Abstract

The well-known periodic task model of Liu and Layland [1] assumes a worst-case execution time bound for every task and may be too pessimistic if the worst-case execution time of a task is much longer than the average. In this paper, we give a multiframe real-time task model which allows the execution time of a task to vary from one instance to another by specifying the execution time of a task in terms of a sequence of numbers. We investigate the schedulability problem for this model for the preemptive fixed priority scheduling policy. We show that a significant improvement in the utilization bound can be established in our model. This work is supported by a grant from the Office of Naval Research under grant number N00014-94-1-0582. 1 INTRODUCTION 2 1 Introduction The well-known periodic task model by Liu and Layland(L&L) [1] assumes a worst-case execution time bound for every task. While this is a reasonable assumption for process-control-type real-time applications, it may be o...

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