f7b18aaf13
Target: tiny_region_id_write_header (3.35% self%) - Hypothesis: Headers redundant for reused blocks - Strategy: Write headers ONCE at refill boundary, skip in hot alloc Implementation: - ENV gate: HAKMEM_TINY_HEADER_WRITE_ONCE=0/1 (default 0) - core/box/tiny_header_write_once_env_box.h: ENV gate - core/box/tiny_header_write_once_stats_box.h: Stats counters - core/box/tiny_header_box.h: Added tiny_header_finalize_alloc() - core/front/tiny_unified_cache.c: Prefill at 3 refill sites - core/box/tiny_front_hot_box.h: Use finalize function A/B Test Results (Mixed, 10-run, 20M iters): - Baseline (WRITE_ONCE=0): 44.22M ops/s (mean), 44.53M ops/s (median) - Optimized (WRITE_ONCE=1): 44.42M ops/s (mean), 44.36M ops/s (median) - Improvement: +0.45% mean, -0.38% median Decision: NEUTRAL (within ±1.0% threshold) - Action: FREEZE as research box (default OFF, do not promote) Root Cause Analysis: - Header writes are NOT redundant - existing code writes only when needed - Branch overhead (~4 cycles) cancels savings (~3-5 cycles) - perf self% ≠ optimization ROI (3.35% target → +0.45% gain) Key Lessons: 1. Verify assumptions before optimizing (inspect code paths) 2. Hot spot self% measures time IN function, not savings from REMOVING it 3. Branch overhead matters (even "simple" checks add cycles) Positive Outcome: - StdDev reduced 50% (0.96M → 0.48M) - more stable performance Health Check: PASS (all profiles) Next Candidates: - free_tiny_fast_cold: 7.14% self% - unified_cache_push: 3.39% self% - hakmem_env_snapshot_enabled: 2.97% self% Deliverables: - docs/analysis/PHASE5_E5_2_HEADER_REFILL_ONCE_DESIGN.md - docs/analysis/PHASE5_E5_2_HEADER_REFILL_ONCE_AB_TEST_RESULTS.md - CURRENT_TASK.md (E5-2 complete, FROZEN) 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Docs Overview
このフォルダは hakmem の設計・計測・運用メモを体系化して管理する場所です。
- INDEX.md: 目次（各ドキュメントへのリンク）
- benchmarks/: ベンチマーク手順とスイープ結果の保存先
- specs/: 現在の仕様（SACS‑3/HW/ENV）を集約
- roadmap/: これからの実装計画・優先度・タスク
運用ルール（提案）
- 1つの変更/計測のまとまりにつき1ファイル（or 1フォルダ）
- 再現コマンド・環境変数・ハード構成は必ず記載
- 大きな連続出力はファイルへ保存し、本文からは抜粋/要約を記載