ASCENT: Communication Scheduling for SDF on Bufferless Software-defined NoC

Abstract

Bufferless software-defined Network-on-Chip (NoC) is a promising alternative to conventional dynamic routing as it offers predictable data movement with real-time guarantees. Existing Time-Division Multiplexing (TDM)-based mechanisms for predictability assume the worst-case communication pattern (e.g., all-to-all) and compute a fixed schedule wherein the cores can only communicate during the allocated time-slots. These approaches lead to low application throughput as they cannot adapt to application characteristics. In this paper, we present an application-specific, non-TDM based communication scheduling mechanism for bufferless software-defined NoCs. We choose Synchronous Dataflow (SDF) model-of-computation to represent the input streaming applications. We propose ASCENT, a novel offline approach that takes the SDF-specified streaming application and the NoC architecture as input, exploits the task interactions and the timing information in the SDF, and generates the task-to-core mapping and communication schedule that is represented compactly in hardware. ASCENT achieves 5.8x better performance on average than existing TDM-based NoCs and manages to achieve the performance of an ideal dynamically routed NoC, yet ensuring predictability.