| Summary: | 碩士 === 國立臺灣科技大學 === 資訊管理系 === 92 === This paper considers migratory and non-migratory tasks in a multiprocessor Pfair scheduling system. Pfairness, first proposed by Baruah et al., is the current proposed optimal periodic scheduling algorithm to schedule periodic tasks in a real-time system. By using the original Pfair scheduling algorithm, a task set of migratory and non-migratory tasks may result in some tasks missing their deadlines, and this problem is first exposed by Moir and Ramamurthy.
A new MPD scheduling algorithm is proposed by us to schedule tasks in order to meet their Pfair requirements and not to miss their deadlines. MPD algorithm does not increase each task’s weight or waste the precious processor time. MPD is modified from the original Pfair scheduling algorithm, and combines all non-migratory tasks that must be scheduled on the same processor into a single supertask. Furthermore, we also modify supertask priority definition.
The time complexity of MPD algorithm is the same as that of the original Pfair scheduling algorithm. Its main advantage is to reduce the requirement of reweighting each supertask; hence, some of these additional time slots are required to schedule some non-migratory tasks that will miss their deadlines. Some time slots which are allocated to the supertask may not be utilized by component tasks. However, MPD does not result in this problem and waste the processor time.
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