Java Magazine, Mar/Apr 2018
ORACLE COM JAVAMAGAZINE MARCH APRIL 2018 80 inside the jvm Metaspace used 2665K capacity 4490K committed 4864K reserved 1056768K class space used 286K capacity 386K committed 512K reserved 1048576K In this case you can clearly see the GC events that are caused by allocation failure as the Eden area of memory fills up and needs to be collected Conclusion The addition of EA to the Java HotSpot VM is a useful improvement When EA was in development an additional 3 to 6 performance increase in real world tests was seen that was directly attributable to it However for the developer who is also interested in the how and why of platform features EA provides an interesting insight it is a feature that depends upon another optimization automatic inlining and is essentially useless without it The low level details and the source code of the JVMs implementation can be found in opto escape hpp in the Java HotSpot VM source code It is a modified form of the algorithm presented in the Escape Analysis for Java proceedings of the ACM SIGPLAN Object Oriented Programming Systems Languages and Applications OOPSLA conference in November 1999 by Jong Deok Choi Manish Gupta Mauricio Serrano Vugranam C Sreedhar and Sam Midkif In addition to allocation elimination within the Java HotSpot VM there are several other optimization techniques that depend upon similar scope analysis to that which is used for allocation elimination These mostly work with the intrinsic locks that Java provides for each object Well discuss those optimizations in the next issue 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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