Update on DeviceKit

[Holger Macht]

On Do 08. Mai - 18:27:29, Matthew Garrett wrote:
> On Thu, May 08, 2008 at 06:02:14PM +0200, Holger Macht wrote:
> 
> > I don't expect desktop application to be so intelligent to care about all
> > different policy knobs a CPU might export. But they want to tune the
> > setting depending on AC or Battery. Then consider the 1-100 scale as just
> > two settings, "on AC" and "on battery". It's basically used as that these
> > days.
> 
> *No*! There is basically nothing you can do in processor power 
> management that is sensible on battery but bad on AC (or vice-versa). 
> Modern processors (basically anything that can run any current Linux 
> distribution) are most efficient when they're doing nothing. The only 
> sensible way to use these processors is to ensure that they spend most 
> of their time doing nothing, which means that you want them to run as 
> fast as possible when they need to do something. Once they've stopped 
> running code, it doesn't matter what clock frequency you're running them 
> at. The execution units are turned off.
> 
> The idea that CPUs have a power/performance tradeoff is basically 
> untrue. The best power saving is obtained in a configuration that also 
> gives you the best performance. Reducing performance increases overall 
> power usage, which means it's certainly not something you want to do 
> when you're on battery.

With you're argumentation being true, it wouldn't make sense to have
something like an ondemand governor at all. Not to mention having an
up_threshold exported to userspace. Just always run at full speed.

Regards,
	Holger