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performance-analyzer

Testing & Quality
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Analyze Rust code for performance issues, allocation hot spots, and optimization opportunities

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How to use this skill

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Source SKILL.md: https://github.com/majiayu000/claude-skill-registry/blob/HEAD/skills/performance/performance-analyzer-ahrav-scratch-scanner-rs/SKILL.md

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Performance Analyzer

Analyze performance-critical code in this secret scanning engine.

When to Use

  • After writing hot-path code (scanning, decoding, validation)
  • Before committing changes to src/engine/ modules
  • When benchmark results show unexpected regressions
  • During optimization work on data structures in src/stdx/

Analysis Checklist

Memory & Allocation

  • Unnecessary allocations in loops (Vec, String, Box)
  • Missing with_capacity() for known-size collections
  • Cloning where borrowing would suffice
  • Large structs passed by value instead of reference

CPU & Cache

  • False sharing in concurrent data structures
  • Cache-unfriendly access patterns (strided, random)
  • Missing #[inline(always)] on hot functions
  • Branch-heavy code that could use branchless alternatives

Async & Concurrency

  • Blocking operations in async contexts
  • Lock contention patterns
  • Oversized futures (check with std::mem::size_of)
  • Unnecessary Arc when Rc or ownership would work

Rust-Specific

  • Bounds checks in hot loops (consider get_unchecked with proof)
  • Iterator vs manual loop performance
  • &str vs String in function signatures
  • Zero-cost abstraction violations

Project-Specific Patterns

This codebase uses these performance patterns:

  • NONE_U32 = u32::MAX as sentinel (avoid Option overhead)
  • #[inline(always)] on hot-path functions
  • debug_assert! for invariant checks (zero cost in release)
  • Const generics (G) for compile-time granularity selection

Output Format

## Performance Analysis: [file/function]

### Findings

| Severity | Issue | Location | Impact |
|----------|-------|----------|--------|
| HIGH | Allocation in hot loop | line:XX | ~Xns per call |
| MEDIUM | Missing inline hint | line:XX | Potential call overhead |

### Recommendations

1. **[Issue]**: [Specific fix with code example]
   ```rust
   // Before
   // After

Validation

Run these benchmarks to verify:

  • cargo bench --bench <relevant_bench>

## Related Skills

- `/bench-compare` - Before/after measurement
- `/rust-hotspot-finder` - Systematic hotspot scanning
- `/perf-regression` - Full regression workflow