Full-credit Flow Control: A Novel Technique to Implement Deadlock-free Adaptive Routing

Abstract

Deadlock-free adaptive routing is extensively adopted in interconnection networks to improve communication bandwidth and reduce latency. However, existing deadlock-free flow control schemes either underutilize memory resources due to inefficient buffer management for simple hardware implementations, or rely on complicated coordination and synchronization mechanisms with high hardware complexity. In this work, we solve the deadlock problem from a different perspective by considering the deadlock as a lack of credit. With minor modifications of the credit accumulation procedure, our proposed full-credit flow control (FFC) ensures atomic buffer usage only based on local credit status while making full use of the buffer space. FFC can be easily integrated in the industrial router to achieve deadlock freedom with less area and power consumption, but 112% higher throughput, compared to the critical bubble scheme (CBS). We further propose a credit reservation strategy to eliminate the escape virtual channel (VC) cost for fully adaptive routing implementation. The synthesizing results demonstrate that FFC along with credit reservation (FFC-CR) can reduce the area by 29% and power consumption by 26% compared with CBS.