Computer Laboratory

Technical reports

Scheduling for a share of the machine

J. Larmouth

October 1974, 29 pages

Abstract

This paper describes the mechanism used to schedule jobs and control machine use on the IBM 370/165 at Cambridge University, England. The same algorithm is currently being used in part at the University of Bradford and implementations are in progress or under study for a number of other British Universities.

The system provides computer management with a simple tool for controlling machine use. The managerial decision allocates a share of the total machine resources to each user of the system, either directly, or via a hierarchial allocation scheme. The system then undertakes to vary the turnaround of user jobs to ensure that those decisions are effective, no matter what sort of work the user is doing.

At the user end of the system we have great flexibility in the way in which he uses the resources he has received, allowing him to get a rapid turnaround for those (large or small) jobs which require it, and a slower turnaround for other jobs. Provided he does not work at a rate exceeding that appropriate to his share of the machine, he can request, for every job he submits, the ‘deadline’ by which he wants it running, and the system will usually succeed in running his job at about the requested time – rarely later, and only occasionally sooner.

Every job in the machine has its own ‘deadline’, and the machine is not underloaded. Within limits, each user can request his jobs back when he wants them, and the system keeps his use to within the share of the machine he has been given. The approach is believed to be an original one and to have a number of advantages over more conventional scheduling and controlling algorithms.

Full text

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BibTeX record

@TechReport{UCAM-CL-TR-2,
  author =	 {Larmouth, J.},
  title = 	 {{Scheduling for a share of the machine}},
  year = 	 1974,
  month = 	 oct,
  url = 	 {http://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-2.pdf},
  institution =  {University of Cambridge, Computer Laboratory},
  number = 	 {UCAM-CL-TR-2}
}