Brinkley Sprunt, David Kirk, Lui Sha

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The effect of three I/O controller architectures on schedulable utilization, which is the highest attainable resource utilization at or below which all deadlines can be guaranteed, is examined. FIFO (first-in-first-out) request queuing, priority queuing, and priority queuing with preemptable service are simulated for a range of CPU computation to I/O traffic ratios. The results show that, for I/O-bound task sets and zero preemption costs, priority queuing with preemptable service can provide a level of schedulable utilization 35% higher than that attainable with FIFO queuing, and 20% higher than priority queuing and nonpreemptable service. Although the potential gain for priority queuing with preemptable service is large, further simulations that incorporate a time penalty for each preemption show that the gain is very sensitive to preemption cost. With preemption cost represented as a ratio of preemption time to the minimum-task period, the level of schedulable utilization for priority queuing with preemptable service degrades to that of priority queuing with nonpre-emptable service, for a preemption cost ratio of 0. 04. A high-level design of a preemptable I/O controller is described and the issues determining preemption cost are detailed, along with techniques for its minimization.

Original languageEnglish (US)
Title of host publicationUnknown Host Publication Title
Number of pages8
ISBN (Print)0818608617
StatePublished - 1988
Externally publishedYes

ASJC Scopus subject areas

  • Engineering(all)


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