Scheduling periodic time-critical tasks on a multiprocessor system (abstract only)

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We study the problem of scheduling periodic-time-critical tasks on a multiprocessor system. A periodic-time-critical task consists of a certain number of computations, each arising at a fixed interval of time, called the period of the task. The ratio of the computation time to the period is called the utilization factor of the task. Each computation has a prescribed deadline which must be guaranteed to be met, failing which there is likely to result an irrepairable loss. The scheduling problem is to specify the processor on which a computation is to be made and the order in which such computations will be made, such that every computation meets its deadline. The goal is to minimize the number of processors needed. The problem is NP-complete. As such, we devise a heuristic algorithm and analyze its performance. The algorithm assigns tasks based on the utilization factors of the tasks. We analyze the worst case performance of the algorithm by obtaining bounds on the ratio of the maximum number of processors needed by the algorithm to the minimum number of processors required. It is shown that this ratio is 2.