Algorithms and complexity for periodic real-time scheduling

  • Authors:
  • Vincenzo Bonifaci;Ho-Leung Chan;Alberto Marchetti-Spaccamela;Nicole Megow

  • Affiliations:
  • Max Planck Institute for Informatics, Saarbrucken, Germany;University of Hong Kong, Hong Kong;Sapienza University of Rome, Rome, Italy;Max Planck Institute for Informatics, Saarbrucken, Germany

  • Venue:
  • ACM Transactions on Algorithms (TALG)
  • Year:
  • 2012

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Abstract

We investigate the preemptive scheduling of periodic tasks with hard deadlines. We show that, even in the uniprocessor case, no pseudopolynomial-time algorithm can test the feasibility of a task system within a constant speedup bound, unless P = NP. This result contrasts with recent results for sporadic task systems. For two special cases, synchronous task systems and systems with a constant number of different task types, we provide the first polynomial-time constant-speedup feasibility tests for multiprocessor platforms. Furthermore, we show that the problem of testing feasibility is coNP-hard for synchronous multiprocessor task systems. The complexity of some of these problems has been open for a long time. We also propose a weight maximization variant of the feasibility problem, where every task has a nonnegative weight, and the goal is to find a subset of tasks that can be scheduled feasibly and has maximum weight. We give the first constant-speed, constant-approximation algorithm for the case of synchronous task systems, together with related hardness results.