cargo-bench - Execute benchmarks of a package
cargo bench [OPTIONS] [BENCHNAME] [-- BENCH-OPTIONS]
Compile and execute benchmarks.
The benchmark filtering argument BENCHNAME and all the arguments following the two dashes (--) are passed to the benchmark binaries and thus to libtest (rustc’s built in unit-test and micro-benchmarking framework). If you’re passing arguments to both Cargo and the binary, the ones after -- go to the binary, the ones before go to Cargo. For details about libtest’s arguments see the output of cargo bench -- --help. As an example, this will run only the benchmark named foo (and skip other similarly named benchmarks like foobar):
cargo bench -- foo --exact
Benchmarks are built with the --test option to rustc which creates an executable with a main function that automatically runs all functions annotated with the #[bench] attribute. Cargo passes the --bench flag to the test harness to tell it to run only benchmarks.
The libtest harness may be disabled by setting harness = false in the target manifest settings, in which case your code will need to provide its own main function to handle running benchmarks.
Note: The #[bench] attribute
is currently unstable and only available on the nightly
There are some packages available on crates.io
<https://crates.io/keywords/benchmark> that may help with
running benchmarks on the stable channel, such as
By default, when no package selection options are given, the packages selected depend on the selected manifest file (based on the current working directory if --manifest-path is not given). If the manifest is the root of a workspace then the workspaces default members are selected, otherwise only the package defined by the manifest will be selected.
The default members of a workspace can be set explicitly with the workspace.default-members key in the root manifest. If this is not set, a virtual workspace will include all workspace members (equivalent to passing --workspace), and a non-virtual workspace will include only the root crate itself.
-p SPEC..., --package SPEC...
When no target selection options are given, cargo bench will build the following targets of the selected packages:
The default behavior can be changed by setting the bench flag for the target in the manifest settings. Setting examples to bench = true will build and run the example as a benchmark. Setting targets to bench = false will stop them from being benchmarked by default. Target selection options that take a target by name ignore the bench flag and will always benchmark the given target.
Passing target selection flags will benchmark only the specified targets.
The feature flags allow you to control the enabled features for the "current" package. The "current" package is the package in the current directory, or the one specified in --manifest-path. If running in the root of a virtual workspace, then the default features are selected for all workspace members, or all features if --all-features is specified.
When no feature options are given, the default feature is activated for every selected package.
This may also be specified with the build.target config value <https://doc.rust-lang.org/cargo/reference/config.html>.
Note that specifying this flag makes Cargo run in a different mode where the target artifacts are placed in a separate directory. See the build cache <https://doc.rust-lang.org/cargo/guide/build-cache.html> documentation for more details.
By default the Rust test harness hides output from benchmark execution to keep results readable. Benchmark output can be recovered (e.g., for debugging) by passing --nocapture to the benchmark binaries:
cargo bench -- --nocapture
May also be specified with the term.color config value <https://doc.rust-lang.org/cargo/reference/config.html>.
These may be used in environments where you want to assert that the Cargo.lock file is up-to-date (such as a CI build) or want to avoid network access.
Beware that this may result in different dependency resolution than online mode. Cargo will restrict itself to crates that are downloaded locally, even if there might be a newer version as indicated in the local copy of the index. See the cargo-fetch(1) command to download dependencies before going offline.
May also be specified with the net.offline config value <https://doc.rust-lang.org/cargo/reference/config.html>.
The --jobs argument affects the building of the benchmark executable but does not affect how many threads are used when running the benchmarks. The Rust test harness runs benchmarks serially in a single thread.
-j N, --jobs N
Profiles may be used to configure compiler options such as optimization levels and debug settings. See the reference <https://doc.rust-lang.org/cargo/reference/profiles.html> for more details.
Benchmarks are always built with the bench profile. Binary and lib targets are built separately as benchmarks with the bench profile. Library targets are built with the release profiles when linked to binaries and benchmarks. Dependencies use the release profile.
If you need a debug build of a benchmark, try building it with cargo-build(1) which will use the test profile which is by default unoptimized and includes debug information. You can then run the debug-enabled benchmark manually.
See the reference <https://doc.rust-lang.org/cargo/reference/environment-variables.html> for details on environment variables that Cargo reads.
cargo bench --bench bench_name -- modname::some_benchmark