Lock-free garbage collection for multiprocessors

Abstract

Garbage collection algorithms for shared-memory multiprocessors typically rely on some form of global synchro- nization to preserve consistency. Such global synchronization may lead to problems on asynchronous architectures: if one process is halted or delayed, other, nonfaulty processes will be unable to progress. By contrast, a storage management algorithm is lock- free if (in the absence of resource exhaustion) a process that is allocating or collecting memory can be delayed at any point without forcing other processes to block. This paper presents the first algorithm for lock-free garbage collection in a realistic model. The algorithm assumes that processes synchronize by applying read, write, and cornpre&swap operations to shared memory. This algorithm uses no locks, busy-waiting, or barrier synchronization, it does not assume that processes can observe or modify one another's local variables or registers, and it does not use inter-process interrupts. Index Terms-Garbage collection, lock-free algorithms, mem- ory management, multiprocessors, shared memory, wait-free al- gorithms.