Empirical evaluation of distributed mutual exclusion algorithms

We evaluate various distributed mutual exclusion algorithms on the IBM SP2 machine and the Intel iPSC/860 system. The empirical results are compared in terms of such criteria as the number of message exchanges and the response time. Our results indicate that the Star algorithm (M.L. Neilsen and M. Mizuno, 1991) achieves the shortest response time in most cases among all the algorithms on a small to medium sized system, when processors request for the critical section many times before involving any barrier synchronization. On the other hand, if every processor enters the critical section only once before encountering a barrier, the improved Ring algorithm (S.S. Fu and N.-F. Tzeng, 1995) is found to outperform others under a heavy load; but the Star algorithm and the CSL algorithm (Y.I. Chang et al., 1990) prevail when the request rate becomes light. The best solution to mutual exclusion in distributed memory systems is determined by how participating sites generate their mutual exclusion requests.