Worst-Case Response Time Analysis of a Synchronous Dataflow Graph in a Multiprocessor System with Real-Time Tasks

In this article, we propose a novel technique that estimates a tight upper bound of the worst-case response time (WCRT) of a synchronous dataflow (SDF) graph when the SDF graph shares processors with other real-time tasks. When an SDF graph is executed at runtime under a self-timed or static assignment scheduling policy on a multi-processor system, static scheduling of the SDF graph does not guarantee the satisfaction of latency constraints since changes to the schedule may result in timing anomalies. To estimate the WCRT of an SDF graph with a given mapping and scheduling result, we first construct a task instance dependency graph that depicts the dependency between node executions in a static schedule. The proposed technique combines two techniques in a novel way: schedule time bound analysis and response time analysis. The former is used to consider the interference between task instances in the same SDF graph, and the latter is used to consider the interference from other real-time tasks. Through extensive experiments with synthetic examples and benchmarks, we verify the superior performance of the proposed technique compared to other existent techniques.