TECHNICAL ARTICLE Simulation Study of Task Scheduling and Resequencing in a Multiprocessing System

The performance of parallel programs such as fork-join jobs is significantly affected by the choice of policy used to schedule tasks. In this paper we present the results of a simulation study comparing three basic policies that schedule independent tasks in conjunction with resequencing of jobs. A closed queuing network model is considered; the CPU consists of homogeneous and independent processors, each serving its own queue. The simulation results reveal that the performance of the three policies is affected by the resequencing delay. It is shown that over a wide range of system parameters the first-come-first-served policy exhibits better performance than the policy that gives priority to tasks of a job having the smallest number of tasks. It is also shown that the policy that gives priority to the smallest task performs best when there are large variations in the task service times