free_area_init_core() setting struct zone

[start_kernel() -> setup_arch() -> paging_init() -> zone_sizes_init() -> free_area_init_nodes() -> free_area_init_node() -> free_area_init_core()]

---

The heavy work involved in the initialization of zone data structures is carried out by free_area_init_core, which iterates over all zones of the node one after the other.


/*
 * Set up the zone data structures:
 * - mark all pages reserved
 * - mark all memory queues empty
 * - clear the memory bitmaps
 */
static void __paginginit free_area_init_core(struct pglist_data *pgdat,
        unsigned long *zones_size, unsigned long *zholes_size)
{
    enum zone_type j;
    int nid = pgdat->node_id;
    unsigned long zone_start_pfn = pgdat->node_start_pfn;
    int ret;

    pgdat_resize_init(pgdat);
    pgdat->nr_zones = 0;
    init_waitqueue_head(&pgdat->kswapd_wait);
    pgdat->kswapd_max_order = 0;
    pgdat_page_cgroup_init(pgdat);
    
    for (j = 0; j < MAX_NR_ZONES; j++) {
        struct zone *zone = pgdat->node_zones + j;
        unsigned long size, realsize, memmap_pages;
        enum lru_list l;

        size = zone_spanned_pages_in_node(nid, j, zones_size);
        realsize = size - zone_absent_pages_in_node(nid, j,
                                zholes_size);

        /*
         * Adjust realsize so that it accounts for how much memory
         * is used by this zone for memmap. This affects the watermark
         * and per-cpu initialisations
         */
        memmap_pages =
            PAGE_ALIGN(size * sizeof(struct page)) >> PAGE_SHIFT;
        if (realsize >= memmap_pages) {
            realsize -= memmap_pages;
            if (memmap_pages)
                printk(KERN_DEBUG
                 " %s zone: %lu pages used for memmap\n",
                 zone_names[j], memmap_pages);
        } else
            printk(KERN_WARNING
                " %s zone: %lu pages exceeds realsize %lu\n",
                zone_names[j], memmap_pages, realsize);

        /* Account for reserved pages */
        if (j == 0 && realsize > dma_reserve) {
            realsize -= dma_reserve;
            printk(KERN_DEBUG " %s zone: %lu pages reserved\n",
                    zone_names[0], dma_reserve);
        }

        if (!is_highmem_idx(j))
            nr_kernel_pages += realsize;
        nr_all_pages += realsize;

        zone->spanned_pages = size;
        zone->present_pages = realsize;
#ifdef CONFIG_NUMA
        zone->node = nid;
        zone->min_unmapped_pages = (realsize*sysctl_min_unmapped_ratio)
                        / 100;
        zone->min_slab_pages = (realsize * sysctl_min_slab_ratio) / 100;
#endif
        zone->name = zone_names[j];
        spin_lock_init(&zone->lock);
        spin_lock_init(&zone->lru_lock);
        zone_seqlock_init(zone);
        zone->zone_pgdat = pgdat;

        zone->prev_priority = DEF_PRIORITY;

        zone_pcp_init(zone);
        for_each_lru(l) {
            INIT_LIST_HEAD(&zone->lru[l].list);
            zone->reclaim_stat.nr_saved_scan[l] = 0;
        }
        zone->reclaim_stat.recent_rotated[0] = 0;
        zone->reclaim_stat.recent_rotated[1] = 0;
        zone->reclaim_stat.recent_scanned[0] = 0;
        zone->reclaim_stat.recent_scanned[1] = 0;
        zap_zone_vm_stats(zone);
        zone->flags = 0;
        if (!size)
            continue;

        set_pageblock_order(pageblock_default_order());
        setup_usemap(pgdat, zone, size);
        ret = init_currently_empty_zone(zone, zone_start_pfn,
                        size, MEMMAP_EARLY);
        BUG_ON(ret);
        memmap_init(size, nid, j, zone_start_pfn);
        zone_start_pfn += size;
    }
}