Quality-Assuring Scheduling-Using Stochastic Behavior to Improve Resource Utilization

  • Authors:
  • Claude-Joachim Hamann;Lars Reuther;Jork Wolter;Hermann Härtig;Jork Löser;Sebastian Schönberg

  • Affiliations:
  • -;-;-;-;-;-

  • Venue:
  • RTSS '01 Proceedings of the 22nd IEEE Real-Time Systems Symposium
  • Year:
  • 2001

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Abstract

We present a unified model for admission and scheduling,applicable for various active resources such as CPU or diskto assure a requested quality in situations of temporaryoverload. The model allows us to predict and control thebehavior of applications based on given quality requirements.It uses the variations in the execution time, i.e., the time anyactive resource is needed.We split resource requirements into a mandatory partwhich must be available and an optional part which shouldbe available as often as possible but at least with a certainpercentage.In combination with a given distributionfor the execution time we can move away from worst-casereservations and drastically reduce the amount of reservedresources for applications which can tolerate occasionaldeadline misses. This increases the number of admittableapplications.For example, with negligible loss of qualityour system can admit more than two times the disk band-widththan a system based on the worst-case.Finally, we validated the predictions of our model byMeasurements using a prototype real-time system and observeda high accuracy between predicted and measured values.