I am running load against Tomcat 6 running on Java 6. I want to collect a heapdump of the Java heap while the Tomcat server is under load. I normally use jmap -dump to collect my heapdumps.
However, when I try to do this when Tomcat is handling a high load I find that the heapdump collection fails.
Is jmap the best tool for collecting a heap dump from a process under load? What are the possible causes which would cause jmap to fail to collect a heapdump?
If jmap is not the best tool – what is better?
It is entirely acceptable to me for jmap (or some other tool) to stop the world within the Java process while the heap dump is taken.
I have found that running Tomcat with a JMX port allows me to take a remote heapdump using visualvm. This succeeded for me when jmap failed.