Famfs: Get Ready for Big Pools of Disaggregated Shared Memory

CXL enables disaggregated memory, both for composable capacity-on-demand and shared-memory. That is memory is not private to one server. Adding system-ram capacity should largely “just work”, but shared memory is more complex. The Fabric-Attached Memory File System (famfs) enables disaggregated shared memory to be used as memory-mappable files that map directly to the shared memory. Famfs is open source software which is on-track to be merged into the upstream Linux kernel in the coming months. This talk covers the following: * Brief: shared memory challenges before memory disaggregation * Shared memory challenges with disaggregation * CXL: what will disaggregated shared memory look like? 1. Dynamic Capacity Device (DCD) overview 2. Coherency options 3. Using raw disaggregated memory * Famfs: Putting disaggregated shared memory to use with little or no app modifications Famfs background * Famfs on github * Famfs at the Linux Plumbers Conference (2023, 2024) * Famfs at the Linux Storage, File System and Memory Management summit (LSFMM – 2024, 2025) * Famfs at the Usenix File and Storage Technologies conference (FAST – 2025)