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Performance Requirements Realizable by Scheduling Strategies in TimeShared Systems
Hisao KAMEDA
Publication
IEICE TRANSACTIONS (19761990)
Vol.E69
No.12
pp.13341341 Publication Date: 1986/12/25
Online ISSN:
DOI:
Print ISSN: 00000000 Type of Manuscript: PAPER Category: Computer System Keyword:
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Summary:
Realization of performance requirements by scheduling strategies is investigated on a finitesource queueing model, which has often been used as a model of timeshared systems. The model consists of a singleserver station (processor) and a multipleserver station (terminals); each job has a distinct mean service time at the processor. Performance requirements that are stated in terms of the performance vector, each element of which is the utilization factor of the processor for a job, are investigated, and the following results are obtained. First, the optimization of performance measures is discussed under Markovian assumptions. Linear performance measures such as the throughput and the mean response time can be optimized by preemptive priority disciplines, and their implementation may be simple. However, the optimization of nonlinear performance measures such as the average cost per interaction may lead to a linearly constrained nonlinear programming problem, and the schedules which optimize them may be hard to implement. Second, realization of the equal response ratio is discussed. The processor sharing (or preemptiveresume LCFS) discipline, although it attains the equal response ratio in M/G/1, gives a smaller response ratio to a job with a longer mean processor time. It is shown under Markovian assumptions that the equal response ratio is achievable by another scheduling strategy.

