[ltp] Direct Rendering's affect on battery life?

[Laurent Gilson]

Hello,

> One thing, though, that I think I noticed, was that my power was draining
> faster... by about 1.0 to 1.5 Watts (so not exactly an insignificant  
> amount).

Yepp, that's normal and has 2 possible causes:

1. the DRI/DRM-part of the driver keeps the CPU awake even if there is  
nothing to do. The CPU will switch to lower frequencies w/o any problems,  
but it will stay in the first 1-2 C-States. W/o DRI/DRM it can enter C3 or  
even C4 which reduce the power needed to run the CPU. Have a look at  
/proc/acpi/processor/CPU/power and the "bus master activity". Optimal for  
a idle desktop is 00000000.

2. The driver can disable some parts (3D, mem-management) of the chip if  
DRI is inactive. I don't think you get 1 watt from that.

> Feel free to throw in any other comments you might have too; I'm not  
> trying to
> make this too targeted a question.

About cause 1: USB can create the same situation.

cu