The future of Power Management - together with Activities

Dario Freddi drf54321 at
Mon Oct 3 12:14:18 BST 2011

On Monday 03 October 2011 10:44:35 Alexander Neundorf wrote: 
> Maybe one thing which could make things more clear to others would be to
> explain which things, potentially related to power management, are managed
> by what (or not) and how much they actually affect power consumption,
> like:
> FooWireless
> * managed via FooApplet or a hardware switch
> * saves a lot of energy when disabled
> This could contain:
> -WiFi
> -Wired Network
> -Bluetooth
> -Sound hardware
> -Builtin camera
> -other builtin peripherals ?
> -Screen Brightness
> -CPU frequency
> -(Rotating) Hard Disks
> -strigi/nepomuk indexing
> ...

This question is answered in the mail I just sent to Scott (sorry to play the 
redirect game again, but that mail was LONG and I don't have an additional 20 
mins to write it again :D)

About "what consumes power", it's something which is not exactly explainable 
in a mail. To oversimplify the concept, every time you wake up something (CPU, 
HD, etc...) you are consuming power. If a daemon is giving the CPU and the HD 
hard times, it's going to be wasting a lot of power. The screen brightness is 
like having 1 or 10 lightbulbs turned on at the same time.

> (I know a lot of these things have been touched in the thread, but having
> this information in one place would be a good thing. Also e.g. you stated
> that CPU settings were removed due to request from the kernel developers,
> but now people not involved (like me) wonder how this is managed now by
> the kernel (e.g. for writing emails I'd be fine with one of my two cores
> being powered down...)).

The ondemand governor (which is what every distribution uses now) is smart 
enough to analyze the system load and scale up or down the CPU depending on 
how much power is needed. So again, you can and should trust your system to do 
the right thing for you. As I said in the previous mail, your system by 
default is striving to save as much power as posible.

> Alex
> _______________________________________________
> Plasma-devel mailing list
> Plasma-devel at


Dario Freddi
KDE Developer
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