A Dynamic Sufficient Condition of Deadlock-Freedom for High-Performance Fault-Tolerant Routing in Networks-on-Chips

Networks-on-Chips (NoCs) are considered to be the paradigm of choice for on-chip communication and are today widely adopted in many-core systems. Many existing routing solutions make use of virtual channels (VCs) to avoid deadlocks while offering enough routing flexibility to avoid faulty and congested areas in a NoC. However, most of the current solutions rely on an overly restrictive, static partitioning of VCs, which results in an underutilization of their throughput enhancement capabilities. To overcome the limitations of such approaches, we introduce a new sufficient condition of deadlock-freedom that greatly relaxes the restrictions imposed by the classic VC-based deadlock-avoidance methods. The strength of our condition lies in the fact that it is imposed on packets at runtime and does not require any partitioning of virtual channels, which makes it possible to fully exploit them to reduce packet blocking and boost performance. Based on this condition, we present a generic, topology-agnostic routing algorithm design methodology that can be used to construct highly flexible routing algorithms in only a few steps. Several examples are presented to showcase the usefulness of our approach for the construction of fault-tolerant routing algorithms, as well as the enhancement and the proof of existing routing algorithms. The implementation of all the required mechanisms in hardware is also described in detail, thereby demonstrating its feasibility in an on-chip environment.