Phase v7-5b: C5+C6 multi-class expansion (+4.3% improvement)
- Add C5 (256B blocks) support alongside C6 (512B blocks) - Same segment shared between C5/C6 (page_meta.class_idx distinguishes) - SMALL_V7_CLASS_SUPPORTED() macro for class validation - Extend small_v7_block_size() for C5 (switch statement) A/B Result: C6-only v7 avg 7.64M ops/s → C5+C6 v7 avg 7.97M ops/s (+4.3%) Criteria: C6 protected ✅, C5 net positive ✅, TLS bloat none ✅ ENV: HAKMEM_SMALL_HEAP_V7_CLASSES=0x60 (bit5+bit6) 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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@ -102,17 +102,18 @@ typedef struct SmallPageStatsV7 {
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void small_cold_v7_publish_stats(const SmallPageStatsV7* stats);
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// ============================================================================
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// Block Size Lookup (C6-only for v7-2)
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// Block Size Lookup (v7-5b: C5+C6)
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// ============================================================================
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/// Get block size for class index
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/// v7-2: Only C6 (512B) is implemented
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/// v7-5b: C5 (256B) and C6 (512B) supported
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static inline size_t small_v7_block_size(uint32_t class_idx) {
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// v7-2: C6-only
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if (class_idx == SMALL_V7_C6_CLASS_IDX) {
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return SMALL_V7_C6_BLOCK_SIZE; // 512
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// v7-5b: C5+C6 multi-class
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switch (class_idx) {
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case SMALL_V7_C5_CLASS_IDX: return SMALL_V7_C5_BLOCK_SIZE; // 256
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case SMALL_V7_C6_CLASS_IDX: return SMALL_V7_C6_BLOCK_SIZE; // 512
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default: return 0; // Unsupported class
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}
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return 0; // Unsupported class
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}
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#endif // HAKMEM_SMALLOBJECT_COLD_IFACE_V7_BOX_H
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@ -1,14 +1,18 @@
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// smallobject_hotbox_v7_box.h - SmallObject HotBox v7 (Phase v7-5a: Hot path極限最適化)
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// smallobject_hotbox_v7_box.h - SmallObject HotBox v7 (Phase v7-5b: C5+C6 Multi-class)
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//
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// Role:
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// - SmallObject v7 fast path for alloc/free
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// - C6-only implementation (512B blocks, 64KiB pages, 2MiB segments)
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// - C5+C6 implementation (256B/512B blocks, 64KiB pages, 2MiB segments)
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// - Uses SmallHeapCtx_v7 + SmallSegment_v7 + ColdIface_v7
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//
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// v7-5a optimizations:
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// - Stats (alloc_count, free_count, live_current) removed from hot path
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// - Global atomic stats gated by ENV (HAKMEM_V7_HOT_STATS)
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// - Header write kept (required due to intrusive freelist overlapping block[0])
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//
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// v7-5b additions:
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// - C5 support (256B blocks) with minimal TLS overhead
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// - Same segment shared between C5 and C6 (page_meta.class_idx distinguishes)
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#pragma once
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@ -67,7 +71,7 @@ static inline void small_v7_log_class_mismatch(void* ptr, uint8_t hint, uint8_t
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// Alloc Fast Path
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// ============================================================================
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// small_heap_alloc_fast_v7() - v7 alloc (C6-only, v7-5a: Hot path極限最適化)
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// small_heap_alloc_fast_v7() - v7 alloc (v7-5b: C5+C6 multi-class)
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//
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// Flow:
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// 1. Get TLS context
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@ -80,9 +84,11 @@ static inline void small_v7_log_class_mismatch(void* ptr, uint8_t hint, uint8_t
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// - Per-page stats (alloc_count, live_current) removed from hot path
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// - Global atomic stats gated by ENV (HAKMEM_V7_HOT_STATS)
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//
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// v7-5b: C5+C6 support (same code path, different block sizes)
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//
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static inline void* small_heap_alloc_fast_v7(size_t size, uint8_t class_idx) {
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// v7-2: Only C6 is implemented
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if (unlikely(class_idx != SMALL_V7_C6_CLASS_IDX)) {
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// v7-5b: C5 or C6 supported
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if (unlikely(!SMALL_V7_CLASS_SUPPORTED(class_idx))) {
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return NULL; // Unsupported class -> front falls back
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}
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@ -152,7 +158,7 @@ static inline void* small_heap_alloc_fast_v7(size_t size, uint8_t class_idx) {
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// Free Fast Path
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// ============================================================================
