[systemd-devel] systemd and power management

[Ivan Shapovalov]

On Wednesday 29 October 2014 at 13:00:42, Daniel Hollocher 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?

You could write a bunch of units pulled in by a target... well, two targets,
one for power-saving and second for performance mode. And then just start the
targets from an udev rule. Just remember to use `--no-block` as udev kills
workers after some time.

I've already done something along these lines for my own purposes, see
https://github.com/intelfx/power-management

However, I still want to know if I this is OK wrt systemd "spirit".

-- 
Ivan Shapovalov / intelfx /
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