A Feedback Control Real-time Scheduling Algorithm Based on Normalized QoS Fairness
Gong Yu-chang · Journal of Chinese Computer Systems · 2007
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.