How to find out which process eats up memory?

My MacBook Pro has 8G RAM. Recently memory leak offen happened. Page outs and swap used kept increasing. The last time it used ~8G swap space. But in Activity Monitor, I can't find any process has a large value in 'Real Mem', 'Private Mem' nor 'Shared Mem' column. I checked the %MEM column in output of 'ps -ev', all processes occupied less than 1% of memory. The full output is put in this gist: https://gist.github.com/aleung/4760556 What the way to diagnose OSX memory leak issue?