Swap before RAM is filled (Score 1)

I didn't see this mentioned here, but swap space is used up before the machine fills up the physical memory. This is useful so you have a couple of megs free to run a new program, instead of having to wait to swap crap out first.
You can tune this by echoing 3 numbers to /proc/sys/vm/freepages. I can't remember where the documentation for this is, but it specifies the limits of when to start swapping and when there's so much memory free it can move it back out of swap even if its not yet been requested.
I like to set these numbers big to force swapping out sleeping processes and leave plenty free RAM to speed up starting netscape or emacs, whatever.