Bandwidth-based Application-Aware Multipath Routing for NoCs

Abstract

Most of routing algorithms for On-chip communication are neither application-aware nor routing packets using multiple paths. In addition, they hardly consider link bandwidth variation r esulting from widely applied global asynchronous local synchronous (GALS ) mechanism. In this paper, we propose a bandwidth-based application-aware multipath routing (BAMR) algorithm to assign multiple routing paths by leveraging the knowledge of application and network bandwidth features. With the increase of number of flows resulting from the split of flows, we present a new method named dynamic-amount fixed-number (DAFN) flow control mechanism to avoid deadlock. We compare our algorithm with XY, YX, an d O1TURN with synthetic traffic patterns and traffic trace of parallel implementation of H.264. Experiments demonstrate that BAMR achieves higher throughput with decrease in latency. Furthermore, the proposed algorithm achieves better workload balance by distributing traffic over multiple paths. To address the aforementioned three challenges, we propose a bandwidth-based application-aware mu ltipath routing (BAMR) algorith m. Our algorith m is flexible to different kinds of NoC topologies and traffic patterns. We first decide routing order of flows based on application graph and the bandwidth requirement. Then, considering the transmission capacity of network links, we split some flows into mu ltiple subflows to alleviate network congestion. Our algorithm can detect communication bottlenecks and make split based on link's residual bandwidth. For multipath routing, more flows may increase the possibility of deadlock. To this end, we propose a buffer management mechanism called dynamic- amount fixed-nu mber (DAFN), the number of Virtual Channels (VCs) for each individual router port and VC depth are predetermined at design phase based on the BAMR's results. Specifically, the number of VCs for a specified port at a specified router is depending on the number of flows passing through it. DAFN allocates each VC at a router with an identical global label with assigned flow's label. DAFN achieves deadlock freedom by restricting each flow to its exclusive VC, it takes full advantage of buffer space and avoids deadlock without additional hardware resources. Our work makes following contributions: We propose a mu ltipath routing algorithm named BAM R for GA LS No C. A flow splitting method aiming at to alleviate network congestion is presented, as part of BAMR.A static VC regulator named DAFN, with the co mbination of BAMR to make the full utilization of VC resources and avoid deadlock is also proposed.