• linux早期内存管理：memblock完全介绍

    内核版本

    4.19.114

    背景

    linux启动阶段，在伙伴系统初始化之前，也是需要动态内存分配的，比如dts、sparse_vmemmap、页表等，称早期内存管理，early mem manger。此阶段采用简单的内存管理器，有bootmem和memblock，bootmem是早期内核采用。4.x以后内核内核采用memblock，配置了NO_BOOTMEM宏。

    实现

    memblock内存分配采用first match算法。刚开始，内存是一整个大块，随着内存分配被切成，多个小块。内存分配查找的方向可以是从高到低，也可以是从低到高。内存管理的区域是从linux代码段数据段等的结束到低端内存最高地址。

    数据结构

    管理结构

    全局context

    struct memblock {
	bool bottom_up;  /* is bottom up direction? */
	phys_addr_t current_limit;
	struct memblock_type memory;
	struct memblock_type reserved;
#ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
	struct memblock_type physmem;
#endif
};

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    bottom_up： 内存分配的方向：从高到低，还是从低到高。

    current_limit：最大内存地址。

    memblock_type： 内存区域的类型。有memory和reserve、physmem。

    • memory 可管理的总内存区域

    • reserve: 已分配的内存区域

    • physmem: 物理映射内存区域，固定映射的内存。

    struct memblock_type {
	unsigned long cnt;
	unsigned long max;
	phys_addr_t total_size;
	struct memblock_region *regions;
	char *name;
};

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    memblock_type 形容内存区域

    • regions 内存块的描述，数组串起来。

    • cnt：当前内存块的个数

    • max: 最大内存块限制。

    • total_size: 内存区域的总大小。

    memblock_region: 形容内存块

    • base: 起始地址
    • size：大小
    • flags：分配的flag
    • nid: NUMA架构的nid信息。
    struct memblock_region {
	phys_addr_t base;
	phys_addr_t size;
	enum memblock_flags flags;
#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
	int nid;
#endif
};

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    memblock_flags的取值。

    enum memblock_flags {
	MEMBLOCK_NONE		= 0x0,	/* No special request */
	MEMBLOCK_HOTPLUG	= 0x1,	/* hotpluggable region */
	MEMBLOCK_MIRROR		= 0x2,	/* mirrored region */
	MEMBLOCK_NOMAP		= 0x4,	/* don't add to kernel direct mapping */
};

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    管理结构都是全局静态数据，分配在BSS段中。

    struct memblock memblock __initdata_memblock = {
	.memory.regions		= memblock_memory_init_regions,
	.memory.cnt		= 1,	/* empty dummy entry */
	.memory.max		= INIT_MEMBLOCK_REGIONS,
	.memory.name		= "memory",

	.reserved.regions	= memblock_reserved_init_regions,
	.reserved.cnt		= 1,	/* empty dummy entry */
	.reserved.max		= INIT_MEMBLOCK_REGIONS,
	.reserved.name		= "reserved",

#ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
	.physmem.regions	= memblock_physmem_init_regions,
	.physmem.cnt		= 1,	/* empty dummy entry */
	.physmem.max		= INIT_PHYSMEM_REGIONS,
	.physmem.name		= "physmem",
#endif

	.bottom_up		= false,
	.current_limit		= MEMBLOCK_ALLOC_ANYWHERE,
};

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    regions的管理结构，也是提前预分配的静态数组。INIT_MEMBLOCK_REGIONS值为128，每个区域最大支持128个内存块(region)。

    static struct memblock_region memblock_memory_init_regions[INIT_MEMBLOCK_REGIONS] __initdata_memblock;
static struct memblock_region memblock_reserved_init_regions[INIT_MEMBLOCK_REGIONS] __initdata_memblock;
#ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
static struct memblock_region memblock_physmem_init_regions[INIT_PHYSMEM_REGIONS] __initdata_memblock;
#endif

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    数据结构图

    在这里插入图片描述

    API

    • memblock_add：将内存区域加入memblock可管理的内存区域，即memory的region队列。
    int memblock_add(phys_addr_t base, phys_addr_t size);

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    • memblock_remove：从可管理的内存区域中去掉一些内存。
    int memblock_remove(phys_addr_t base, phys_addr_t size);

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    • memblock_alloc：分配内存
    phys_addr_t memblock_alloc(phys_addr_t size, phys_addr_t align);

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    • memblock_free：释放内存，释放时进行响铃内存块合并。
    int memblock_free(phys_addr_t base, phys_addr_t size);

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    • memblock_reserve：将内存区域加入reserved链表
    int memblock_reserve(phys_addr_t base, phys_addr_t size);

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    初始化

    memblock如何初始化可管理的内存区域，可以通过2种方式

    • bootargs
    • dts

    bootargs方式

    通过linux的启动参数bootargs，传递内存大小，初始化memblock。

    early_mem-> arm_add_memory->memblock_add

    bootargs的格式

    mem=size@start

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    bootargs的解析

    static int __init early_mem(char *p)
{
	static int usermem __initdata = 0;
	u64 size;
	u64 start;
	char *endp;

