Demystifying CXL type-2 devices—with composable CXL-SSDS as a case study

CXL is a PCIe-based interconnect that defines three protocols for three classes of devices, each with distinct capabilities. Commercial adoption has arrived first for CXL Type-3 devices, with CXL Type-2 devices emerging afterward—making it timely to clarify CXL Type-2 device’s capabilities and applications. We first examine three core CXL Type-2 device features: cache-coherent device accelerator to host memory, device accelerator to device memory, and host CPU to device memory accesses. We then introduce CXL-AnySSD, a composable, memory-semantic CXL-SSD that exploits hardware-managed device-to-host transfers in CXL Type-2 devices. By loosely coupling DRAM with commodity SSDs, CXL-AnySSD decouples capacity from performance, supports heterogeneous SSD choices, and removes OS-managed swap overheads. We implement a CXL-AnySSD prototype on a real CXL Type-2 device and show CXL-AnySSD improves end-to-end throughput by 2.3–6.2× over OS-managed SSD swap on a vector-database workload.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Electrical & Computer Engr

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Zhou, Yang

Contributors dc:contributor

• Kim, Nam Sung

• Compute Express Link
• Heterogeneous Computing

Statement dc:rights

• Copyright 2025 Yang Zhou

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132701

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132701