Direct Access, High-Performance Memory Disaggregation with DirectCXL

New cache coherent interconnects such as CXL have recently attracted great attention thanks to their excellent hardware heterogeneity management and resource disaggregation capabilities. Even though there is yet no real product or platform integrating CXL into memory disaggregation, it is expected to make memory resources practically and efficiently disaggregated much better than ever before. In this paper, we propose directly accessible memory disaggregation, DIRECTCXL that straight connects a host processor complex and remote memory resources over CXL's memory protocol (CXL.mem). To this end, we explore a practical design for CXL-based memory disaggregation and make it real. As there is no operating system that supports CXL, we also offer CXL software runtime that allows users to utilize the underlying disaggregated memory resources via sheer load/store instructions. Since DIRECTCXL does not require any data copies between the host memory and remote memory, it can expose the true performance of remote-side disaggregated memory resources to the users.