Michael Terry michael.terry at
Fri Jun 12 05:08:50 PDT 2009

On Fri, 2009-06-12 at 09:52 +0100, Richard Hughes wrote: 
> > Is it just a feature that is yet to be written, or is the expectation
> > that pm-powersave is not part of the dk-p stack?
> I think a lot of that functionality needs to be moved down into the
> kernel, and connected up with pmqos so we can control this as a policy
> action. I've written tons of stuff about pmqos and latency on my blog.

OK.  I'm slightly familiar with your writings on the matter and don't
have strong feelings about the actual ondemand/latency aspects.

But one additional thing that pm-powersave does is allow applications to
hook into am-I-on-battery? events and run a script (by dropping them
in /usr/lib/pm-utils/power.d).  Is there a replacement for such a
mechanism?  I suppose apps that are daemons could just listen to dk-p
(if they don't mind the dependency), but this let non-running apps
listen for the event too.

In all of Ubuntu, only three apps use the mechanism:
anacron (to not consume CPU when in battery mode)
distributed-net (to not consume CPU when in battery mode)
hdparm (to set disk APM modes)

Notably hdparm is useful for parking disk heads when the laptop is
moving (using battery power as a proxy for that information -- it would
also be cute to hook into an accelerometer if available.  :)).

mterry | UI & App Engineer, Canonical Ltd. | +1 781 761 9092
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