A good start to debug various slowdowns in programs is to analyze virtual memory usage, especially on machines with low amounts of RAM.
I wrote swaptop to
calculate which processes use swap, and how much swapped:
% swaptop
293240 hotot 29421
140880 firefox 26337
90760 evince 1856
84472 skype 1674
...
It shows kbytes of swap used by the process and its pid.
Since some kernel version the swap usage is presented directly in
/proc/$$/status, which makes the script pretty trivial. But before
that, you had to calculate swap usage by adding up swapped pages from
/proc/$$/smaps, which makes the script a bit slow on such old kernels.
NP: Die Schnitter—Aderlass