RT-Gang: Real-Time Gang Scheduling Framework for Safety-Critical Systems
RT-Gang: Real-Time Gang Scheduling Framework for Safety-Critical Systems
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DOI：
10.1109/rtas.2019.00020
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发表时间：
2019-03
期刊：
影响因子：
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通讯作者：
Waqar Ali;H. Yun
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文献类型：
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作者：
Waqar Ali;H. Yun
在本文中，我们介绍了RT-Gang：一种新型的实时帮派调度框架，它强制执行一次一个帮派的策略。我们发现，在一个多核平台上，共同调度多个并行实时任务将需要高度悲观的最坏情况下的执行时间（WCET）和可扩展性分析，即使有足够的核心，由于在共享的硬件资源，如高速缓存和DRAM控制器的竞争。在RT-Gang中，一个并行实时任务的所有线程组成一个实时组，调度器全局执行一次一组的调度策略，以保证紧凑和准确的任务WCET。为了最大限度地减少利用率不足，我们集成了最先进的内存带宽节流框架，以允许安全执行尽力而为的任务。具体地，任何空闲核（如果存在）被用于调度尽力而为任务，但是它们的最大存储器带宽使用被严格地节流以将干扰紧密地绑定到实时群任务。我们在Linux内核中实现了RT-Gang，并使用合成和真实世界的DNN工作负载在两个代表性的嵌入式多核平台上对其进行了评估。结果表明，RT-Gang显著提高了系统的可预测性，开销可以忽略不计。
In this paper, we present RT-Gang: a novel real-time gang scheduling framework that enforces a one-gang-at-a-time policy. We find that, in a multicore platform, co-scheduling multiple parallel real-time tasks would require highly pessimistic worst-case execution time (WCET) and schedulability analysis—even when there are enough cores—due to contention in shared hardware resources such as cache and DRAM controller. In RT-Gang, all threads of a parallel real-time task form a real-time gang and the scheduler globally enforces the one-gang-at-a-time scheduling policy to guarantee tight and accurate task WCET. To minimize under-utilization, we integrate a state-of-the-art memory bandwidth throttling framework to allow safe execution of best-effort tasks. Specifically, any idle cores, if exist, are used to schedule best-effort tasks but their maximum memory bandwidth usages are strictly throttled to tightly bound interference to real-time gang tasks. We implement RT-Gang in the Linux kernel and evaluate it on two representative embedded multicore platforms using both synthetic and real-world DNN workloads. The results show that RT-Gang dramatically improves system predictability and the overhead is negligible.