flatcar Container Linux uses the “performance” CPU governor meaning that the CPU operates at the maximum frequency regardless of load. This is reasonable for a system that is under constant load or cannot tolerate increased latency. On the other hand, if the system is idle much of the time and latency is not a concern, power savings may be desired.

    Several governors are available:

    Governor Description
    performance Default. Operate at the maximum frequency
    ondemand Dynamically scale frequency at 75% cpu load
    conservative Dynamically scale frequency at 95% cpu load
    powersave Operate at the minimum frequency
    userspace Controlled by a userspace application via the scaling_setspeed file

    The “conservative” governor can be used instead using the following shell commands:

    modprobe cpufreq_conservative
    echo "conservative" | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor > /dev/null
    

    This can be configured with a Container Linux Config as well:

    systemd:
      units:
        - name: cpu-governor.service
          enable: true
          contents: |
            [Unit]
            Description=Enable CPU power saving
    
            [Service]
            Type=oneshot
            RemainAfterExit=yes
            ExecStart=/usr/sbin/modprobe cpufreq_conservative
            ExecStart=/usr/bin/sh -c '/usr/bin/echo "conservative" | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor'
    
            [Install]
            WantedBy=multi-user.target        
    

    More information on further tuning each governor is available in the Kernel Documentation