Abstract

As Compute Express Link (CXL) emerges as a key memory interconnect, interest in optimization opportunities and challenges has grown. However, due to the different characteristics of the CXL Memory Module (CMM) compared to traditional DRAM-based Dual In-line Memory Modules (DIMMs), existing optimizations may not be effectively applied. In this paper, we propose an Proactively Write-back Policy that leverages the fullduplex nature and features of the CMM to optimize bandwidth, enhance reliability, and reduce area overhead. First, the Proactively Write-back improves bandwidth efficiency by minimizing dirty cachelines in the last-level cache through dead block prediction, proactively identifying and writing back cachelines that are unlikely to be rewritten. Second, the Utilization-aware Policy dynamically monitors the internal bandwidth of the CMM, sending write-back requests only when the module is under low load rate, thus preventing performance degradation during high traffic. Finally, the robust Buddy ECC scheme enhances data reliability by separating Error Detection Code (EDC) for clean cachelines and stronger Error Correction Code (ECC) for dirty cachelines. Buddy ECC improved bandwidth utilization by 46%, limited performance degradation to 0.33%, and kept energy consumption increase under 1%.