Phase v7-2: SmallObject v7 C6-only implementation with RegionIdBox integration
- SmallSegment_v7: 2MiB segment with TLS slot and free page stack - ColdIface_v7: Page refill/retire between HotBox and SegmentBox - HotBox_v7: Full C6-only alloc/free with header writing (HEADER_MAGIC|class_idx) - Free path early-exit: Check v7 route BEFORE ss_fast_lookup (separate mmap segment) - RegionIdBox: Register v7 segment for ptr->region lookup - Benchmark: v7 ON ~54.5M ops/s (-7% overhead vs 58.6M legacy baseline) v7 correctly balances alloc/free counts and page lifecycle. RegionIdBox overhead identified as primary cost driver. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
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core/box/smallsegment_v7_box.h
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core/box/smallsegment_v7_box.h
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// smallsegment_v7_box.h - SmallSegment v7 (Phase v7-2: C6-only implementation)
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//
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// Purpose:
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// - SmallObject v7 segment structure with 2MiB/64KiB geometry
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// - Supports free_page stack for page management
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// - RegionIdBox integration via REGION_KIND_SMALL_V7
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#ifndef HAKMEM_SMALLSEGMENT_V7_BOX_H
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#define HAKMEM_SMALLSEGMENT_V7_BOX_H
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#include <stdint.h>
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#include <stddef.h>
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// ============================================================================
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// Segment Constants (same geometry as V6/ULTRA)
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// ============================================================================
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#define SMALL_SEGMENT_V7_SIZE (2u * 1024u * 1024u) // 2 MiB
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#define SMALL_PAGE_V7_SIZE (64u * 1024u) // 64 KiB
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#define SMALL_PAGES_PER_SEG_V7 (SMALL_SEGMENT_V7_SIZE / SMALL_PAGE_V7_SIZE) // 32
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#define SMALL_PAGE_V7_SHIFT 16 // log2(64KiB)
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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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// ============================================================================
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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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// ============================================================================
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// Page Index Calculation
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// ============================================================================
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#define SMALL_V7_PAGE_IDX(seg, addr) (((uintptr_t)(addr) - (seg)->base) >> SMALL_PAGE_V7_SHIFT)
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// ============================================================================
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// Forward Declarations
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// ============================================================================
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typedef struct SmallSegment_v7 SmallSegment_v7;
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typedef struct SmallPageMeta_v7 SmallPageMeta_v7;
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// ============================================================================
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// SmallPageMeta_v7 - Page metadata (per-page hot/cold fields)
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// ============================================================================
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typedef struct SmallPageMeta_v7 {
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// ---- Hot fields (cache line 0, accessed in alloc/free) ----
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void* free_list; // LIFO freelist: block -> next
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uint32_t used; // Current used slot count
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uint32_t capacity; // Total block slots in this page
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uint16_t class_idx; // Size class (C0..C7)
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uint16_t flags; // HOT/PARTIAL/FULL/REMOTE_PENDING
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uint16_t page_idx; // Index within segment (0..31)
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uint16_t reserved0; // Alignment padding
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SmallSegment_v7* segment; // Back pointer to owning segment
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// Intrusive list pointer for partial pages (optional)
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SmallPageMeta_v7* segment_next_partial;
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// ---- Cold fields (Stats/Policy, cache line 1+) ----
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uint64_t alloc_count; // Cumulative alloc count
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uint64_t free_count; // Cumulative free count
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uint64_t remote_free_count; // Cumulative remote free count
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uint16_t live_current; // Current live objects
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uint16_t peak_live; // Lifetime peak live
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uint16_t remote_burst_max; // Max remote drain in one pass
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uint16_t reserved1;
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uint32_t epoch_first_alloc; // Coarse epoch (for L3/Learner)
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uint32_t epoch_last_free; // Coarse epoch (for L3/Learner)
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} SmallPageMeta_v7;
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// ============================================================================
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// SmallSegment_v7 - 2MiB segment with page metadata
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// ============================================================================
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typedef struct SmallSegment_v7 {
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uintptr_t base; // Segment base address (2MiB aligned)
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uint32_t num_pages; // Number of pages (32)
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uint32_t owner_tid; // Owner thread ID
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uint32_t flags; // SEGMENT_IN_USE / RETIRED etc.
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uint32_t magic; // SMALL_SEGMENT_V7_MAGIC
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uint32_t region_kind; // REGION_KIND_SMALL_V7
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uint32_t segment_idx; // RegionIdBox index
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uint32_t free_page_head; // Free page stack head (page_idx, 0xFFFFFFFF = empty)
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uint32_t free_page_count; // Number of free pages
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SmallPageMeta_v7 page_meta[SMALL_PAGES_PER_SEG_V7];
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} SmallSegment_v7;
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// ============================================================================
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// Inline Helper Functions
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// ============================================================================
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/// Check if page is valid and active
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static inline int small_page_v7_valid(SmallPageMeta_v7* page) {
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return page != NULL && page->capacity > 0;
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}
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/// Check if pointer is within segment bounds
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static inline int small_ptr_in_segment_v7(SmallSegment_v7* seg, void* ptr) {
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uintptr_t addr = (uintptr_t)ptr;
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return addr >= seg->base && addr < seg->base + SMALL_SEGMENT_V7_SIZE;
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}
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/// Check if segment is valid and initialized
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static inline int small_segment_v7_valid(SmallSegment_v7* seg) {
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return seg != NULL && seg->magic == SMALL_SEGMENT_V7_MAGIC;
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}
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// ============================================================================
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// Segment API (Cold Path)
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// ============================================================================
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/// Allocate a new segment for thread
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/// @param owner_tid: Thread ID of owner
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/// @return: Segment pointer on success, NULL on failure
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SmallSegment_v7* small_segment_alloc_v7(uint32_t owner_tid);
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/// Free a segment and unmap memory
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/// @param seg: Segment to free
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void small_segment_free_v7(SmallSegment_v7* seg);
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// ============================================================================
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// Page API (Cold Path - called from ColdIface)
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// ============================================================================
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/// Take a page from segment's free stack
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/// @param seg: Segment to take page from
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/// @param class_idx: Size class for the page
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/// @return: Page metadata pointer on success, NULL if no free pages
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SmallPageMeta_v7* small_segment_take_page_v7(SmallSegment_v7* seg, uint32_t class_idx);
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/// Release a page back to segment's free stack
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/// @param seg: Segment owning the page
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/// @param page: Page to release
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void small_segment_release_page_v7(SmallSegment_v7* seg, SmallPageMeta_v7* page);
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// ============================================================================
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// TLS Segment Access
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// ============================================================================
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/// Get or acquire TLS segment for current thread
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SmallSegment_v7* small_segment_v7_get_tls(void);
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/// Get page metadata for a pointer (O(1) via TLS segment)
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/// @param ptr: Pointer to lookup (USER or BASE pointer)
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/// @return: Page metadata if ptr is in v7 segment, NULL otherwise
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SmallPageMeta_v7* small_page_meta_v7_of(void* ptr);
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#endif // HAKMEM_SMALLSEGMENT_V7_BOX_H
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