Eclipse: Java Monitor won't show cpu statistics

Question

I am profiling a java application using jvisualvm. The CPU profile from jvisualvm has narrowed down the slow part of the code to one particular method. It doesn't say which part of the method is slow though.

To get more information I tried debugging through Eclipse using Java Monitor (available through Eclipse Marketplace). Java Monitor will attach to the application but it won't display CPU statistics. I don't know why. I have modified the JVM options using:

-agentlib:jdwp=transport=dt_socket,address=8000,server=y,suspend=y

Then I create a profile in Eclipse using:

Remote Java Application > myapplication

Here I select the source code for the project I am profiling. I start the application and it waits for the debugger to attach:

Listening for transport dt_socket at address: 8000

I right click the PID under local host and click 'Start Monitoring'

Then in Eclipse I press F11 to kick off the application. It starts running, but under 'Properties' I get everything except CPU. Any ideas greatly appreciated..

Answer 1

I don't know any Java profiler which can tell you which part of a method eats most of the time. If you can't tell by looking at the method, then your method is probably too big to understand anyway. Try to refactor it into several methods.

If you have lots of local variables, use a worker object and turn local variables into fields of the worker. That way, you can avoid writing methods with a dozen parameters and still cut a overly complex method to size.

As for why Java Monitor doesn't do what you want: You need to tell it which packages to monitor and which profiling method to use. See the documentation for details.