hakmem/PHASE8_EXECUTIVE_SUMMARY.md

Phase 8 - Executive Summary

Date: 2025-11-30 Status: COMPLETE Next Phase: Phase 9 - SuperSlab Deep Dive (CRITICAL PRIORITY)

What We Did

Executed comprehensive benchmarks comparing HAKMEM (Phase 8) against System malloc and mimalloc:

• 30 benchmark runs total (3 allocators × 2 working sets × 5 runs each)
• Statistical analysis with mean, standard deviation, min/max
• Root cause analysis from debug logs
• Detailed technical reports generated

Key Findings

Performance Results

Benchmark	HAKMEM	System	mimalloc	Gap vs System	Gap vs mimalloc
WS256 (Hot Cache)	79.2	86.7	114.9	-9.4%	-45.2%
WS8192 (Realistic)	16.5	57.1	96.5	-246%	-485%

All values in M ops/s (millions of operations per second)

Critical Issues Identified

1. SuperSlab Scaling Failure (SEVERITY: CRITICAL)

   • HAKMEM degrades 4.80x from hot cache to realistic workload
   • System malloc degrades only 1.52x
   • mimalloc degrades only 1.19x
   • Root cause: SuperSlab architecture doesn't scale
   • Evidence: "shared_fail→legacy" messages in logs

2. Fast Path Overhead (SEVERITY: MEDIUM)

   • Even with hot cache, HAKMEM is 9.4% slower than System malloc
   • Root cause: TLS drain overhead, SuperSlab lookup costs

3. Competitive Position (SEVERITY: CRITICAL)

   • At realistic workloads, HAKMEM is 3.46x slower than System malloc
   • mimalloc is 5.85x faster than HAKMEM
   • Conclusion: HAKMEM is not production-ready

What This Means

The Good

• Benchmarking infrastructure works perfectly
• Statistical methodology is sound (low variance, reproducible)
• We have clear diagnostic data and debug logs
• We know exactly what's broken

The Bad

• SuperSlab architecture has fundamental scalability issues
• Performance gap is too large to fix with incremental optimizations
• 246% slower than System malloc at realistic workloads is unacceptable

The Ugly

• May need architectural redesign (Hybrid approach or complete rewrite)
• Current SuperSlab work may need to be abandoned
• Timeline to production-ready could extend by 4-8 weeks

Recommendations

Immediate Next Steps (Phase 9 - 2 weeks)

Week 1: Investigation

• Add comprehensive profiling (cache misses, TLB misses)
• Analyze "shared_fail→legacy" root cause
• Measure SuperSlab fragmentation
• Benchmark different SuperSlab sizes (1MB, 2MB, 4MB)

Week 2: Targeted Fixes

• Implement hash table for SuperSlab lookup
• Fix shared slab capacity issues
• Optimize fast path (more inlining, fewer branches)
• Test larger SuperSlab sizes

Success Criteria:

• Minimum: WS8192 improves from 16.5 → 35 M ops/s (2x improvement)
• Stretch: WS8192 reaches 45 M ops/s (80% of System malloc)

Decision Point (End of Phase 9)

If successful (>35 M ops/s at WS8192):

• Continue with SuperSlab optimizations
• Path to production-ready: 6-8 weeks
• Confidence: Medium (60%)

If unsuccessful (<30 M ops/s at WS8192):

• Switch to Hybrid Architecture
  • Keep: TLS fast path layer (working well)
  • Replace: SuperSlab backend with proven design
• Path to production-ready: 8-10 weeks
• Confidence: High (75%)

Deliverables

All benchmark data and analysis available in:

1. PHASE8_QUICK_REFERENCE.md - TL;DR for developers (START HERE)
2. PHASE8_VISUAL_SUMMARY.md - Charts and decision matrix
3. PHASE8_TECHNICAL_ANALYSIS.md - Deep dive into root causes
4. PHASE8_COMPREHENSIVE_BENCHMARK_REPORT.md - Full statistical report
5. phase8_comprehensive_benchmark_results.txt - Raw benchmark output (222 lines)

Risk Assessment

Technical Risks

• HIGH: SuperSlab architecture may be fundamentally flawed
• MEDIUM: Fixes may provide only incremental improvements
• LOW: Benchmarking methodology (methodology is solid)

Schedule Risks

• HIGH: May need architectural redesign (adds 3-4 weeks)
• MEDIUM: Phase 9 investigation could reveal deeper issues
• LOW: Tooling and infrastructure (all working well)

Mitigation Strategies

• Have Hybrid Architecture plan ready as fallback (Option B)
• Set clear success criteria for Phase 9 (measurable, time-boxed)
• Don't over-invest in SuperSlab if early results are negative

Competitive Landscape

Production Allocators (Benchmark: WS8192):
  1. mimalloc:      96.5 M ops/s  [TIER 1 - Best in class]
  2. System malloc: 57.1 M ops/s  [TIER 1 - Production ready]

Experimental Allocators:
  3. HAKMEM:        16.5 M ops/s  [TIER 3 - Research/development]

Target for Production: 45-50 M ops/s (80% of System malloc)

Budget and Timeline

Best Case (Phase 9 successful)

• Phase 9: 2 weeks (investigation + fixes)
• Phase 10-12: 4 weeks (optimizations)
• Total: 6 weeks to production-ready
• Cost: Low (mostly optimization work)

Likely Case (Hybrid Architecture)

• Phase 9: 2 weeks (investigation reveals need for redesign)
• Phase 10: 1 week (planning Hybrid approach)
• Phase 11-13: 4 weeks (implementation)
• Phase 14: 1 week (validation)
• Total: 8 weeks to production-ready
• Cost: Medium (partial rewrite of backend)

Worst Case (Complete rewrite)

• Phase 9: 2 weeks (investigation)
• Phase 10: 2 weeks (architecture design)
• Phase 11-15: 8 weeks (implementation)
• Total: 12 weeks to production-ready
• Cost: High (throw away SuperSlab work)

Recommended: Plan for Likely Case (8 weeks), prepare for Worst Case

Success Metrics

Phase 9 Targets (2 weeks from now)

• WS256: 79.2 → 85+ M ops/s
• WS8192: 16.5 → 35+ M ops/s
• Degradation: 4.80x → 2.50x
• Zero "shared_fail→legacy" events
• Understand root cause of scalability issue

Phase 12 Targets (6-8 weeks from now)

• WS256: 90+ M ops/s (match System malloc)
• WS8192: 45+ M ops/s (80% of System malloc)
• Degradation: <2.0x (competitive with System malloc)
• Production-ready: passes all stress tests

Conclusion

Phase 8 benchmarking successfully identified critical performance issues with HAKMEM. The data is statistically robust, reproducible, and provides clear direction for Phase 9.

Bottom Line:

• SuperSlab architecture is broken at scale
• We have 2 weeks to fix it (Phase 9)
• If unfixable, we have a viable fallback plan (Hybrid Architecture)
• Timeline to production-ready: 6-10 weeks depending on Phase 9 results

Recommendation: Proceed with Phase 9 investigation IMMEDIATELY. This is the critical path to success.

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Prepared by: Claude (Benchmark Automation) Reviewed by: [Your review] Approved for Phase 9: [Pending]

Questions? See PHASE8_QUICK_REFERENCE.md or PHASE8_VISUAL_SUMMARY.md for details.