Low Overhead Method Profiling with Java Mission Control | Marcus Hirt

Low Overhead Method Profiling with Java Mission Control | Marcus Hirt

With the Hotspot JDK 7u40 there is a nifty new tool called Java Mission Control. Users of the nifty old tool JRockit Mission Control will recognize a lot of the features. This blog focuses on the Flight Recorder tool, and the method profiling information you can get from the flight recorder.

So you want to know why all your CPUs are saturated. Perhaps you even want to get some hints as to what changes can be done to your application to make it less CPU-hungry. Don't despair – Java Mission Control to the rescue!

Built into the HotSpot JVM is something called the Java Flight Recorder. It records a lot of information about/from the JVM runtime, and can be thought of as similar to the Data Flight Recorders you find in modern airplanes. You normally use the Flight Recorder to find out what was happening in your JVM when something went wrong, but it is also a pretty awesome tool for production time profiling. Since Mission Control (using the default templates) normally don't cause more than a per cent overhead, you can use it on your production server.

Getting the Data

So, to do method profiling with JMC, simply go about producing a recording like you normally would. Here is an example:

1. Start the application you want to profile with the following arguments to enable the flight recorder:
    -XX:+UnlockCommercialFeatures -XX:+FlightRecorder 
2. Next start Mission Control. You can just double click on jmc in the bin folder of your 7u40 JDK.
3. (Close the Welcome screen if this is your first time starting JMC.)
4. Right click on the JVM you wish to start a flight recording on in the JVM browser and select Start Flight Recording.

Read full article from Low Overhead Method Profiling with Java Mission Control | Marcus Hirt