Current processor allocation techniques for highly parallel systems are typically restricted to con­tiguous allocation strategies for which performance suffers significantly due to the inherent problem of fragmentation. As a result, message passing systems have yet to achieve the high utilization levels exhibited by traditional vector supercomputers. We are investigating processor allocation algorithms which lift the restriction on contiguity of processors in order to address the problem of fragmentation.

Three non-contiguous processor allocation strategies: Paging allocation, Random allocation and the Multiple Buddy Strategy (MBS) are proposed and studied in this paper. Simulations compare the performance of the non-contiguous strategies with that of several well-known contiguous algorithms. We show that non-contiguous allocation algorithms perform better overall than the contiguous ones, even when message-passing contention is considered. We also present the results of experiments on an Intel Paragon XP/S-15 with 208 nodes that show non-contiguous allocation is feasible with current technologies.