Research: Effective queueing strategies for co-scheduling in a pool of processors

  • Authors:

  • Margaret A. Schaar;Kemal Efe

  • Affiliations:

  • Department of Mathematics and Computer Science, Grambling State University, Grambling, LA 71245, USA;Center for Advanced Computer Studies, University of Southwestern Louisiana, Lafayette, LA 70504, USA

  • Venue:
  • Computer Communications
  • Year:
  • 1996

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Abstract

We consider a connected set of workstations as a 'pool of processors' and develop a queueing model to analyse the performance of optimal co-scheduling algorithms. The pool of processors model was originally developed for the Amoeba operating system. It was also used in the design of the recent IBM supercomputer model 9076 SPI. Recently, co-scheduling has been suggested as an approach for scheduling computationally intensive tasks in the pool of processors model. Co-scheduling algorithms select the best possible subset of workstations for a task to minimize its completion time. The queueing model developed here allows us to investigate the dynamic performance of co-scheduling algorithms from the system point of view under several queueing strategies. We use six different queueing strategies in combination with co-scheduling, and compare the results to the M/M/m system, where arriving tasks would be assigned to workstations as whole computations, and no co-scheduling would take place. The results show that the co-scheduling approach is viable under a wide range of system parameters. Moreover, performance differences of queueing strategies tend to diminish as the number of workstations grows. This suggests that co-scheduling is universally applicable across the queueing disciplines considered here when there are a large number of workstations.