Efficient Exact Schedulability Tests for Fixed Priority Real-Time Systems

Efficient exact schedulability tests are required both for on-line admission of applications to dynamic systems and as an integral part of design tools for complex distributed real-time systems. This paper addresses performance issues with exact response time analysis (RTA) for fixed priority preemp...

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Veröffentlicht in:IEEE transactions on computers Jg. 57; H. 9; S. 1261 - 1276
Hauptverfasser: Davis, R.I., Zabos, A., Burns, A.
Format: Journal Article
Sprache:Englisch
Veröffentlicht: New York IEEE 01.09.2008
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Schlagworte:
Algorithms
Dynamical systems
Dynamics
Multiprocessing/multiprogramming/multitasking
On-line systems
Priorities
Real time
Real-time systems and embedded systems
Response time
Scheduling
Studies
Multiprocessing/multiprogramming/multitasking
Scheduling
Real-time systems and embedded systems
ISSN:0018-9340, 1557-9956
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Zusammenfassung:Efficient exact schedulability tests are required both for on-line admission of applications to dynamic systems and as an integral part of design tools for complex distributed real-time systems. This paper addresses performance issues with exact response time analysis (RTA) for fixed priority preemptive systems. Initial values are introduced that improve the efficiency of the standard RTA algorithm (i) when exact response times are required, and (ii) when only exact schedulability need be determined. The paper also explores modifications to the standard RTA algorithm, including; the use of a response time upper bound to determine when exact analysis is needed, incremental computation aimed at faster convergence, and checking tasks in reverse priority order to identify unschedulable task sets early. The various initial values and algorithm implementations are compared by means of experiments on a PC recording the number of iterations required, and execution time measurements on a real-time embedded microprocessor. Recommendations are provided for engineers tasked with the problem of implementing exact schedulability tests, as part of on-line acceptance tests and spare capacity allocation algorithms, or as part of off-line system design tools.
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ISSN:0018-9340
1557-9956
DOI:10.1109/TC.2008.66