Efficient monitoring and display of thread state in Java

How many times have you asked yourself the question "what is my program doing now?" JIVE is a system that tries to answer this question. It provides insights into the execution of Java programs. It does so with minimal overhead so it can be used on arbitrary systems at any time. A large portion of the complexity of Java systems comes from the behavior and interaction of multiple threads. Thus, JIVE concentrates in part on showing what the various threads are doing. This paper describes how JIVE does this. It first describes our original approach, which simply monitored the state of each thread, displaying the time spent in each state on an interval basis. We then describe how we extended this framework to provide additional detailed information on state changes and on thread interactions. The core of this paper describes the problems that arose here, their solutions, and the resultant visualizations.