D.K. Krecker

Publications (2)0 Total impact

• Source

  Available from: wustl.edu

  Conference Proceeding: Practical Schedulability Analysis for Generalized Sporadic Tasks in Distributed Real-Time Systems

  Yuanfang Zhang, D.K. Krecker, C. Gill, Chenyang Lu, G.H. Thaker
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  ABSTRACT: Existing off-line schedulability analysis for real-time systems can only handle periodic or sporadic tasks with known minimum inter-arrival times. Modeling sporadic tasks with fixed minimum inter-arrival times is a poor approximation for systems in which tasks arrive in bursts, but have longer intervals between the bursts. In such cases, schedulability analysis based on the existing sporadic task model is pessimistic and seriously overestimates the task's time demand. In this paper, we propose a generalized sporadic task model that characterizes arrival times more precisely than the traditional sporadic task model, and we develop a corresponding schedulability analysis that computes tighter bounds on worst-case response times. Experimental results show that when arrival time jitter increases, the new analysis more effectively guarantees schedulability of sporadic tasks.
  Real-Time Systems, 2008. ECRTS '08. Euromicro Conference on; 08/2008
• Source

  Available from: lmco.com

  Conference Proceeding: Empirical quantification of pessimism in state-of-the-art scheduling theory techniques for periodic and sporadic DRE tasks

  G.H. Thaker, P.J. Lardieri, D.K. Krecker, M. Price
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  ABSTRACT: Distributed, Real-time, Embedded (DRE) systems present numerous challenges with respect to certification of their real-time behavior. Ideally, to address these we would like to build a model of our system that captures relevant information about end to end real-time requirements, resource consumptions requirements and resource availability, and subject the model to real-time scheduling analysis to predict performance. Presently, scheduling theory techniques have seen limited application in DRE systems for multiple reasons including pessimistic predictions of worst-case response times. Our study quantifies the pessimism in the predictions of worst-case response times of competing end-to-end distributed periodic tasks by comparing values observed in simulation with values computed using multiple scheduling theory techniques. Specifically we consider nongreedy synchronization protocols for tasks with a high degree of recurrence. Our results show that for an end-to-end task model nongreedy techniques, when used with proportional deadline monotonic scheduling, reduce the pessimism in worst-case response time predictions to within 5% of the actual value in over 90% of cases. These (quasi) static techniques represent a baseline against which we can evaluate emerging, control theoretic, adaptive scheduling methods.
  Real-Time and Embedded Technology and Applications Symposium, 2004. Proceedings. RTAS 2004. 10th IEEE; 06/2004