Garbage Collection and Skipped Turns
What profiling tool do you use? I haven't tried that many, but I've been rather unsuccessful trying to use profiling tools on Robocode. The last one I tried was Visual VM, but when you try to profile a running instance of Robocode with Visual VM, it prompts for a username and password. I kind of gave up and assumed I would run into similar trouble with all profiling tools, either due to the Robocode security setup or due to the odd way that Robocode loads classes and sandboxes robots. If you know of a profiling tool that works with existing Robocode, please share!
I tried VisualVM and when it asked for username/pw I just did a/a and it worked, I suspect it asks for them but doesn't actually use them.
Make sure you start robocode with -Ddebug=true so that it disables skipped turns!
I got Visual VM working and running through Eclipse too. Its a bit unintuitive to set up through Eclipse but its working now and easy to run. As MN says you can filter out any results from specific packages and just profile your bot (though its worth noting that you might want to leave any java data structure packages such as the Vector class if you use it a lot in your robot).
I managed to get my movement running pretty fast within an hour of getting Visual VM running! :D
If I find the time I might write a wiki page on how to get it up and running in Eclipse and how to set it up to profile your robot.