powerd(8)

[Eric Anderson]

Poul-Henning Kamp wrote:
> In message <4263A33A.3030201 at centtech.com>, Eric Anderson writes:
> 
>>Lukas Ertl wrote:
>>
>>There's been some discussion on the -mobile list (I believe) about
>>this kind of thing before.  I think powerd is currently running with
>>a 'best shot' configuration, and I'm pretty sure that if anyone has 
>>a better algorithm in a patch form for people to try, I'm certain the 
>>good people with commit bits would easily commit a patched better version.
> 
> 
> I don't think a proportional approach will work in this case, the steps
> are too far apart.
> 
> I also think the switch to full speed is wrong.  Such see-saw
> algorithms waste far too much time decaying.  A less steep flank
> should be used.
> 
> For instance:
> 
> 	if (idle > 90%)
> 		reduce clock one step.
> 	if (idle < 80%)
> 		increase clock two steps.
> 

Mostly what I see on my laptop when it is 'idle' (meaning I'm in X, with my mail 
client running, window manager, etc, but not actively using anything (not even 
moving the mouse)), is the speed dropping down to 100Mhz (going through about 5 
steps, ~ half the speed each step), then shooting back to 100% speed.  This ends 
up looking like a sawtooth, so it wastes lots of energy on the fall back to 
100Mhz.  I essentially end up with an average of the mid-way point between max 
speed and lowest speed (1.8GHz and 100MHz for me), which of course isn't ideal.

Eric




-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
A lost ounce of gold may be found, a lost moment of time never.
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