hakmem/PHASE8_VISUAL_SUMMARY.md

# Phase 8 Comprehensive Benchmark - Visual Summary

## Performance Comparison Charts

### Working Set 256 (Hot Cache) - Bar Chart

```
HAKMEM    ████████████████████████████████████████ 79.2 M ops/s (1.00x)
System    ███████████████████████████████████████████ 86.7 M ops/s (1.09x) ↑ 9%
mimalloc  ██████████████████████████████████████████████████████████ 114.9 M ops/s (1.45x) ↑ 45%
```

### Working Set 8192 (Realistic Workload) - Bar Chart

```
HAKMEM    ████ 16.5 M ops/s (1.00x)
System    ██████████████ 57.1 M ops/s (3.46x) ↑ 246%
mimalloc  ████████████████████████ 96.5 M ops/s (5.85x) ↑ 485%
```

## Scalability Comparison

### Performance Degradation (WS256 → WS8192)

```
mimalloc  ████ 1.19x degradation  [EXCELLENT]
System    ██████ 1.52x degradation  [GOOD]
HAKMEM    ███████████████████ 4.80x degradation  [CRITICAL ISSUE]
```

## Performance Gap Analysis

### Cycle Budget (Estimated at 3.5 GHz)

| Allocator | Cycles/Op | Extra Cycles vs Best |
|-----------|-----------|---------------------|
| mimalloc  | 36        | 0 (baseline)        |
| System    | 61        | +25 (+69%)          |
| HAKMEM    | 212       | +176 (+489%)        |

**HAKMEM uses 176 extra cycles per operation compared to mimalloc!**

### Where Are The Cycles Going?

```
Estimated cycle breakdown for HAKMEM WS8192:

SuperSlab Lookup:      ████████████████ 50-80 cycles
Legacy Fallback:       ██████████████ 30-50 cycles (when triggered)
Fragmentation:         ███████████ 30-50 cycles
TLS Drain Logic:       ███ 10-15 cycles
Actual Work:           ████████ 30-40 cycles
                       ─────────────────────────
Total:                 ~212 cycles/operation

mimalloc for comparison:
Optimized Fast Path:   ████████ 36 cycles total
```

## Priority Ranking

### Critical Issues (Must Fix)

```
1. SuperSlab Scaling          Priority: CRITICAL    Impact: 246% perf loss
   └─ 4.8x degradation vs 1.5x for System malloc
   └─ "shared_fail→legacy" messages indicate capacity issues

2. Fragmentation             Priority: HIGH        Impact: 30-50 cycles/op
   └─ SuperSlab list becomes inefficient at scale

3. TLB Pressure              Priority: HIGH        Impact: Unknown, likely high
   └─ Many 512KB SuperSlabs → TLB misses
```

### Important Issues (Should Fix)

```
4. TLS Drain Overhead        Priority: MEDIUM      Impact: 9.4% on hot cache
   └─ Affects even best-case performance

5. Fast Path Efficiency      Priority: MEDIUM      Impact: 9.4% on hot cache
   └─ Need more aggressive inlining
```

### Nice-to-Have

```
6. Metadata Optimization     Priority: LOW         Impact: Unknown
   └─ Reduce cache pollution from slab metadata
```

## Competitive Position

### Current Status: Phase 8

```
Tier 1 (Production-Ready):
  mimalloc   ████████████████████████ 96.5 M ops/s
  System     ██████████████ 57.1 M ops/s

Tier 2 (Needs Work):
  (empty)

Tier 3 (Experimental):
  HAKMEM     ████ 16.5 M ops/s  ← YOU ARE HERE
```

### Target for Phase 12 (6 months)

```
Tier 1 (Production-Ready):
  mimalloc   ████████████████████████ 96.5 M ops/s
  HAKMEM     ████████████████████ 80+ M ops/s  ← TARGET
  System     ██████████████ 57.1 M ops/s

Goal: Match or exceed System malloc, get within 20% of mimalloc
```

## Decision Matrix for Phase 9

### Option A: Fix SuperSlab Architecture (Recommended)

**Pros**:
- Preserve existing work
- Targeted fixes may yield big gains
- Debug logs provide clear direction

**Cons**:
- May be fundamentally flawed architecture
- Risk of incremental fixes not solving core issue

**Time estimate**: 2-3 weeks
**Success probability**: 60%

### Option B: Hybrid Architecture

**Pros**:
- Keep TLS fast path (working well)
- Replace SuperSlab backend with proven design
- Best of both worlds

**Cons**:
- Major refactoring required
- Lose SuperSlab work
- Integration complexity

**Time estimate**: 4-6 weeks
**Success probability**: 75%

### Option C: Start Over (Not Recommended Yet)

**Pros**:
- Clean slate
- Can copy proven designs (mimalloc, jemalloc)

**Cons**:
- Lose all current work
- No learning from mistakes
- 3+ months delay

**Time estimate**: 3-4 months
**Success probability**: 85% (but high cost)

## Recommended Path Forward

### Phase 9: SuperSlab Deep Dive (2 weeks)

**Week 1: Investigation**
- Add comprehensive profiling
- Measure cache/TLB misses
- Analyze fragmentation patterns
- Understand "shared_fail→legacy" root cause

**Week 2: Targeted Fixes**
- Implement hash table for SuperSlab lookup
- Experiment with larger SuperSlabs (1-2MB)
- Optimize fragmentation handling
- Add better capacity management

**Success criteria**:
- WS8192: 16.5 → 35+ M ops/s (2x improvement)
- Understand root cause even if fix incomplete

### Phase 10: Decision Point

**If Phase 9 successful (>35 M ops/s)**:
- Continue with SuperSlab optimizations
- Focus on fast path improvements
- Target: 50 M ops/s by Phase 12

**If Phase 9 unsuccessful (<30 M ops/s)**:
- Switch to Hybrid Architecture (Option B)
- Keep TLS layer, replace backend
- Target: 60 M ops/s by Phase 14

## Key Metrics to Track

### Performance Metrics
- [ ] WS256 throughput (target: 85+ M ops/s)
- [ ] WS8192 throughput (target: 35+ M ops/s)
- [ ] Degradation ratio (target: <2.5x)

### Architecture Metrics
- [ ] SuperSlab lookup latency (target: <20 cycles)
- [ ] Cache miss rate (target: <5%)
- [ ] TLB miss rate (target: <1%)
- [ ] Fragmentation ratio (target: <20%)

### Debug Metrics
- [ ] "shared_fail→legacy" events (target: 0)
- [ ] TLS_SLL_HDR_RESET events (target: 0)
- [ ] Average SuperSlab count (target: <10 at WS8192)

## Conclusion

**Phase 8 Status**: COMPLETE
- ✓ Comprehensive benchmarks executed
- ✓ Statistical analysis completed
- ✓ Root cause hypotheses identified
- ✓ Clear path forward defined

**Phase 9 Ready**: YES
- Clear investigation targets
- Specific metrics to measure
- Decision criteria established

**Confidence Level**: HIGH
- Data is robust (low variance)
- Gaps are well-understood
- Multiple viable paths forward

---

**Next Action**: Begin Phase 9 - SuperSlab Deep Dive and Profiling

**Timeline**:
- Phase 9: 2 weeks (investigation + targeted fixes)
- Phase 10: 1 week (decision point + planning)
- Phase 11-12: 3-4 weeks (major optimizations)
- Target completion: 6-8 weeks to production-ready

**Risk Level**: MEDIUM
- SuperSlab may be unfixable → fallback to Hybrid (Option B)
- Hybrid adds 2-3 weeks but higher success probability
- Total timeline stays within 10 weeks worst case