The upcoming release of JRockit will contain a new, completely killing, tool for memory leak detection.
It allows you to (among many other things) to profile an application running in production with (almost) zero overhead (without shutting it down or any preparation whatsoever).
If you are interested to find out more, we have set up a webinar demo that anyone can join. Drop me an email at [jboner AT gmail DOT com] and I will send you the 'dial in info'.
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Update: here is the dial in info (no need to mail me):
---------------------------- Web Meeting ---------------------------------
When: Wednesday, March 23, 2005 10:00 AM-11:00 AM (GMT-07:00) Arizona.
Where: Dial In/Web Meeting
Web Meeting Address: https://www.webmeeting.att.com
Toll Free Dial In Number: (866)214-3176
Int'l Access/Caller Paid Dial In Number: (404)827-9098
ACCESS CODE: 5519740
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