Scheduling periodic tasks in a hard real-time environment

  • Authors:
  • Friedrich Eisenbrand;Nicolai Hähnle;Martin Niemeier;Martin Skutella;José Verschae;Andreas Wiese

  • Affiliations:
  • EPFL, Lausanne, Switzerland;EPFL, Lausanne, Switzerland;EPFL, Lausanne, Switzerland;TU Berlin, Germany;TU Berlin, Germany;TU Berlin, Germany

  • Venue:
  • ICALP'10 Proceedings of the 37th international colloquium conference on Automata, languages and programming
  • Year:
  • 2010

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Abstract

We give a rigorous account on the complexity landscape of an important real-time scheduling problem that occurs in the design of software-based aircraft control. The goal is to distribute tasks τi = (ci, pi) on a minimum number of identical machines and to compute offsets ai for the tasks such that no collision occurs. A task τi releases a job of running time ci; at each time ai + k ċ pi, k ∈ N0 and a collision occurs if two jobs are simultaneously active on the same machine. Our main results are as follows: (i) We show that the minimization problem cannot be approximated within a factor of n1-ε for any ε 0. (ii) If the periods are harmonic (for each i, j one has pi | pj or pj | pi), then there exists a 2-approximation for the minimization problem and this result is tight, even asymptotically. (iii) We provide asymptotic approximation schemes in the harmonic case if the number of different periods is constant.