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hakmem/docs/analysis
Moe Charm (CI) ea417200d2 Phase 62: C7 ULTRA Hotpath Optimization - Planning & Profiling Analysis
Complete planning for Phase 62 based on runtime profiling of Phase 59b baseline.

Key Findings (200M ops Mixed benchmark):
- tiny_c7_ultra_alloc: 5.18% (new primary target, 5x larger than Phase 61)
- tiny_region_id_write_header: 3.82% (reconfirmed, Phase 61 showed 2.32%)
- Allocation-specific hot path: 12.37% (C7 + header + cache)

Phase 62 Recommendation: Option A (C7 ULTRA Inline + IPC Analysis)
- Expected gain: +1-3% (higher absolute margin than Phases 46A/61)
- Risk level: Medium (layout tax precedent from Phase 46A -0.68%, Phase 43 -1.18%)
- Approach: Deep profiling → ASM inspection → A/B test with ENV gate

Alternative Options:
- Option B: tiny_region_id_write_header (3.82%, higher risk)
- Option C: Algorithmic redesign (post-50% milestone)

Box Theory Compliance:
- Single conversion point: tiny_c7_ultra_alloc() boundary
- Reversible: ENV gate HAKMEM_TINY_C7_ULTRA_INLINE_OPT (0/1)
- No side effects: Pure dependency chain reordering

Timeline: Single phase, 4-6 hours (profile + ASM + test)

Documentation:
- PHASE62_NEXT_TARGET_ANALYSIS.md: Complete planning document with profiling data
- CURRENT_TASK.md: Updated next phase guidance

Profiling tools prepared:
- perf record with extended events (cycles, cache-misses, branch-misses)
- ASM inspection methodology documented
- A/B test threshold: ±0.5% (micro-scale)

🤖 Generated with Claude Code

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
2025-12-17 16:27:06 +09:00
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