[maemo-developers] 770 Power Management and power states --- WAS: Re: [maemo-developers] Maemo Alarm/Notifier Interface

[From: Igor Stoppa]

On Fri, 2006-01-20 at 16:17 +0200, Riku Voipio wrote: 
> On Wednesday 18 January 2006 15:07, Igor Stoppa wrote:
> > The price for it is that we had to fix drivers and applications so that
> > they would behave decently, without keeping resources (clocks)
> > constantly allocated and without generating unnecessary activity.
> 
> The problem is 3rd party developers who are not aware of such situation.
> for example, a periodically updating statusbar plugin will eat your battery
> away. "STOP DOING STUFF WHEN YOU GET system_inactivity_ind" should
> be in big red letters in the first part of api documentation.
> 
They will be, when next version of maemo will be relesed. Those
requirements are already 

However almost everything that optimises cpu performance is good for
power consumption too (on a fixed frequency system).


If I had to summarise, well it would go like:
-1)Thou shan't busy-loop
-2)Thou shan't poll poll
-3)Thou shan't use libraries that will do 1) and 2) in your place. 


Then we move to a grayer area, like "don't do unnecessary stuff".

Screen updates with unlit screen are a good example, but only when the
effect of the update is not going to be needed later on. Typical case:
blinking, glowing and such eyecandies.

> > But that is GOOD anyway because it means having better code, better
> > algorithms.
> 
> With this argument, multitasking of windows 3.11 is better since it forces 
> developers to write code so that they give time to others.
> 

I disagree: this case is just making obvious to people how to leverage
hw that they are already using. Quite different. 

> > So the 770 can save power even when you have the device in your hand
> > with the screen lit and a wireless connection open, as long as it's not
> > actually doing something, like rendering a web page.
> 
> Which is a *very* good thing, I don't think anyone suggested removing current
> dyntick and PM setup, but rather added suspend as well. Many users have grown
> accustomed in manual suspending, so perhaps adding no-op "suspend" button
> to the powerkey menu would make them happy =) 
bad habits should be discontinued, not supported. Don't tell me that you would
 like to have a crank on the front of your car so that you can start the engine =) 

> hmm.. maybe just sending
> SIGSTOP to all user apps is enough to make them release clocks? 
I doubt: apps are not directly involved in clocks handling: it would be a possible approach
for a suspend-based system, but what is really desirable here is that apps just make sure to 
avoid keeping the processor busy. The system can take care of itself as long as it's idle.
-- 
Igor Stoppa (Nokia M - OSSO / Tampere)