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// small_heap_free_fast_v7() - v7 free (C6-only, v7-5a: Hot path極限最適化)
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// small_heap_free_fast_v7() - v7 free (v7-5b: C5+C6 multi-class)
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//
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// Flow:
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// 1. TLS segment hint hit (skip RegionIdBox)
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@ -162,6 +168,8 @@ static inline void* small_heap_alloc_fast_v7(size_t size, uint8_t class_idx) {
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// - Stats (free_count, live_current) removed from hot path
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// - Global atomic stats gated by ENV
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//
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// v7-5b: C5+C6 support (page->class_idx determines actual class)
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//
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// @param ptr: USER pointer to free
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// @param class_idx_hint: Class index hint from front/header (may be ignored)
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// @return: true if handled by v7, false if not v7-managed (front should fallback)
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@ -194,8 +202,8 @@ static inline bool small_heap_free_fast_v7(void* ptr, uint8_t class_idx_hint) {
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SmallPageMeta_v7* page = &seg->page_meta[page_idx];
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// Validate page is in use and C6-only
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if (unlikely(page->capacity == 0 || page->class_idx != SMALL_V7_C6_CLASS_IDX)) {
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// v7-5b: Validate page is in use and C5 or C6
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if (unlikely(page->capacity == 0 || !SMALL_V7_CLASS_SUPPORTED(page->class_idx))) {
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return false;
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}
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@ -245,8 +253,8 @@ regionid_fallback:
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SmallPageMeta_v7* page = &seg->page_meta[page_idx];
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// Validate page is in use and C6-only
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if (unlikely(page->capacity == 0 || page->class_idx != SMALL_V7_C6_CLASS_IDX)) {
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// v7-5b: Validate page is in use and C5 or C6
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if (unlikely(page->capacity == 0 || !SMALL_V7_CLASS_SUPPORTED(page->class_idx))) {
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return false;
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}
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@ -22,12 +22,20 @@
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#define SMALL_SEGMENT_V7_MAGIC 0xC07E57u // C0(re) v7
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// ============================================================================
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// C6 Class Configuration (v7-2: C6-only)
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// Class Configuration (v7-5b: C5+C6)
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// ============================================================================
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// C6: 513-768B → 512B blocks
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#define SMALL_V7_C6_CLASS_IDX 6
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#define SMALL_V7_C6_BLOCK_SIZE 512
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// C5: 257-512B → 256B blocks (v7-5b)
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#define SMALL_V7_C5_CLASS_IDX 5
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#define SMALL_V7_C5_BLOCK_SIZE 256
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// v7-5b: Class support check macro
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#define SMALL_V7_CLASS_SUPPORTED(ci) ((ci) == 5 || (ci) == 6)
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// ============================================================================
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// Page Index Calculation
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// ============================================================================
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@ -1,12 +1,16 @@
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// smallobject_cold_iface_v7.c - SmallObject ColdIface v7 implementation (Phase v7-5a)
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// smallobject_cold_iface_v7.c - SmallObject ColdIface v7 implementation (Phase v7-5b)
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//
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// Purpose:
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// - Page refill: acquire page from segment, carve freelist
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// - Page retire: release empty page back to segment, publish stats
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//
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// v7-5a optimizations:
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// - Header written at carve time (not on hot path alloc)
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// - Header written at alloc time (not carve - freelist overlaps block[0])
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// - Stats collected at retire time (not on hot path)
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//
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// v7-5b additions:
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// - C5 support (256B blocks) alongside C6 (512B blocks)
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// - Same segment shared between C5/C6, page_meta.class_idx distinguishes
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#include <stdlib.h>
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#include <string.h>
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@ -129,7 +133,7 @@ SmallPageMeta_v7* small_cold_v7_refill_page(SmallHeapCtx_v7* ctx, uint32_t class
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return NULL;
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}
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// v7-2: Only C6 is supported
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// v7-5b: C5 (256B) and C6 (512B) supported
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size_t block_size = small_v7_block_size(class_idx);
