A Practical Nonblocking Queue Algorithm Using Compare-and-Swap

Many nonblocking algorithms have been proposed for shared queues. Previous studies indicate that link-based algorithms perform best. However, these algorithms have a memory management problem: a dequeued node can not be freed or reused without proper handling. The problem is usually overlooked; one just assumes the existence of a lower level mechanism, which takes care of all the details of handling the problem. Employing such a mechanism incurs significant overheads, and consequently the link-based queues may not perform as well as claimed. A new nonblocking queue algorithm based on a finite array is proposed in this paper. Comparing with the link-based algorithms, the new algorithm provides the same degree of concurrency without being subject to the memory problem, hence suggests a good performance.