How to Track File Size with Bencher

Bencher supports the most popular benchmarking harnesses out-of-the-box. Sometimes though, you want to measure the size of your deliverables themselves, such as the binary size of an executable. Lucky for you, Bencher also supports tracking file size. The easiest way to track file size is to use the bencher run CLI subcommand with the --file-size option. The --file-size option expects a file path to the file who’s size will be measured. Under the hood, bencher run outputs the results as Bencher Metric Format (BMF) JSON. It is therefore good practice to explicitly use the json adapter.

If you had a script located at ./my_build_script.sh that built your binary at the path ./path/to/my_binary, then you could track the size of this binary file with bencher run and the json adapter. This would work both with a benchmark command and without one.

With a benchmark command:

bencher run --file-size ./path/to/my_binary --adapter json ./my_build_script.sh

Without a benchmark command:

./my_build_script.sh && bencher run --file-size ./path/to/my_binary --adapter json

In either case, the generated BMF JSON would look like this, if my_binary had a size of 42 bytes:

{
  "my_binary": {
    "file-size": {
      "value": 42.0
    }
  }
}

In this example, the key my_binary is the binary file name. It is used as the name of the Benchmark. The my_binary object contains the file-size key. file-size is the slug for the built-in File Size Measure. The File Size Measure is not created by default for all Projects. However, when you use the File Size Measure, it will be automatically created for your Project. The File Size Measure object contains a Metric with the file size value in bytes, 42.0.

The File Size will always be a whole byte increment. That is, it will never have a decimal like 42.5. However, BMF JSON needs to support a wide range of possible values, so it uses floats instead of integers.

Multiple File Sizes

If you want to track the size of multiple files, you can simply use the --file-size option multiple times in the same bencher run command. For example, you could track both my_binary and a Windows executable version, my_binary.exe.

bencher run --file-size ./path/to/my_binary --file-size ./path/to/my_binary.exe --adapter json ./my_build_script.sh

The generated BMF JSON would look like this if my_binary.exe had a size of 48 bytes:

{
  "my_binary": {
    "file-size": {
      "value": 42.0
    }
  },
  "my_binary.exe": {
    "file-size": {
      "value": 48.0
    }
  }
}

Track Build Time

You may want to track the build time of your deliverables, in addition to tracking their file size. bencher run supports tracking both file sizes and build times.

You could track both the binary size and the compile time for my_binary with this command:

bencher run --file-size ./path/to/my_binary --build-time --adapter json ./my_build_script.sh

If your build script took 87.0 seconds to complete, the generated BMF JSON would look like this:

{
  "my_binary": {
    "file-size": {
      "value": 42.0
    }
  },
  "/bin/sh -c ./my_build_script.sh": {
    "build-time": {
      "value": 87.0
    }
  }
}

🐰 Congrats! You have learned how to track your file size! 🎉

Keep Going: How to Track Benchmarks in CI ➡