A New Approach for Scheduling of Parallelizable Tasks inReal-Time Multiprocessor Systems

  • Authors:
  • G. Manimaran;C. Siva Ram Murthy;Krithi Ramamritham

  • Affiliations:
  • Dept. of Computer Science and Engg., Indian Institute of Technology, Madras - 600 036, INDIA;Dept. of Computer Science and Engg., Indian Institute of Technology, Madras - 600 036, INDIA;Dept. of Computer Science, University of Massachusetts. Amherst, MA 01003, USA

  • Venue:
  • Real-Time Systems
  • Year:
  • 1998

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Abstract

In a parallelizable task model, a task can be parallelizedand the component tasks can be executed concurrently on multipleprocessors. We use this parallelism in tasks to meet their deadlinesand also obtain better processor utilisation compared to non-parallelizedtasks. Non-preemptive parallelizable task scheduling combinesthe advantages of higher schedulability and lower schedulingoverhead offered by the preemptive and non-preemptive task schedulingmodels, respectively. We propose a new approach to maximize thebenefits from task parallelization. It involves checking theschedulability of periodic tasks (if necessary, by parallelizingthem) off-line and run-time scheduling of the schedulable periodictasks together with dynamically arriving aperiodic tasks. Toavoid the run-time anomaly that may occur when the actual computationtime of a task is less than its worst case computation time,we propose efficient run-time mechanisms.Wehave carried out extensive simulation to study the effectivenessof the proposed approach by comparing the schedulability offeredby it with that of dynamic scheduling using Earliest DeadlineFirst (EDF), and by comparing its storage efficiency with thatof the static table-driven approach. We found that the schedulabilityoffered by parallelizable task scheduling is always higher thanthat of the EDF algorithm for a wide variety of task parametersand the storage overhead incurred by it is less than 3.6% ofthe static table-driven approach even under heavy task loads.