Shared CXL 3 Memory Requirements and Use Cases

Explore the implications of CXL 3's introduction of sharable fabric-attached memory (FAM) in this informative conference talk. Dive into use cases and discuss necessary functionality in the cxl and dax stack. Begin with an overview of DCD and tagged capacity, explaining how tagged capacity creates a namespace of memory allocations that apps can use to find relevant memory. Learn about sharable tagged capacity's file-like and pmem-like characteristics. Examine the argument against onlining sharable tagged capacity as system-ram by default, and understand the limitations of using dax as a complete solution for memory-mapped file support. Discover proposed evolutions for devdax to support a sharable file system on sharable tagged capacity, including the need for iomap* functionality. Investigate the potential for a minimal viable product "famfs" and its practical limitations. Gain insights into app classes that could readily adapt to shared data sets in shared FAM, with a focus on data science tools using "zero copy" formats like Apache Arrow. Conclude with an overview of a famfs prototype, drawing inspiration from ramfs, hugetlbfs, and xfs for dax file support.