Recent update introduces horrific transparency compositing performance

[Daniel Farina]

Recently I updated to the latest packages in Raring on a computer I use day to day. The performance of alt-tab has become very, very slow -- multiple seconds -- especially at higher resolutions, and chews up a lot of compute time while it's running. It's bad enough that I consciously try to avoid alt-tab to switch windows.

Interestingly, composite effects like 'scale' (used when clicking on the Unity bar) do not have any slow down. The compositing of the fading or the window switcher itself seem at fault.

[Daniel Farina (drfarina)]

Distro version: ubuntu raring

[Tim Lichtenberg (timlichtenberg)]

experiencing the same problem. rly horrible for multi-tasking work... (raring)
by pressing super-key starter comes up very slow as well.

[Daniel Farina (drfarina)]

Yes, I can confirm that too: when the Unity search (which is how application are launched, etc) is on screen, the problem is marked and persistent: it takes many seconds to enter a single character, and the problem goes beyond the transition. Throughout the mouse is smooth though.

It seems that this has something to do with compositing transparency. Let's see if I can change the title.