Shared resources on the multicore chip, such as main memory, are increasingly becoming a point of contention. Traditional real-time task scheduling policies focus on solely on the CPU, and do not take in account memory access and cache effects. In this paper, we propose parallel real-time tasks scheduling (PRTTS) policy on multicore platforms. Each set of tasks is represented as a directed acyclic graph (DAG). The priorities of tasks are assigned according to task periods Rate Monotonic (RM). Each task is composed of three phases. The first phase is read memory stage, the second phase is execution phase and the third phase is write memory phase. The tasks use locks and critical sections to protect data access. The global scheduler maintains the task pool in which tasks are ready to be executed which can run on any core. PRTTS scheduling policy consists of two levels: the first level scheduling schedules ready real-time tasks in the task pool to cores, and the second level scheduling schedules real-time tasks on cores. Tasks can preempt the core on running tasks of low priority. The priorities of tasks which want to access memory are dynamically increased above all tasks that do not access memory. When the data accessed by a task is in the cache, the priority of the task is raised to the highest priority, and the task is scheduled immediately to preempt the core on running the task not accessing memory. After accessing memory, the priority of these tasks is restored to the original priority and these tasks are pended, the preempted task continues to run on the core. This paper analyzes the schedulability of PRTTS scheduling policy. We derive an upper-bound on the worst-case response-time for parallel real-time tasks. A series of extensive simulation experiments have been performed to evaluate the performance of proposed PRTTS scheduling policy. The results of simulation experiment show that PRTTS scheduling policy offers better performance in terms of core utilization and schedulability rate of tasks.

中文翻译：

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多核系统的内存感知调度并行实时任务

多核芯片上的共享资源，例如主存储器，正日益成为争论的焦点。传统的实时任务调度策略只关注 CPU，没有考虑内存访问和缓存的影响。在本文中，我们提出了多核平台上的并行实时任务调度 (PRTTS) 策略。每组任务都表示为有向无环图（DAG）。任务的优先级是根据任务周期单调速率（RM）分配的。每个任务由三个阶段组成。第一阶段是读内存阶段，第二阶段是执行阶段，第三阶段是写内存阶段。这些任务使用锁和临界区来保护数据访问。全局调度程序维护任务池，其中准备好执行的任务可以在任何内核上运行。PRTTS调度策略由两个层次组成：第一级调度将任务池中就绪的实时任务调度到内核上，第二级调度将实时任务调度到内核上。任务可以抢占核心运行低优先级的任务。想要访问内存的任务的优先级比所有不访问内存的任务动态增加。当一个任务访问的数据在缓存中时，该任务的优先级被提升到最高优先级，并且该任务被立即调度以抢占核心在运行不访问内存的任务。访问内存后，这些任务的优先级恢复到原来的优先级并且这些任务被挂起，被抢占的任务继续在核心上运行。本文分析了 PRTTS 调度策略的可调度性。我们得出了并行实时任务的最坏情况响应时间的上限。已经进行了一系列广泛的模拟实验来评估所提出的 PRTTS 调度策略的性能。仿真实验结果表明，PRTTS调度策略在核心利用率和任务可调度率方面具有更好的性能。