This paper investigates scheduling methods for two-stage real-time systems (2S-RTSs) that execute aperiodic tasks with firm and soft end-to-end deadlines. 2S-RTSs are often used to capture task execution in reactive systems where the first stage is responsible for detecting and preprocessing irregularly occurring external events and the second stage for taking certain actions to react to the identified situations. Since aperiodic tasks have no regular arrival patterns, it is more appropriate for such 2S-RTS to adopt an online scheduler to make scheduling decisions according to the current system state. We prove that the 2S-RTS scheduling problem is NP-hard, and present a novel share-based heuristic scheduling algorithm, referred to as HS-2S-RTS, to accomplish efficient online scheduling. Different from traditional optimal schedulers that aim to ensure all hard and soft deadline constraints, the goal of HS-2S-RTS consists of ensuring all firm deadline constraints and maximizing the minimum processor share assigned to soft tasks. Since the processor resource assigned to soft tasks is optimized without affecting firm deadline constraints, the schedulability of both firm and soft tasks can be improved. To reduce the actual run-time overhead, we further propose a quasi-shared-based scheduling algorithm, referred to as qHS-2S-RTS, that can achieve equivalent scheduling performance to HS-2S-RTS. We also design a new admission control algorithm for HS-2S-RTS and qHS-2S-RTS, called HSAC-2S-RTS. Simulation results validate our theoretical analysis that qHS-2S-RTS and HS-2S-RTS are able to satisfy all feasible firm deadline constraints while improving the schedulability of soft tasks.

中文翻译：

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在两阶段系统中使用端到端的固定和软截止日期共同调度非周期性实时任务

本文研究了两阶段实时系统 (2S-RTS) 的调度方法，这些系统执行具有严格和软的端到端截止日期的非周期性任务。2S-RTS 通常用于捕获反应式系统中的任务执行，其中第一阶段负责检测和预处理不规则发生的外部事件，第二阶段负责采取某些行动对识别的情况做出反应。由于非周期性任务没有规律的到达模式，因此这种2S-RTS采用在线调度器根据当前系统状态做出调度决策更为合适。我们证明了 2S-RTS 调度问题是 NP-hard 问题，并提出了一种新颖的基于共享的启发式调度算法，称为 HS-2S-RTS，以实现高效的在线调度。与旨在确保所有硬和软截止日期约束的传统最佳调度程序不同，HS-2S-RTS 的目标包括确保所有确定的截止日期约束和最大化分配给软任务的最小处理器份额。由于分配给软任务的处理器资源在不影响固定期限约束的情况下进行了优化，因此可以提高固定任务和软任务的可调度性。为了减少实际运行时开销，我们进一步提出了一种基于准共享的调度算法，称为 qHS-2S-RTS，可以实现与 HS-2S-RTS 等效的调度性能。我们还为 HS-2S-RTS 和 qHS-2S-RTS 设计了一种新的准入控制算法，称为 HSAC-2S-RTS。