Eca-Router : On Achieving Endpoint Congestion Aware Switch Allocation in the On-Chip Network

Abstract

As the critical pipeline stage in on-chip routers, switch allocation assigns output ports to input ports and allow flits transiting through the switch without conflicts. Previous works strive to design efficient switch allocaiton strategies by maximizing the matching at each cycle, with the information from the current cycle or multiple cycles in time series. However, those works have not taken endpoint congestion into considerations. Tree-saturation, caused by endpoint congestion, can degrade NoC performance due to the congestion fanning out from the original point to upstream routers. In this paper, a novel router design, Eca-Router, is proposed to relieve the impact of endpoint congestion by switch allocation optimization. Eca-Router detects endpoint congestion by recording the destinations of packets in switch allocation. Endpoint congestion is decided in switch allocation once there are multiple input ports competing for the same output port and the packets in these input ports contain the same destination. During switch allocation, requests that contribute to endpoint congestion will be given lower priority to be allocated, and starvation control is also introduced to ensure allocation fairness. Evaluation results show that Eca-Router is efficient in reducing packet latency.