linux啟動內存分配器 2
linux啟動內存分配器 2
static void __init link_bootmem(bootmem_data_t *bdata)
{
struct list_head *iter;
/*添加到全局鏈表bdata_list中*/
list_for_each(iter, &bdata_list) {
bootmem_data_t *ent;
ent = list_entry(iter, bootmem_data_t, list);
if (bdata->node_min_pfn < ent->node_min_pfn)
break;
}
list_add_tail(&bdata->list, iter);
}
/*
* link bdata in order
*/
/*添加到鏈表，由添加的代碼可知
鏈表中的數據開始位置為遞增的*/
static void __init link_bootmem(bootmem_data_t *bdata)
{
struct list_head *iter;
/*添加到全局鏈表bdata_list中*/
list_for_each(iter, &bdata_list) {
bootmem_data_t *ent;
ent = list_entry(iter, bootmem_data_t, list);
if (bdata->node_min_pfn < ent->node_min_pfn)
break;
}
list_add_tail(&bdata->list, iter);
}view plaincopy to clipboardprint?/**
* free_bootmem_with_active_regions - Call free_bootmem_node for each active range
* @nid: The node to free memory on. If MAX_NUMNODES, all nodes are freed.
* @max_low_pfn: The highest PFN that will be passed to free_bootmem_node
*
* If an architecture guarantees that all ranges registered with
* add_active_ranges() contain no holes and may be freed, this
* this function may be used instead of calling free_bootmem() manually.
*/
/*用active_region來初始化bootmem分配器，基於低端內存區*/
void __init free_bootmem_with_active_regions(int nid,
unsigned long max_low_pfn)
{
int i;
/*對每個節點上得活動內存區*/
for_each_active_range_index_in_nid(i, nid) {
unsigned long size_pages = 0;
unsigned long end_pfn = early_node_map.end_pfn;
if (early_node_map.start_pfn >= max_low_pfn)
continue;
if (end_pfn > max_low_pfn)
end_pfn = max_low_pfn;
/*計算活動區的頁面數*/
size_pages = end_pfn - early_node_map.start_pfn;
/*釋放這部分內存，起始就是對應點陣圖值0*/
free_bootmem_node(NODE_DATA(early_node_map.nid),
PFN_PHYS(early_node_map.start_pfn),
size_pages << PAGE_SHIFT);
}
}
/**
* free_bootmem_with_active_regions - Call free_bootmem_node for each active range
* @nid: The node to free memory on. If MAX_NUMNODES, all nodes are freed.
* @max_low_pfn: The highest PFN that will be passed to free_bootmem_node
*
* If an architecture guarantees that all ranges registered with
* add_active_ranges() contain no holes and may be freed, this
* this function may be used instead of calling free_bootmem() manually.
*/
/*用active_region來初始化bootmem分配器，基於低端內存區*/
void __init free_bootmem_with_active_regions(int nid,
unsigned long max_low_pfn)
{
int i;
/*對每個節點上得活動內存區*/
for_each_active_range_index_in_nid(i, nid) {
unsigned long size_pages = 0;
unsigned long end_pfn = early_node_map.end_pfn;
if (early_node_map.start_pfn >= max_low_pfn)
continue;
if (end_pfn > max_low_pfn)
end_pfn = max_low_pfn;
/*計算活動區的頁面數*/
size_pages = end_pfn - early_node_map.start_pfn;
/*釋放這部分內存，起始就是對應點陣圖值0*/
free_bootmem_node(NODE_DATA(early_node_map.nid),
PFN_PHYS(early_node_map.start_pfn),
size_pages << PAGE_SHIFT);
}
}view plaincopy to clipboardprint?/**
* free_bootmem_node - mark a page range as usable
* @pgdat: node the range resides on
* @physaddr: starting address of the range
* @size: size of the range in bytes
*
* Partial pages will be considered reserved and left as they are.
*
* The range must reside completely on the specified node.
*/
void __init free_bootmem_node(pg_data_t *pgdat, unsigned long physaddr,
unsigned long size)
{
unsigned long start, end;
/*相關宏進行控制,調試用*/
kmemleak_free_part(__va(physaddr), size);
start = PFN_UP(physaddr);/*取上界*/
end = PFN_DOWN(physaddr + size);/*取下界*/
/*調用此函數對相關bit位清0，表示沒有分配，這裡保留位為0*/
mark_bootmem_node(pgdat->bdata, start, end, 0, 0);
}
/**
* free_bootmem_node - mark a page range as usable
* @pgdat: node the range resides on
* @physaddr: starting address of the range
* @size: size of the range in bytes
*
* Partial pages will be considered reserved and left as they are.
*
* The range must reside completely on the specified node.
