DAG (directed acyclic graph) tasks are widely used to model parallel real-time workload. The real-time performance of a DAG task not only depends on its total workload, but also its graph structure. Intuitively, with the same total workload, a DAG task with looser precedence constraints tends to have better real-time performance in terms of worst-case response time. However, this paper shows that actually we can shorten the worst-case response time of a DAG task by carefully adding new edges and constructing longer paths. We develop techniques based on the state-of-the-art DAG response time analysis techniques to properly add new edges so that the worst-case response time bound guaranteed by formal analysis can be significantly reduced. Experiments under different parameter settings demonstrate the effectiveness of the proposed techniques.

翻译：DAG（有向无环图）任务被广泛用于建模并行实时工作负载。DAG任务的实时性能不仅取决于其总工作量，还取决于其图结构。直观上，在总工作量相同的情况下，具有更宽松优先约束的DAG任务在最坏情况响应时间方面往往表现出更好的实时性能。然而，本文表明，通过精心添加新边并构建更长的路径，我们实际上可以缩短DAG任务的最坏情况响应时间。我们基于最先进的DAG响应时间分析技术开发了相应方法，以适当添加新边，从而显著降低通过形式化分析保证的最坏情况响应时间边界。不同参数设置下的实验验证了所提方法的有效性。