Document Open Access Logo

Preempt Less, Schedule Better: Revisiting PCG for Real-Time Uniform Processors

Authors Yahya Hamdani , Pascal Richard , Antoine Bertout , Joël Goossens , Emmanuel Grolleau

PDF

File

Thumbnail PDF
PDF
LIPIcs.ECRTS.2026.2.pdf
  • Filesize: 1.15 MB
  • 23 pages

Document Identifiers

Subject Classification

ACM Subject Classification
  • Computer systems organization → Real-time systems
Keywords
  • Real-Time Scheduling
  • Uniform Multiprocessor Platforms

Metrics

Abstract

We address the problem of scheduling periodic implicit-deadline real-time tasks on m uniform processors. We introduce PCG^*, an optimal TL-plane algorithm based on PCG [Chen and Hsueh, 2008], which guarantees at most 2(m - 1) preemptions per TL-plane, matching the best-known theoretical bound for uniform platforms. The proposed algorithm advances the state of the art by offering an optimal real-time scheduling solution with a tight preemption bound within TL-planes. The numerical experiments presented in this work provide strong evidence that PCG^* yields a substantial reduction in the number of preemptions relative to PCG. When applied to identical processor platforms, PCG^* is also a best-possible polynomial time algorithm in terms of preemptions in a TL-plane, matching the (m-1) preemption bound achieved by LRE-TL [Funk, 2010].

Cite As Get BibTex

Yahya Hamdani, Pascal Richard, Antoine Bertout, Joël Goossens, and Emmanuel Grolleau. Preempt Less, Schedule Better: Revisiting PCG for Real-Time Uniform Processors. In 38th European Conference on Real-Time Systems (ECRTS 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 375, pp. 2:1-2:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026) https://doi.org/10.4230/LIPIcs.ECRTS.2026.2

Author Details

Yahya Hamdani
  • LIAS, ISAE-ENSMA, Université de Poitiers, France
Pascal Richard
  • LIAS, Université de Poitiers, ISAE-ENSMA, France
Antoine Bertout
  • LIAS, Université de Poitiers, ISAE-ENSMA, France
Joël Goossens
  • Université libre de Bruxelles, Belgium
Emmanuel Grolleau
  • LIAS, ISAE-ENSMA, Université de Poitiers, France

Funding

  • Bertout, Antoine: ANR JCJC program, https://anr.fr/Projet-ANR-21-CE25-0023, project SHRIMP.

