MinBD: A Minimally-Buffered Deflection Router Approaching Conventional Buffered-Router Performance
Chris Fallin, Greg Nazario, Xiangyao Yu, Kevin K. Chang, Rachata Ausavarungnirun, Onur Mutlu · 2011
As interconnect becomes an important component of modern Chip Multiprocessors (CMPs), significant work has gone into finding the best tradeoff between performance and energy efficiency for the Network-on-Chip (NoC). Increasing core counts lead to high bandwidth demands and tight power and area constraints. One recent line of work examines bufferless deflection routing, which eliminates buffers in the NoC and instead handles contention by deflecting (misrouting) traffic. While bufferless NoC design has shown promising area and power reductions, and offers similar performance to conventional buffered designs for many workloads, such designs provide lower throughput than conventional, more complex, buffered routers at high network load. This degradation is a significant hurdle for widespread adoption of bufferless NoCs. In this work, we introduce a new minimally-buffered deflection router design, MinBD (Minimally-Buffered Deflection), that aims to obtain the performance of buffered design with nearly the area and power reductions of bufferless design. Unlike past routers that combine buffers and deflection, MinBD buffers only a fraction of the traffic that passes through it, and it decides which traffic to buffer on a fine-grained basis. We observe that a significant portion of the performance degradation in bufferless networks comes not from fundamental limits of deflection routing, but from