hakmem/PHASE8_QUICK_REFERENCE.md

# Phase 8 Benchmark - Quick Reference Card

## TL;DR - The Numbers

```
Working Set 256 (Hot Cache):
  HAKMEM:    79.2 M ops/s
  System:    86.7 M ops/s  (1.09x faster)
  mimalloc: 114.9 M ops/s  (1.45x faster)

Working Set 8192 (Realistic):
  HAKMEM:    16.5 M ops/s  ⚠️ CRITICAL
  System:    57.1 M ops/s  (3.46x faster) ⚠️ CRITICAL
  mimalloc:  96.5 M ops/s  (5.85x faster) ⚠️ CRITICAL

Scalability (WS256 → WS8192):
  HAKMEM:   4.80x degradation  🔴 BROKEN
  System:   1.52x degradation  ✅ Good
  mimalloc: 1.19x degradation  ✅ Excellent
```

## Critical Issues Found

### 1. SuperSlab Scaling Failure (SEVERITY: CRITICAL)
- **Impact**: 246% slower than System malloc at WS8192
- **Evidence**: "shared_fail→legacy" logs show slab exhaustion
- **Root cause**: SuperSlab architecture doesn't scale beyond hot cache

### 2. Fast Path Overhead (SEVERITY: MEDIUM)
- **Impact**: 9.4% slower than System malloc at WS256
- **Evidence**: Even with everything in cache, HAKMEM lags
- **Root cause**: TLS drain overhead, SuperSlab lookup costs

### 3. Fragmentation Issues (SEVERITY: HIGH)
- **Impact**: 4.8x performance degradation vs 1.5x for System
- **Evidence**: Linear performance collapse with working set size
- **Root cause**: SuperSlab list becomes inefficient

## Phase 9 Priorities

### Week 1: Investigation
1. Profile SuperSlab lookup latency
2. Measure cache/TLB miss rates
3. Analyze "shared_fail→legacy" root cause
4. Measure fragmentation at different working set sizes

### Week 2: Targeted Fixes
1. Implement hash table for SuperSlab lookup
2. Experiment with 1MB/2MB SuperSlab sizes
3. Fix shared slab capacity issues
4. Optimize fast path (inline more, reduce branches)

## Success Criteria

### Minimum (Required)
- WS256: 79.2 → 85 M ops/s (+7%)
- WS8192: 16.5 → 35 M ops/s (+112%)
- Degradation: 4.80x → 2.50x or better

### Stretch Goal
- WS256: 90+ M ops/s (match System malloc)
- WS8192: 45+ M ops/s (80% of System malloc)
- Degradation: 2.00x or better

## If Phase 9 Fails (<30 M ops/s at WS8192)

Switch to **Hybrid Architecture**:
- Keep: TLS fast path layer
- Replace: SuperSlab backend → jemalloc-style arenas
- Timeline: +3 weeks
- Success probability: 75%

## Benchmark Reproducibility

All benchmarks available at:
- `/mnt/workdisk/public_share/hakmem/phase8_comprehensive_benchmark_results.txt` (raw data)
- `./bench_random_mixed_hakmem 10000000 8192` (reproduce HAKMEM)
- `./bench_random_mixed_system 10000000 8192` (reproduce System)
- `./bench_random_mixed_mi 10000000 8192` (reproduce mimalloc)

5 runs per benchmark, StdDev < 2.5% (statistically robust).

## Reports Generated

1. **PHASE8_COMPREHENSIVE_BENCHMARK_REPORT.md** - Full statistical analysis
2. **PHASE8_TECHNICAL_ANALYSIS.md** - Deep dive into root causes
3. **PHASE8_VISUAL_SUMMARY.md** - Visual charts and decision matrix
4. **PHASE8_QUICK_REFERENCE.md** - This file (quick lookup)

## Next Steps

1. Read PHASE8_VISUAL_SUMMARY.md for decision matrix
2. Read PHASE8_TECHNICAL_ANALYSIS.md for root cause details
3. Begin Phase 9 investigation (Week 1)
4. Re-evaluate after 2 weeks

---

**Date**: 2025-11-30
**Status**: Phase 8 COMPLETE, Phase 9 READY
**Critical Path**: Fix SuperSlab scaling or switch to Hybrid architecture