A circular list based mutual exclusion scheme for large shared-memory multiprocessors

Mutual exclusion in shared-memory multiprocessors is realized by employing a lock to determine the processor among those which compete for the critical section. Accesses to such a mutual exclusion lock may create heavy synchronization traffic and/or serious contention over the network, thereby degrading system performance considerably. In this paper, we introduce an efficient scheme which keeps synchronization traffic low and avoids serious hot-spot contention. This is made possible by constructing a circular list of the processors waiting for the critical section and by dispersing accesses to the lock. Extensive simulation of the proposed approach was conducted and the lower bound on the elapsed time was derived. Our simulation results demonstrate that the proposed scheme indeed achieves better performance than prior techniques, with its elapsed time close to the lower bound for the whole range of simulated system sizes, thus promising good scalability for large systems.