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Parametric Dispatching of Hard Real-Time Tasks
March 1995 (vol. 44 no. 3)
pp. 471-479

Abstract—In many real-time systems relative timing constraints are imposed on a set of tasks. Generating a correct ordering for the tasks and deriving their proper start-time assignments is an NP-hard problem; it subsumes the Non-preemptive Scheduling Problem. Even when the application imposes a total order on the tasks, generating proper start-times is still nontrivial if execution times may range between upper and lower bounds.

We present the technique of parametric dispatching to enforce such timing constraints. During an off-line component, we check if the constraints can be guaranteed. If so, a calendar is produced that allows our on-line algorithm to generate upper and lower bounds on the start time of each task, based on the start times and execution times of previous tasks. A suitable start time for the task may then be selected taking into account the presence of other non-critical tasks in the system.

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Index Terms:
Real-time, scheduling, dispatching, operating systems, linear constraints, variable elimination, programming languages.
Citation:
William Pugh, Richard Gerber, Manas Saksena, "Parametric Dispatching of Hard Real-Time Tasks," IEEE Transactions on Computers, vol. 44, no. 3, pp. 471-479, March 1995, doi:10.1109/12.372041
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