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Tardiness bounds under global EDF scheduling on a multiprocessor

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Abstract

We consider the scheduling of a sporadic real-time task system on an identical multiprocessor. Though Pfair algorithms are theoretically optimal for such task systems, in practice, their runtime overheads can significantly reduce the amount of useful work that is accomplished. On the other hand, if all deadlines need to be met, then every known non-Pfair algorithm requires restrictions on total system utilization that can approach approximately 50% of the available processing capacity. This may be overkill for soft real-time systems, which can tolerate occasional or bounded deadline misses (i.e. bounded tardiness). In this paper we derive tardiness bounds under preemptive and non-preemptive global \(\mathsf{EDF}\) when the total system utilization is not restricted, except that it not exceed the available processing capacity. Hence, processor utilization can be improved for soft real-time systems on multiprocessors. Our tardiness bounds depend on the total system utilization and per-task utilizations and execution costs—the lower these values, the lower the tardiness bounds. As a final remark, we note that global \(\mathsf{EDF}\) may be superior to partitioned \(\mathsf{EDF}\) for multiprocessor-based soft real-time systems in that the latter does not offer any scope to improve system utilization even if bounded tardiness can be tolerated.

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Authors and Affiliations

  1. Department of Computer Science, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA

    UmaMaheswari C. Devi & J. H. Anderson

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  1. UmaMaheswari C. Devi
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  2. J. H. Anderson
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Correspondence to UmaMaheswari C. Devi.

Additional information

Work supported by NSF grants CCR 0204312, CNS 0309825, CNS 0408996, CCF 0541056, and CNS 0615197, and by ARO grant W911NF-06-1-0425. This work was presented in preliminary form at the 26th IEEE Real-Time Systems Symposium (Devi and Anderson 2005).

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Devi, U.C., Anderson, J.H. Tardiness bounds under global EDF scheduling on a multiprocessor. Real-Time Syst 38, 133–189 (2008). https://doi.org/10.1007/s11241-007-9042-1

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