Dynamic Global Adaptive Routing in High-Radix Networks

Global adaptive routing is a critical component of high-radix networks in large-scale systems and is necessary to fully exploit the path diversity of a high-radix topology. The routing decision in global adaptive routing is made between minimal and non-minimal paths, often based on local information (e.g., queue occupancy) and rely on "approximate" congestion information through backpressure. Different heuristic-based adaptive routing algorithms have been proposed for high-radix topologies; however, heuristic-based routing has performance trade-off for different traffic patterns and leads to inefficient routing decisions. In addition, previously proposed global adaptive routing algorithms are static as the same routing decision algorithm is used, even if the congestion information changes. In this work, we propose a novel global adaptive routing that we refer to as dynamic global adaptive routing that adjusts the routing decision algorithm through a dynamic bias based on the network traffic and congestion to maximize performance. In particular, we propose DGB - Decoupled, Gradient descent-based Bias global adaptive routing algorithm. DGB introduces a dynamic bias to the global adaptive routing decision by leveraging gradient descent to dynamically adjust the adaptive routing bias based on the network congestion. In addition, both the local and global congestion information are decoupled in the routing decision - global information is used for the dynamic bias while local information is used in the routing decision to more accurately estimate the network congestion. Our evaluations show that DGB consistently outperforms previously proposed routing algorithms across diverse range of traffic patterns and workloads. For asymmetric traffic pattern, DGB improves throughput by 65% compared to the state-of-the-art global adaptive routing algorithm while matching the performance for symmetric traffic patterns. For trace workloads, DGB provides average performance improvement of 26%.