[systemd-devel] systemd and power management

[Lennart Poettering]

On Wed, 29.10.14 13:00, Daniel Hollocher (danielhollocher at gmail.com) wrote:

> Hey folks,
> I'm a not expert here, so please forgive the low quality/interest of my
> question.
> 
> I'm curious what the ideal systemd way is to set various power management
> settings in the /sys tree.  For me personally, I'm looking to set
> sampling_down_factor as without it, ondemand has terrible performance on my
> particular computer (a 10-30% loss compared to performance or conservative).
> 
> Currently, Ubuntu uses a sysv init script to set ondemand after boot, and I
> could edit that.  It would be cool to know the ideal systemd way, that
> could also be aware of power saving stuff.
> 
> >From googling, it seems that tempfiles or sysctrl is not the way to go,
> since those only happen at boot.  Udev?  The examples I've found seem to
> make basic usage of udev to detect power changes, and then drop to a script
> to do the bulk of the work.  Is that it?

Yes, sysctl.d and tmpfiles.d (with the f option) are the way we
propose this is done.

Note that in general we try to follow the rule that what is good for
mobile use cannot hurt in plugged-in mode either, hence we have no
special support for reconfiguring the system depending on plug state.

systemd does not listen to power plug events. upower does however,
hence you could check if you can hook things into that.

Lennart

-- 
Lennart Poettering, Red Hat