Issue No. 10 - Oct. (1986 vol. 12)
C. M. Woodside , Department of Systems and Computer Engineering, Carleton University, Ottawa, Ont. K1S 5B6, Canada
Adjustable feedback schedulers control the relative performance obtained from a computer system by different classes of users. This work examines the control of relative throughputs (or other related measures such as relative utilizations or response times) by feedback of departure counts. Counts from key resources in the system are used to dynamically adjust the priorities of the different classes at certain queues, to attempt to achieve preset values of the ratios of the class throughputs. An iterative mean-value algorithm is given which approximates the throughputs actually achieved by this scheduler, within a few percent of error. Using the algorithm and some simulation results, limits of controllability are observed, beyond which the achieved throughput ratios cannot follow the preset values. A characterization is given for this “controllable performance set.” It is also shown how, using this set, the scheduler can be tuned to have approximately optimal set points for the ratios.
Throughput, Time factors, Controllability, Approximation algorithms, Indexes, Approximation methods, Computers, queue networks, Adjustable priorities, computer scheduling, control of queue networks, dynamic properties, fair sharing
C. M. Woodside, "Controllability of computer performance tradeoffs obtained using controlled-share queue schedulers," in IEEE Transactions on Software Engineering, vol. 12, no. , pp. 1041-1048, 1986.