Automated just-in-time compiler tuning
Managed runtime systems, such as a Java virtual machine (JVM), are complex pieces of software with many interacting components. The Just-In-Time (JIT) compiler is at the core of the virtual machine, however, tuning the compiler for optimum performance is a challenging task. There are (i) many compiler optimizations and options, (ii) there may be multiple optimization levels (e.g., -O0, -O1, -O2), each with a specific optimization plan consisting of a collection of optimizations, (iii) the Adaptive Optimization System (AOS) that decides which method to optimize to which optimization level requires fine-tuning, and (iv) the effectiveness of the optimizations depends on the application as well as on the hardware platform. Current practice is to manually tune the JIT compiler which is both tedious and very time-consuming, and in addition may lead to suboptimal performance. This paper proposes automated tuning of the JIT compiler through multi-objective evolutionary search. The proposed framework (i) identifies optimization plans that are Pareto-optimal in terms of compilation time and code quality, (ii) assigns these plans to optimization levels, and (iii) fine-tunes the AOS accordingly. The key benefit of our framework is that it automates the entire exploration process, which enables tuning the JIT compiler for a given hardware platform and/or application at very low cost. By automatically tuning Jikes RVM using our framework for average performance across the DaCapo and SPECjvm98 benchmark suites, we achieve similar performance to the hand-tuned default Jikes RVM. When optimizing the JIT compiler for individual benchmarks, we achieve statistically significant speedups for most benchmarks, up to 40% for startup and up to 19% for steady-state performance. We also show that tuning the JIT compiler for a new hardware platform can yield significantly better performance compared to using a JIT compiler that was tuned for another platform.