performance-analyzer

name	performance-analyzer
description	Use when writing hot-path code in coordination or scanner engine, before committing changes to scanner-engine modules, when benchmarks show unexpected regressions, or during optimization of gossip-stdx data structures. Static performance analysis.
metadata	{"author":"ahrav"}

Performance Analyzer

Analyze performance-critical code in the gossip-rs workspace (coordination, scanner engine, data structures).

When to Use

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

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
- `/asm-forge` - ASM-guided optimization
- `/perf-regression` - Full regression workflow

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