Google Benchmark

Google Benchmark is a open source C++ library for performance benchmarking snippets of C++/C code.

A screenshot of the Google Benchmark repository as viewed on GitHub.¹

Installation

You can easily add Google Benchmark as a dependency to your CMake C++ project by using FetchContent in your CMakeLists.txt file.

CMakeLists.txt

set(CMAKE_BUILD_TYPE Release CACHE STRING "Build type")
include(FetchContent)
set(BENCHMARK_ENABLE_TESTING off)
FetchContent_Declare(googlebenchmark
                     GIT_REPOSITORY https://github.com/google/benchmark
                     GIT_TAG main)
FetchContent_MakeAvailable(googlebenchmark)

This will automatically download and build Google Benchmark and make it available to your project.

This sets the BUILD_TYPE to Release to prevent warnings that Google Benchmark emits when it is built in Debug mode. set(BENCHMARK_ENABLE_TESTING off) prevents Google Benchmark from running it’s own unit tests (we can trust it works well!).

Tip

You may want to replace the GIT_TAG main with a specific hash to lock down the version of Google Benchmark you are using. GIT_TAG main will always pull whatever version the main branch is currently at.

Preventing Optimizations

benchmark::ClobberMemory() can be used to force the compiler to flush pending writes to global memory. This acts as a read/write barrier. This is implemented with std::atomic_signal_fence(std::memory_order_acq_rel);.

Saving Results to a File

To save Google Benchmark results to a file, you can pass in the --benchmark_out and --benchmark_out_format flags to the compiled executable. For example, so save the results to a file called output.json:

my_benchmark_program --benchmark_out=output.json --benchmark_out_format=json

Footnotes

1. GitHub. google/benchmark [repository]. Retrieved 2025-04-28, from https://github.com/google/benchmark. ↩