Sounds easy, doesn’t it? Well it actually is quite simple but the error messages along the way can really trip you up!
My first attempt at profiling a bit of code was to use the full-boat Eclipse stack: Eclipse Test & Performance Tools Platform Project! Well, what they don’t tell you anywhere on the project page is that it’s only supported on Windows and Linux. A Mac port was started sometime around 2004 and never completed. Yeah, it’s been that long!
And so this brings us to Apple’s Shark: an extremely barebones, no-frills profiler, but, what the heck, it’s free. For the basics on using this tool with your Java app, this great post has all the details. There’s just one catch: 64-bit support. There is none. If you’re on a 64-bit stack and you try to run it, you’ll see something like the following:
$ java -agentlib:Shark -cp foo.jar com.foo.Bar
Error occurred during initialization of VM
Could not find agent library: libShark.jnilib (searched /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Libraries:/System/Library/Java/Extensions:/Library/Java/Extensions:.)
Er, what? Now let’s see here…
$ ls -al /System/Library/Java/Extensions/libShark.jnilib
-rwxr-xr-x 1 root wheel 50352 Oct 24 2010 /System/Library/Java/Extensions/libShark.jnilib
Well, that’s odd. But it said it looked there, right?! Well, as it turns out, the Shark JNI library only supports 32-bit JVMs. So finally, we arrive at the following:
$ java -d32 -agentlib:Shark -cp foo.jar com.foo.Bar
2011-05-18 23:05:20.756 java[84473:20f] Shark for Java enabled...
Great sucess! And now, back to work, just a little less sane…