start_kernel->setup_arch->paging_init->bootmem_init() 之 1

linux-2.6.14/arch/arm/mm/init.c

static void __init bootmem_init(struct meminfo *mi)
{
    struct node_info node_info[MAX_NUMNODES], *np = node_info;
    unsigned int bootmap_pages, bootmap_pfn, map_pg;
    int node, initrd_node;

 

    bootmap_pages = find_memend_and_nodes(mi, np);

    //计算内存页帧位码表所占页数的大小（这里只需用1页）
    bootmap_pfn   = find_bootmap_pfn(0, mi, bootmap_pages);

    //计算存储页帧位码表的物理页号（这里为第 0x303ae 页）
    initrd_node   = check_initrd(mi);

    map_pg = bootmap_pfn;

    /*
     * Initialise the bootmem nodes.
     *
     * What we really want to do is:
     *
     *   unmap_all_regions_except_kernel();
     *   for_each_node_in_reverse_order(node) {
     *     map_node(node);
     *     allocate_bootmem_map(node);
     *     init_bootmem_node(node);
     *     free_bootmem_node(node);
     *   }
     *
     * but this is a 2.5-type change.  For now, we just set
     * the nodes up in reverse order.
     *
     * (we could also do with rolling bootmem_init and paging_init
     * into one generic "memory_init" type function).
     */
    np += num_online_nodes() - 1;     // num_online_nodes()  = 1
   

for (node = num_online_nodes() - 1; node >= 0; node--, np--) {
        /*
         * If there are no pages in this node, ignore it.
         * Note that node 0 must always have some pages.
         */
        if (np->end == 0 || !node_online(node)) {
            if (node == 0)
                BUG();
            continue;
        }

        /*
         * Initialise the bootmem allocator.
         */
        init_bootmem_node(NODE_DATA(node), map_pg, np->start, np->end);

        //将页帧位表内的所有页帧位码置为1
        free_bootmem_node_bank(node, mi);

        //将页帧位表内的所有页帧位码清0
        map_pg += np->bootmap_pages;

        /*
         * If this is node 0, we need to reserve some areas ASAP -
         * we may use bootmem on node 0 to setup the other nodes.
         */
        if (node == 0)
            reserve_node_zero(bootmap_pfn, bootmap_pages);

            //将内存中已经使用的物理内存所对应的页帧位置为1
    }

#ifdef CONFIG_BLK_DEV_INITRD
    if (phys_initrd_size && initrd_node >= 0) {
        reserve_bootmem_node(NODE_DATA(initrd_node), phys_initrd_start,
                     phys_initrd_size);
        initrd_start = __phys_to_virt(phys_initrd_start);
        initrd_end = initrd_start + phys_initrd_size;
    }
#endif

    BUG_ON(map_pg != bootmap_pfn + bootmap_pages);
}