Open JDK Meets Xeon Phi: A Comprehensive Study of Java HPC on Intel Many-Core Architecture

Abstract

The increasing demand for performance has stimulated the wide adoption of many-core accelerators like Intel Xeon Phi Coprocessor, which is based on Intel's Many Integrated Core architecture. While many HPC applications running in native mode have been tuned to run efficiently on Xeon Phi, it is still unclear how a managed runtime like JVM performs on such an architecture. In this paper, we present the first measurement study of a set of Java HPC applications on Xeon Phi under JVM. One key obstacle to the study is that there is currently little support of Java for Xeon Phi. This paper presents the result based on the first porting of Open JDK platform to Xeon Phi, in which Hot Spot VM acts as the kernel execution engine. The main difficulty includes the incompatibility between Xeon Phi ISA and the assembly library of Hotspot VM. By evaluating the multithreaded Java Grande benchmark suite, we quantitatively study the performance and scalability issues of JVM on Xeon Phi and draw several conclusions from the study. To fully utilize the vector computing capability, we also present a semi-automatic vectorization in Hot Spot VM. Together with this optimization and tuning, our optimized JVM achieves up to 3.4X speedup with 60 physical cores compared to that on Xeon CPU processor. Our study indicates that it is viable and potentially performance-beneficial to run applications written for managed runtime on Xeon Phi.