mem_map在哪里被初始化（ARM 架构）

1.定义

在mm/memory.c文件中定义

mm/memory.c

    70 #ifndef CONFIG_NEED_MULTIPLE_NODES
    71 /* use the per-pgdat data instead for discontigmem - mbligh */
    72 unsigned long max_mapnr;
    73 struct page *mem_map;
    74
    75 EXPORT_SYMBOL(max_mapnr);
    76 EXPORT_SYMBOL(mem_map);
    77 #endif

 

2.在哪里被初始化

在mm/page_alloc.c文件中的alloc_node_mem_map函数被初始化。

mm/page_alloc.c

4146 static void __init_refok alloc_node_mem_map(struct pglist_data *pgdat)
4147 {
4148 /* Skip empty nodes */
4149 if (!pgdat->node_spanned_pages)
4150 return;
4151
4152 #ifdef CONFIG_FLAT_NODE_MEM_MAP
4153 /* ia64 gets its own node_mem_map, before this, without bootmem */
4154 if (!pgdat->node_mem_map) {
4155 unsigned long size, start, end;
4156 struct page *map;
4157
4158 /*
4159 * The zone's endpoints aren't required to be MAX_ORDER
4160 * aligned but the node_mem_map endpoints must be in order
4161 * for the buddy allocator to function correctly.
4162 */
4163 start = pgdat->node_start_pfn & ~(MAX_ORDER_NR_PAGES - 1);
4164 end = pgdat->node_start_pfn + pgdat->node_spanned_pages;
4165 end = ALIGN(end, MAX_ORDER_NR_PAGES);
4166 size = (end - start) * sizeof(struct page);
4167 map = alloc_remap(pgdat->node_id, size);
4168 if (!map)
4169 map = alloc_bootmem_node(pgdat, size);
4170 pgdat->node_mem_map = map + (pgdat->node_start_pfn - start);
4171 }
4172 #ifndef CONFIG_NEED_MULTIPLE_NODES
4173 /*
4174 * With no DISCONTIG, the global mem_map is just set as node 0's
4175 */
4176 if (pgdat == NODE_DATA(0)) {
4177 mem_map = NODE_DATA(0)->node_mem_map;
4178 #ifdef CONFIG_ARCH_POPULATES_NODE_MAP
4179 if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
4180 mem_map -= (pgdat->node_start_pfn - ARCH_PFN_OFFSET);
4181 #endif /* CONFIG_ARCH_POPULATES_NODE_MAP */
4182 }
4183 #endif
4184 #endif /* CONFIG_FLAT_NODE_MEM_MAP */
4185 }

 

3.从start_kernel函数调用alloc_node_mem_map函数的流程

 

start_kernel(init/main.c)->setup_arch(arch/arm/kernel/setup.c)->paging_init(arch/arm/mm/mmu.c)->bootmem_init(arch/arm/mm/init.c)->bootmem_free_node(arch/arm/mm/init.c)

->free_area_init_node(mm/page_alloc.c)->alloc_node_mem_map(mm/page_alloc.c)