A Delay-Optimal Quorum-Based Mutual Exclusion Algorithm for Distributed Systems

ÐThe performance of a mutual exclusion algorithm is measured by the number of messages exchanged per critical section execution and the delay between successive executions of the critical section. There is a message complexity and synchronization delay trade-off in mutual exclusion algorithms. The Lamport algorithm and the Ricart-Agrawal algorithm both have a synchronization delay of T (T is the average message delay), but their message complexity is O…N†. Maekawa's algorithm reduces the message complexity to O…  N p †; however, it increases the synchronization delay to 2T . After Maekawa's algorithm, many quorum-based mutual exclusion algorithms have been proposed to reduce the message complexity or the increase the resiliency to site and communication link failures. Since these algorithms are Maekawa-type algorithms, they also suffer from the long synchronization delay. In this paper, we propose a delay-optimal quorum-based mutual exclusion algorithm which reduces the synchronization delay to T and still has a low message complexity of O…K† (K is the size of the quorum which can be as low as logN). A correctness proof and a detailed performance analysis are provided. Index TermsÐQuorum, synchronization delay, distributed mutual exclusion, fault tolerance.