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Power friendliness is in the hands of the app developers, but...

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maemo at csipa

Oct 23, 2009, 1:39 PM

Post #1 of 3 (332 views)
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Power friendliness is in the hands of the app developers, but...

... are there actual examples for what we should do ? Sure, save as much power
as we can, don't do things you don't have to, etc, etc. It's easy to say, but
where are the 'good practice' examples (e.g. CODE) that demonstrate the
suggested guidelines ? I'm starting to swim in boilerplate code trying account
for all the ways power-saving might be an issue. For example do I really need
to watch focus and window state events like a hawk to see when I have been
minimized and thus in a position to cut some slack for the CPU ?

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vivainio at gmail

Oct 24, 2009, 1:07 AM

Post #2 of 3 (297 views)
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Re: Power friendliness is in the hands of the app developers, but... [In reply to]

On Fri, Oct 23, 2009 at 11:39 PM, Attila Csipa <maemo [at] csipa> wrote:

> ... are there actual examples for what we should do ? Sure, save as much power
> as we can, don't do things you don't have to, etc, etc. It's easy to say, but
> where are the 'good practice' examples (e.g. CODE) that demonstrate the
> suggested guidelines ? I'm starting to swim in boilerplate code trying account

It's more about what you don't do than what you do, so code examples
are not the best way ;-).

- Minimize network & disk access
- Time "periodic" network access with "ip heartbeat" (iphb_*). You can
check how modest does it for details.
- Do not wake up unnecessarily (e.g. periodic g_timeout_add stuff).

> for all the ways power-saving might be an issue. For example do I really need
> to watch focus and window state events like a hawk to see when I have been
> minimized and thus in a position to cut some slack for the CPU ?

That stuff isn't too bad because your process will be in running state
on those occasions anyway. The badness comes from waking up, raher
than not doing something when having woken up.

--
Ville M. Vainio
http://tinyurl.com/vainio
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maemo at csipa

Oct 26, 2009, 4:28 AM

Post #3 of 3 (267 views)
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Re: Power friendliness is in the hands of the app developers, but... [In reply to]

On Saturday 24 October 2009 10:07:34 Ville M. Vainio wrote:
> > for all the ways power-saving might be an issue. For example do I really
> > need to watch focus and window state events like a hawk to see when I
> > have been minimized and thus in a position to cut some slack for the CPU
> > ?
>
> That stuff isn't too bad because your process will be in running state
> on those occasions anyway. The badness comes from waking up, raher
> than not doing something when having woken up.

The point I'm trying to make is that there are several distinct levels of
power-usage scenarios (think about it as like what governors are to CPU
speed), and a 'fixed' powersave scheme (like the don't do this and don't do
that), while good, is still not optimal. I would like to see a recommended
power strategy list (like - how to react when you're a CPU heavy program and
you're backgrounded, or the screen is blanked, or an inactivity timer is
triggered, etc, etc), basically the things an application can *proactively*
do to conserve energy, and in that context code examples CAN help standardize
this .
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