Dalvik Tracing JIT 虛擬函式呼叫效能改進

Abstract

Many devirtualization techniques had been proposed to reduce the runtime overhead of dynamic method calls for various object-oriented languages. However, most of devirtualization techniques are unsuitable for mobile devices because mobile device are resource-constrained. For instance, guarded test with method inlining raises the memory requirement for programs. Furthermore, some of the devirtualization techniques are hard to implement on a Just-In-Time (JIT) compiler since they are too complicate to satisfy the requirement of the JIT compiler. In this thesis, our experiments are implemented base on one of the major mobile device operating system, Android. We improve several well-known devirtualization techniques to fit the demand for Android’s runtime virtual machine – Dalvik. Since Dalvik is trace-based JIT compiler, we increase the opportunity of flow sensitive devirtualization by utilizing the property of trace. Dalvik JIT compiler had introduced guarded test for prediction of virtual method. In order to reduce the action of jump back to interpreter when miss prediction, we increase the prediction cache size. Overall, we improve the execution performance by ranging from 5% to 10%.