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Decrypting the Java Gene Pool: Predicting Object Lifetimes With Micro-Patterns

Sebastien Marion, Richard Jones and Chris Ryder

The 2007 International Symposium on Memory Management (ISMM 2007)
Montreal, Canada, 21-22 October, 2007


Pretenuring long-lived and immortal objects into regions that are infrequently or never collected can reduce garbage collection costs significantly. However, extant approaches to pretenuring are either application-specific, which require extremely computationally expensive off-line profiling, or use only 'build-time' prediction based on behaviour common to all programs, i.e. of allocation by the virtual machine itself rather than application programs.

In contrast, we show how a simple program analysis, combined with an object lifetime knowledge bank, can be exploited to match both runtime system and application program structure with object lifetimes. The analysis is cheap (with complexity linear in the size of the program), so need not be run ahead of time. We obtain performance gains of up to 48% in garbage collection time against a generational copying collector.

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