Detecting unwanted synchronization in java programs

Abstract

A program's performance can be significantly improved by removing unwanted synchronization that causes time consuming tasks to run serially instead of in parallel. In large programs, especially those using libraries, it is usually difficult to manually detect unwanted synchronization. We describe an approach for automatically detecting unwanted synchronization in Java programs, including a detailed algorithm for computing the monitors involved in the synchronization. Our approach is highly scalable and is thus applicable to programs of realistic size. We have implemented this approach and tested it on several real problems, some of which are large. We present computational experience on both small and large examples, demonstrating that unwanted synchronization exists in practice, and that significant performance improvements are obtainable when unwanted synchronization is removed.