This is a video presentation on the status of dtrace on FreeBSD.

DTrace, also known as Dynamic Tracing, was developed by Sun™ as a tool for locating performance bottlenecks in production and pre-production systems. It is not, in any way, a debugging tool, but a tool for real time system analysis to locate performance and other issues.

DTrace is a remarkable profiling tool, with an impressive array of features for diagnosing system issues. It may also be used to run pre-written scripts to take advantage of its capabilities. Users may even author their own utilities using the DTrace D Language, allowing them to customize their profiling based on specific needs.” (source)