Mosaic: A non-intrusive complete garbage collector for DSM systems

Abstract

Little work has been done in garbage collection algorithms for distributed systems. Mosaic is a safe and complete garbage collection system that collects garbage in object systems that are implemented above page-based distributed shared memory systems. It is non-intrusive in its impact on application performance. Mosaic partitions the virtual address space into separately managed regions, which form the basic unit of object storage. Garbage collection operates by moving objects between these partitions in a manner that associates live objects together leaving unreachable objects behind so that partitions may be reused. To provide for safe operation of the collector a distributed update protocol maintains sufficient local knowledge of pointer duplication and destruction to allow safe determination of object reachability without the need to globally trace the object space. Mosaic exploits the semantics of pointer operations in type-safe object languages to allow for a weakened consistency model of pointer update during garbage collection.