MMC: Metadata Migration for Efficient Memory Management in CXL DRAM Systems

Abstract

CXL-DRAM enables cost-efficient memory expansion in data-center servers, but introduces new challenges for operating system memory management. In particular, large in-kernel metadata structures can occupy a significant portion of DDR-DRAM, reducing the space available for application data and increasing accesses to slower CXL-DRAM. Placing all metadata in CXL-DRAM frees DDR-DRAM space but can cause severe tail latency due to inefficient memory reclamation. We propose MMC, a hot-cold metadata migration mechanism that balances application performance and reclamation efficiency by dynamically placing metadata across DDR-DRAM and CXL-DRAM. Our results show that MMC improves throughput while reducing tail latency across diverse workloads.