This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
You need to track what the garbage collector is doing. See my paper at ceCMG for one way you could do this. (And no, using JConsole does not provide the necessary information - you need to know how much heap space is in use after each major collection.)