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R Dobrin, G. Fohler, P. Puschner:
"Translating Offline Schedules into Task Attributes for Fixed Priority Scheduling";
Vortrag: IEEE Real-Time Systems Symposium, London, United Kingdom; 04.12.2001 - 06.12.2001; in: "Proceedings of the 22nd IEEE Real-Time Systems Symposium", (2001), S. 225 - 234.

Off­line scheduling and fixed priority scheduling (FPS) are often considered as complementing and incompatible paradigms. A number of industrial applications demand temporal properties (predictability, jitter constraints, end­ to­end deadlines, etc.) that are typically achieved by using off­line scheduling. The rigid off­line scheduling schemes used, however, do not provide for flexibility. FPS has been widely studied and used in a number of applications, mostly due to its simple run­time scheduling, and small overhead. It can provide more flexibility, but is limited with respect to predictability, as actual start and completion times of exe­ cution depend on run­time events. In this paper we show how off­line scheduling and FPS run­time scheduling can be combined to get the advantages of both -- the capability to cope with complex timing con­ straints and flexibility. The paper assumes that a schedule for a set of tasks with complex constraints has been con­ structed off­line. It presents a method to analyze the off­line schedule and derive an FPS task set with FPS attributes priority, offset, and period, such that the runtime FPS exe­ cution matches the off­line schedule. It does so by analyzing the schedule and setting up inequality relations for the pri­ orities of the tasks under FPS. Integer linear programming (ILP) is then used to find a FPS priority assignment that ful­ fils the relations. In case the priority relations for the tasks of the off­line schedule are not solvable we split tasks into the number of instances, to obtain a new task set with con­ sistent task attributes. Our schedule translation algorithm keeps the number of newly generated artifact tasks minimal.

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