mm_init分析(Zoned Buddy Allocator)

1 mm_init分析

file:init/main.c

start_kernel函数

{

...

setup_arch(&command_line);

//处理器相关的初始化代码，paging_init,详细见bootmem_init分析

mm_init_owner(&init_mm, &init_task);

setup_command_line(command_line);

setup_nr_cpu_ids();

setup_per_cpu_areas();

smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */

build_all_zonelists(NULL);

page_alloc_init();

printk(KERN_NOTICE "Kernel command line: %s/n", boot_command_line);

parse_early_param();

parse_args("Booting kernel", static_command_line, __start___param,

__stop___param - __start___param,

&unknown_bootoption);

pidhash_init();

vfs_caches_init_early();

sort_main_extable();

trap_init();

mm_init();

//当启动初始化完后，node_bootmem_map会被释放，系统初始化mem_map,

//利用struct page数据结构来管理所有的内存。

...

}

mem_init->free_all_bootmem_node->free_all_bootmem_core

//释放node_bootmem_map，使用mem_map管理物理内存，以页框为单位

static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)

{

int aligned;

struct page *page;

unsigned long start, end, pages, count = 0;

if (!bdata->node_bootmem_map)

return 0;

start = bdata->node_min_pfn;

end = bdata->node_low_pfn;

/*

* If the start is aligned to the machines wordsize, we might

* be able to free pages in bulks of that order.

*/

aligned = !(start & (BITS_PER_LONG - 1));

bdebug("nid=%td start=%lx end=%lx aligned=%d/n",

bdata - bootmem_node_data, start, end, aligned);

while (start < end) {

unsigned long *map, idx, vec;

map = bdata->node_bootmem_map;

idx = start - bdata->node_min_pfn;

vec = ~map[idx / BITS_PER_LONG];

//查询改为是否为"0",当空闲时将page标志为PG_Reserved

if (aligned && vec == ~0UL && start + BITS_PER_LONG < end) {

int order = ilog2(BITS_PER_LONG);

__free_pages_bootmem(pfn_to_page(start), order);

count += BITS_PER_LONG;

} else {

unsigned long off = 0;

while (vec && off < BITS_PER_LONG) {

if (vec & 1) {

page = pfn_to_page(start + off);

__free_pages_bootmem(page, 0);

count++;

}

vec >>= 1;

off++;

}

}

start += BITS_PER_LONG;

}

page = virt_to_page(bdata->node_bootmem_map);

//得到node_bootmem_map的page地址

pages = bdata->node_low_pfn - bdata->node_min_pfn;

//得到物理内存的页框数

pages = bootmem_bootmap_pages(pages);

//node_bootmem_map共占了(
(pages/8)>>12 )页

count += pages;

while (pages--)

__free_pages_bootmem(page++, 0); //释放node_bootmem_map占用的页框

bdebug("nid=%td released=%lx/n", bdata - bootmem_node_data, count);

return count;

}

Author:Woodpecker <Pecker.hu@gmail.com>