CXL-Tracer: Accurate, Full-System Memory Tracing on Commercial Hardware via CXL Memory

Accurate, full-system physical memory traces are critical for computer architecture research, but existing collection methods based on software instrumentation or simulation suffer from a lack of fidelity, while prior hardware-based solutions are often intrusive or proprietary. We introduce CXL-Tracer, a non-intrusive tracing framework that uses a commodity FPGA as a CXL Type-3 memory device to capture complete, high-fidelity memory traces from a real system. Traces are offloaded over a dedicated PCIe link to a separate collection server, ensuring no performance interference with the system under test. Our evaluation demonstrates that CXL-Tracer captures the full spectrum of system activity, recording up to 70x more memory traffic than binary instrumentation for I/O-heavy workloads. Furthermore, we show that replaying these real-system traces in a cycle-accurate DRAM simulator yields significantly more realistic memory latency results compared to traces generated by a full-system simulator such as gem5. CXL-Tracer provides an accessible and accurate platform for designing and evaluating future memory subsystems.