Combining Single-Space and Two-Space Compacting Garbage Collectors

The garbage collector presented in this paper makes use of two well known compaction garbage collection algorithms with very diierent performance characteristics: Cheney's two-space copying collector and Jon-ker's single-space sliding compaction collector. We propose a scheme which allows either collector to be used. The run-time memory requirements of the program being executed are used to determine the most appropriate collector. This enables us to achieve a fast collector for heap requirements less than half of the heap memory but allows the heap utilization to increase beyond this threshold. Using these ideas we develop a particularly attractive extension to Appel's generational collector.