Comment 13 for bug 19711

(In reply to comment #6)
>
> well presumably, if the the display has entered the DPMS off state, then you
> aren't using the GUI, so the it should be safe to shut down the CP.

Ahh, o.k. But I think this would not really make a big difference, as then CPU
power saving would only occur when the screen has turned off. However, as long
as one is actively working, there will be no benefit. E.g. at the moment I am
writing this text, I have some six to seven apps running (several open office
docs, firefox, kontact and a vmware winxp session). Nonetheless, the cpu is in
c3 about 33% of the time, thus giving me nearly 20 min more battery life (2:35
instead of 2:15).

> I'm not sure why there would be bus master activity if there are no
> commands being sent; that's what we need to figure out.
>

I feel that is the main question. I don't know what bus mastering is used for in
the driver. But it can't be something essential as I can work now without any
problems or "slowliness" without the dri module. Maybe bus mastering is
necessary for 3D apps in order to achieve high rendering performance? But right
now (with only the "office" apps running), I think, it should be perfectly o.k.,
when no bus mastering is used even with the dri module loaded.

However, if bus mastering is absolutely necessary for 3D, then with the advent
of xgl, when the whole desktop will use 3D commands, there will be no
possibility to enter c3 power saving mode, I guess. In this case, it's maybe not
worth the work to find out what's the cause for the bus mastering activity in
pure 2D apps with the dri module.

What do you think? Is it much work to find out what's the cause of the bus
mastering activity?

Cheers,

Michael