CARGO-BENCH(1) User Commands 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 and check out the rustc book's
chapter on how tests work at
<https://doc.rust-lang.org/rustc/tests/index.html>.

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 a
special executable by linking your code with libtest. The executable
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, regardless of whether the harness is
libtest or a custom harness.

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
<https://doc.rust-lang.org/nightly/unstable-book/library-features/test.html>
is currently unstable and only available on the nightly channel
<https://doc.rust-lang.org/book/appendix-07-nightly-rust.html>.
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 Criterion
<https://crates.io/crates/criterion>.

By default, cargo bench uses the bench profile
<https://doc.rust-lang.org/cargo/reference/profiles.html#bench>,
which enables optimizations and disables debugging information. If
you need to debug a benchmark, you can use the --profile=dev
command-line option to switch to the dev profile. You can then run
the debug-enabled benchmark within a debugger.

Working directory of benchmarks

The working directory of every benchmark is set to the root directory
of the package the benchmark belongs to. Setting the working
directory of benchmarks to the package's root directory makes it
possible for benchmarks to reliably access the package's files using
relative paths, regardless from where cargo bench was executed from.

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 and
supports common Unix glob patterns like *, ? and []. However, to
avoid your shell accidentally expanding glob patterns before
Cargo handles them, you must use single quotes or double quotes
around each pattern.

--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
and supports common Unix glob patterns like *, ? and []. However,
to avoid your shell accidentally expanding glob patterns before
Cargo handles them, you must use single quotes or double quotes
around each pattern.

Target Selection

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

+o lib -- used to link with binaries and benchmarks

+o bins (only if benchmark targets are built and required features
are available)

+o lib as a benchmark

+o bins as benchmarks

+o 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, replacing the
example's main function with the libtest harness.

Setting targets to bench = false will stop them from being
benchmarked by default. Target selection options that take a target
by name (such as --example foo) ignore the bench flag and will always
benchmark the given target.

See Configuring a target
<https://doc.rust-lang.org/cargo/reference/cargo-targets.html#configuring-a-target>
for more information on per-target settings.

Binary targets are automatically built if there is an integration
test or benchmark being selected to benchmark. This allows an
integration test to execute the binary to exercise and test its
behavior. The CARGO_BIN_EXE_<name> environment variable
<https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-crates>
is set when the integration test is built so that it can use the env
macro <https://doc.rust-lang.org/std/macro.env.html> to locate the
executable.

Passing target selection flags will benchmark only the specified
targets.

Note that --bin, --example, --test and --bench flags also support
common Unix glob patterns like *, ? and []. However, to avoid your
shell accidentally expanding glob patterns before Cargo handles them,
you must use single quotes or double quotes around each glob pattern.

--lib
Benchmark the package's library.

--bin name<?>
Benchmark the specified binary. This flag may be specified
multiple times and supports common Unix glob patterns.

--bins
Benchmark all binary targets.

--example name<?>
Benchmark the specified example. This flag may be specified
multiple times and supports common Unix glob patterns.

--examples
Benchmark all example targets.

--test name<?>
Benchmark the specified integration test. This flag may be
specified multiple times and supports common Unix glob patterns.

--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 and supports common Unix glob patterns.

--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 which features are enabled.
When no feature options are given, the default feature is activated
for every selected package.

See the features documentation
<https://doc.rust-lang.org/cargo/reference/features.html#command-line-feature-options>
for more details.

-F features, --features features
Space or comma separated list of features to activate. Features
of workspace members may be enabled with
package-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 selected packages.

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 flag may be specified
multiple times.

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/reference/build-cache.html>
documentation for more details.

--profile name
Benchmark with the given profile. See the reference
<https://doc.rust-lang.org/cargo/reference/profiles.html> for
more details on profiles.

--timings=fmts
Output information how long each compilation takes, and track
concurrency information over time. Accepts an optional
comma-separated list of output formats; --timings without an
argument will default to --timings=html. Specifying an output
format (rather than the default) is unstable and requires
-Zunstable-options. Valid output formats:

+o html (unstable, requires -Zunstable-options): Write a
human-readable file cargo-timing.html to the
target/cargo-timings directory with a report of the
compilation. Also write a report to the same directory with a
timestamp in the filename if you want to look at older runs.
HTML output is suitable for human consumption only, and does
not provide machine-readable timing data.

+o json (unstable, requires -Zunstable-options): Emit
machine-readable JSON information about timing information.

