Evaluation and optimization of method calls in java

Recent advances in Virtual Machine\u2019s technology have led to the diffusion of Java execution environments which provide performance levels comparable to those of traditional languages such as C/C++ and Fortran. This paper\u2019s focus is on method calls, a well researched area of compilers\u2019 optimization. In particular, we evaluate the impact on the performance of the Java virtual call mechanism and the advantages which can be obtained through the inlining optimization. Moreover, we propose a new heuristic methodology which allows us to consider whole sequences of methods for the inlining decision and not only simple couples of caller\u2013callee methods. The proposed methodology operates at bytecode level and is applicable only to the calls that can be resolved at compile time. Thus, we execute a devirtualization algorithm before the inlining decision, in order to enlarge the basis for the optimization. We made empirical measures on three major platforms (Unix, Windows and Linux) by using the SPEC JVM98 benchmark suite. Results reveal an average performance improvement of 1.9% with devirtualization and 5.5% with inlining. We discuss the different behaviour of single benchmarks and virtual machines, arguing that dynamic compilers are not yet able to fully exploit the wider scope for intraprocedural optimization offered by eliminating the calls. Finally, we show that taking into consideration whole sequences of calls\u2014instead of single calls\u2014is effective only on a few benchmarks where hotspots of execution involve cycles of nested methods