Power Management

[Marcelo Tosatti]

Hi Richard,

On Fri, Jun 08, 2007 at 02:51:00PM +0100, Richard Hughes wrote:
> OLPC now uses the olpc-hardware-manager python service to do power
> management tasks. This is not really suitable for long term use, and we
> can't easily do clever things with this infrastructure.
> 
> I'm proposing to use OHM (ohm.freedesktop.org) to do the clever things,
> and apply system wide policy. OHM has working code, and I'm currently
> preparing a package for olpc. I've got some time now I'm interning at
> Red Hat (and now I've finished my exams...). I want to integrate this,
> and hopefully have a kick-ass solution that is long-term supportable in
> as little time as possible.
> 
> OHM sits above HAL and lets HAL do the heavy lifting for reporting
> events and doing actions. HAL is already packaged and being used for
> OLPC. OHM is incredibly lightweight, and has a flexible compiled plugin
> system for the rules, making it an ideal choice in my opinion. I wrote
> most of the code, so consider my opinion very biased :-)
> 
> I'm thinking about system power management interactions for the OLPC. So
> far I've got:
> 
> • When system idle for > 10 seconds and on battery we dim screen to 40%
> • When system idle for > 30 seconds we turn the screen off
> • When system idle for > 1 minute we suspend, assuming we have no
> inhibits and CPU load is low

In more detail, the amount of time of idleness necessary to trigger
suspend depends on:

- How long we take to suspend/resume.
- How much power that consumes.

Certainly we want something more aggressive than "idle for > 1 minute"
in the near future, but thats fine for a start.