Java Virtual Machines are optimized for performing well on traditional Java benchmarks, which consist almost exclusively of code generated by the Java source compiler (javac). Code generated by compilers for other languages has not received nearly as much attention, which results in performance problems for those languages.
One important specimen of "another language" is Scala, whose syntax and features encourage a programming style that differs significantly from traditional Java code. It suffers from the same problem -- its code patterns are not optimized as well as the ones originating from Java code. JVM developers need to be aware of the differences between Java and Scala code, so that both types of code can be executed with optimal performance.
This paper presents a detailed investigation of the performance impact of a large number of optimizations on the Scala DaCapo and the Java DaCapo benchmark suites. It describes the optimization techniques and analyzes the differences between traditional Java applications and Scala applications. The results help compiler engineers in understanding the characteristics of Scala.
We performed these experiments on the work-in-progress Graal compiler. Graal is a new dynamic compiler for the HotSpot VM which aims to work well for a diverse set of workloads, including languages other than Java.