ACF: Networks-on-Chip Deadlock Recovery with Accurate Detection and Elastic Credit

Abstract

The key idea of progressive deadlock recovery scheme is providing an escape path outside the deadlock cycle. State-of-the-art schemes, such as Virtual Channel Reallocation (VCR) and DISHA, set up escape paths by dedicated deadlock-handling channels. These channels use additional data paths, central buffers and bypass logic. This paper proposed a novel deadlock recovery scheme for NoC, using Accurate on-Cycle Forwarding (ACF) path inside deadlock cycle to drain blocked packets. ACF does not decouple deadlock-handling channels from normal routing channels, but enhanced credit flow control on each channels to allow accurate deadlock detection and recovery. ACF method is constructed by three tightly combined components: adaptive routing, run-time accurate deadlock detection, and deadlock removal. We implemented ACF algorithm by O(n) time complexity and by distributed modules cooperating with NoC. The rigorous valuation on multiple traffic patterns shows that our scheme achieves significant performance improvement. ACF detected 10-20 times less fake deadlock alarms than approximation and heuristic time-out approaches. In high packet injection rates interval (40%-75%) where network is more frequently troubled by deadlock, ACF provides 67% communication latency improvement comparing to dimension order routing, and 14%-45% to VCR and DISHA. Moreover, the power consumption and hardware overhead of ACF are light.