*/
void __init free_bootmem_node(pg_data_t *pgdat, unsigned long physaddr,
unsigned long size)
{
unsigned long start, end;
/*相關宏進行控制,調試用*/
kmemleak_free_part(__va(physaddr), size);
start = PFN_UP(physaddr);/*取上界*/
end = PFN_DOWN(physaddr + size);/*取下界*/
/*調用此函數對相關bit位清0，表示沒有分配，這裡保留位為0*/
mark_bootmem_node(pgdat->bdata, start, end, 0, 0);
}view plaincopy to clipboardprint?static int __init mark_bootmem_node(bootmem_data_t *bdata,
unsigned long start, unsigned long end,
int reserve, int flags)
{
unsigned long sidx, eidx;
bdebug("nid=%td start=%lx end=%lx reserve=%d flags=%x\n",
bdata - bootmem_node_data, start, end, reserve, flags);
BUG_ON(start < bdata->node_min_pfn);
BUG_ON(end > bdata->node_low_pfn);
/*此兩個變數為到節點最小內存頁面的偏移量*/
sidx = start - bdata->node_min_pfn;
eidx = end - bdata->node_min_pfn;
if (reserve)/*如果設置了保留位*/
return __reserve(bdata, sidx, eidx, flags);
else/*相關的map位清0*/
__free(bdata, sidx, eidx);
return 0;
}
static int __init mark_bootmem_node(bootmem_data_t *bdata,
unsigned long start, unsigned long end,
int reserve, int flags)
{
unsigned long sidx, eidx;
bdebug("nid=%td start=%lx end=%lx reserve=%d flags=%x\n",
bdata - bootmem_node_data, start, end, reserve, flags);
BUG_ON(start < bdata->node_min_pfn);
BUG_ON(end > bdata->node_low_pfn);
/*此兩個變數為到節點最小內存頁面的偏移量*/
sidx = start - bdata->node_min_pfn;
eidx = end - bdata->node_min_pfn;
if (reserve)/*如果設置了保留位*/
return __reserve(bdata, sidx, eidx, flags);
else/*相關的map位清0*/
__free(bdata, sidx, eidx);
return 0;
}view plaincopy to clipboardprint?/*bootmem分配器的保留操作*/
static int __init __reserve(bootmem_data_t *bdata, unsigned long sidx,
unsigned long eidx, int flags)
{
unsigned long idx;
int exclusive = flags & BOOTMEM_EXCLUSIVE;
bdebug("nid=%td start=%lx end=%lx flags=%x\n",
bdata - bootmem_node_data,
sidx + bdata->node_min_pfn,
eidx + bdata->node_min_pfn,
flags);
/*對連續的幾個頁面設置為保留*/
for (idx = sidx; idx < eidx; idx++)
if (test_and_set_bit(idx, bdata->node_bootmem_map)) {
if (exclusive) {
__free(bdata, sidx, idx);
return -EBUSY;
}
bdebug("silent double reserve of PFN %lx\n",
idx + bdata->node_min_pfn);
}
return 0;
}
/*bootmem分配器的保留操作*/
static int __init __reserve(bootmem_data_t *bdata, unsigned long sidx,
unsigned long eidx, int flags)
{
unsigned long idx;
int exclusive = flags & BOOTMEM_EXCLUSIVE;
bdebug("nid=%td start=%lx end=%lx flags=%x\n",
bdata - bootmem_node_data,
sidx + bdata->node_min_pfn,
eidx + bdata->node_min_pfn,
flags);
/*對連續的幾個頁面設置為保留*/
for (idx = sidx; idx < eidx; idx++)
if (test_and_set_bit(idx, bdata->node_bootmem_map)) {
if (exclusive) {
__free(bdata, sidx, idx);
return -EBUSY;
}
bdebug("silent double reserve of PFN %lx\n",
idx + bdata->node_min_pfn);
}
return 0;
}view plaincopy to clipboardprint?/*bootmem分配器中釋放內存*/
static void __init __free(bootmem_data_t *bdata,
unsigned long sidx, unsigned long eidx)
{
unsigned long idx;
bdebug("nid=%td start=%lx end=%lx\n", bdata - bootmem_node_data,
sidx + bdata->node_min_pfn,
eidx + bdata->node_min_pfn);
if (bdata->hint_idx > sidx)
bdata->hint_idx = sidx;/*更新變數hint_idx，用於分配*/
for (idx = sidx; idx < eidx; idx++)/*對應位清0*/
if (!test_and_clear_bit(idx, bdata->node_bootmem_map))
BUG();
}
/*bootmem分配器中釋放內存*/
static void __init __free(bootmem_data_t *bdata,
unsigned long sidx, unsigned long eidx)
{
unsigned long idx;
bdebug("nid=%td start=%lx end=%lx\n", bdata - bootmem_node_data,
sidx + bdata->node_min_pfn,
eidx + bdata->node_min_pfn);
