此處接前文，分析free_area_init_nodes()函數最後部分，分析其末尾的迴圈： 這裡面的關鍵函數是free_area_init_node()，其入參find_min_pfn_for_node()用於獲取node節點中最低的記憶體頁框號。 而free_area_init_node()其實現 ...
此處接前文，分析free_area_init_nodes()函數最後部分，分析其末尾的迴圈：
for_each_online_node(nid) {
pg_data_t *pgdat = NODE_DATA(nid);
free_area_init_node(nid, NULL,
find_min_pfn_for_node(nid), NULL);
/* Any memory on that node */
if (pgdat->node_present_pages)
node_set_state(nid, N_MEMORY);
check_for_memory(pgdat, nid);
}這裡面的關鍵函數是free_area_init_node()，其入參find_min_pfn_for_node()用於獲取node節點中最低的記憶體頁框號。
而free_area_init_node()其實現：
【file：/mm/page_alloc.c】
void __paginginit free_area_init_node(int nid, unsigned long *zones_size,
unsigned long node_start_pfn, unsigned long *zholes_size)
{
pg_data_t *pgdat = NODE_DATA(nid);
unsigned long start_pfn = 0;
unsigned long end_pfn = 0;
/* pg_data_t should be reset to zero when it's allocated */
WARN_ON(pgdat->nr_zones || pgdat->classzone_idx);
pgdat->node_id = nid;
pgdat->node_start_pfn = node_start_pfn;
init_zone_allows_reclaim(nid);
#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
#endif
calculate_node_totalpages(pgdat, start_pfn, end_pfn,
zones_size, zholes_size);
alloc_node_mem_map(pgdat);
#ifdef CONFIG_FLAT_NODE_MEM_MAP
printk(KERN_DEBUG "free_area_init_node: node %d, pgdat %08lx, node_mem_map %08lx\n",
nid, (unsigned long)pgdat,
(unsigned long)pgdat->node_mem_map);
#endif
free_area_init_core(pgdat, start_pfn, end_pfn,
zones_size, zholes_size);
}該函數中，其中init_zone_allows_reclaim()用於計算評估記憶體管理區是否可回收以及合適的node節點數，如果非NUMA環境，則該函數為空。而基於CONFIG_HAVE_MEMBLOCK_NODE_MAP的配置下，接下來將是get_pfn_range_for_nid()：
【file：/mm/page_alloc.c】
/**
* get_pfn_range_for_nid - Return the start and end page frames for a node
* @nid: The nid to return the range for. If MAX_NUMNODES, the min and max PFN are returned.
* @start_pfn: Passed by reference. On return, it will have the node start_pfn.
* @end_pfn: Passed by reference. On return, it will have the node end_pfn.
*
* It returns the start and end page frame of a node based on information
* provided by an arch calling add_active_range(). If called for a node
* with no available memory, a warning is printed and the start and end
* PFNs will be 0.
*/
void __meminit get_pfn_range_for_nid(unsigned int nid,
unsigned long *start_pfn, unsigned long *end_pfn)
{
unsigned long this_start_pfn, this_end_pfn;
int i;
*start_pfn = -1UL;
*end_pfn = 0;
for_each_mem_pfn_range(i, nid, &this_start_pfn, &this_end_pfn, NULL) {
*start_pfn = min(*start_pfn, this_start_pfn);
*end_pfn = max(*end_pfn, this_end_pfn);
}
if (*start_pfn == -1UL)
*start_pfn = 0;
}此函數主要是將記憶體node節點的起始和末尾頁框號返回給接下來的calculate_node_totalpages()來使用。
calculate_node_totalpages()實現：
【file：/mm/page_alloc.c】
static void __meminit calculate_node_totalpages(struct pglist_data *pgdat,
unsigned long node_start_pfn,
unsigned long node_end_pfn,
unsigned long *zones_size,
unsigned long *zholes_size)
{
unsigned long realtotalpages, totalpages = 0;
enum zone_type i;
for (i = 0; i < MAX_NR_ZONES; i++)
totalpages += zone_spanned_pages_in_node(pgdat->node_id, i,
node_start_pfn,
node_end_pfn,
zones_size);
pgdat->node_spanned_pages = totalpages;
realtotalpages = totalpages;
for (i = 0; i < MAX_NR_ZONES; i++)
realtotalpages -=
zone_absent_pages_in_node(pgdat->node_id, i,
node_start_pfn, node_end_pfn,
zholes_size);
pgdat->node_present_pages = realtotalpages;
printk(KERN_DEBUG "On node %d totalpages: %lu\n", pgdat->node_id,
realtotalpages);
}其中zone_spanned_pages_in_node()：
【file：/mm/page_alloc.c】
/*
* Return the number of pages a zone spans in a node, including holes
* present_pages = zone_spanned_pages_in_node() - zone_absent_pages_in_node()
*/
static unsigned long __meminit zone_spanned_pages_in_node(int nid,
unsigned long zone_type,
unsigned long node_start_pfn,
unsigned long node_end_pfn,
unsigned long *ignored)
{
unsigned long zone_start_pfn, zone_end_pfn;
/* Get the start and end of the zone */
zone_start_pfn = arch_zone_lowest_possible_pfn[zone_type];
zone_end_pfn = arch_zone_highest_possible_pfn[zone_type];
adjust_zone_range_for_zone_movable(nid, zone_type,
node_start_pfn, node_end_pfn,
&zone_start_pfn, &zone_end_pfn);
/* Check that this node has pages within the zone's required range */
if (zone_end_pfn < node_start_pfn || zone_start_pfn > node_end_pfn)
return 0;
/* Move the zone boundaries inside the node if necessary */
zone_end_pfn = min(zone_end_pfn, node_end_pfn);
zone_start_pfn = max(zone_start_pfn, node_start_pfn);
/* Return the spanned pages */
return zone_end_pfn - zone_start_pfn;
}其主要是統計node管理節點的記憶體跨度，該跨度不包括movable管理區的，裡面調用的adjust_zone_range_for_zone_movable()則是用於剔除movable管理區的部分。
另外的zone_absent_pages_in_node()：
【file：/mm/page_alloc.c】
/* Return the number of page frames in holes in a zone on a node */
static unsigned long __meminit zone_absent_pages_in_node(int nid,
unsigned long zone_type,
unsigned long node_start_pfn,
unsigned long node_end_pfn,
unsigned long *ignored)
{
unsigned long zone_low = arch_zone_lowest_possible_pfn[zone_type];
unsigned long zone_high = arch_zone_highest_possible_pfn[zone_type];
unsigned long zone_start_pfn, zone_end_pfn;
zone_start_pfn = clamp(node_start_pfn, zone_low, zone_high);
zone_end_pfn = clamp(node_end_pfn, zone_low, zone_high);
adjust_zone_range_for_zone_movable(nid, zone_type,
node_start_pfn, node_end_pfn,
&zone_start_pfn, &zone_end_pfn);
return __absent_pages_in_range(nid, zone_start_pfn, zone_end_pfn);
}該函數主要用於計算記憶體空洞頁面數的。完了將會得到物理頁面總數併在calculate_node_totalpages()中將頁面總數列印出來：
再往下的mminit_verify_pageflags_layout()函數主要用於記憶體初始化調測使用的，由於未開啟CONFIG_DEBUG_MEMORY_INIT配置項，此函數為空。而setup_nr_node_ids()是用於設置記憶體節點總數的，此處如果最大節點數MAX_NUMNODES不超過1，則是空函數。
free_area_init_nodes()函數末了還有一個遍歷各個節點做初始化的操作，暫且留待後面再分析。
