The system monitor carries on a bug in xgl package wrt incorrect reporting of memory usage, and shows processes using zillion bytes of memory.
I started using xserver-xgl from the times in Gutsy when Compiz would not run on my hardware without that. However, I didnt quite notice this until I involved myself with beta release of hardy.
As it happened, I raised this issue on the Ubuntu forums (more than once actually, link-1, link-2), and finally after a few discussions/posts, it was discovered that
- xserver-xgl has a few bugs
- no more active development is happening on this stream of packages
- Compiz should work without needing this package as well.
Attaching two screenshots here to give the idea of the Martian numbers...