Getting YourKit. You can download YourKit from the URL above, but have also installed YourKit into the javaplt account on CSnet. Here are instructions if you want to use it. Please note that this is for the Linux environment on CSnet. For Windows and MacOS, or away from CSnet, these steps don't apply.

Location of YourKit on CSnet. YourKit is located in the directory /home/javaplt/packages/yjp-6.0.11 . You should add the bin path to your PATH environment variable. Make the following directory accessible from everywhere: /home/javaplt/packages/yjp-6.0.11/bin . That gives you access to the two most important scripts, yjp.sh and yjpjava .

Adding the Library. Before you can use Yourkit, you have to set the following environment variable: export LD_LIBRARY_PATH="/home/javaplt/packages/yjp-6.0.11/bin/linux-x86-32" . If you already have an LD_LIBRARY_PATH variable, then you should extend it by adding a colon and the path: export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:/home/javaplt/packages/yjp-6.0.11/bin/linux-x86-32" .

Starting YourKit. To start YourKit, run the following script from the command line: yjp.sh & . The & at the end will make YourKit run in the background, i.e. you can still use the same command line window you've been using. The first time you start YourKit, it should ask you for your license information. If you are a member of the core DrJava development team, you should have by now received your personalized license key.

Starting the Application to Profile. You need to pass a special command line argument to your java executable when you're running a program that you want to profile: -agentlib:yjpagent . To make that easier to remember, I have written a script that passes that arguments, and all the argument passed to the script, to java. It's located in the same directory as Yourkit: /home/javaplt/packages/yjp-6.0.11/bin/yjpjava . If you added YourKit to your path in step 2, it should be directly accessible. If you want to use it to run a program that you would normally start with: java MyClass . now just use: yjpjava MyClass . Here is a more complicated example to start DrJava. Instead of writing java -cp drjava-15.jar edu.rice.cs.drjava.DrJava . now write the following, which avoids the restart, which may cause trouble: yjpjava -cp drjava-15.jar edu.rice.cs.drjava.DrJavaRoot . For this to work, you have to make sure that you have the tools.jar file on your Java CLASSPATH environment variable. Regardless, the application you just started should launch now.

Starting to Profile. When you actually want to record usage times and counts, press the "Start CPU Profiling" button. That will open another pane. There are two selections, "Sampling" and "Tracing", and as far as I know, "Sampling" records times only and doesn't give you invocation counts and call stacks, but is faster. "Tracing" is a lot slower but gives you more information.

Viewing Data. When you want to view the data, i.e. when you're done performing the action you want to profile, press the "Capture Snapshot" button. That will bring up a dialog that tells you the file name as which the snapshot has been saved, and it asks you whether you want to open the snapshot. You probably want to press "Open" if you want to look at the data right now.

Taking a Snapshot Stops Profiling. Note that taking a snapshot stops profiling, so if you want to continue to profile, you need to press the "Start CPU Profiling" button again.

Sorting Methods. On the page that displays CPU snapshot informations, there are lots of ways to gather information. I haven't explored everything. I found selecting "Method List" on the left the most useful. That will give you a lsit of all methods that were called, and you can sort by name, time, own time, and invocation count (if you used tracing). Time includes time spent in calls to other methods, i.e. the time from method entry to method exit. Own time is only the time spent in the actual method, i.e. the time from method entry to method exit EXCLUDING the time spent in other methods that were called.

Finding the Hotspot. Usually I found a very sharp break between the times, i.e. going from 40 seconds in some methods (that were probably in a call chain) to 5 seconds. My intuition tells me that the last method to have a lot of time spent is one of the "hot spots". You should also look at the invocation count: The program may spend a lot of time in a method, but if it's called very often, that may not mean very much.