Perf Regression

Performance Regression Workflow

IMPORTANT: Follow this workflow before merging any feature that touches hot paths (src/engine/, regex changes, validation logic).

When This Applies

Invoke this skill when modifying:

• src/engine/ modules (scratch.rs, stream_decode.rs, work_items.rs)
• Regex patterns or validation logic
• Data structures in src/stdx/
• Rule definitions in default_rules.yaml or src/rules/

Workflow Steps

1. Stash Changes and Build Baseline

git stash push -m "feature-name"
RUSTFLAGS="-C target-cpu=native" cargo build --release

2. Run Baseline Scans (3x each)

for i in 1 2 3; do
  ./target/release/scanner-rs ../gitleaks 2>&1 | tail -1
  ./target/release/scanner-rs ../linux 2>&1 | tail -1
  ./target/release/scanner-rs ../tigerbeetle 2>&1 | tail -1
done

Record average throughput for each repository.

3. Run Baseline Benchmarks

cargo bench --bench scanner_throughput -- --save-baseline before
cargo bench --bench vectorscan_overhead -- --save-baseline before

4. Restore Changes and Rebuild

git stash pop
RUSTFLAGS="-C target-cpu=native" cargo build --release

5. Run Comparison Scans and Benchmarks

# Same scan loop as step 2
for i in 1 2 3; do
  ./target/release/scanner-rs ../gitleaks 2>&1 | tail -1
  ./target/release/scanner-rs ../linux 2>&1 | tail -1
  ./target/release/scanner-rs ../tigerbeetle 2>&1 | tail -1
done

# Compare against baseline
cargo bench --bench scanner_throughput -- --baseline before
cargo bench --bench vectorscan_overhead -- --baseline before

6. Analyze Results

Calculate average throughput delta per repository:

% change = (after_throughput - baseline_throughput) / baseline_throughput * 100

Acceptance Criteria

PR Documentation

Include in PR description:

• Average throughput delta per test repository
• Criterion benchmark comparison summary
• Justification for any regression >2%

Output Format

Report results as:

## Performance Regression Results

### Scan Throughput

| Repository | Baseline | After | Delta |
|------------|----------|-------|-------|
| gitleaks | X MB/s | Y MB/s | +/-Z% |
| linux | X MB/s | Y MB/s | +/-Z% |
| tigerbeetle | X MB/s | Y MB/s | +/-Z% |

### Criterion Benchmarks

[Paste relevant benchmark comparison output]

### Verdict

[None/Minor/Moderate/Major] regression - [justification if >2%]

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