10fb0497e2
Implemented C7 ULTRA allocation hotpath optimization attempt as per Phase 62A instructions. Objective: Reduce dependency chain in tiny_c7_ultra_alloc() by: 1. Eliminating per-call tiny_front_v3_c7_ultra_header_light_enabled() checks 2. Using TLS headers_initialized flag set during refill 3. Reducing branch count and register pressure Implementation: - New ENV box: core/box/c7_ultra_alloc_depchain_opt_box.h - HAKMEM_C7_ULTRA_ALLOC_DEPCHAIN_OPT=0/1 gate (default OFF) - Modified tiny_c7_ultra_alloc() with optimized path - Preserved original path for compatibility Results (Mixed benchmark, 10-run): - Baseline (OPT=0): 59.300 M ops/s (CV 1.98%) - Treatment (OPT=1): 58.879 M ops/s (CV 1.83%) - Delta: -0.71% (NEUTRAL, within ±1.0% threshold but negative) - Status: NEUTRAL → Research box (default OFF) Root Cause Analysis: 1. LTO optimization already inlines header_light function (call cost = 0) 2. TLS access (memory load + offset) not cheaper than function call 3. Layout tax from code addition (I-cache disruption pattern from Phases 43/46A/47) 4. 5.18% stack % is not optimizable hotspot (already well-optimized) Key Lessons: - LTO-optimized function calls can be cheaper than TLS field access - Micro-optimizations on already-optimized paths show diminishing/negative returns - 48.34% gap to mimalloc is likely algorithmic, not micro-architectural - Layout tax remains consistent pattern across attempted micro-optimizations Decision: - NEUTRAL verdict → kept as research box with ENV gate (default OFF) - Not adopted as production default - Next phases: Option B (production readiness pivot) likely higher ROI than further micro-opts Box Theory Compliance: ✅ Compliant (single point, reversible, clear boundary) Performance Compliance: ❌ No (-0.71% regression) Documentation: - PHASE62A_C7_ULTRA_DEPCHAIN_OPT_RESULTS.md: Full A/B test analysis - CURRENT_TASK.md: Updated with results and next phase options 🤖 Generated with Claude Code Co-Authored-By: Claude Haiku 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