Visualization of Multithreaded Behavior to Facilitate Maintenance of Complex Software Systems

Maintenance accounts for the major part of a software system´s total costs. Therein, program comprehension is an important, but complex activity: Typically, up-to-date documentation is not available, so the main reliable source of information on the implementation represent the artifacts of the system´s implementation. Understanding software systems is difficult, in particular, if multithreading concepts are involved because state-of-the art development tools provide only limited support for maintenance activities. In addition, concurrency is often not directly reflected by the source code, i.e., there is only a non-obvious correlation between control structures in the source code and a system´s runtime behavior. We present a program comprehension technique that helps to analyze and understand runtime behavior of multithreaded software systems and, thereby, facilitates software maintenance tasks. Our approach contains the following concepts: First, light-weight dynamic analysis records executed method calls at runtime. Second, visualization of multithreading trace data allows developers to explore the system behavior post-mortem. The technique forms part of a scalable tool suite for understanding the behavior of complex software systems. We also show how to apply the technique on industrial software systems to solve common maintenance problems.