In hard real-time systems timeliness is as important as functional correctness. Such systems contain so called hard real-time tasks (HRT tasks) which must be finished by a given deadline. One of the methods of scheduling of HRT tasks is periodic loading introduced by Schweitzer, Dror, and Trudeau. The paper presents an extension to that method which allows for deterministic utilization of cache memory in hard real-time systems. It is based on a new version of the Knapsack problem named Knapsack-Lightening. In the paper the Knapsack- Lightening problem is defined, its complexity is analyzed, and an exact algorithm along with two heuristics are presented. Moreover the application of the Knapsack-Lightening problem to scheduling HRT tasks is described.

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