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 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.
By default, cargo bench
uses the bench
profile, 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:
- 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, replacing the example’s main
function with
the libtest harness.
Setting targets to bench = false
will stop them from being bencharmked 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 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
is set when the integration test is built so that it can use the
env
macro 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 thetest
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 thebench
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 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>
. Runrustc --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.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.
--profile
name- Benchmark with the given profile. See the reference for more details on profiles.
--ignore-rust-version
- Benchmark the target even if the selected Rust compiler is older than the
required Rust version as configured in the project’s
rust-version
field. --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:html
(unstable, requires-Zunstable-options
): Write a human-readable filecargo-timing.html
to thetarget/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.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 thebuild.target-dir
config value. Defaults totarget
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
- Do not print cargo log messages.
May also be specified with the
term.quiet
config value. --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. Conflicts withshort
andjson
.short
: Emit shorter, human-readable text messages. Conflicts withhuman
andjson
.json
: Emit JSON messages to stdout. See the reference for more details. Conflicts withhuman
andshort
.json-diagnostic-short
: Ensure therendered
field of JSON messages contains the “short” rendering from rustc. Cannot be used withhuman
orshort
.json-diagnostic-rendered-ansi
: Ensure therendered
field of JSON messages contains embedded ANSI color codes for respecting rustc’s default color scheme. Cannot be used withhuman
orshort
.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 withhuman
orshort
.
Manifest Options
--manifest-path
path- Path to the
Cargo.toml
file. By default, Cargo searches for theCargo.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. --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 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 examplecargo -C path/to/my-project build
.This option is only available on the nightly channel and requires the
-Z unstable-options
flag to enable (see #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. 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 stringdefault
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 for details on environment variables that Cargo reads.
EXIT STATUS
0
: Cargo succeeded.101
: Cargo failed to complete.
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