-XX:+HeapDumpOnOutOfMemoryError specify memory

Question

Hi,

I would like to specify amount of memory used when -XX:+HeapDumpOnOutOfMemoryError VM argument is used. Normally, I control the heap size using -Xmx<size> VM argument. But when I do that the out of memory error never occurs. Does anybody know a way to specify such a parameter so that when the heap size (or even the stack size) reaches that parameter the out of memory error is thrown and I can get the heap dump?

Thanks.

Answer 1

-Xmx is the right way to do this along with -Xss for the stack size to cause a StackOverflowException. If you don't get the expected OutOfMemoryError you might need to try lower values for -Xmx since the JVM tends to go somewhat beyond that limit before it throws the error and it seems to ignore anything below 15m for -Xmx.

Answer 2

To answer your question more precisely than what was provided by x4u, it would help to know the following:

Question #1: When you explicitly set -Xmx, what are you setting it to? What is the difference between the two heap sizes (with and without -Xmx). I'm assuming you're increasing the heap size when you set it explicitly.

Question #2: Does your program terminate, or run forever? If it terminates and you're not seeing the OOM, it could be that you don't have a leak, you're just not providing enough memory to your Java process.