Performance Impact of Multithreaded Java Semantics on Multiprocessor Memory Consistency Models

The semantics of Java multithreading dictates all possible behaviors that a multithreaded Java program can exhibit on any platform. This is called the Java memory model and describes the allowed re-orderings among the operations in a thread. However, multiprocessor platforms traditionally have a memory consistency model of their own. Consequently memory barriers may have to be inserted to ensure that the multiprocessor execution of a multithreaded Java program respects the Java Memory Model. In this paper, we study the impact of these additional memory barriers on multiprocessor performance. We also study how different choices of the Java Memory Model affect multiprocessor performance. Our experimental results are obtained by simulating multithreaded Java Grande benchmarks under various software and hardware memory models.