Java Magazine, May/June 2018
ORACLE COM JAVAMAGAZINE MAY JUNE 2018 85 inside the jvm EscapeTestArraySize arraySize63 49814492787 2K ops s EscapeTestArraySize arraySize64 49815595566 6K ops s EscapeTestArraySize arraySize65 49818143279 2K ops s Notice the parity in the results Conclusion This article and the previous one on escape analysis show some of the magic that occurs behind the scenes in the HotSpot JVM They also convey some of the complexity of the operations Each major release of Java tends to add new features to the JVM In fact Oracle is investing in a new generation of compiler technology Known as Graal it is a just in time JIT compiler that is pluggable user extensible and written in Java It is a major effort within Project Metropolis which aims to build as much of a runtime in Java as is practical The Graal compiler is an experimental addition to Java 10 as described in JEP 317 The principal aim is to provide a way for developers and specialist platform owners to write their own JIT compilers to meet their specific needs Graal is a very amenable environment in which to introduce and prototype optimization techniques This article and its predecessor described scope analysis that enables a variety of optimization techniques First among these is allocation elimination that is scalar replacement but related locking techniques were discussed as well These are just some examples of JIT compilation techniques that are present in the mature C2 compiler in the HotSpot JVM Upcoming articles will examine other techniques that the HotSpot JVM uses to improve code performance article Ben Evans @ kittylyst is a Java Champion a tech fellow and founder at jClarity an organizer for the London Java Community LJC and a member of the Java SE EE Executive Committee Chris Newland @ chriswhocodes is a Java Champion He invented and still leads developers on the JITWatch project an open source log analyzer to visualize and inspect just in time compilation decisions made by the HotSpot JVM
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