Affine Data-Flow Graphs for the Synthesis of Hard Real-Time Applications

• Published in: 2012 12th International Conference on Application of Concurrency to System Design pp. 183 - 192
• Main Authors: Bouakaz, A., Talpin, J., Vitek, J.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.06.2012
• Subjects: Affine relation; Analytical models; Buffer minimization; Clocks; Computational modeling; Concurrent computing; Data-flow graphs; Linear programming; Priority-driven scheduling; Processor scheduling; Schedules; Semantics
• ISBN: 9781467316873; 1467316873
• ISSN: 1550-4808; 2374-8567
• DOI: 10.1109/ACSD.2012.16

Data-flow models ease the task of constructing feasible schedules of computations and communications of high-assurance embedded applications. One key and open issue is how to schedule data-flow graphs so as to minimize the buffering of data and reduce end-to-end latency. Most of the proposed techniques in that respect are based on either static or data-driven scheduling. This paper looks at the problem in a different way by considering priority-driven preemptive scheduling theory of periodic tasks to execute a data-flow program. Our approach to the problem can be detailed as follows. (1) We propose a model of computation in which the activation clocks of actors are related by affine functions. The affine relations describe the symbolic scheduling constraints of the data-flow graph. (2) Based on this framework, we present an algorithm that computes affine schedules in a way that minimizes buffering requirements and, in addition, guarantees the absence of overflow and underflow exceptions over communication channels. (3) Depending on the chosen scheduling policy (earliest-deadline first or rate-monotonic), we concretize the symbolic schedule by defining the period and the phase of each actor. This concretization guarantees schedulability and maximizes the processor utilization factor.