An Analysis of Preemptive Multiprocessor Job Scheduling

Abstract

The preemptive scheduling of a partially ordered set of tasks is studied. A class of scheduling heuristics is introduced, and the performance of schedules in this class is analyzed with respect to the least finishing time optimality criterion. If there are m processors, then the finishing time of any schedule in the class is at most √m + (1/2) times worse than optimal, independent of the speeds of the processors. Examples are given which indicate that there are schedules whcih may be as bad as √m-1 times worse than optimal even for machines with one fast processor.