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hakmem/docs/analysis
Moe Charm (CI) ef8e2ab9b5 Phase 59b & 61: Speed-first Rebase + C7 ULTRA Header-Light Optimization
Phase 59b: Speed-first Mode Baseline Rebase
- Rebase on MIXED_TINYV3_C7_SAFE profile (Speed-first, no prewarm suppression)
- hakmem: 58.478 M ops/s (CV 2.52%)
- mimalloc: 120.979 M ops/s (CV 0.90%)
- Ratio: 48.34% of mimalloc (down from 49.13% Balanced mode in Phase 59)
- Reason for difference: Profile selection (Speed-first vs Balanced) and mimalloc environment variance
- Status: COMPLETE (measurement-only, zero code changes)

Phase 61: C7 ULTRA Header-Light Optimization Attempt
- Objective: Skip header write on C7 ULTRA alloc hit (write only on refill)
- Implementation: ENV gate HAKMEM_TINY_C7_ULTRA_HEADER_LIGHT (default OFF)
- Result: +0.31% (NEUTRAL, below +1.0% GO threshold)
  - Baseline: 59.543 M ops/s (CV 1.53%)
  - Treatment: 59.729 M ops/s (CV 2.66%)
- Root cause analysis:
  - tiny_region_id_write_header only 2.32% of time (lower than Phase 42 estimate 4.56%)
  - Header-light mode adds branch to hot path, negating write savings
  - Mixed workload dilutes C7-specific optimization effectiveness
  - Variance increased due to branch prediction variability
- Decision: Kept as research box with ENV gate (default OFF)
- Lesson: Workload-specific optimizations need careful verification with full workloads

Updated Documentation:
- PHASE59B_SPEED_FIRST_REBASE_RESULTS.md: Full measurement results and analysis
- PHASE61_C7_ULTRA_HEADER_LIGHT_RESULTS.md: A/B test results and root cause analysis
- PHASE61_C7_ULTRA_HEADER_LIGHT_IMPLEMENTATION.md: Implementation details and design
- CURRENT_TASK.md: Updated status and next phase planning (Phase 62)
- PERFORMANCE_TARGETS_SCORECARD.md: Updated baseline and M1 milestone status

M1 (50%) Milestone Status:
- Current: 48.34% (Speed-first profile)
- Gap: -1.66% (within measurement noise)
- Profile recommendation: Speed-first as canonical default for throughput focus

🤖 Generated with Claude Code

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
2025-12-17 16:25:26 +09:00
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