if (bdata->hint_idx > sidx)
bdata->hint_idx = sidx;/*更新變數hint_idx，用於分配*/
for (idx = sidx; idx < eidx; idx++)/*對應位清0*/
if (!test_and_clear_bit(idx, bdata->node_bootmem_map))
BUG();
}view plaincopy to clipboardprint?void __init early_res_to_bootmem(u64 start, u64 end)
{
int i, count;
u64 final_start, final_end;
count = 0;
for (i = 0; i < MAX_EARLY_RES && early_res.end; i++)
count++;/*計算保留塊的個數*/
printk(KERN_INFO "(%d early reservations) ==> bootmem [%010llx - %010llx]\n",
count, start, end);
for (i = 0; i < count; i++) {
struct early_res *r = &early_res;
printk(KERN_INFO " #%d [%010llx - %010llx] %16s", i,
r->start, r->end, r->name);
final_start = max(start, r->start);
final_end = min(end, r->end);
if (final_start >= final_end) {
printk(KERN_CONT "\n");
continue;
}
printk(KERN_CONT " ==> [%010llx - %010llx]\n",
final_start, final_end);
/*將指定區間置為保留*/
reserve_bootmem_generic(final_start, final_end - final_start,
BOOTMEM_DEFAULT);
}
}
void __init early_res_to_bootmem(u64 start, u64 end)
{
int i, count;
u64 final_start, final_end;
count = 0;
for (i = 0; i < MAX_EARLY_RES && early_res.end; i++)
count++;/*計算保留塊的個數*/
printk(KERN_INFO "(%d early reservations) ==> bootmem [%010llx - %010llx]\n",
count, start, end);
for (i = 0; i < count; i++) {
struct early_res *r = &early_res;
printk(KERN_INFO " #%d [%010llx - %010llx] %16s", i,
r->start, r->end, r->name);
final_start = max(start, r->start);
final_end = min(end, r->end);
if (final_start >= final_end) {
printk(KERN_CONT "\n");
continue;
}
printk(KERN_CONT " ==> [%010llx - %010llx]\n",
final_start, final_end);
/*將指定區間置為保留*/
reserve_bootmem_generic(final_start, final_end - final_start,
BOOTMEM_DEFAULT);
}
}上面的保留指定區間reserve_bootmem_generic()函數最終調用如下函數view plaincopy to clipboardprint?/**
* reserve_bootmem - mark a page range as usable
* @addr: starting address of the range
* @size: size of the range in bytes
* @flags: reservation flags (see linux/bootmem.h)
*
* Partial pages will be reserved.
*
* The range must be contiguous but may span node boundaries.
*/
int __init reserve_bootmem(unsigned long addr, unsigned long size,
int flags)
{
unsigned long start, end;
start = PFN_DOWN(addr);/*下界*/
end = PFN_UP(addr + size);/*上界*/
return mark_bootmem(start, end, 1, flags);
}
/**
* reserve_bootmem - mark a page range as usable
* @addr: starting address of the range
* @size: size of the range in bytes
* @flags: reservation flags (see linux/bootmem.h)
*
* Partial pages will be reserved.
*
* The range must be contiguous but may span node boundaries.
*/
int __init reserve_bootmem(unsigned long addr, unsigned long size,
int flags)
{
unsigned long start, end;
start = PFN_DOWN(addr);/*下界*/
end = PFN_UP(addr + size);/*上界*/
return mark_bootmem(start, end, 1, flags);
}view plaincopy to clipboardprint?/*保留指定內存區間*/
static int __init mark_bootmem(unsigned long start, unsigned long end,
int reserve, int flags)
{
unsigned long pos;
bootmem_data_t *bdata;
pos = start;
/*通過bdata_list鏈表找到在指定區間的bdata*/
list_for_each_entry(bdata, &bdata_list, list) {
int err;
unsigned long max;
if (pos < bdata->node_min_pfn ||
pos >= bdata->node_low_pfn) {
BUG_ON(pos != start);
continue;
}
max = min(bdata->node_low_pfn, end);
/*設置為保留*/
err = mark_bootmem_node(bdata, pos, max, reserve, flags);
if (reserve && err) {/*如果出錯，遞歸調用*/
mark_bootmem(start, pos, 0, 0);
return err;
}
if (max == end)
return 0;
pos = bdata->node_low_pfn;
}
BUG();
}
/*保留指定內存區間*/
