cargo-bench(1)

NAME

cargo-bench - Execute benchmarks of a package

SYNOPSIS

cargo bench [options] [benchname] [-- bench-options]

DESCRIPTION

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 are 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 channel. There are some packages available on crates.io that may help with running benchmarks on the stable channel, such as Criterion.

OPTIONS

Benchmark Options

--no-run
Compile, but don't run benchmarks.
--no-fail-fast
Run all benchmarks regardless of failure. Without this flag, Cargo will exit after the first executable fails. The Rust test harness will run all benchmarks within the executable to completion, this flag only applies to the executable as a whole.

Package Selection

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...
Benchmark only the specified packages. See cargo-pkgid(1) for the SPEC format. This flag may be specified multiple times.
--workspace
Benchmark all members in the workspace.
--all
Deprecated alias for --workspace.
--exclude SPEC...
Exclude the specified packages. Must be used in conjunction with the --workspace flag. This flag may be specified multiple times.

Target Selection

When no target selection options are given, cargo bench will build the following targets of the selected packages:

  • lib — used to link with binaries and benchmarks
  • bins (only if benchmark targets are built and required features are available)
  • lib as a benchmark
  • bins as benchmarks
  • benchmark targets

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.

--lib
Benchmark the package's library.
--bin name...
Benchmark the specified binary. This flag may be specified multiple times.
--bins
Benchmark all binary targets.
--example name...
Benchmark the specified example. This flag may be specified multiple times.
--examples
Benchmark all example targets.
--test name...
Benchmark the specified integration test. This flag may be specified multiple times.
--tests
Benchmark all targets in test mode that have the test = true manifest flag set. By default this includes the library and binaries built as unittests, and integration tests. Be aware that this will also build any required dependencies, so the lib target may be built twice (once as a unittest, and once as a dependency for binaries, integration tests, etc.). Targets may be enabled or disabled by setting the test flag in the manifest settings for the target.
--bench name...
Benchmark the specified benchmark. This flag may be specified multiple times.
--benches
Benchmark all targets in benchmark mode that have the bench = true manifest flag set. By default this includes the library and binaries built as benchmarks, and bench targets. Be aware that this will also build any required dependencies, so the lib target may be built twice (once as a benchmark, and once as a dependency for binaries, benchmarks, etc.). Targets may be enabled or disabled by setting the bench flag in the manifest settings for the target.
--all-targets
Benchmark all targets. This is equivalent to specifying --lib --bins --tests --benches --examples.

Feature Selection

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.

--features features
Space or comma separated list of features to activate. These features only apply to the current directory's package. Features of direct dependencies may be enabled with <dep-name>/<feature-name> syntax. This flag may be specified multiple times, which enables all specified features.
--all-features
Activate all available features of all selected packages.
--no-default-features
Do not activate the default feature of the current directory's package.

Compilation Options

--target triple
Benchmark for the given architecture. The default is the host architecture. The general format of the triple is <arch><sub>-<vendor>-<sys>-<abi>. Run rustc --print target-list for a list of supported targets.

This may also be specified with the build.target config value.

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 documentation for more details.

Output Options

--target-dir directory
Directory for all generated artifacts and intermediate files. May also be specified with the CARGO_TARGET_DIR environment variable, or the build.target-dir config value. Defaults to target in the root of the workspace.

Display Options

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
-v
--verbose
Use verbose output. May be specified twice for "very verbose" output which includes extra output such as dependency warnings and build script output. May also be specified with the term.verbose config value.
-q
--quiet
No output printed to stdout.
--color when
Control when colored output is used. Valid values:

  • auto (default): Automatically detect if color support is available on the terminal.
  • always: Always display colors.
  • never: Never display colors.

May also be specified with the term.color config value.

--message-format fmt
The output format for diagnostic messages. Can be specified multiple times and consists of comma-separated values. Valid values:

  • human (default): Display in a human-readable text format.
  • short: Emit shorter, human-readable text messages.
  • json: Emit JSON messages to stdout. See the reference for more details.
  • json-diagnostic-short: Ensure the rendered field of JSON messages contains the "short" rendering from rustc.
  • json-diagnostic-rendered-ansi: Ensure the rendered field of JSON messages contains embedded ANSI color codes for respecting rustc's default color scheme.
  • json-render-diagnostics: Instruct Cargo to not include rustc diagnostics in in JSON messages printed, but instead Cargo itself should render the JSON diagnostics coming from rustc. Cargo's own JSON diagnostics and others coming from rustc are still emitted.

Manifest Options

--manifest-path path
Path to the Cargo.toml file. By default, Cargo searches for the Cargo.toml file in the current directory or any parent directory.
--frozen
--locked
Either of these flags requires that the Cargo.lock file is up-to-date. If the lock file is missing, or it needs to be updated, Cargo will exit with an error. The --frozen flag also prevents Cargo from attempting to access the network to determine if it is out-of-date.

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.

--offline
Prevents Cargo from accessing the network for any reason. Without this flag, Cargo will stop with an error if it needs to access the network and the network is not available. With this flag, Cargo will attempt to proceed without the network if possible.

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.

Common Options

+toolchain
If Cargo has been installed with rustup, and the first argument to cargo begins with +, it will be interpreted as a rustup toolchain name (such as +stable or +nightly). See the rustup documentation for more information about how toolchain overrides work.
-h
--help
Prints help information.
-Z flag
Unstable (nightly-only) flags to Cargo. Run cargo -Z help for details.

Miscellaneous Options

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
Number of parallel jobs to run. May also be specified with the build.jobs config value. Defaults to the number of CPUs.

PROFILES

Profiles may be used to configure compiler options such as optimization levels and debug settings. See the reference 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.

ENVIRONMENT

See the reference for details on environment variables that Cargo reads.

EXIT STATUS

  • 0: Cargo succeeded.
  • 101: Cargo failed to complete.

EXAMPLES

  1. Build and execute all the benchmarks of the current package:

    cargo bench

  2. Run only a specific benchmark within a specific benchmark target:

    cargo bench --bench bench_name -- modname::some_benchmark

SEE ALSO

cargo(1), cargo-test(1)