Abstract
A real-time system may have tasks with soft deadlines, as well as hard deadlines. While earliest-deadline-first scheduling is effective for hard-deadline tasks, applying it to soft-deadline tasks may waste schedulable processor capacity or sacrifice average response time. Better average response time may be obtained, while still guaranteeing hard deadlines, with an aperiodic server. Three scheduling algorithms for aperiodic servers are described, and schedulability tests are derived for them. A simulation provides performance data for these three algorithms on random aperiodic tasks. The performances of the deadline aperiodic servers are compared with those of several alternatives, including background service, a deadline polling server, and rate-monotonic servers, and with estimates based on the M/M/1 queueing model. This adds to the evidence in support of deadline scheduling,versus fixed priority scheduling.
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References
Baker, T. P. 1991. Stack-based scheduling of realtime processes.The Real-Time Systems Journal 3(1): 67–100.
Chen, M. I., and Lin, K. J. 1989. Dynamic priority ceilings: a concurrency control protocol for real-time systems. Department of Computer Science, University of Illinois at Urbana-Champaign, Technical Report UIUCDCS-R-89-1511.
Coffman, E. G., Jr., and Denning, P. J. 1973.Operating Systems Theory. New Jersey: Prentice-Hall.
Ghazalie, T. 1991. Improving response time of aperiodic tasks with deadline scheduling. Department of Computer Science, Florida State University, thesis for Master of Science.
1992. Scheduling sporadic tasks with shared resources in hard-real-time systems.Proceedings of the IEEE Real-Time Systems Symposium 89–99.
Joseph and Pandya. 1986. Finding response times in a real-time system.BCS Computing Journal 29(5): 390–395.
Lehoczky, J. L., Sha, L., and Strosnider, J. K. 1987. Enhanced aperiodic responsiveness in hard real-time environments.Proceedings of the IEEE Real-Time Systems Symposium 261–270.
Leung, J. Y. T., and Merrill, M. L. 1989. A note on preemptive scheduling of periodic, real-time tasks.Information Processing Letters 11(3): 115–118.
Liu, C. L., and Layland, J. W. 1973. Scheduling algorithms for multiprogramming in a hard-real-time environment.Journal of the Association for Computing Machinery 20(1): 46–61.
Sha, L., Rajkumar, R., and Lehoczky, J. P. 1990. Priority inheritance protocols: an approach to real-time synchronization.IEEE Transactions on Computers 39(9): 1175–1185.
Sprunt, B., Sha, L., and Lehoczky, J. P. 1989. Aperiodic task scheduling for hard-real-time systems.The Journal of Real-Time Systems 1(1): 27–60.
Strosnider, J. K., Lehoczky, J. L., and Sha, L. The deferrable server algorithm for enhanced aperiodic responsiveness in hard real-time environments.IEEE Transactions on Computers (to appear).
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Ghazalie, T.M., Baker, T.P. Aperiodic servers in a deadline scheduling environment. Real-Time Syst 9, 31–67 (1995). https://doi.org/10.1007/BF01094172
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DOI: https://doi.org/10.1007/BF01094172