static int __init mark_bootmem(unsigned long start, unsigned long end,
int reserve, int flags)
{
unsigned long pos;
bootmem_data_t *bdata;
pos = start;
/*通過bdata_list鏈表找到在指定區間的bdata*/
list_for_each_entry(bdata, &bdata_list, list) {
int err;
unsigned long max;
if (pos < bdata->node_min_pfn ||
pos >= bdata->node_low_pfn) {
BUG_ON(pos != start);
continue;
}
max = min(bdata->node_low_pfn, end);
/*設置為保留*/
err = mark_bootmem_node(bdata, pos, max, reserve, flags);
if (reserve && err) {/*如果出錯，遞歸調用*/
mark_bootmem(start, pos, 0, 0);
return err;
}
if (max == end)
return 0;
pos = bdata->node_low_pfn;
}
BUG();
}三、內存的分配和釋放
介紹了上面的初始化流程，對於分配和釋放就簡單了，分配就是將分配器映射點陣圖中對應的位置1，釋放過程相反。view plaincopy to clipboardprint?/*分配size大小的空間*/
static void * __init alloc_bootmem_core(struct bootmem_data *bdata,
unsigned long size, unsigned long align,
unsigned long goal, unsigned long limit)
{
unsigned long fallback = 0;
unsigned long min, max, start, sidx, midx, step;
bdebug("nid=%td size=%lx [%lu pages] align=%lx goal=%lx limit=%lx\n",
bdata - bootmem_node_data, size, PAGE_ALIGN(size) >> PAGE_SHIFT,
align, goal, limit);
BUG_ON(!size);
BUG_ON(align & (align - 1));
BUG_ON(limit && goal + size > limit);
/*如果沒有映射點陣圖返回空，分配失敗*/
if (!bdata->node_bootmem_map)
return NULL;
min = bdata->node_min_pfn;
max = bdata->node_low_pfn;
goal >>= PAGE_SHIFT;
limit >>= PAGE_SHIFT;
if (limit && max > limit)
max = limit;
if (max <= min)
return NULL;
/*step為需要對齊於頁面數*/
step = max(align >> PAGE_SHIFT, 1UL);
/*計算起始頁面*/
if (goal && min < goal && goal < max)
start = ALIGN(goal, step);
else
start = ALIGN(min, step);
/*計算分配頁面區間*/
sidx = start - bdata->node_min_pfn;
midx = max - bdata->node_min_pfn;
/*前一次分配的頁號比這次開始分配的頁面號大
那麼，如果第一次沒有分配到，回退到這次的
開始重新試，因為第一次分配是從上一次分配
的位置開始的*/
if (bdata->hint_idx > sidx) {
* Handle the valid case of sidx being zero and still
* catch the fallback below.
*/
fallback = sidx + 1;
/*從上一次分配的位置開始，對齊與頁面*/
sidx = align_idx(bdata, bdata->hint_idx, step);
}
while (1) {
int merge;
void *region;
unsigned long eidx, i, start_off, end_off;
find_block:
/*查找第一個為0的位*/
sidx = find_next_zero_bit(bdata->node_bootmem_map, midx, sidx);
sidx = align_idx(bdata, sidx, step);
eidx = sidx + PFN_UP(size);/*結束位置*/
if (sidx >= midx || eidx > midx)/*找到結束了*/
break;
for (i = sidx; i < eidx; i++)/*檢查這段區域是否空閑*/
if (test_bit(i, bdata->node_bootmem_map)) {/*如果不是，將跳過這段繼續查找*/
sidx = align_idx(bdata, i, step);
if (sidx == i)
sidx += step;
goto find_block;
}
if (bdata->last_end_off & (PAGE_SIZE - 1) &&/*如果為相鄰的頁面，也就是說上次分配的頁面和這次分配的開始頁面為相鄰的*/
PFN_DOWN(bdata->last_end_off) + 1 == sidx)
start_off = align_off(bdata, bdata->last_end_off, align);
else
start_off = PFN_PHYS(sidx);
/*merge==1表示上次結束和這次開始不在同一個頁面上*/
merge = PFN_DOWN(start_off) < sidx;
end_off = start_off + size;
/*更新數據*/
bdata->last_end_off = end_off;
bdata->hint_idx = PFN_UP(end_off);
/*
* Reserve the area now:
*/
/*設定新加入的頁面為保留,就是將對應的映射位置1*/
if (__reserve(bdata, PFN_DOWN(start_off) + merge,
PFN_UP(end_off), BOOTMEM_EXCLUSIVE))
BUG();
/*對應開始地址的虛擬地址返回*/
region = phys_to_virt(PFN_PHYS(bdata->node_min_pfn) +
start_off);
memset(region, 0, size);/*分配的大小*/
/*
* The min_count is set to 0 so that bootmem allocated blocks
* are never reported as leaks.
*/
/*調試用*/
kmemleak_alloc(region, size, 0, 0);
return region;
}
if (fallback) {/*回退，重新查看*/
sidx = align_idx(bdata, fallback - 1, step);
fallback = 0;
goto find_block;
}
return NULL;
}
《解決方案》
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