hakmem/core/smallobject_cold_iface_v6.c

// smallobject_cold_iface_v6.c - SmallObject ColdIface v6 実装（Phase v6-3）

#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include "box/smallobject_cold_iface_v6.h"
#include "box/smallsegment_v6_box.h"

#ifndef likely
#define likely(x)   __builtin_expect(!!(x), 1)
#define unlikely(x) __builtin_expect(!!(x), 0)
#endif

// Refill page for given class (C6, C5, C4 in v6-6)
SmallPageMetaV6* small_cold_v6_refill_page(uint32_t class_idx) {
    // v6-6: Support C4, C5, and C6
    size_t block_size;
    if (class_idx == SMALL_V6_C6_CLASS_IDX) {
        block_size = SMALL_V6_C6_BLOCK_SIZE;  // 512
    } else if (class_idx == SMALL_V6_C5_CLASS_IDX) {
        block_size = SMALL_V6_C5_BLOCK_SIZE;  // 256
    } else if (class_idx == SMALL_V6_C4_CLASS_IDX) {
        block_size = SMALL_V6_C4_BLOCK_SIZE;  // 128
    } else {
        return NULL;  // Unsupported class
    }

    // Get or acquire TLS segment
    SmallSegmentV6* seg = small_segment_v6_acquire_for_thread();
    if (unlikely(!seg)) {
        return NULL;
    }

    // Find an available page (simple linear scan)
    SmallPageMetaV6* page = NULL;
    for (uint32_t i = 0; i < seg->num_pages; i++) {
        if (seg->page_meta[i].capacity == 0) {
            page = &seg->page_meta[i];
            break;
        }
    }

    if (unlikely(!page)) {
        return NULL;  // All pages in use
    }

    // Initialize page metadata
    page->class_idx = (uint8_t)class_idx;
    page->capacity = SMALL_PAGE_V6_SIZE / block_size;  // C6: 128, C5: 256
    page->used = 0;
    page->flags = 0;

    // Build freelist for the page
    uintptr_t page_offset = (uintptr_t)page->page_idx * SMALL_PAGE_V6_SIZE;
    uintptr_t page_base = seg->base + page_offset;
    uint8_t* base = (uint8_t*)page_base;

    // Build intrusive freelist (last to first for cache locality)
    void* freelist = NULL;
    for (int i = (int)page->capacity - 1; i >= 0; i--) {
        uint8_t* block = base + ((size_t)i * block_size);

        // Build freelist using BASE pointers
        void* next = freelist;
        memcpy(block, &next, sizeof(void*));
        freelist = block;
    }

    page->free_list = freelist;

    return page;
}

// Retire page (simple reset for v6-2)
void small_cold_v6_retire_page(SmallPageMetaV6* page) {
    if (unlikely(!page)) {
        return;
    }

    // v6-2: Simple reset (no actual deallocation)
    page->free_list = NULL;
    page->used = 0;
    page->capacity = 0;
    page->class_idx = 0;
    page->flags = 0;
}

// Remote operations (dummy for v6-2, C6-heavy is mostly same-thread)
void small_cold_v6_remote_push(SmallPageMetaV6* page, void* ptr, uint32_t tid) {
    (void)page;
    (void)ptr;
    (void)tid;
    // Not implemented in v6-2
}

void small_cold_v6_remote_drain(SmallHeapCtxV6* ctx) {
    (void)ctx;
    // Not implemented in v6-2
}