一种基于标准化QoS公平的反馈控制实时调度算法

任务间的QoS公平性是多QoS级别的可调节动态实时调度系统中的一个重要问题.本文引入了标准化QoS公平的概念,在公平性中加入了任务的重要性因素,并构造了具有PID反馈控制环节的实时调度算法NF-QoS来达到标准化QoS公平.利用NF-QoS对系统截止期错失率进行实时采样,定期反馈给PID控制器,根据PID控制器计算的结果对各任务QoS级别进行调整,以保证各任务公平地得到处理器资源.实验结果表明,NF-QoS不仅合理地协调了系统利用率和截止期错失率,并且有效地提高了系统的QoS公平性.

A Feedback Control Real-time Scheduling Algorithm Based on Normalized QoS Fairness

QoS fairness is an important problem in multi-QoS-level adjustable dynamic real-time scheduling systems. In this paper, a concept named normalized QoS fairness is presented to add task importance factor to fairness. The NF-QoS (Normalized Fair QoS) real-time scheduling algorithm is constructed, which incorporates a PID feedback controller to achieve the normalized QoS fairness purpose. NF-QoS samples DMR (Deadline Miss Ratio) as the system runs which is fed back to PID controller periodically. Then QoS levels of tasks are adjusted according to feedback computing results so that all tasks could get CPU resources fairly. The experimental results show that NF-QoS can balance system utilization and DMR reasonably, and effectively enhance the system QoS fairness.