The performance of processor co-allocation in multicluster systems

In systems consisting of multiple clusters of processors which are interconnected by relatively slow communication links and which employ space sharing for scheduling jobs, such as our Distributed ASCI Supercomputer (DAS), co-allocation, i.e., the simultaneous allocation of processors to single jobs in different clusters, may be required. We study the performance of co-allocation by means of simulations for the mean response time of jobs depending on the structure and sizes of jobs, the scheduling policy, and the communication speed ratio. Our main conclusion is that for current communication speed ratios in multiclusters, coallocation is a viable option.