A comprehensive survey of CXL interconnect technology and its applications

Driven by emerging high-performance computing applications, the demand for high-speed interconnects across heterogeneous computing system components has surged dramatically, making interconnect technologies a key research focus in the computer architecture field in recent years. The open standard CXL (Compute Express Link), with its advantages of high scalability, high bandwidth, and low latency, has become the mainstream of interconnect technology in heterogeneous computing systems, which has gained much attention from academy and industry. This survey comprehensively analyzes and summarizes CXL technology from three aspects, including CXL protocol architecture, device types and its performance characteristics, as well as CXL memory management and application research. Firstly, the overall architecture of the CXL protocol is introduced. The cache coherence mechanisms is analyzed based on typical protocol transaction flows. Then, we provide an overview of CXL device types and development progress in industrial products domestically and abroad, followed by systematical analysis of real CXL device’s performance characteristics. Finally, we summarize current academic application research, scenarios and challenges on the CXL technology from the perspective of CXL device types. On this basis, future research directions are discussed to promote its application research and industrial implementation in various fields, such as memory pooling, CXL-based processing-in-memory architecture and heterogeneous cooperative computing.