Efficient Scheduling for Real-Time Pinwheel Tasks on DVS Processors

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In this paper, we focus on the pinwheel task model for a variable voltage processor with d discrete voltage/speed levels. We propose an intra-task DVS algorithm which constructs a minimum energy schedule for k tasks in O(d+ k log k) time. Previous approaches solve this problem by generating a canonical schedule beforehand and adjusting the tasks' speed in O(dn log n) or O(n3) time. However, the length of a canonical schedule depends on the hyperperiod of those task periods and is of exponential length in general. In our approach, the tasks with arbitrary periods are first transformed into harmonic periods and then profile their key features. Afterward, an optimal discrete voltage schedule can be computed directly from those features.