= cargo-bench(1)
:idprefix: cargo_bench_
:doctype: manpage
:actionverb: Benchmark
:nouns: benchmarks
== 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'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.
== OPTIONS
=== Benchmark Options
include::options-test.adoc[]
=== Package Selection
include::options-packages.adoc[]
=== 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.
include::options-targets.adoc[]
include::options-features.adoc[]
=== Compilation Options
include::options-target-triple.adoc[]
=== Output Options
include::options-target-dir.adoc[]
=== 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
include::options-display.adoc[]
include::options-message-format.adoc[]
=== Manifest Options
include::options-manifest-path.adoc[]
include::options-locked.adoc[]
=== Common Options
include::options-common.adoc[]
=== 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.
include::options-jobs.adoc[]
== PROFILES
Profiles may be used to configure compiler options such as optimization levels
and debug settings. See
linkcargo:reference/manifest.html#the-profile-sections[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
man: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.
include::section-environment.adoc[]
include::section-exit-status.adoc[]
== EXAMPLES
. Build and execute all the benchmarks of the current package:
cargo bench
. Run only a specific benchmark within a specific benchmark target:
cargo bench --bench bench_name -- modname::some_benchmark
== SEE ALSO
man:cargo[1], man:cargo-test[1]