Paper Accepted at the Outstanding International Conference International Symposium on the Modeling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS)

▶ (From left) Jung Hyun-seon, master's student; Park Jun-hyuk, master's student (supervisor: Kim Young-jae)

The paper 'OpenCXD: An Open Real-Device-Guided Hybrid Evaluation Framework for CXL-SSDs', written by Jung Hyun-seon, master's student (joint first author), and Park Jun-hyuk, master's student (joint first author), of the Data-Centric Computing and AI Systems Laboratory (DISCOS) with Noh Tae-wan (undergraduate), Ahn Seong-hoon (master's), Kim Ki-hwan (master's), Professor Ming Zhao (Arizona State University) and Professor Kim Young-jae (corresponding author), has been accepted for publication at The 33rd International Symposium on the Modeling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS) 2025.

The research is set against the background of CXL, a new interface that enables memory expansion where memory is scarce in workloads such as AI model training and inference. It targets in particular the CXL-SSD idea — expanding memory using the SSD's internal NAND and DRAM on an existing SSD architecture — among the new devices that use CXL. Because no CXL-SSD device actually exists today, most recent work has evaluated CXL-SSD research on the basis of host-side software-level SSD simulation. This research problematizes and experimentally verifies the fact that such software-based simulations do not accurately represent the latency variability arising from the dynamic interaction of the device's internal Arm core, DRAM and NAND while firmware is running.

To improve CXL-SSD evaluation methods, the research then presents OpenCXD, a new development and evaluation framework. Using an x86 system simulator, OpenCXD captures and evaluates realistic CXL-SSD performance at the points where a given workload accesses the CXL-SSD — not through a host-side software-level SSD simulator, but through the hardware-based OpenSSD platform, reflecting the dynamic hardware interactions that occur while firmware runs. Execution time inside the OpenSSD is returned via NVMe commands and reflected in the latency performance evaluation.

Using the OpenSSD platform's reconfigurable SSD firmware, the team implemented SkyByte [HPCA '25], a recent paper on CXL-SSD architecture, on OpenSSD and re-evaluated this state-of-the-art approach.

The evaluation showed that when SkyByte's optimization techniques are applied to real SSD hardware, latency is 2.4 times higher than before and latency spikes of more than 2μs appear that are invisible in simulation. The research is expected to allow more accurate evaluation of future firmware optimization designs inside CXL-SSDs.

Jung Hyun-seon, joint first author of the paper, said: "It was good to be able to complete this research successfully in the direction best suited to our laboratory on CXL, a topic attracting a great deal of attention. I would like to thank my senior Park Jun-hyuk (master's), who made the start possible with a good idea; Ahn Seong-hoon (master's), Kim Ki-hwan (master's) and Noh Tae-wan (undergraduate), who helped despite their busy schedules; and Professor Kim Young-jae, who supported and guided the paper to the very end."

The International Symposium on the Modeling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS) is a distinguished conference on the modeling and performance analysis of computer systems and networks. MASCOTS is listed at an adjusted IF of 2 among the outstanding international conferences in computer science under BK21, and as an outstanding conference in the Korean Institute of Information Scientists and Engineers' 2024 list of outstanding conferences in the software field. This year it will be held at Sorbonne University in Paris, France, from 21 to 23 October.

References:

- The 33rd International Symposium on the Modeling, Analysis, and Simulation of Computer and Telecommunication Systems

- Website: https://mascots25.iitis.pl/