References

  1. Matteo Bambagini, Marko Bertogna, Mauro Marinoni, and Giorgio Buttazzo. Energy-aware scheduling for real-time systems: A survey. ACM Transactions on Embedded Computing Systems, 15(1):7:1-7:34, 2016. URL: https://doi.org/10.1145/2808231.
  2. Sanjoy Baruah. Scheduling periodic tasks on uniform multiprocessors. Information Processing Letters, 80(2):97-104, 2001. URL: https://doi.org/10.1016/S0020-0190(01)00148-X.
  3. Sanjoy K. Baruah, N. K. Cohen, C. Greg Plaxton, and Donald A. Varvel. Proportionate progress: A notion of fairness in resource allocation. Algorithmica, 15(6):600-625, 1996. URL: https://doi.org/10.1007/BF01940883.
  4. Shih-Ying Chen and Chih-Wen Hsueh. Optimal dynamic-priority real-time scheduling algorithms for uniform multiprocessors. In 2008 Real-Time Systems Symposium, pages 147-156, 2008. URL: https://doi.org/10.1109/RTSS.2008.35.
  5. Hyeonjoong Cho, Binoy Ravindran, and E Douglas Jensen. An optimal real-time scheduling algorithm for multiprocessors. In 2006 27th IEEE International Real-Time Systems Symposium (RTSS'06), pages 101-110. IEEE, 2006. URL: https://doi.org/10.1109/RTSS.2006.10.
  6. Robert I Davis and Alan Burns. A survey of hard real-time scheduling for multiprocessor systems. ACM computing surveys (CSUR), 43(4):1-44, 2011. URL: https://doi.org/10.1145/1978802.1978814.
  7. Tomáš Ebenlendr and Jiří Sgall. Optimal and online preemptive scheduling on uniformly related machines. J. of Scheduling, 12(5):517-527, October 2009. URL: https://doi.org/10.1007/s10951-009-0119-7.
  8. S. Funk, J. Goossens, and S. Baruah. On-line scheduling on uniform multiprocessors. In Proceedings 22nd IEEE Real-Time Systems Symposium (RTSS 2001), pages 183-192, 2001. URL: https://doi.org/10.1109/REAL.2001.990609.
  9. Shelby Funk. LRE-TL: an optimal multiprocessor algorithm for sporadic task sets with unconstrained deadlines. Real-Time Syst., 46(3):332-359, December 2010. URL: https://doi.org/10.1007/s11241-010-9109-2.
  10. Shelby H Funk and Archana Meka. U-LLREF: An optimal scheduling algorithm for uniform multiprocessors. In The 9th Workshop on Models and Algorithms for Planning and Scheduling Problems, page 262, 2009. Google Scholar
  11. Thomas Gaspard, Antoine Bertout, Pascal Richard, Joël Goossens, and Emmanuel Grolleau. An unfair optimal scheduling algorithm for uniform multiprocessors. In 2025 IEEE 30th International Conference on Emerging Technologies and Factory Automation (ETFA), pages 1-8. IEEE, 2025. URL: https://doi.org/10.1109/ETFA65518.2025.11205723.
  12. Teofilo Gonzalez and Sartaj Sahni. Preemptive scheduling of uniform processor systems. J. ACM, 25(1):92-101, January 1978. URL: https://doi.org/10.1145/322047.322055.
  13. Edward C. Horvath, Shui Lam, and Ravi Sethi. A level algorithm for preemptive scheduling. J. ACM, 24(1):32-43, 1977. URL: https://doi.org/10.1145/321992.321995.
  14. Leonard Kleinrock. Queueing Systems, Volume II: Computer Applications. Wiley-Interscience, New York, 1976. Google Scholar
  15. Greg Levin, Shelby Funk, Caitlin Sadowski, Ian Pye, and Scott Brandt. Dp-fair: A simple model for understanding optimal multiprocessor scheduling. In 2010 22nd Euromicro Conference on Real-Time Systems, pages 3-13, 2010. URL: https://doi.org/10.1109/ECRTS.2010.34.
  16. Charles U. Martel. A parallel algorithm for preemptive scheduling of uniform machines. Journal of Parallel and Distributed Computing, 5(6):700-715, 1988. URL: https://doi.org/10.1016/0743-7315(88)90037-8.
  17. Robert McNaughton. Scheduling with deadlines and loss functions. Manage. Sci., 6(1):1-12, October 1959. URL: https://doi.org/10.1287/mnsc.6.1.1.
  18. Guillaume Phavorin, Pascal Richard, Joël Goossens, Claire Maiza, Laurent George, and Thomas Chapeaux. Online and offline scheduling with cache-related preemption delays. Real-Time Systems, 54(3):662-699, 2018. URL: https://doi.org/10.1007/s11241-017-9275-6.
  19. Padmanabhan Pillai and Kang G. Shin. Real-time dynamic voltage scaling for low-power embedded operating systems. In Proceedings of the 18th ACM Symposium on Operating System Principles (SOSP 2001), pages 89-102. ACM, 2001. URL: https://doi.org/10.1145/502034.502044.
  20. Michael L. Pinedo. Scheduling: Theory, Algorithms, and Systems. Springer Publishing Company, Incorporated, 6th edition, 2022. URL: https://doi.org/10.1007/978-3-031-05921-6.
  21. Gurulingesh Raravi, Björn Andersson, and Konstantinos Bletsas. Assigning real-time tasks on heterogeneous multiprocessors with two unrelated types of processors. Real-Time Systems, 49(1):29-72, 2013. URL: https://doi.org/10.1007/s11241-012-9161-1.
  22. Hadas Shachnai, Tami Tamir, and Gerhard J Woeginger. Minimizing makespan and preemption costs on a system of uniform machines. Algorithmica, 42:309-334, 2005. URL: https://doi.org/10.1007/s00453-005-1171-0.
  23. Evgeny V Shchepin and Nodari Vakhania. On the geometry, preemptions and complexity of multiprocessor and shop scheduling. Annals of Operations Research, 159(1):183-213, 2008. URL: https://doi.org/10.1007/s10479-007-0266-1.
  24. Mark Weiser, Brent Welch, Alan Demers, and Scott Shenker. Scheduling for reduced CPU energy. In First Symposium on Operating Systems Design and Implementation (OSDI 94), Monterey, CA, November 1994. USENIX Association. URL: http://dl.acm.org/citation.cfm?id=1267640.
  25. Kecheng Yang and James H. Anderson. An optimal semi-partitioned scheduler for uniform heterogeneous multiprocessors. In 2015 27th Euromicro Conference on Real-Time Systems, pages 199-210, 2015. URL: https://doi.org/10.1109/ECRTS.2015.25.
Any Issues?
X

Feedback on the Current Page

CAPTCHA

Thanks for your feedback!

Feedback submitted to Dagstuhl Publishing

Could not send message

Please try again later or send an E-mail
© 2023-2026 Schloss Dagstuhl – LZI GmbH Schloss Dagstuhl – LZI GmbH About DROPS Imprint Privacy Contact