cargo-perf

Preventive performance analysis for Rust. Catch performance anti-patterns before they reach production.

Installation

cargo install --path .

Usage

# Analyze current directory
cargo perf

# Analyze specific path
cargo perf check src/

# Output as JSON
cargo perf --format json

# Output as SARIF (for GitHub integration)
cargo perf --format sarif

# List available rules
cargo perf rules

# Initialize config file
cargo perf init

Rules

Rule	Severity	Description
`async-block-in-async`	Error	Detects blocking std calls inside async functions
`clone-in-hot-loop`	Warning	Detects `.clone()` calls on heap types inside loops
`regex-in-loop`	Warning	Detects `Regex::new()` inside loops
`collect-then-iterate`	Warning	Detects `.collect()` immediately followed by `.iter()`

Configuration

Create cargo-perf.toml in your project root:

[rules]
# Set rule severity: "deny" (error), "warn" (warning), "allow" (ignore)
async-block-in-async = "deny"
clone-in-hot-loop = "warn"
regex-in-loop = "allow"

[output]
format = "console"  # "console", "json", "sarif"
color = "auto"      # "auto", "always", "never"

Dog-fooding Results

cargo-perf is tested on itself. During development, it detected a real issue in its own codebase:

$ cargo-perf check src/
warning: `.clone()` called inside loop; consider borrowing or moving the clone outside [clone-in-hot-loop]
  --> src/reporter/sarif.rs:101:40
  help: Use a reference or move the clone outside the loop

Found 1 warning(s)

The warning identified a .clone() call inside a loop in the SARIF reporter. This was refactored to collect data outside the loop, eliminating the unnecessary allocations. After the fix:

$ cargo-perf check src/
No performance issues found.

This demonstrates that cargo-perf catches real performance issues, even in well-reviewed code.

CI Integration

GitHub Actions with SARIF

- name: Run cargo-perf
  run: |
    cargo install cargo-perf
    cargo perf --format sarif > results.sarif

- name: Upload SARIF
  uses: github/codeql-action/upload-sarif@v2
  with:
    sarif_file: results.sarif

Fail on Warnings

cargo perf --fail-on warning

License

MIT OR Apache-2.0

cargo-perf 0.1.0