QoS scheduling for NoCs: Strict Priority Queueing versus Weighted Round Robin

Strict Priority Queueing (SPQ) andWeighted Round Robin (WRR) are two common scheduling techniques to achieve Quality-of-Service (QoS) while using shared resources. Based on network calculus, we build analytical models for traffic flows under SPQ and WRR scheduling in on-chip wormhole networks. With these models, we can derive per-flow end-to-end delay bound. We compare the service behavior and show that WRR is not only more fair but also more flexible for QoS provision. To exhibit the potential and flexibility enabled by WRR, we develop a weight allocation algorithm to automatically assign proper weights for individual flows to satisfy their delay constraints. In particular, the weights are assigned in a way not more than necessary, in other words, to approach flows' delay constraints in order to leave room for other flows. Our experimental results validate our analysis technique and algorithms.