Trace-driven optimization of networks-on-chip configurations

Abstract

Networks-on-chip (NoCs) are becoming increasingly important in general-purpose and application-specific multi-core designs. Although uniform router configurations are appropriate for general-purpose NoCs, router configurations for application-specific NoCs can be non-uniformly optimized to application-specific traffic characteristics. In this paper, we specifically consider the problem of virtual channel (VC) allocation in application-specific NoCs. Prior solutions to this problem have been average-rate driven. However, average-rate models are poor representations of real application traffic, and can lead to designs that are poorly matched to the application. We propose an alternate trace-driven paradigm in which configuration of NoCs is driven by application traces. We propose two simple greedy trace-driven VC allocation schemes. Compared to uniform allocation, we observe up to 51% reduction in the number of VCs under a given average packet latency constraint, or up to 74% reduction in average packet latency with same number of VCs. Our results suggest that average-rate driven methods cannot effectively select appropriate links for VC allocation because they fail to consider the impact of traffic bursts. As a case study, we compare our proposed approach with an existing average-rate driven method and observe up to 35% reduction in the number of VCs for a given target latency.