sAXI: A High-Efficient Hardware Inter-Node Link in ARM Server for Remote Memory Access

The ever-growing need for fast big-data operations has made in-memory processing increasingly important in modern datacenters. To mitigate the capacity limitation of a single server node, techniques of inner-rack cross-node memory access have drawn attention recently. However, existing proposals exhibit inefficiency in remote memory access among server nodes due to inter-protocol conversions and non-transparent coarse-grained accesses. In this study, we propose the high-performance and efficient serialized AXI (sAXI) link and its associated cross-node memory access mechanism for emerging ARM-based servers. The key idea behind sAXI is directly extending the on-chip AMBA AXI-4.0 interconnection of the SoC in a local server node to the outside, and then bringing into remote server nodes via high-speed serial lanes. As a result, natively accessing remote memory in adjacent nodes in the same manner of local assets is supported by purely using existing software. Experimental results show that, using the sAXI data-path, performance of remote memory access in the user-level micro-benchmark is very promising (min. latency: 1.16μs, max. bandwidth: 1.52GB/s on our in-house FPGA prototype). In addition, through this efficient hardware inter-node link, performance of an in-memory key-value framework, Redis, can be improved up to 1.72x and large latency overhead of database query can be effectively hidden.