Traffic Aware Deflection Rerouting Mechanism for Mesh Network on Chip

In two dimensional mesh Network on Chips (NoC), efficient routing algorithms route majority of the flits through the central routers of the network, whereas routers at the edges and corners experience relatively lesser flit flow. This in turn leads to higher traffic towards central routers than to edge and corner routers. Such uneven traffic distribution causes thermal hot-spots at the center of the chip where the load is high, and reduces the average life-time of the chip. In existing buffer-less deflection routing techniques, load balanced traffic distribution is not considered as a factor during assignment of links to mis-routed flits. Devising deflection routing techniques with greater load balancing capability is a major challenge for efficient thermal management of the chip. This paper proposes an adaptive routing mechanism that can provide a more balanced traffic profile in a deflection router based mesh NoC. Significant number of deflected flits are rerouted towards the edges/corners of the mesh, thereby reducing the load on the central routers. From evaluations, it is seen that the proposed technique reduces traffic variance compared to NoCs using baseline deflection routers. Transient temperature variation studies using Hotspot tool substantiate our findings.