"DTrace can be used to get a global overview of a running system, such as the amount of memory, CPU time, filesystem and network resources used by the active processes. It can also provide much more fine-grained information, such as a log of the arguments with which a specific function is being called, or a list of the processes accessing a specific file."

For anyone else that wasn't aware what Dtrace does.

Wikipedia Link: http://en.wikipedia.org/wiki/DTrace