Response Time Analysis of Dataflow Applications on a Many-Core Processor with Shared-Memory and Network-on-Chip

International audienc

Towards a unified approach for worst-case analysis of Tilera-like and KalRay-like NoC architectures

International audiencen this paper, we consider two Network-on-Chip (NoC) architectures used within commercially available many-core systems, namely Tilera TILE64 which implements flow regulation within routers and KalRay MPPA 256 which implements flow regulation in source nodes. The Worst-Case Traversal Time (WCTT) on the NoC has to be bounded for real-time applications, and buffers should never overflow. Different worst-case analysis approaches have been proposed for each of these NoC architectures. However, no general worst-case analysis supporting both NoC architectures exists in the literature and most approaches are specific to one of the studied NoC. In this paper, we propose to use Recursive Calculus (RC) method for Tilera and KalRay. Furthermore, we compare the performances on a preliminary case study, in terms of WCTT and required buffer capacity. It allows to quantify the trade-off between delays and buffer occupancy

Comparaison de strategies de calcul de bornes sur NoC

The Kalray MPPA2-256 processor integrates 256 processing cores and 32 management cores on a chip. Theses cores are grouped into clusters, and clusters are connected by a high-performance network on chip (NoC). This NoC provides some hardware mechanisms (egress traffic limiters) that can be configured to offer bounded latencies. This paper presents how network calculus can be used to bound these latencies while computing the routes of data flows, using linear programming. Then, its shows how other approaches can also be used and adapted to analyze this NoC. Their performances are then compared on three case studies: two small coming from previous studies, and one realistic with 128 or 256 flows. On theses cases studies, it shows that modeling the shaping introduced by links is of major importance to get accurate bounds. And when packets are of constant size, the Total Flow Analysis gives, on average, bounds 20%-25% smaller than all other methods