MC 2

Abstract

Java is becoming an important platform for memory-constrained consumer devices such as PDAs and cellular phones, because it provides safety and portability. Since Java uses garbage collection, efficient garbage collectors that run in constrained memory are essential. Typical collection techniques used on these devices are mark-sweep and mark-compact. Mark-sweep collectors can provide good throughput and pause times but suffer from fragmentation. Mark-compact collectors prevent fragmentation, have low space overheads, and provide good throughput. However, they can suffer from long pause times. Copying collectors can provide higher throughput than either of these techniques, but because of their high space overhead, they previously were unsuitable for memory-constrained devices. This paper presents MC² (Memory-Constrained Copying), a copying generational garbage collector that meets the needs of memory-constrained devices with soft real-time requirements. MC² has low space over-head and tight space bounds, prevents fragmentation, provides good throughput, and yields short pause times. These qualities make MC² attractive for other environments, including desktops and servers.