Java: Heap Dump on OutOfMemoryError

You can request the jvm create a heap dump when an OutOfMemoryError is thrown. This is handy if you have a process that consumes a ton of RAM and you don't know why. Set the max heap size to something around 500M (or less. It needs to be fairly small if you're going to inspect the heap with 'jhat'). Use the -XX:+HeapDumpOnOutOfMemoryError flag to request the heap dump. This will output to java_pid.hprof by default. You can set the output filename manually using -XX:HeapDumpPath=<filename>.

e.g.

> java -Xmx100m -XX:+HeapDumpOnOutOfMemoryError -XX:HeadDumpPath=/tmp/dump.hprof com.geekbraindump.MyMemoryHoggingClass