Performance Characterizations and Usage Guidelines of Samsung CMM-H

This article presents the first publicly available study for comprehensive characterizations of an FPGA-based Samsung’s CXL Memory Module Hybrid (CMM-H) prototype. It leverages emerging CXL technology to enable high-speed and cacheline-granular communication between CPUs and NAND flash, offering three-fold benefits: byte-addressability, scalable capacity, and persistence at a low cost. Samsung’s CMM-H delivers these benefits through a hardware-only solution, i.e., it does not incur any OS/IO overheads like conventional block devices. In particular, CMM-H integrates a DRAM cache with NAND flash in a single device to deliver near-DRAM latency. Through this study, we address users’ concerns about whether a wide variety of applications can successfully run on a memory device backed by NAND flash medium. Additionally, based on these characterizations, we provide key insights into how to best take advantage of the CMM-H device.