In the context of least slack first scheduling, switching may frequently be caused. The extra overheads of preemptions among tasks debase the performance of soft real-time systems significantly. In this paper, we present a novel scheduling algorithm, named dynamic fuzzy threshold least slack first (DFTLSF) scheduling, which solved the switching problem when use least slack first scheduling algorithm in tasks. The notion of dynamic fuzzy threshold coefficient was defined to fuzzy the threshold dynamicly. The slack time of the running task is reduced to its fuzzy threshold to avoid thrashing. Comparing to the traditional least slack first scheduling algorithm, the simulation results show that, the dynamic fuzzy preemption make the switching number of the novel algorithm smaller and the missed deadline percentage decreased.
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