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if (unlikely(block_size == 0)) {
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return NULL; // Unsupported class
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@ -599,5 +599,110 @@ Phase v7-3 時点の -4.3% overhead を ±0% 以下に改善し、v7 を本線
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---
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## 11. Phase v7-5b: C5+C6 Multi-class Expansion
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### 11-1. スコープ
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**Target**: C5 限定（C4 は ULTRA に残す）
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**理由**:
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- v4/v6 multi-class で TLS context 肥大 → L1 cache thrash の経験あり
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- C5 の legacy share が大きい（Decision Matrix: 53%）ので先に検証
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**設計方針**:
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```
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C6: いまの TLS lane のまま（本命クラス）
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C5: TLS lane なし or local_freelist 極小（数個）
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C4: ULTRA に残す（触らない）
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```
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### 11-2. 実装構造
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#### Segment 共有モデル
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```c
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// C5 と C6 は同じ 2MiB segment を共有
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// page_meta[].class_idx で class を区別
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SmallSegment_v7:
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page_meta[0]: class_idx=6 (C6 page)
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page_meta[1]: class_idx=5 (C5 page)
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page_meta[2]: class_idx=6 (C6 page)
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...
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```
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#### Block Size 拡張
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```c
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// smallsegment_v7_box.h
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#define SMALL_V7_C5_CLASS_IDX 5
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#define SMALL_V7_C5_BLOCK_SIZE 256
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static inline size_t small_v7_block_size(uint32_t class_idx) {
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switch (class_idx) {
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case 5: return 256; // C5
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case 6: return 512; // C6
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default: return 0; // Unsupported
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}
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}
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```
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#### HotBox 拡張 (minimal)
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```c
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// C5/C6 両対応（TLS 構造は変更なし）
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static inline void* small_heap_alloc_fast_v7(size_t size, uint8_t class_idx) {
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// v7-5b: C5 or C6
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if (unlikely(class_idx != SMALL_V7_C6_CLASS_IDX &&
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class_idx != SMALL_V7_C5_CLASS_IDX)) {
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return NULL;
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}
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// ... 以下同じ
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}
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```
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### 11-3. A/B 判断基準
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| ベンチ | 条件 | 判定 |
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|--------|------|------|
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| C6-heavy | C6-only v7 vs C5+C6 v7 | C6 性能が落ちていないこと |
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| Mixed 16-1024B | 同上 | C5 legacy コスト削減がトータルでプラス |
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**採用ライン**: 「C6 を守りつつ C5 がトータルでプラスなら採用」
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### 11-4. ENV/Profile
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```bash
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# C5+C6 v7 実験プロファイル
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HAKMEM_SMALL_HEAP_V7_ENABLED=1
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HAKMEM_SMALL_HEAP_V7_CLASSES=0x60 # bit5(C5) + bit6(C6)
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```
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### 11-5. A/B ベンチマーク結果
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**ベンチ条件**:
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- Range: 257-768B (C5+C6 mixed)
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- Benchmark: bench_mid_large_mt_hakmem
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- 5 iterations each
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| Config | Run 1 | Run 2 | Run 3 | Run 4 | Run 5 | Avg |
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|--------|-------|-------|-------|-------|-------|-----|
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| C6-only v7 | 8.04M | 6.66M | 7.26M | 8.14M | 8.11M | **7.64M** |
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| C5+C6 v7 | 8.35M | 8.34M | 7.87M | 7.81M | 7.49M | **7.97M** |
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**結果: +4.3% improvement**
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### 11-6. 評価
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| 基準 | 結果 | 判定 |
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|------|------|------|
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| C6 性能維持 | C6-only と同等以上 | ✅ PASS |
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| C5 net positive | +4.3% 改善 | ✅ PASS |
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| TLS bloat | なし（segment 共有） | ✅ PASS |
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**Phase v7-5b 達成**: C5 を v7 に載せて、C6 を守りつつトータル +4.3% 改善。
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---
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**Document Updated**: 2025-12-12
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**Phase v7-5a Status**: COMPLETE
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**Phase v7-5b Status**: COMPLETE
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