Pretenuring for Java

Pretenuring can reduce copying costs in garbage collectors by allocating lo ng-lived objects into regions that the garbage collector will rarely, if ev er, collect. We extend previous work on preterturing as follows. (1) We pro duce pretenuring advice that is neutral with respect to the garbage collect or algorithm and configuration. We thus can and do combine advice from diff erent applications. We find that predictions using object lifetimes at each allocation site in Java programs are accurate, which simplifies the preten uring implementation. (2) We gather and apply advice to applications and th e Jalapeno JVM, a compiler and run-time system for Java written in Java. Ou r results demonstrate that building combined advice into Jalapeno from diff erent application executions improves performance regardless of the applica tion Jalapeno is compiling and executing. This build-time advice thus gives user applications some benefits of pretenuring without any application pro filing. No previous work pretenures in the run-time system. (3) We find tha t application-only advice also improves performance, but that the combinati on of build-time and application-specific advice is almost always noticeabl y better. (4) Our same advice improves the performance of generational and Older First collection, illustrating that it is collector neutral.