Optimal online multiprocessor scheduling of sporadic real-time tasks is impossible
Optimal online scheduling algorithms are known for sporadic task systems scheduled upon a single processor. Additionally, optimal online scheduling algorithms are also known for restricted subclasses of sporadic task systems upon an identical multiprocessor platform. The research reported in this article addresses the question of existence of optimal online multiprocessor scheduling algorithms for general sporadic task systems. Our main result is a proof of the impossibility of optimal online scheduling for sporadic task systems upon a system comprised of two or more processors. The result is shown by finding a sporadic task system that is feasible on a multiprocessor platform that cannot be correctly scheduled by any possible online, deterministic scheduling algorithm. Since the sporadic task model is a subclass of many more general real-time task models, the nonexistence of optimal scheduling algorithms for the sporadic task systems implies nonexistence for any model which generalizes the sporadic task model.
KeywordsReal-time scheduling Multiprocessor systems Sporadic task model Optimal scheduling algorithms
Unable to display preview. Download preview PDF.
- Audsley NC, Burns A, Richardson MF, Wellings AJ (1991) Hard real-time scheduling: the deadline monotonic approach. In: Proceedings 8th IEEE workshop on real-time operating systems and software, Atlanta, May 1991, pp 127–132 Google Scholar
- Baker T, Cirinei M (2006) A necessary and sometimes sufficient condition for the feasibility of sets of sporadic hard-deadline tasks. In: Proceedings of the IEEE real-time systems symposium, Rio de Janeiro, December 2006. IEEE Computer Society, Los Alamitos, pp 178–187 Google Scholar
- Baker T, Cirinei M (2007) Brute-force determination of multiprocessor schedulability for sets of sporadic hard-deadline tasks. In: Proceedings of the 10th international conference on principles of distributed systems, Guadeloupe, December 2007, pp 62–75 Google Scholar
- Baruah S, Fisher N (2007) Global deadline-monotonic scheduling of arbitrary-deadline sporadic task systems. In: Proceedings of the 11th international conference on principles of distributed systems, Guadeloupe, French West Indies, December 2007. Springer, Berlin Google Scholar
- Dertouzos M (1974) Control robotics: the procedural control of physical processors. In: Proceedings of the IFIP congress, pp 807–813 Google Scholar
- Jeffay K, Stanat D, Martel C (1991) On non-preemptive scheduling of periodic and sporadic tasks. In: Proceedings of the 12th real-time systems symposium, San Antonio, TX, December 1991. IEEE Computer Society, Los Alamitos, pp 129–139 Google Scholar
- Mok AK (1983) Fundamental design problems of distributed systems for the hard-real-time environment. PhD thesis, Laboratory for Computer Science, Massachusetts Institute of Technology. Available as Technical Report No. MIT/LCS/TR-297 Google Scholar
- Phillips CA, Stein C, Torng E, Wein J (1997) Optimal time-critical scheduling via resource augmentation. In: Proceedings of the twenty-ninth annual ACM symposium on theory of computing, El Paso, TX, 4–6 May 1997, pp 140–149 Google Scholar
- Srinivasan A, Anderson J (2002) Optimal rate-based scheduling on multiprocessors. In: Proceedings of the 34th ACM symposium on the theory of computing, May 2002, pp 189–198 Google Scholar