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Discontiguous memory support，即非连续内存管理

主要数据结构 struct bootmem_data

#ifndef CONFIG_NO_BOOTMEM/* * node_bootmem_map is a map pointer - the bits represent all physical  * memory pages (including holes) on the node. */typedef struct bootmem_data {	unsigned long node_min_pfn;	unsigned long node_low_pfn;	void *node_bootmem_map;	unsigned long last_end_off;	unsigned long hint_idx;	struct list_head list;} bootmem_data_t;extern bootmem_data_t bootmem_node_data[];#endif

相关数据对象定义：

#ifndef CONFIG_NEED_MULTIPLE_NODESstruct pglist_data __refdata contig_page_data = {	.bdata = &bootmem_node_data[0]};EXPORT_SYMBOL(contig_page_data);#endifunsigned long max_low_pfn;unsigned long min_low_pfn;unsigned long max_pfn;unsigned long long max_possible_pfn;bootmem_data_t bootmem_node_data[MAX_NUMNODES] __initdata;static struct list_head bdata_list __initdata = LIST_HEAD_INIT(bdata_list);static int bootmem_debug;

bootmem 对外提供了两个初始化函数，即init_bootmem()和init_bootmem_node()，很容易理解这两个函数不同，

/** * init_bootmem_node - register a node as boot memory * @pgdat: node to register * @freepfn: pfn where the bitmap for this node is to be placed * @startpfn: first pfn on the node * @endpfn: first pfn after the node * * Returns the number of bytes needed to hold the bitmap for this node. */unsigned long __init init_bootmem_node(pg_data_t *pgdat, 

unsigned long freepfn,				unsigned long startpfn, 

unsigned long endpfn){	return init_bootmem_core(pgdat->bdata, freepfn, startpfn, endpfn);}/** * init_bootmem - register boot memory * @start: pfn where the bitmap is to be placed * @pages: number of available physical pages * * Returns the number of bytes needed to hold the bitmap. */unsigned long __init init_bootmem(unsigned long start, 

unsigned long pages){	max_low_pfn = pages;	min_low_pfn = start;	return init_bootmem_core(NODE_DATA(0)->bdata, start, 0, pages);}

/* * Called once to set up the allocator itself. */static unsigned long __init init_bootmem_core(bootmem_data_t *bdata,	unsigned long mapstart, unsigned long start, unsigned long end){	unsigned long mapsize;	mminit_validate_memmodel_limits(&start, &end);	bdata->node_bootmem_map = phys_to_virt(PFN_PHYS(mapstart));	bdata->node_min_pfn = start;	bdata->node_low_pfn = end;	link_bootmem(bdata);	/*	 * Initially all pages are reserved - setup_arch() has to	 * register free RAM areas explicitly.	 */	mapsize = bootmap_bytes(end - start);	memset(bdata->node_bootmem_map, 0xff, mapsize);	bdebug("nid=%td start=%lx map=%lx end=%lx mapsize=%lx\n",		bdata - bootmem_node_data, start, mapstart, end, mapsize);	return mapsize;}

/* * link bdata in order */static void __init link_bootmem(bootmem_data_t *bdata){	bootmem_data_t *ent;	list_for_each_entry(ent, &bdata_list, list) {		if (bdata->node_min_pfn < ent->node_min_pfn) {			list_add_tail(&bdata->list, &ent->list);			return;		}	}	list_add_tail(&bdata->list, &bdata_list);}

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