I'm the systems programmer. Feeling much more confident, the closer I get to the hardware, I have a very extensive knowledge of the JRE on its lowest levels including instrumentation, bytecode processing, native implementation, JNA, and JNI.
Things that irk me:
People who shun others for asking performance questions out of curiosity. There is nothing wrong with looking under the hood of the JRE. I'll defend the original posters' low level questions from the high level zealots til my dying breath.