Optimizing object reference checks on real-time Java virtual machine

Thanks to Real-Time Specification for Java (RTSJ), Java now can be applied in real-time systems. However, in RTSJ´s memory management system, assignment rules which aimed to prevent the creation of dangling references must be checked by real-time Java virtual machines (JVMs) at runtime. These frequent runtime object reference checks lead to additional time overhead and unpredictable running time, which has great impact on real-time systems. This paper presents an equivalence class based, context sensitive and flow insensitive escape analysis algorithm which could eliminate unnecessary runtime reference checkpoints. This optimization framework has been implemented in an open-source real-time JVM jRate 0.3.7.2–3.3.3 and evaluated by CDx, a relative authority real-time Java benchmark suite. The results show that this optimization algorithm eliminates 94.92% static reference checkpoints, on average removes 42.28%∼54.44% runtime reference checkpoints, and improves the runtime performance of average 3.13%, max 8.93%.