compiz jerky when twinview enabled

[lcolitti]

Hi,

I am using compiz on two 1920x1200 LCD panels. When TwinView is enabled, compiz animations are slow and jerky and use a lot of CPU. If I switch off TwinView by reconfiguring X and restarting, or by switching to a MetaMode with only one screen (I have Option "MetaModes" "1920x1200,1920x1200; 1920x1200,NULL") and restarting compiz, they become smooth as butter.

Any idea why this might be? I am using the 9746 drivers on a Quadro NVS 285 with X.org 7.1.1 on Ubuntu Edgy.

Thanks!
Lorenzo

[Ta0]

Same thing here. I have posted a bug in beryl trac and they said it could be a driver bug... http://bugs.beryl-project.org/ticket/223

[netllama]

I'd be curious why the Beryl developers believe that this is a driver bug.

However, this could just be a hardware limitation, as using a compositor (such as compiz) on a desktop that is 3840x1200 requires a non-trivial amount of horsepower. If you use modes smaller than 1920x1200 in Twinview, is the performance any better?

Thanks,
Lonni

[Ta0]

In fact, the performance seriously drop down even in a clone mode, but it shouldn't require more power because it is the same output on the two screen...

Thanks

[netllama]

See: http://www.nvnews.net/vbulletin/showthread.php?t=46678

[Ta0]

Description :
- If I start Beryl in a single screen mode (metamodes "1280x960, NULL"), the performance are fine. Then, if I switch to "1280x960, 800x600@1280x960" (twinview clone mode) without restarting beryl, performance are still fine and the clone mode is enabled. So in this case, it's ok.
- If I start beryl in a clone mode ("1280x960, 800x600@1280x960"), animations are jerky (and the performance plugin show a fps 50% lower than before). Then if I switch to "1280x960, NULL", performance are still bad.

I think it is the same issue than lcolitti, to be confirmed by his detailed description.

[lcolitti]

Originally Posted by netllama

If you use modes smaller than 1920x1200 in Twinview, is the performance any better?

I did a few tests today:

960x600,960x960: OK
1280x800,1280x800: jerky
1600x1200,1600x1200: jerky

As you say, it could be a hardware limitation. Perhaps it's hitting a maximum texture size limitation such as 2048x2048? It doesn't seem to be caused by number of pixels, because 1920x1200 on a single screen (2.3 megapixels) is smooth as butter, and 1280x800 on two screens (2.0 megapixels) is much jerkier...

Cheers,
Lorenzo

[lcolitti]

This looks like a driver bug.

I just tested Xgl using the same hardware and same X configuration and it's *massively* smoother. Unfortunately, I can't use Xgl as window placement with two monitors is all wrong.