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Slack-based multiprocessor scheduling of aperiodic real-time tasks
Responsible organisation
2011 (English)In: Real-time systems, ISSN 0922-6443, E-ISSN 1573-1383, Vol. 47, no 6, p. 618-638Article in journal (Refereed) Published
Abstract [en]

We provide a constant time schedulability test and priority assignment algorithm for an on-line multiprocessor server handling aperiodic tasks. The so called Dhall's effect is avoided by dividing tasks in two priority classes based on their utilization: heavy and light. The improvement in this paper is due to assigning priority of light tasks based on slack-not on deadlines. We prove that if the load on the multiprocessor stays below (3 - √5)/2 ≈ 38.197%, the server can accept an incoming aperiodic task and guarantee that the deadlines of all accepted tasks will be met. This is better than the current state-of-the-art algorithm where the priorities of light tasks are based on deadlines (the corresponding bound is in that case 35.425%). The bound (3 - √5)/ 2 can be improved if the number of processors m is known. There is a formula for the sharp bound Uthreshold(m) = 3m - 2 - √5m 2 - 8m + 4/2(m - 1), which converges to (3 - √5)/2 from above as m→∞. For m≥3, the bound is higher (i.e., better) than the corresponding sharp bound for the state-of-the-art algorithm where the priorities of light tasks are based on deadlines. A simulation study also indicates that when m>3 the best effort behavior of the priority assignment scheme suggested here is better than that of the traditional scheme where priorities are based on deadlines.

Place, publisher, year, edition, pages
Springer , 2011. Vol. 47, no 6, p. 618-638
Keywords [en]
Aperiodic tasks, Global multiprocessor scheduling, Real-time scheduling, Slack-based priorities, Static priorities
National Category
Computer Sciences
Identifiers
URN: urn:nbn:se:bth-7377DOI: 10.1007/s11241-011-9134-9ISI: 000295793000004Local ID: oai:bth.se:forskinfo414CF03F21E97B09C1257979003474CFOAI: oai:DiVA.org:bth-7377DiVA, id: diva2:834985
Available from: 2012-09-18 Created: 2012-01-02 Last updated: 2018-01-11Bibliographically approved

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Lundberg, Lars

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