Under Linux, how do I find out which process is using the swap space more?
I suppose you could get a good guess by running top and looking for active processes using a lot of memory. Doing this programatically is harder---just look at the endless debates about the Linux OOM killer heuristics.
Swapping is a function of having more memory in active use than is installed, so it is usually hard to blame it on a single process. If it is an ongoing problem, the best solution is to install more memory, or make other systemic changes.