Java : Get heap dump without jmap or without hanging the application

Question

In few circumstance, our application is using around 12 GB of memory. We tried to get the heap dump using jmap utility. Since the application is using some GB of memory it c

Answer 1

Try the following. It comes with JDK >= 7:

/usr/lib/jvm/jdk-YOUR-VERSION/bin/jcmd PID GC.heap_dump FILE-PATH-TO-SAVE

Example:

/usr/lib/jvm/jdk1.8.0_91/bin/jcmd 25092 GC.heap_dump /opt/hd/3-19.11-jcmd.hprof

This dumping process is much faster than dumping with jmap! Dumpfiles are much smaller, but it's enough to give your the idea, where the leaks are.

At the time of writing this answer, there are bugs with Memory Analyzer and IBM HeapAnalyzer, that they cannot read dumpfiles from jmap (jdk8, big files). You can use Yourkit to read those files.