Comment 766 for bug 500069

because the gnome compositor is going to end up stalling waiting to get data back. Ditto switching to/from X will be pulling in lots off disk if your machine has been paging stuff out. To actually get detailed data you need to start profiling the system and generating detailed information to analyse - thats way beyond a bugzilla discussion (but the linux-mm list might be a starting point if you want to get involved in understanding what is a very complicated area - because so many things interact).

Ultimately though I suspect that unless someone does something drastic about its memory footprint the "fix" is not to run huge bloated inefficient desktops on a box with 1GB of RAM.