Providing Differentiated Services, Congestion Management, and Deadlock Freedom in Dragonfly Networks

摘要

High-Performance Computing (HPC) systems and Datacenters are growing in size to meet the performance required by the applications. This makes the interconnection network a central element in these systems, which must provide high-communication bandwidth and low latency. One of the most important aspects in the design of interconnection networks is their topology. In that sense, the Dragonfly topology is nowadays very popular as it offers high scalability, low diameter, diversity of paths, high bisection bandwidth, etc. Routing in Dragonfly topologies is an important issue, since deadlocks must be prevented, usually by means of escape ways to break cycles. However, even with a deadlock-free routing, the performance of Dragonfly topologies degrades when the negative effects of congestion appear (e.g. the Head-of-Line-HoL-blocking). Hence, some techniques are used to reduce HoL blocking, usually based on separating traffic flows into different queues implemented by means of Virtual Channels (VCs) or similar structures. VCs are also used to implement differentiated-services provision in systems supporting applications with different levels of priority. The combination of HoL-blocking reduction and differentiated-services provision through an integrated management of VCs has been previously studied. However, this integrated management of VCs does not consider the additional use of VCs as escape ways, thus it cannot be applied to Dragonfly topologies. For that reason, in this paper, we adapt the integrated management of VCs to Dragonfly topologies, so that by using a reduced number of VCs, our proposal is able to offer differentiated-services provision, HoL-blocking reduction and deadlock freedom. Performance results, obtained through simulation experiments in medium-to-large size Dragonfly networks, show that the proposed technique outperforms other solutions.