An exhaustive benchmark for Btrfs transparent compression

Compbench is a C tool that benchmarks Btrfs compression algorithms (zstd, lzo) by measuring read and write throughput, compression ratio, CPU usage, and disk I/O — all through direct kernel interfaces with zero text parsing of external tool output.

Features

• Direct kernel interfaces — compression ratio via statvfs(), CPU via /proc/stat, disk I/O via /sys/block/*/stat, timing via clock_gettime(CLOCK_MONOTONIC_RAW), data copy via copy_file_range()
• Exhaustive testing — configurable zstd level range (-15..15), lzo, zlib, and no compression
• Cold-cache reads — the page cache is dropped before the read test, so RdMiB/s reflects real disk throughput, not memory
• Force mode comparison — run standard compress and/or compress-force mount options, with a side-by-side percentage comparison table
• HDD zone testing — benchmark first/last N% of disk to evaluate spatial performance variations, with interpolated results
• Repeatable — average results over multiple runs, with throughput standard deviation reported in the CSV
• Disk-level I/O stats — actual bytes written to physical media, separate from apparent throughput
• CSV export — machine-readable output with full metadata (archive, dataset, host, kernel, date)

Requirements

System Packages (Debian/Ubuntu)

sudo apt install gcc make btrfs-progs xz-utils gdisk curl

tar and util-linux are typically installed by default.

Building

make
sudo make install

This installs the compbench binary and its man page (compbench(1)). The binary is dynamically linked against libm and libc only.

Usage

Warning: This tool formats the target device, erasing all existing data.

Basic Command

sudo compbench /dev/sdX https://example.com/archive.tar.xz

Command-Line Options

Usage: compbench [OPTIONS] DEVICE ARCHIVE

DEVICE is the block device to test (e.g. /dev/sdX).
ARCHIVE is a local path or URL to a .tar.xz archive.

Options:
  -n, --repeat N          Repeat each test N times (default: 1)
      --zstd MIN-MAX      zstd level range (default: 1-15)
  -f, --force MODE        Force mode: none|zstd|lzo|all|both (default: none)
      --hdd PERCENT       Test on first/last N% of disk (1-50)
  -o, --output FILE       Export results to CSV
      --no-integrity-check
                         Skip archive integrity verification
  -v, --verbose           Verbose output
  -h, --help              Show help
  -V, --version           Show version

Force Modes

Mode	Effect
none	Standard compress= for all tests
zstd	compress-force= for zstd, standard for lzo
lzo	compress-force= for lzo, standard for zstd
all	compress-force= for all algorithms
both	Run each test twice (standard + force) and show comparison

Example

sudo compbench /dev/sdX https://example.com/archive.tar.xz -n 3 --zstd 1-10 -f both --hdd 10 -v

This will:

• Test zstd levels 10 down to 1, plus lzo and no compression
• Repeat the sequence 3 times with averaged results
• Run both standard and force modes with a comparison table
• Test on the first and last 10% of the disk
• Run in verbose mode

Measured Metrics

All metrics use kernel interfaces directly:

Column	Description	Source
WrMiB/s	Synced write throughput (copy + sync)	clock_gettime
RdMiB/s	Read throughput after cache clear (page cache dropped + remount + full tree read)	clock_gettime
WrDisk*	Actual bytes written to physical media	/sys/block/*/stat
RdDisk*	Actual bytes read from physical media	/sys/block/*/stat
Ratio	Space consumed vs uncompressed	statvfs
WrCPU%	System CPU usage during write	/proc/stat
RdCPU%	System CPU usage during read	/proc/stat
Sec/Red	Seconds per 1% space reduction	Derived

Installation (Debian Package)

Download the .deb from GitHub Releases and install:

sudo dpkg -i compbench_*.deb
sudo apt-get install -f

Building a Debian Package

dpkg-buildpackage -us -uc

Running Tests

The test suite uses loop devices (no real disks needed):

sudo bash test.sh

Contributing

Contributions, bug reports, and suggestions are welcome! Please open an issue or submit a pull request on GitHub.

License

GNU General Public License v3.0