Speculative Multithreading in a Java Virtual Machine

Speculative multithreading (SpMT) is a dynamic program parallelisation technique that promises dramatic speedup of irregular, pointer-based programs as well as numerical, loop-based programs. We present the design and implementation of software-only SpMT for Java at the virtual machine level. We take the full Java language into account and we are able to run and analyse real world benchmarks in reasonable execution times on commodity multiprocessor hardware. We provide an experimental analysis of benchmark behaviour, uncovered parallelism, the impact of return value prediction, processor scalability, and a breakdown of overhead costs.