Faced with troubleshooting a performance issue, developers are most likely to rely on a combination of loggers, debuggers and various open-source profilers. But what if you could develop your own profiler, that too almost effortlessly.

I came across this article which explains how easily and quickly you can write your own profiler. Profilers tend to be rather expensive to run, although most have features (like selective instrumentation, sampling, etc.) that are designed to minimize their run-time impact. But they provide a general functionality, and if you learn how they are built, you can develop a compact profiler that is narrowly targeted to meet exactly what you need to do.

http://java.dzone.com/articles/java-profiling-under-covers