'ondemand' systemd service is not disabled when governor option is set to performance or powersave

[David Negreira]

On Bionic, and probably on Focal, when installing the sysconfig charm, the 'ondemand' service that comes with the 'systemd' package stays enabled by default.
This causes some race condition with the 'cpufrequtils' service, where sometimes the ondemand unit comes last, hence the governor is set to ondemand instead of 'performance' or 'powersave' is set.

We should disable the 'ondemand' service when we set the governor option on the charm, and to have to enable it again when removing the sysconfig charm.

Workaround is to disable 'ondemand' service manually with 'systemctl disable ondemand'.

[Bryan Quigley (bryanquigley)]

Related bug, why not remove ondemand service: https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1503773.

[Dan Hill (hillpd)]

See bug 1806012 for detailed analysis. A merge proposal [0] to address the ondemand - cpufrequtils race stalled and was ultimately rejected. This needs to be revisited and hashed out.

You've already identified the best work-around: disabling the ondemand service.

[0] https://code.launchpad.net/~joalif/ubuntu/+source/systemd/+git/systemd/+merge/367469