Posted 19 February 2013 - 13:23
I found this today. Not sure if it'll help.
"Ubuntu’s Unity desktop uses desktop compositing. Windows draw their contents off the screen and the desktop compositing manager draws them back onto the screen. This allows the Unity desktop (and other desktops such as GNOME Shell and KDE 4 with compositing enabled) to provide slick, 3D effects.
With most applications, you won’t notice any slowdown. However, if you’re playing a game, this adds additional overhead, slowing down the game. Some people have reported the redirection can reduce performance by up to 20%.
With the latest updates, both Ubuntu 12.10 and 12.04 now have the “Unredirect Fullscreen Windows” option enabled by default. When this option is enabled, full-screen games will run at maximum speed, skipping the compositing manager and its slowdowns. Ensure you’re updated using Ubuntu’s Update Manager so you can take advantage of this improvement."