Tight Tardiness Bounds for Pseudo-Harmonic Tasks Under Global-EDF-Like Schedulers

Authors Shareef Ahmed, James H. Anderson

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Shareef Ahmed
  • University of North Carolina at Chapel Hill, NC, USA
James H. Anderson
  • University of North Carolina at Chapel Hill, NC, USA

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Shareef Ahmed and James H. Anderson. Tight Tardiness Bounds for Pseudo-Harmonic Tasks Under Global-EDF-Like Schedulers. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 11:1-11:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)


The global earliest-deadline-first (GEDF) scheduler and its variants are soft-real-time (SRT) optimal for periodic/sporadic tasks, meaning they provide bounded tardiness so long as the underlying platform is not over-utilized. Although their SRT-optimality has long been known, tight tardiness bounds for these schedulers have remained elusive. In this paper, a tardiness bound, that does not depend on the processor or task count, is derived for pseudo-harmonic periodic tasks, which are commonly used in practice, under global-EDF-like (GEL) schedulers. This class of schedulers includes both GEDF and first-in-first-out (FIFO). This bound is shown to be generally tight via an example. Furthermore, it is shown that exact tardiness bounds for GEL-scheduled pseudo-harmonic periodic tasks can be computed in pseudo-polynomial time.

Subject Classification

ACM Subject Classification
  • Computer systems organization → Real-time systems
  • soft real-time systems
  • multicore
  • tardiness bounds


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