intel 2.6.0: EXA choppy, UXA has artifacts

[Peter Clifton]

On Sun, 2009-01-18 at 00:11 +0100, Khashayar Naderehvandi wrote:
> On Sat, Jan 17, 2009 at 10:57 PM, Peter Clifton <pcjc2 at cam.ac.uk> wrote:
> > On Sat, 2009-01-17 at 18:48 +0100, Khashayar Naderehvandi wrote:
> >> Hi!
> >>
> >> I'm trying out the newly released intel driver on a X4500 chipset.
> >> The stack is composed of:
> >>
> >> * kernel 2.6.28 with the patches from
> >> http://intellinuxgraphics.org/2008Q4.html applied
> >> * libdrm 2.4.4
> >> * mesa 7.3rc1
> >> * xorg-server 1.5.99.901.
> >> * intel driver 2.6.0
> >>
> >> With EXA compiz becomes unusably choppy and slow. I don't know how to
> >> explain the behavior in a good way, but it's like everything is run
> >> through a stroboscope. Sort of.
> >> With UXA, on the other hand, everything's smooth and nice, but there
> >> are certain artifacts. Like this:
> >> http://dl.getdropbox.com/u/175461/uxa-artifacts.png.
> >>
> >> Are these issues known? Any workarounds?
> >
> > The screen-saver you're previewing probably uses GL. Sounds like there
> > is a chance you've not got DRI2 working properly?
> >
> > I've got a similar setup to you, and UXA is working nicely. (Just turn
> > sync to vblank off in Compiz if you want framerate > 1/3 fps!)
> >
> > Check the Xorg.0.log to see if DRI2 is enabled.
> >
> 
> DRI2 definitely seems to be working well:
> khashayar at dionysos ~ $ cat /var/log/Xorg.0.log | grep -i dri2
> (II) LoadModule: "dri2"
> (II) Loading /usr/lib/xorg/modules/extensions//libdri2.so
> (II) Module dri2: vendor="X.Org Foundation"
> (II) Loading extension DRI2
> (II) intel(0): [DRI2] Setup complete
> (II) intel(0): direct rendering: DRI2 Enabled
> (II) GLX: Initialized DRI2 GL provider for screen 0
> 
> Sync to VBlank is off.
> 
> I've noticed that the artifacts come from translucency effects. If you
> look at the screenshot I linked to, all those windows have some
> translucency to them.
> 
> I don't understand the part about the screen saver, though.

Now you mentioned it, I see the other artifacts.. didn't notice at first
round.

I noticed some strange effects with translucency. I thought it might be
a compiz bug, and dismissed it (I turned off the fade in / out of
windows because it annoyed me).

What I noticed, was that often I'd get a flash of rendered objects,
without the background of the window being redraw, followed by the
background + objects being repainted (not sure if that was simultaneous
or not).

In the gnome menus it did distinctly appear as if the menu item text and
icons were painted onto the desktop, then a second expose happened which
painted the background and the rest of the image.

Does look like some kind of bug in the compositing relating to alpha
channel handling though.. you are right.

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)