From cc398e4a0e90a19aa32c64f53dad3bfb8ded8672 Mon Sep 17 00:00:00 2001
From: "Moe Charm (CI)" <moecharm@example.com>
Date: Sat, 13 Dec 2025 16:08:24 +0900
Subject: [PATCH] Phase 2 B1 & B3: Routing optimization research (NO-GO on B1,
 ADOPT B3)
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## B1 (Header tax reduction v2) - NO-GO
- HAKMEM_TINY_HEADER_MODE=LIGHT: -2.54% on Mixed (regression)
- Decision: FREEZE as research box, ENV opt-in only

## B3 (Routing branch shape optimization) - ADOPT
- Mixed: +2.89% (48.41M → 49.80M ops/s)
- C6-heavy: +9.13% (8.97M → 9.79M ops/s)
- Strategy: LIKELY on LEGACY (hot path), cold helper for rare routes
- Implementation: Already in malloc_tiny_fast.h:252-267, now enabled by default
- Profile updates: bench_profile.h adds HAKMEM_TINY_ALLOC_ROUTE_SHAPE=1 to MIXED_TINYV3_C7_SAFE and C6_HEAVY_LEGACY_POOLV1

🤖 Generated with Claude Code

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
---
 CURRENT_TASK.md | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/CURRENT_TASK.md b/CURRENT_TASK.md
index 685ca988..c4858c2d 100644
--- a/CURRENT_TASK.md
+++ b/CURRENT_TASK.md
@@ -5,7 +5,7 @@
 ### Phase 1 Quick Wins: FREE 昇格 + 観測税ゼロ化
 - ✅ **A1（FREE 昇格）**: `MIXED_TINYV3_C7_SAFE` で `HAKMEM_FREE_TINY_FAST_HOTCOLD=1` をデフォルト化
 - ✅ **A2（観測税ゼロ化）**: `HAKMEM_DEBUG_COUNTERS=0` のとき stats を compile-out（観測税ゼロ）
-- ❌ **A3（inline header）**: `tiny_region_id_write_header()` always_inline → **NO-GO**
+- ❌ **A3（always_inline header）**: `tiny_region_id_write_header()` always_inline → **NO-GO**（指示書/結果: `docs/analysis/TINY_HEADER_WRITE_ALWAYS_INLINE_A3_DESIGN.md`）
   - A/B Result: Mixed -4.00% (I-cache pressure), C6-heavy +6.00%
   - Decision: Freeze as research box (default OFF)
   - Commit: `df37baa50`
@@ -18,7 +18,22 @@
 - 結果: Mixed -0.27%（中立）、C6-heavy +1.68%（SSOT 効果）
 - Commit: `d0f939c2e`
 
-## 現在地: ALLOC-GATE-SSOT-1 + DUALHOT-2 完了 ✅ (C6-heavy +1.68% SSOT gain)
+### Phase 2 B1 & B3: ルーティング最適化 (2025-12-13)
+
+**B1（Header tax 削減 v2）: HEADER_MODE=LIGHT** → ❌ **NO-GO**
+- Mixed (10-run): 48.89M → 47.65M ops/s (**-2.54%**, regression)
+- Decision: FREEZE (research box, ENV opt-in)
+- Rationale: Conditional check overhead outweighs store savings on Mixed
+
+**B3（Routing 分岐形最適化）: ALLOC_ROUTE_SHAPE=1** → ✅ **ADOPT**
+- Mixed (10-run): 48.41M → 49.80M ops/s (**+2.89%**, win)
+  - Strategy: LIKELY on LEGACY (hot), cold helper for rare routes (V7/MID/ULTRA)
+- C6-heavy (5-run): 8.97M → 9.79M ops/s (**+9.13%**, strong win)
+- Decision: **ADOPT as default** in MIXED_TINYV3_C7_SAFE and C6_HEAVY_LEGACY_POOLV1
+- Implementation: Already in place (lines 252-267 in malloc_tiny_fast.h), now enabled by default
+- Profile updates: Added `bench_setenv_default("HAKMEM_TINY_ALLOC_ROUTE_SHAPE", "1")` to both profiles
+
+## 現在地: B3 採用完了 ✅ (Mixed +2.89%, C6-heavy +9.13%)
 
 ### Phase ALLOC-GATE-SSOT-1 + ALLOC-TINY-FAST-DUALHOT-2: COMPLETED