A Comparative Analysis of Space- and Time-Sharing Techniques for Parallel Job Scheduling in Large Scale Parallel Systems

Effective scheduling strategies to improve response times, throughput, and utilization are an important consideration in large supercomputing environments. Such machines have traditionally used spacesharing strategies to accommodate multiple jobs at the same time. 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 greatly improve the performance figures 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.