Xserver needs to run as "root" on Linux / was: Re: [Xorg] Server side widgets

Michel Dänzer michel at daenzer.net
Tue Jul 13 04:57:36 PDT 2004

On Mon, 2004-07-12 at 19:22 -0700, Jon Smirl wrote:
> --- John Dennis <jdennis at redhat.com> wrote:
> > Maintaining optimal performance while balancing the balance of labor
> > between a driver and user level rendering process is tricky. How do
> > you propose to migrate things to a driver without degrading
> > performance in the general case?
> > 
> > The problem is that the transition between system and user is
> > expensive and if the operations performed by the driver are too 
> > small and fine grained you're going to kill performance.

I think this problem has been very well explored and solved in the DRI
drivers. So long as OpenGL isn't used too pathologically, I don't
foresee major problems there.

> I've asked Keithp about how damage is going to work in a double
> buffered system where the main screen you want to update is one frame
> behind. He's still thinking about the answer.

Actually, the point is page flipping as opposed to copying the back
buffer to the front buffer for each frame, isn't it? I tend to think the
answer is to just draw the whole screen contents for each frame; of
course, the area that hasn't changed can be copied from the previous
frame when that requires less effort than drawing everything from

Earthling Michel Dänzer      |     Debian (powerpc), X and DRI developer
Libre software enthusiast    |   http://svcs.affero.net/rm.php?r=daenzer

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