Implementation and Analysis of History-Based Output Channel Selection Strategies for Adaptive Routers in Mesh NoCs

The efficiency and effectiveness of an adaptive router in an NoC-based multicore system is evaluated by the performance it achieves under varying inter-core communication traffic. A well-designed selection strategy plays an important role in an adaptive router to act upon dynamic traffic variations. The effectiveness of a selection strategy depends on what metric is used to represent congestion, how precisely this metric captures the actual congestion, and how much cost is involved in capturing the congestion on a real-time scale. Congestion is formed over a period of time due to cumulative and chain reaction effects. We propose novel history-based selection strategies that could be used with any adaptive, deadlock-free, minimal routing in mesh NoCs. Buffer occupancy time and rate of flit flow across reachable ports of neighboring routers in the recent past are captured, propagated, and maintained in a cost-effective way to compute the selection metric. Experimental results on real and synthetic workloads show that our proposed selection strategies significantly outperform state-of-the-art techniques.