DBMS with CXL Memory: What's New and What's Next

Compute Express Link (CXL) is an open industry-standard interconnect protocol designed for communication between processors and devices, e.g., memory expansions. It brings new opportunities for enhancing system performance, particularly for workloads constrained by memory capacity. Consequently, CXL opens new avenues for the design of database management systems (DBMS), which is highly beneficial for managing complex data tasks. However, traditional techniques focused on addressing I/O bottlenecks are insufficient to meet the new challenges brought by CXL memory management. In this tutorial, we introduce the advantages and application scenarios of tiered CXL memory, pooled CXL memory, and shared CXL memory, as well as the new challenges that arise, including: (1) reducing data access, data exchange, and data transfer cost; (2) optimizing memory allocation and competition to improve memory utilization; (3) managing shared data for failure, series operators, and distributed transactions. We also review emerging techniques aimed at addressing these issues. Finally, we summarize new opportunities and highlight open research problems in this evolving area.