CXL Block Device "CBD" Looking Very Promising For The Linux Kernel In 2025

Originally proposed for the Linux kernel nearly one year ago was CBD as the CXL Block Device. Now up to its third revision, the Linux CBD patches are calming down and the performance gains are looking quite nice.

CBD allows creating CXL block devices for both single and multi-host setups and allows for using PMEM devices as a block device cache for lowering latency and driving higher concurrency performance. Benchmarks shown by Dongsheng Yang of EasyStack who has been working on these CBD patches, there is around a 300% improvement to the latency compared to using the existing Linux kernel block cache (Bcache). CBD also allows for around a 600% improvement for the IOPS over Bcache.

With the CBD v3 patches, there is now CRC verification for all data and metadata. Plus some code clean-ups, cbd-utils is now available as the user-space tools to CBD, and various fixes.

Those wanting to learn more about the latest on the CXL Block Device code for some interesting storage caching possibilities for the Linux kernel, see the v3 patches. There is also this GitHub site serving as the project site for the CXL Block Device effort. Hopefully this CBD work will make it over the finish line for the mainline kernel in 2025.