An integrated approach to parallel scheduling using gang-scheduling, backfilling, and migration

Effective scheduling strategies to improve response times, throughput, and utilization are an important consideration in large supercomputing environments. Parallel machines in these environments have traditionally used space-sharing strategies to accommodate multiple jobs at the same time by dedicating the nodes to a single job until it completes. This approach, however, can result in low system utilization and large job wait times. This paper discusses three techniques that can be used beyond simple space-sharing to improve the performance of large parallel systems. The first technique we analyze is backfilling, the second is gang-scheduling, and the third is migration. The main contribution of this paper is an analysis of the effects of combining the above techniques. Using extensive simulations based on detailed models of realistic workloads, the benefits of combining the various techniques are shown over a spectrum of performance criteria.