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Issue No.09 - September (2008 vol.57)

pp: 1261-1276

Attila Zabos , University of York, York

Robert I. Davis , University of York, York

DOI Bookmark: http://doi.ieeecomputersociety.org/10.1109/TC.2008.66

ABSTRACT

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 pre-emptive 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 tasksets 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.

INDEX TERMS

Multiprocessing/multiprogramming/multitasking, Scheduling, Real-time systems and embedded systems

CITATION

Attila Zabos, Robert I. Davis, "Efficient Exact Schedulability Tests for Fixed Priority Real-Time Systems",

*IEEE Transactions on Computers*, vol.57, no. 9, pp. 1261-1276, September 2008, doi:10.1109/TC.2008.66REFERENCES

- [1] M.S. Fineberg and O. Serlin, “Multiprogramming for Hybrid Computation,”
Proc. AFIPS Fall Joint Computing Conf., pp. 1-13, 1967.- [2] O. Serlin, “Scheduling of Time Critical Processes,”
Proc. AFIPS Spring Computing Conf., pp. 925-932, 1972.- [10] K.W. Tindell, “Using Offset Information to Analyse Static Priority Pre-Emptively Scheduled Task Sets,” Technical Report YCS-92-182, Dept. of Computer Science, Univ. of York, 1992.
- [11] N.C. Audsley, A. Burns, M. Richardson, K.W. Tindell, and A.J. Wellings, “Applying New Scheduling Theory to Static Priority Pre-Emptive Scheduling,”
Software Eng. J., vol. 8, no. 5, pp. 284-292, Sept. 1993.- [17] W-C. Lu, K-J. Lin, H-W. Wei1, and W-K. Shih, “Period-Dependent Initial Values for Exact Schedulability Test of Rate Monotonic Systems,”
Proc. 21st Int'l Parallel and Distributed Processing Symp., pp. 1-8, Mar. 2007.- [18] E. Bini and S.K. Baruah, “Efficient Computation of Response Time Bounds under Fixed-Priority Scheduling,”
Proc. 15th Int'l Conf. Real-Time and Network Systems, pp. 95-104, Mar. 2007.- [20] A. Zuhily and A. Burns, “Optimality of (D-J)-Monotonic Priority Assignment,”
Information Processing Letters, no. 103, pp. 247-250, Apr. 2007.- [22] N.C. Audsley, “Flexible Scheduling of Hard Real-Time Systems,” PhD thesis, Dept. of Computer Science, Univ. of York, 1993.
- [23] http:/www.frescor.org/, 2007.
- [24] “RapiTime White Paper: Worst-Case Execution Time Analysis,” www.rapitasystems.com, 2007.
- [28] R.I. Davis, A. Zabos, and A. Burns, “Efficient Exact Schedulability Tests for Fixed Priority Pre-Emptive Systems,” Technical Report YCS-418-2007, Dept. of Computer Science, Univ. of York, 2007.
- [29] R.I. Davis and A. Burns, “Robust Priority Assignment for Fixed Priority Real-Time Systems,”
Proc. 28th IEEE Real-Time Systems Symp., pp. 1-12, 2007. |