| name | perf-regression |
| description | Use when modifying hot-path code in coordination or scanner engine, before merging performance-sensitive changes, or when CI benchmarks flag a regression. Performance regression testing with before/after comparison. |
| user-invocable | false |
Performance Regression Workflow
IMPORTANT: Follow this workflow before merging any feature that touches hot paths in the gossip-rs workspace.
When This Applies
Invoke this skill when modifying:
- Data structures in
crates/gossip-stdx/src/ (InlineVec, RingBuffer, ByteSlab)
- Coordination protocol in
crates/gossip-coordination/src/
- Contract types in
crates/gossip-contracts/src/
- Scanner engine in
crates/scanner-engine/src/
- Scanner runtime in
crates/gossip-scanner-runtime/src/
- Scanner scheduler in
crates/scanner-scheduler/src/
- Git scan pipeline in
crates/scanner-git/src/
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 Benchmarks
Save baselines for all relevant benchmark suites:
cargo bench --workspace -- --save-baseline before
cargo bench -p gossip-stdx -- --save-baseline before
cargo bench -p gossip-contracts -- --save-baseline before
cargo bench -p gossip-coordination -- --save-baseline before
3. Restore Changes and Rebuild
git stash pop
RUSTFLAGS="-C target-cpu=native" cargo build --release
4. Run Comparison Benchmarks
cargo bench --workspace -- --baseline before
cargo bench -p gossip-stdx -- --baseline before
cargo bench -p gossip-contracts -- --baseline before
cargo bench -p gossip-coordination -- --baseline before
5. Analyze Results
Look for these patterns in Criterion output:
Performance has improved — Optimization successfulPerformance has regressed — Changes hurt performanceNo change in performance — Within noise threshold
Available Benchmarks
| Crate | Bench File | Measures |
|---|
gossip-contracts | identity.rs | Identity type construction and derivation |
gossip-coordination | coordination.rs | Shard coordination operations |
gossip-coordination | sim.rs | Simulation harness benchmarks |
gossip-stdx | byte_slab.rs | Byte slab pool allocation |
gossip-stdx | inline_vec.rs | InlineVec operations |
gossip-stdx | ring_buffer.rs | RingBuffer throughput |
Acceptance Criteria
| Regression Level | Action |
|---|
| None (<2%) | Ship as-is |
| Minor (2-5%) | Document reason, acceptable for correctness |
| Moderate (5-10%) | Requires compelling justification |
| Major (>10%) | Must investigate and optimize |
PR Documentation
Include in PR description:
- Criterion benchmark comparison summary
- Which crates/benchmarks were affected
- Justification for any regression >2%
Output Format
Report results as:
## Performance Regression Results
### Criterion Benchmarks
| Crate | Benchmark | Baseline | After | Delta |
|-------|-----------|----------|-------|-------|
| gossip-stdx | inline_vec/push | X ns | Y ns | +/-Z% |
| gossip-stdx | ring_buffer/enqueue | X ns | Y ns | +/-Z% |
| gossip-stdx | byte_slab/alloc | X ns | Y ns | +/-Z% |
| gossip-contracts | identity/derive | X ns | Y ns | +/-Z% |
| gossip-coordination | coordination/acquire | X ns | Y ns | +/-Z% |
### Verdict
[None/Minor/Moderate/Major] regression - [justification if >2%]
Related Skills
/bench-compare — Quick before/after benchmark comparison/asm-forge — Assembly-guided optimization for hot functions/linux-perf-profile — ARM-focused deep drill-down (cache, TLB, lock contention)/perf-topdown — Cross-arch TMA classification and branch trace analysis/performance-analyzer — Static hotspot analysis for this project's patterns/pgo-bolt — Apply PGO+BOLT to production builds before regression testing
