Combined Scheduling of Hard and Soft Real-Time Tasks in Multiprocessor Systems

  • B. Duwairi
  • G. Manimaran
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 2913)


Many complex real-time applications involve combined scheduling of hard and soft real-time tasks. In this paper, we propose a combined scheduling algorithm, called Emergency Algorithm, for multiprocessor real-time systems. The primary goal of the algorithm is to maximize the schedulability of soft tasks without jeopardizing the schedulability of hard tasks. The algorithm has the inherent feature of dropping already scheduled soft tasks by employing a technique that switches back and forth between two modes of operation: regular mode, in which all tasks (hard and soft) are considered for scheduling without distinction; emergency mode, in which one or more already scheduled soft tasks can be dropped in order to accommodate a hard task in the schedule. The proposed algorithm has been evaluated by comparing it with the iterative server rate adjustment algorithm (ISRA) [6]. The simulation results show that emergency algorithm outperforms ISRA by offering better schedulability for soft tasks while maintaining lower scheduling overhead.


Multimedia Server Multiprocessor System Hard Task Regular Mode Multimedia Stream 
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  1. 1.
    Buttazzo, G., Sensini, F.: Optimal Deadline Assignment for Scheduling Soft Aperiodic Tasks in Hard Real-Time Environments. IEEE Transactions on Computers 48(10), 1035–1051 (1999)CrossRefGoogle Scholar
  2. 2.
    Davis, R., Tindell, K.W., Burns, A.: Scheduling Slack Time in Fixed Priorty Pre-emptive Systems. In: Proceedings of the 14th Real Time System Symposium, North Carolina, USA, December 1993, pp. 222–231 (1993)Google Scholar
  3. 3.
    Davis, R., Wellings, A.: Dual Priority Scheduling. In: Proceedings of Real-Time Systems Symposium, pp. 100–109 (1995)Google Scholar
  4. 4.
    Deng, Z., Liu, J.W.S., Sun, J.: A Scheme for Scheduling Hard Real-Time Applications in Open System Environment. In: Proceedings of the 9th Euromico Workshop on Real-Time Systems (1997)Google Scholar
  5. 5.
    Ghazalie, T.M., Baker, T.: Aperiodic Servers in a Deadline Scheduling Environment. Real-Time Systems 9 (1995)Google Scholar
  6. 6.
    Kaneko, H., Stankovic, J.A., Sen, S., Ramamritham, K.: Integrated Scheduling of Multimedia and Hard Real-Time Tasks. In: Proceedings of Real-Time Systems Symposium, pp. 206–217 (1996)Google Scholar
  7. 7.
    Lee, S., Kim, H., Lee, J.: A Soft Aperiodic Task Scheduling in Dynamic-Priority Systems. In: Proceedings of the 2nd International Workshop on Real-Time Computing Systems and Applications, IEEE, Los Alamitos (1995)Google Scholar
  8. 8.
    Lehoczky, J.P., Sha, L., Strosnider, J.K.: Enhanced Aperiodic Responsiveness in Hard Real- Time Environments. In: Proceedings of Real-Time Systems Symposium, pp. 261–270 (1987)Google Scholar
  9. 9.
    Ramamritham, K., Stankovic, J.A., Shian, P.-F.: Efficient Scheduling Algorithm for Real-Time Multiprocessor systems. IEEE Transactions on Parallel and Distributed Systems 1(2), 184–194 (1990)CrossRefGoogle Scholar
  10. 10.
    Spuri, M., Buttazzo, G.C.: Efficient Aperiodic Service under Earliest Deadline Scheduling. In: Proceedings of IEEE Real-Time Systems Symposium, San Juan, Puerto Rico (December 1994)Google Scholar
  11. 11.
    Spuri, M., Buttazzo, G.C.: Scheduling Aperiodic Tasks in Dynamic Priority Systems. Real-Time Systems 10(2) (1996)Google Scholar
  12. 12.
    Sprunt, B., Lehoczky, J., Sha, L.: Exploiting Unused Periodic Time for Aperiodic Service Using the Extended Priority Exchange Algorithm. In: Proceedings of the 9th IEEE Real-Time Systems Symposium (December 1988)Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2003

Authors and Affiliations

  • B. Duwairi
    • 1
  • G. Manimaran
    • 1
  1. 1.Department of Electrical and Computer EngineeringIowa State UniversityAmesUSA

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