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
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
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
function to handle running benchmarks.
Compile, but don’t run benchmarks.
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.
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.
Benchmark all members in the workspace.
Deprecated alias for
- --exclude SPEC…
Exclude the specified packages. Must be used in conjunction with the
--workspaceflag. This flag may be specified multiple times.
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
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
Passing target selection flags will benchmark only the specified targets.
Benchmark the package’s library.
- --bin NAME…
Benchmark the specified binary. This flag may be specified multiple times.
Benchmark all binary targets.
- --example NAME…
Benchmark the specified example. This flag may be specified multiple times.
Benchmark all example targets.
- --test NAME…
Benchmark the specified integration test. This flag may be specified multiple times.
Benchmark all targets in test mode that have the
test = truemanifest 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
testflag in the manifest settings for the target.
- --bench NAME…
Benchmark the specified benchmark. This flag may be specified multiple times.
Benchmark all targets in benchmark mode that have the
bench = truemanifest 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
benchflag in the manifest settings for the target.
Benchmark all targets. This is equivalent to specifying
--lib --bins --tests --benches --examples.
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.
Activate all available features of all selected packages.
Do not activate the
defaultfeature of the current directory’s package.
- --target TRIPLE
Benchmark for the given architecture. The default is the host architecture. The general format of the triple is
rustc --print target-listfor a list of supported targets.
This may also be specified with the
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.
- --target-dir DIRECTORY
Directory for all generated artifacts and intermediate files. May also be specified with the
CARGO_TARGET_DIRenvironment variable, or the
build.target-dirconfig value. Defaults to
targetin the root of the workspace.
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
--nocapture to the benchmark binaries:
cargo bench -- --nocapture
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
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
- --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
renderedfield of JSON messages contains the "short" rendering from rustc.
json-diagnostic-rendered-ansi: Ensure the
renderedfield 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-path PATH
Path to the
Cargo.tomlfile. By default, Cargo searches for the
Cargo.tomlfile in the current directory or any parent directory.
Either of these flags requires that the
Cargo.lockfile is up-to-date. If the lock file is missing, or it needs to be updated, Cargo will exit with an error. The
--frozenflag 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.lockfile is up-to-date (such as a CI build) or want to avoid network access.
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
Prints help information.
- -Z FLAG…
Unstable (nightly-only) flags to Cargo. Run
cargo -Z helpfor details.
--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.jobsconfig value. Defaults to the number of CPUs.
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
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
See the reference for details on environment variables that Cargo reads.
Cargo failed to complete.
Build and execute all the benchmarks of the current package:
Run only a specific benchmark within a specific benchmark target:
cargo bench --bench bench_name -- modname::some_benchmark