From 326102599533aee162103378652c17f9e0be9d13 Mon Sep 17 00:00:00 2001
From: "Moe Charm (CI)" <moecharm@example.com>
Date: Wed, 10 Dec 2025 18:18:05 +0900
Subject: [PATCH] Phase v4-4: pilot C6 v4 route with opt-in gate

---
 CURRENT_TASK.md                            | 10 ++++++++++
 core/box/smallobject_hotbox_v4_env_box.h   |  4 ++++
 core/front/malloc_tiny_fast.h              |  2 +-
 core/smallobject_hotbox_v4.c               | 12 ++++++------
 docs/analysis/SMALLOBJECT_V4_BOX_DESIGN.md |  6 ++++++
 5 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/CURRENT_TASK.md b/CURRENT_TASK.md
index a6c608ab..1410f3db 100644
--- a/CURRENT_TASK.md
+++ b/CURRENT_TASK.md
@@ -1061,3 +1061,13 @@ export HAKMEM_POOL_ZERO_MODE=header
   - v3 route: 40,661,560 ops/s
   - v4 route: 40,010,302 ops/s（-1.6% 以内、回帰なし）
 - 所感: C7-only では v4 が逆転し、prepare 増加の問題は解消。Mixed も健康レンジに収まった。次は C7 v4 の pf/partial 再利用 or C6/C5 拡張を検討。
+
+### Phase v4-4: C6 v4 パイロット（C6-heavy 専用、強ゲート）
+- 変更:
+  - v4 ENV マスクに C6(bit6=0x40) を解禁。`smallobject_hotbox_v4_env_box.h` に C6 helper を追加。
+  - `smallobject_hotbox_v4.c` に C6 クラスの alloc/free を追加（Tiny v1 Cold 経由、C7 と同形 freelist/current/partial パス）。
+  - front free の v4 ルートで C6 も small_heap_free_fast_v4 を通すよう修正。
+- A/B (C6-heavy, ws=400, iters=1M, size=257–768):
+  - C6 v1: 28,690,913 ops/s
+  - C6 v4: 30,068,995 ops/s（+4.8%）segv/assert なし
+- Mixed 16–1024B: デフォルトは C6 v1 のまま（`HAKMEM_SMALL_HEAP_V4_CLASSES=0x80` で C7-only）。C6 v4 は研究箱として opt-in（`0x40`）。
diff --git a/core/box/smallobject_hotbox_v4_env_box.h b/core/box/smallobject_hotbox_v4_env_box.h
index 366a22aa..22430381 100644
--- a/core/box/smallobject_hotbox_v4_env_box.h
+++ b/core/box/smallobject_hotbox_v4_env_box.h
@@ -43,3 +43,7 @@ static inline int small_heap_v4_class_enabled(uint8_t class_idx) {
 static inline int small_heap_v4_c7_enabled(void) {
     return small_heap_v4_class_enabled(7);
 }
+
+static inline int small_heap_v4_c6_enabled(void) {
+    return small_heap_v4_class_enabled(6);
+}
diff --git a/core/front/malloc_tiny_fast.h b/core/front/malloc_tiny_fast.h
index dee8a5e0..9eacf96e 100644
--- a/core/front/malloc_tiny_fast.h
+++ b/core/front/malloc_tiny_fast.h
@@ -319,7 +319,7 @@ static inline int free_tiny_fast(void* ptr) {
                     if (__builtin_expect(use_tiny_heap, 0)) {
                         switch (route) {
                             case TINY_ROUTE_SMALL_HEAP_V4:
-                                if (class_idx == 7) {
+                                if (class_idx == 7 || class_idx == 6) {
                                     small_heap_free_fast_v4(small_heap_ctx_v4_get(), class_idx, base);
                                     return 1;
                                 }
diff --git a/core/smallobject_hotbox_v4.c b/core/smallobject_hotbox_v4.c
index 6cced59f..a36a8220 100644
--- a/core/smallobject_hotbox_v4.c
+++ b/core/smallobject_hotbox_v4.c
@@ -106,7 +106,7 @@ static small_page_v4* v4_find_page(small_class_heap_v4* h, const uint8_t* ptr, v
 // -----------------------------------------------------------------------------
 
 static small_page_v4* cold_refill_page_v4(small_heap_ctx_v4* hot_ctx, uint32_t class_idx) {
-    if (__builtin_expect(class_idx != 7, 0)) return NULL;
+    if (__builtin_expect(class_idx != 7 && class_idx != 6, 0)) return NULL;
     (void)hot_ctx;
     tiny_heap_ctx_t* tctx = tiny_heap_ctx_for_thread();
     if (!tctx) return NULL;
@@ -193,10 +193,10 @@ static small_page_v4* small_alloc_slow_v4(small_heap_ctx_v4* ctx, int class_idx)
 }
 
 void* small_heap_alloc_fast_v4(small_heap_ctx_v4* ctx, int class_idx) {
-    if (__builtin_expect(class_idx != 7, 0)) {
-        return NULL;  // C7 専用
+    if (__builtin_expect(class_idx != 7 && class_idx != 6, 0)) {
+        return NULL;  // C6/C7 専用
     }
-    if (!small_heap_v4_c7_enabled()) return NULL;
+    if (!small_heap_v4_class_enabled((uint8_t)class_idx)) return NULL;
     small_class_heap_v4* h = &ctx->cls[class_idx];
     small_page_v4* page = h->current;
 
@@ -240,10 +240,10 @@ static void v4_unlink_from_list(small_class_heap_v4* h, v4_loc_t loc, small_page
 }
 
 void small_heap_free_fast_v4(small_heap_ctx_v4* ctx, int class_idx, void* ptr) {
-    if (__builtin_expect(class_idx != 7, 0)) {
+    if (__builtin_expect(class_idx != 7 && class_idx != 6, 0)) {
         return;
     }
-    if (!small_heap_v4_c7_enabled()) return;
+    if (!small_heap_v4_class_enabled((uint8_t)class_idx)) return;
     if (!ptr) return;
 
     small_class_heap_v4* h = &ctx->cls[class_idx];
diff --git a/docs/analysis/SMALLOBJECT_V4_BOX_DESIGN.md b/docs/analysis/SMALLOBJECT_V4_BOX_DESIGN.md
index bead6afa..ea04346e 100644
--- a/docs/analysis/SMALLOBJECT_V4_BOX_DESIGN.md
+++ b/docs/analysis/SMALLOBJECT_V4_BOX_DESIGN.md
@@ -38,3 +38,9 @@
     - v3 route: 40.66M ops/s
     - v4 route: 40.01M ops/s（-1.6% 以内、回帰なし）
 - どちらも segv/assert なし。C7 v4 の prepare 増加は解消済み。Mixed ではまだ v3 がわずかに優勢だが許容範囲。
+- Phase v4-4 (C6 v4 パイロット):
+  - ENV: `HAKMEM_SMALL_HEAP_V4_ENABLED=1`, `HAKMEM_SMALL_HEAP_V4_CLASSES=0x40`（C6-only v4）。Mixed では標準 OFF（0x80= C7-only）。
+  - C6-heavy ベンチ (ws=400, iters=1M, size 257–768):
+    - C6 v1: 28.69M ops/s
+    - C6 v4: 30.07M ops/s（+4.8%）segv/assert なし
+  - Mixed 16–1024B はデフォルトで C6 v1 のまま（C6 v4 は研究箱）。今後 C6 v4 の安定度を見つつ拡張予定。