# cargo-instruments

Easily profile your rust crate with Xcode [Instruments].

`cargo-instruments` is the glue between Cargo and Xcode's bundled profiling
suite. It allows you to easily profile any binary in your crate, generating
files that can be viewed in the Instruments app.

![Instruments Time Profiler](https://raw.githubusercontent.com/cmyr/cargo-instruments/screenshots/instruments_time1.png)
![Instruments System Trace](https://raw.githubusercontent.com/cmyr/cargo-instruments/screenshots/instruments_sys1.png)

## Pre-requisites

### Xcode Instruments

This crate only works on macOS because it uses [Instruments] for profiling
and creating the trace file. The benefit is that Instruments provides great
templates and UI to explore the Profiling Trace.

To install Xcode Instruments, simply install the Command Line Tools:

```sh
$ xcode-select --install
```

### Compatibility

This crate works on macOS 10.13+. In practice, it transparently detects and
uses the appropriate Xcode Instruments version based on your macOS version:
either `/usr/bin/instruments` on older macOS, or starting with macOS 10.15, the
new `xcrun xctrace`.

## Installation

### brew

The simplest way to install is via Homebrew:

```sh
$ brew install cargo-instruments
```

Alternatively, you can install from source.

### Building from Source

First, ensure that you are running macOS, with Cargo, Xcode, and the Xcode
Command Line Tools installed.

If OpenSSL is installed (e.g., via `brew`), then install with

```sh
$ cargo install cargo-instruments
```

If OpenSSL is not installed or if `cargo install` fails with an error message starting with "Could not find directory of OpenSSL installation, and this `-sys` crate cannot proceed without this knowledge," then install with

```sh
$ cargo install --features vendored-openssl cargo-instruments
```

#### Building from Source on nix

If you're using [nix](https://nixos.org/guides/install-nix.html), this command should provide all dependencies and build `cargo-instruments` from source:

```sh
$ nix-shell --command 'cargo install cargo-instruments' --pure -p \
	darwin.apple_sdk.frameworks.SystemConfiguration \
	darwin.apple_sdk.frameworks.CoreServices \
	rustc cargo sccache libgit2 pkg-config libiconv \
	llvmPackages_13.libclang openssl
```

## Usage

### Basic

`cargo-instruments` requires a binary target to run. By default, it will try to
build the current crate's `main.rs`. You can specify an alternative binary by
using the `--bin` or `--example` flags, or a benchmark target with the `--bench`
flag.

Assuming your crate has one binary target named `mybin`, and you want to profile
using the `Allocations` Instruments template:

_Generate a new trace file_ (by default saved in `target/instruments`)

```sh
$ cargo instruments -t Allocations
```

_Open the trace file in Instruments.app manually_

By default the trace file will immediately be opened with `Instruments.app`. If you do not want this behavior use the `--no-open` flag.

```sh
$ open target/instruments/mybin_Allocations_2021-05-09T12_34_56.trace
```

If there are multiple packages, you can specify the package to profile with
the `--package` flag.

For example, you use Cargo's workspace to manage multiple packages. To profile
the bin `bar` of the package `foo`:

```sh
$ cargo instruments --package foo --template alloc --bin bar
```

In many cases, a package only has one binary. In this case `--package` behaves the
same as `--bin`.

### Profiling application in release mode

When profiling the application in release mode the compiler doesn't provide
debugging symbols in the default configuration.

To let the compiler generate the debugging symbols even in release mode you
can append the following section in your `Cargo.toml`.

```toml
[profile.release]
debug = true
```

### All options

As usual, thanks to Clap, running `cargo instruments -h` prints the compact help.

```
cargo-instruments 0.4.8
Profile a binary with Xcode Instruments.

By default, cargo-instruments will build your main binary.

USAGE:
    cargo instruments [FLAGS] [OPTIONS] --template <TEMPLATE> [ARGS]...

FLAGS:
    -h, --help                   Prints help information
    -l, --list-templates         List available templates
        --no-open                Do not open the generated trace file in Instruments.app
        --release                Pass --release to cargo
    -V, --version                Prints version information
        --all-features           Activate all features for the selected target
        --no-default-features    Do not activate the default features for the selected target

OPTIONS:
        --bench <NAME>                 Benchmark target to run
        --bin <NAME>                   Binary to run
        --example <NAME>               Example binary to run
        --features <CARGO-FEATURES>    Features to pass to cargo
        --manifest-path <PATH>         Path to Cargo.toml
    -p, --package <NAME>               Specify package for example/bin/bench
        --profile <NAME>               Pass --profile NAME to cargo
    -t, --template <TEMPLATE>          Specify the instruments template to run
        --time-limit <MILLIS>          Limit recording time to the specified value (in milliseconds)
    -o, --output <PATH>                Output .trace file to the given path

ARGS:
    <ARGS>...    Arguments passed to the target binary

EXAMPLE:
    cargo instruments -t time    Profile main binary with the (recommended) Time Profiler.
```

And `cargo instruments --help` provides more detail.

### Templates

Instruments has the concept of 'templates', which describe sets of dtrace
probes that can be enabled. You can ask `cargo-instruments` to list available
templates, including your custom ones (see help above). If you don't provide a
template name, you will be prompted to choose one.

Typically, the built-in templates are

    built-in            abbrev
    --------------------------
    Activity Monitor
    Allocations         (alloc)
    Animation Hitches
    App Launch
    Core Data
    Counters
    Energy Log
    File Activity       (io)
    Game Performance
    Leaks
    Logging
    Metal System Trace
    Network
    SceneKit
    SwiftUI
    System Trace        (sys)
    Time Profiler       (time)
    Zombies

### Examples

```sh
# View all args and options
$ cargo instruments --help
```

```sh
# View all built-in and custom templates
$ cargo instruments --list-templates
```

```sh
# profile the main binary with the Allocations template
$ cargo instruments -t alloc
```

```sh
# profile examples/my_example.rs, with the Allocations template,
# for 10 seconds, and open the trace when finished
$ cargo instruments -t Allocations --example my_example --time-limit 10000 --open
```

## Resources

[Instruments Help][instruments]

### WWDC videos

The best source of information about Instruments is likely the various WWDC
sessions over the years:

- [Profiling in Depth](https://developer.apple.com/videos/play/wwdc2015/412/)
- [Using Time Profiler in Instruments](https://developer.apple.com/videos/play/wwdc2016/418/)
- [System Trace in Depth](https://developer.apple.com/videos/play/wwdc2016/411/)
- [Creating Custom Instruments](https://developer.apple.com/videos/play/wwdc2018/410/)

[instruments]: https://help.apple.com/instruments/mac/10.0/
[time profiler]: https://help.apple.com/instruments/mac/10.0/#/dev44b2b437