[FAST'26] Cylon Artifact Evaluation

• The artifact consists of these 3 components.
  • CylonFEMU: Cylon's FEMU extension codebase
  • CylonLinux: Cylon's custom kernel for DER support
  • Cylon-scripts: Benchmark and plot scripts

How to Use Cylon CXL-SSD and Reproduce Experiments

To reduce the burden on the Artifact Evaluation (AE) committee, we provide a pre-configured Cylon environment hosted on CloudLab. The environment includes a virtual machine that emulates CXL-SSD functionality and is ready for experimentation.

Launching the Cylon VM

1. SSH into the CloudLab host machine.

2. Start the Cylon VM:

   cd Cylon/build-femu
   ./run-cxlssh.sh

3. Pin CPUs (run in a separate terminal):

   cd Cylon/build-femu
   ./pin.sh

4. Initializing CXL-SSD Inside the VM

• Once the VM is running, initialize the CXL-SSD device inside the guest VM:

  bash ~/login.sh #ssh into the VM
  ./setup_dev.sh

• After initialization, the CXL-SSD appears as a CPU-less NUMA node:

  numactl -H
  # available: 2 nodes (0-1)
  # node 0 cpus: 0 1 2 3 4 5 6 7
  # node 0 size: 15991 MB
  # node 0 free: 7156 MB
  # node 1 cpus:
  # node 1 size: 65536 MB
  # node 1 free: 65536 MB
  # node distances:
  # node   0   1
  # 0:  10  20
  # 1:  20  10

• Or you can expose Cylon as an devdax device.

  # devdax mode
  daxctl reconfigure-device --mode=devdax --force dax0.0
  
  # systam-ram mode (CPU-less NUMA node)
  daxctl reconfigure-device --mode=system-ram --force dax0.0

Configuring Cylon

• You can adjust Cylon configuration in build-femu/run-cxlssd.sh file.

Caching policy

# CXL-SSD DRAM buffer parameters
policy=2 # Replacement policy [1:LIFO 2:FIFO 3:S3FIFO 4:CLOCK]
prf_dg=0 # Next-n Prefetch degree

ssd_size=$1		# in MegaBytes
bufsz=$((ssd_size/20))

NAND timing

# Latency in nanoseconds
pg_rd_lat=40000      # NAND Read Latency (40us)
pg_wr_lat=200000     # NAND Write (program) Latency (200us)
blk_er_lat=2000000   # NAND Erase Latency (2ms)
ch_xfer_lat=0

Reproducing Experiments

For reproducing experiments, please refer:

• Intel MLC (Figure 2, 4)
• Mio (Figure 3, 6, 9, 10)
• Redis (Figure 7, 11, 12)
• GAPBS (Figure 8)

Which mode should I use for each benchmark?

Cylon can be exposed to the guest OS in two mutually exclusive modes:

• system-ram: the CXL-SSD capacity is hot-plugged into the Linux memory subsystem and shows up as a CPU-less NUMA node. Applications use it through normal malloc()/anonymous memory (often with numactl --membind=<node>).

• devdax: the capacity is exposed as a DAX character device (e.g., /dev/dax0.0). Applications must explicitly mmap() the DAX device (or use a PMem/DAX-aware library). It is not part of the normal page allocator.

  Benchmark	Required mode
  Intel-MLC	system-ram
  MIO	devdax
  Redis YCSB	system-ram
  GAPBS	system-ram

Rule of thumb: if the benchmark/application is unmodified and uses malloc() + numactl, you want system-ram. Use devdax only for benchmarks that explicitly open/mmap /dev/dax*.

Support

If you encounter issues not covered in this document, please contact Dongha Yoon (dongha@vt.edu).