How do I Save the Heap (Dump to a File) in Eclipse

Question

I'm getting this error when I run or debug my GA/AI from MyEclipse:

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space

eclipse.ini looks like this:

-showsplash com.genuitec.myeclipse.product
--launcher.XXMaxPermSize 256m
-vmargs
-Xms128m
-Xmx512m
-Duser.language=en 
-XX:PermSize=128M 
-XX:MaxPermSize=256M

MyEclipse is called like this:

"C:\Program Files\MyEclipse 6.0\eclipse\eclipse.exe" -vm "C:\Program Files\MyEclipse 6.0\jre\bin\javaw.exe"  -vmargs -Xms1448M -Xmx1448M

bumping the vm settings up from this:

"C:\Program Files\MyEclipse 6.0\eclipse\eclipse.exe" -vm "C:\Program Files\MyEclipse 6.0\jre\bin\javaw.exe"  -vmargs -Xms80M -Xmx1024M

has had no effect. So I'm trying to get it to dump the heap to a file, but placing these:

-XX:+HeapDumpOnCtrlBreak
-XX:+HeapDumpOnOutOfMemoryError

in the Program arguments has had no effect. How do I get something to work with more memory usage analysis? jstack, for instance, is not currently available on Windows platforms. And using SendSignal has no effect that I can see.

Answer 1

There are a number of ways to get heap dumps. Here are some I've used:

1. -XX:+HeapDumpOnOutOfMemoryError should get you dump if you hit your OOM.
2. Connect with VisualVM (free) and use its GUI to force a heap dump
3. Use one of the many good commercial profilers (JProfiler, YourKit, ...)
4. Use jmap (see below) to force a dump from a running process

If you're running Java 6, jmap should work on Windows. This might be useful if you want to dump the heap and you haven't hit your OOM. Use Windows Task Manager to find the pid of your Java app, and in a console run this:

jmap -dump:format=b,file=c:\heap.bin <pid>

In addition to VisualVM, the Eclipse Memory Analyzer (also free) can help you analyze what's eating up all the space once you've got the dump.

Answer 2

You can monitor memory usages with JConsole.

The jstat also will help.

Answer 3

-XX:+HeapDumpOnOutOfMemoryError should be put in "VM Arguments" not "Program Arguments"