This Article 
 Bibliographic References 
 Add to: 
Schedulability Analysis of Periodic Fixed Priority Systems
November 2004 (vol. 53 no. 11)
pp. 1462-1473
Feasibility analysis of fixed priority systems has been widely studied in the real-time literature and several acceptance tests have been proposed to guarantee a set of periodic tasks. They can be divided in two main classes: polynomial time tests and exact tests. Polynomial time tests can efficiently be used for on-line guarantee of real-time applications, where tasks are activated at runtime. These tests introduce a negligible overhead, when executed upon a new task arrival, however provide only a sufficient schedulability condition, which may cause a poor processor utilization. On the other hand, exact tests, which are based on response time analysis, provide a necessary and sufficient schedulability condition, but are too complex to be executed on line for large task sets. As a consequence, for large task sets, they are often executed off line. This paper proposes a novel approach for analyzing the schedulability of periodic task sets on a single processor under an arbitrary fixed priority assignment. Using this approach, we derive a new schedulability test which can be tuned through a parameter to balance complexity versus acceptance ratio, so that it can be used on line to better exploit the processor, based on the available computational power. Extensive simulations show that our test, when used in its exact form, is significantly faster than the current response time analysis methods. Moreover the proposed approach, for its elegance and compactness, offers an explanation of some known phenomena of fixed priority scheduling and could be helpful for further work on schedulability analysis.

[1] C.L. Liu and J.W. Layland, Scheduling Algorithms for Multiprogramming in a Hard Real-Time Environment J. ACM, vol. 20, no. 1, pp. 40-61, 1973.
[2] J. Lehoczky, L. Sha, and Y. Ding, The Rate Monotonic Scheduling Algorithm: Exact Characterization and Average Case Behavior Proc. IEEE Real-Time Systems Symp., pp. 166-171, 1989.
[3] M. Joseph and P. Pandya, Finding Response Times in a Real-Time System The Computer J., British Computer Soc., vol. 29, no. 5, pp. 390-395, Oct. 1986.
[4] N.C. Audsley, A. Burns, M. Richardson, K. Tindell, and A. Wellings, "Applying New Scheduling Theory to Static Priority Preemptive Scheduling," Software Eng. J. vol. 8, no. 5, pp. 284-292, Sept. 1993.
[5] Y. Manabe and S. Aoyagi, A Feasibility Decision Algorithm for Rate Monotonic Scheduling of Periodic Real-Time Tasks Proc. First Real-Time Technology and Applications Symp., pp. 297-303, May 1995.
[6] J.Y.-T. Leung and J. Whitehead, On the Complexity of Fixed-Priority Scheduling of Periodic, Real-Time Tasks Performance Evaluation, vol. 2, pp. 237-250, 1982.
[7] L. Sha, R. Rajkuma, and J.P. Lehoczky, "Priority Inheritance Protocols: An Approach to Real-Time Synchronization," IEEE Trans. Computers, vol. 39, no. 9, pp. 1,175-1,185, Sept. 1990.
[8] A. Burns, R. Davis, and S. Punnekkat, “Feasibility Analysis of Fault-Tolerant Real-Time Task Sets,” Proc. Euromicro Workshop Real-Time Systems, pp. 29-33, 1996.
[9] M. Sjodin and H. Hansson, “Improved Response-Time Analysis Calculations,” Proc. IEEE Real-Time Systems Symp., pp. 36-45, Dec. 1998.
[10] Y. Oh and S.H. Son, Allocating Fixed-Priority Periodic Tasks on Multiprocessor Systems Real-Time Systems, vol. 9, pp. 207-239, 1995.
[11] J.W.S. Liu, Real-Time Systems. Prentice Hall, 2000.
[12] E. Bini, G.C. Buttazzo, and G.M. Buttazzo, Rate Monotonic Scheduling: The Hyperbolic Bound IEEE Trans. Computers, vol. 52, no. 7, pp. 933-942, July 2003.
[13] T.-W. Kuo and A.K. Mok, “Load Adjustment in Adaptive Real-Time Systems,” Proc. IEEE Real-Time Systems Symp., Dec. 1991.
[14] D. Chen, A.K. Mok, and T.-W. Kuo, “Utilization Bound Re-Visited,” Proc. Sixth Int'l Conf. Real-Time Computing Systems and Applications, 1999.
[15] D.-W. Park, S. Natarajan, A. Kanevsky, and M.J. Kim, “A Generalized Utilization Bound Test for Fixed-Priority Real-Time Scheduling,” Proc. Second Int'l Workshop Real-Time Computing Systems and Applications, pp. 73-77, 1995.
[16] H. Liu and X. Hu, Efficient Performance Estimation for General Real-Time Task Systems IEEE/ACM Int'l Conf. Computer Aided Design, pp. 464-471, 2001.

Index Terms:
Real-time systems and embedded, systems analysis and design, fixed priority scheduling.
Enrico Bini, Giorgio C. Buttazzo, "Schedulability Analysis of Periodic Fixed Priority Systems," IEEE Transactions on Computers, vol. 53, no. 11, pp. 1462-1473, Nov. 2004, doi:10.1109/TC.2004.103
Usage of this product signifies your acceptance of the Terms of Use.