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
<https://doc.rust-lang.org/cargo/reference/config.html>.
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
<https://doc.rust-lang.org/cargo/reference/config.html>.

-q, --quiet
Do not print cargo log messages. May also be specified with the
term.quiet config value
<https://doc.rust-lang.org/cargo/reference/config.html>.

--color when
Control when colored output is used. Valid values:

+o auto (default): Automatically detect if color support is
available on the terminal.

+o always: Always display colors.

+o never: Never display colors.

May also be specified with the term.color config value
<https://doc.rust-lang.org/cargo/reference/config.html>.

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

+o human (default): Display in a human-readable text format.
Conflicts with short and json.

+o short: Emit shorter, human-readable text messages. Conflicts
with human and json.

+o json: Emit JSON messages to stdout. See the reference
<https://doc.rust-lang.org/cargo/reference/external-tools.html#json-messages>
for more details. Conflicts with human and short.

+o json-diagnostic-short: Ensure the rendered field of JSON
messages contains the "short" rendering from rustc. Cannot be
used with human or short.

+o json-diagnostic-rendered-ansi: Ensure the rendered field of
JSON messages contains embedded ANSI color codes for
respecting rustc's default color scheme. Cannot be used with
human or short.

+o json-render-diagnostics: Instruct Cargo to not include rustc
diagnostics 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. Cannot be used with human or short.

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.

--ignore-rust-version
Ignore rust-version specification in packages.

--locked
Asserts that the exact same dependencies and versions are used as
when the existing Cargo.lock file was originally generated. Cargo
will exit with an error when either of the following scenarios
arises:

+o The lock file is missing.

+o Cargo attempted to change the lock file due to a different
dependency resolution.

It may be used in environments where deterministic builds are
desired, such as in CI pipelines.

--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
<https://doc.rust-lang.org/cargo/reference/config.html>.

--frozen
Equivalent to specifying both --locked and --offline.

--lockfile-path PATH
Changes the path of the lockfile from the default
(<workspace_root>/Cargo.lock) to PATH. PATH must end with
Cargo.lock (e.g. --lockfile-path
/tmp/temporary-lockfile/Cargo.lock). Note that providing
--lockfile-path will ignore existing lockfile at the default
path, and instead will either use the lockfile from PATH, or
write a new lockfile into the provided PATH if it doesn't exist.
This flag can be used to run most commands in read-only
directories, writing lockfile into the provided PATH.

This option is only available on the nightly channel
<https://doc.rust-lang.org/book/appendix-07-nightly-rust.html>
and requires the -Z unstable-options flag to enable (see #14421
<https://github.com/rust-lang/cargo/issues/14421>).

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 <https://rust-lang.github.io/rustup/overrides.html>
for more information about how toolchain overrides work.

--config KEY=VALUE or PATH
Overrides a Cargo configuration value. The argument should be in
TOML syntax of KEY=VALUE, or provided as a path to an extra
configuration file. This flag may be specified multiple times.
See the command-line overrides section
<https://doc.rust-lang.org/cargo/reference/config.html#command-line-overrides>
for more information.

-C PATH
Changes the current working directory before executing any
specified operations. This affects things like where cargo looks
by default for the project manifest (Cargo.toml), as well as the
directories searched for discovering .cargo/config.toml, for
example. This option must appear before the command name, for
example cargo -C path/to/my-project build.

This option is only available on the nightly channel
<https://doc.rust-lang.org/book/appendix-07-nightly-rust.html>
and requires the -Z unstable-options flag to enable (see #10098
<https://github.com/rust-lang/cargo/issues/10098>).

-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
<https://doc.rust-lang.org/cargo/reference/config.html>. Defaults
to the number of logical CPUs. If negative, it sets the maximum
number of parallel jobs to the number of logical CPUs plus
provided value. If a string default is provided, it sets the
value back to defaults. Should not be 0.

While cargo bench involves compilation, it does not provide a
--keep-going flag. Use --no-fail-fast to run as many benchmarks as
possible without stopping at the first failure. To "compile" as many
benchmarks as possible, use --benches to build benchmark binaries
separately. For example:

cargo build --benches --release --keep-going
cargo bench --no-fail-fast

ENVIRONMENT

See the reference
<https://doc.rust-lang.org/cargo/reference/environment-variables.html>
for details on environment variables that Cargo reads.

EXIT STATUS

+o 0: Cargo succeeded.

+o 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)

CARGO-BENCH(1)