Implementation and evaluation of global and partitioned scheduling in a real-time OS

  • Authors:

  • Giovani Gracioli;Antônio Augusto Fröhlich;Rodolfo Pellizzoni;Sebastian Fischmeister

  • Affiliations:

  • Federal University of Santa Catarina, Florianópolis, Brazil;Federal University of Santa Catarina, Florianópolis, Brazil;University of Waterloo, Waterloo, Canada;University of Waterloo, Waterloo, Canada

  • Venue:
  • Real-Time Systems
  • Year:
  • 2013

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Abstract

In this work, we provide an experimental comparison between Global-EDF and Partitioned-EDF, considering the run-time overhead of a real-time operating system (RTOS). Recent works have confirmed that OS implementation aspects, such as the choice of scheduling data structures and interrupt handling mechanisms, impact real-time schedulability as much as scheduling theoretic aspects. However, these studies used real-time patches applied into a general-purpose OS. By measuring the run-time overhead of an RTOS designed from scratch, we show how close the schedulability ratio of task sets is to the theoretical hard real-time schedulability tests. Moreover, we show how a well-designed object-oriented RTOS allows code reuse of scheduling components (e.g., thread, scheduling criteria, and schedulers) and easy real-time scheduling extensions. We compare our RTOS to a real-time patch for Linux in terms of the task set schedulability ratio of several generated task sets. In some cases, Global-EDF considering the overhead of the RTOS is superior to Partitioned-EDF considering the overhead of the patched Linux, which clearly shows how different OSs impact hard real-time schedulers.