String Figure: A Scalable and Elastic Memory Network Architecture

Demand for server memory capacity and performance is rapidly increasing due to expanding working set sizes of modern applications, such as big data analytics, inmemory computing, deep learning, and server virtualization. One promising techniques to tackle this requirements is memory networking, whereby a server memory system consists of multiple 3D die-stacked memory nodes interconnected by a high-speed network. However, current memory network designs face substantial scalability and flexibility challenges. This includes (1) maintaining high throughput and low latency in large-scale memory networks at low hardware cost, (2) efficiently interconnecting an arbitrary number of memory nodes, and (3) supporting flexible memory network scale expansion and reduction without major modification of the memory network design or physical implementation. To address the challenges, we propose String Figure1, a highthroughput, elastic, and scalable memory network architecture. String Figure consists of (1) an algorithm to generate random topologies that achieve high network throughput and nearoptimal path lengths in large-scale memory networks, (2) a hybrid routing protocol that employs a mix of computation and look up tables to reduce the overhead of both in routing, (3) a set of network reconfiguration mechanisms that allow both static and dynamic network expansion and reduction. Our experiments using RTL simulation demonstrate that String Figure can interconnect over one thousand memory nodes with a shortest path length within five hops across various traffic patterns and real workloads.