A Performance Evaluation of Lock-Free Synchronization Protocols

Abstract

In this paper, we investigate the practical performance of lock-free techniques that provide synchronization on shared-memory multiprocessors. Our goal is to provide a technique to allow designers of new protocols to quickly determine an algorithm’s performance characteristics. We develop a simple analytical performance model based on the architectural observations that memory accesses are expensive, synchronization instructions are more expensive, and that optimistic synchronization policies result in wasted communication bandwidth which can slow the system as a whole. Using our model, we evaluate the performance of five existing lock-free synchronization protocols. We validate our analysis by comparing our results with simulations of a parallel machine. Given this analysis, we identify those protocols which show promise of good performance in practice. In addition, we note that no existing protocols provide insensitivity to common delays while still offering performance equivalent to locks. Accordingly, we introduce a protocol, based on a combination of existing lock-free techniques, which satisfies these criteria.