Next-Gen Computing Systems with Compute Express Link: a Comprehensive Survey

Interconnection is crucial for computing systems. However, the current interconnection performance between processors and devices, such as memory devices and accelerators, significantly lags behind their computing performance, severely limiting the overall performance. To address this challenge, Intel proposes Compute Express Link (CXL), an open industry-standard interconnection. With memory semantics, CXL offers low-latency, scalable, and coherent interconnection between processors and devices. This paper introduces recent advances in CXL-based computing systems from single-machine to distributed. In single-machine systems, we classify existing research into two categories: Memory Expansion and Unified Memory. Memory Expansion focus on processors and memory, aims to address memory wall challenge. Unified memory focus on processors and accelerators, aims to enhance collaboration in heterogeneous computing systems. In distributed systems, we present how to build efficient disaggregation systems based on CXL infrastructure, enabling resource pooling and sharing. Finally, we discuss the future research and envision memory-centric computing with CXL.