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 Butane Config as well:

variant: flatcar
version: 1.0.0
systemd:
  units:
    - name: cpu-governor.service
      enabled: 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