Network-on-chip service guarantees on the kalray MPPA-256 bostan processor
Benoît Dupont de Dinechin, Amaury Graillat · 2017
The Kalray MPPA-256 Bostan manycore processor implements a clustered architecture, where clusters of cores share a local memory, and a DMA-capable network-on-chip (NoC) connects the clusters. The NoC implements wormhole switching without virtual channels, with source routing, and can be configured for maximum flow rate and burstiness at ingress. We describe and illustrate the techniques used to configure the MPPA NoC for guaranteed services. Our approach is based on three steps: global selection of routes between end-points and computation of flow rates, by solving the max-min fairness with unsplittable path problem; configuration of the flow burstiness parameters at ingress, by solving an acyclic set of linear inequalities; and end-to-end latency upper bound computation, based on the principles of separated flow analysis (SFA). In this paper, we develop the two last steps, taking advantage of the effects of NoC link shaping on the leaky-bucket arrival curves of flows.