	/*
	 * If the user specifies memory size, we
	 * blow away any automatically generated
	 * size.
	 */
	if (usermem == 0) {
		usermem = 1;
		memblock_remove(memblock_start_of_DRAM(),
			memblock_end_of_DRAM() - memblock_start_of_DRAM());
	}

	start = PHYS_OFFSET;
	size  = memparse(p, &endp);
	if (*endp == '@')
		start = memparse(endp + 1, NULL);

	arm_add_memory(start, size);

	return 0;
}
early_param("mem", early_mem);

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    fdt方式

    需要打开宏CONFIG_OF_EARLY_FLATTREE。

    调用链：

    early_init_dt_scan_memory->early_init_dt_add_memory_arch-> memblock_add

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    dts的解析的代码在目录下。

    解析dts的memory节点。

    另外说明下，dts中的“reserved-memory"节点的解析过程：

    early_init_fdt_scan_reserved_mem->\__fdt_scan_reserved_mem ->__reserved_mem_reserve_reg-> early_init_dt_reserve_memory_arch

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    此reserved-memory不会加入到memblock的reserved节点，而是直接就从memblock的可管理区域去掉了。

    内核等代码段的reserved

    setup_arch-> arm_memblock_init

    void __init arm_memblock_init(const struct machine_desc *mdesc)
{
	/* Register the kernel text, kernel data and initrd with memblock. */
	memblock_reserve(__pa(KERNEL_START), KERNEL_END - KERNEL_START);

	arm_initrd_init();

	arm_mm_memblock_reserve();

	/* reserve any platform specific memblock areas */
	if (mdesc->reserve)
		mdesc->reserve();

	early_init_fdt_reserve_self();
	early_init_fdt_scan_reserved_mem();

	/* reserve memory for DMA contiguous allocations */
	dma_contiguous_reserve(arm_dma_limit);

	arm_memblock_steal_permitted = false;
	memblock_dump_all();
}

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    linux内存管理实现代码
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    reserved的内存：

    • 内核代码段等各段段区域
    • fdt使用区域。

    这些内存是要从memblock可管理的内存中直接去掉的。

    alloc

    早期内存分配的API为early_alloc，其中会调用memblock_alloc进行内存分配。

    early_alloc->early_alloc_aligned->memblock_alloc

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    内存分配过程，调用链:

    memblock_alloc->memblock_alloc_base->__memblock_alloc_base->memblock_alloc_base_nid->memblock_alloc_range_nid

/*找到在memory中，但是不在reserved中的内存*/
->memblock_find_in_range_node
/*将内存区域加入到reserve链表*/
->memblock_reserve

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    1）遍历memblock的可用区域（即memory的region链表），具体区域是从kernel_end到current_limit (低端内存最高地址)。具体方向从高往低还是从低往高，由bottom_up决定。默认是从上往下分配的，bottom_up=false。

    memblock_find_in_range_node函数用于查找可用内存：

    phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t size,
					phys_addr_t align, phys_addr_t start,
					phys_addr_t end, int nid,
					enum memblock_flags flags)
{
	phys_addr_t kernel_end, ret;

	/* pump up @end */
	if (end == MEMBLOCK_ALLOC_ACCESSIBLE)
		end = memblock.current_limit;

	/* avoid allocating the first page */
	start = max_t(phys_addr_t, start, PAGE_SIZE);
	end = max(start, end);
	
	/*内核各段的结束地址*/
	kernel_end = __pa_symbol(_end);

	/*
	 * try bottom-up allocation only when bottom-up mode
	 * is set and @end is above the kernel image.
	 */
	if (memblock_bottom_up() && end > kernel_end) {
		phys_addr_t bottom_up_start;

		/* make sure we will allocate above the kernel */
		bottom_up_start = max(start, kernel_end);

		/* ok, try bottom-up allocation first */
		ret = __memblock_find_range_bottom_up(bottom_up_start, end,
						      size, align, nid, flags);
		if (ret)
			return ret;

		/*
		 * we always limit bottom-up allocation above the kernel,
		 * but top-down allocation doesn't have the limit, so
		 * retrying top-down allocation may succeed when bottom-up
		 * allocation failed.
		 *
		 * bottom-up allocation is expected to be fail very rarely,
		 * so we use WARN_ONCE() here to see the stack trace if
		 * fail happens.
		 */
		WARN_ONCE(IS_ENABLED(CONFIG_MEMORY_HOTREMOVE),
			  "memblock: bottom-up allocation failed, memory hotremove may be affected\n");
	}

	return __memblock_find_range_top_down(start, end, size, align, nid,
					      flags);
}

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    current_limit默认为MEMBLOCK_ALLOC_ANYWHERE，即0xFFFFFFFF，在adjust_lowmem_bounds中设置最大限制，即低端内存。

    void __init adjust_lowmem_bounds(void)
{
	phys_addr_t memblock_limit = 0;
	u64 vmalloc_limit;
	struct memblock_region *reg;
	phys_addr_t lowmem_limit = 0;

	/*
	 * Let's use our own (unoptimized) equivalent of __pa() that is
	 * not affected by wrap-arounds when sizeof(phys_addr_t) == 4.
	 * The result is used as the upper bound on physical memory address
	 * and may itself be outside the valid range for which phys_addr_t
	 * and therefore __pa() is defined.
	 */
	vmalloc_limit = (u64)(uintptr_t)vmalloc_min - PAGE_OFFSET + PHYS_OFFSET;

	/*
	 * The first usable region must be PMD aligned. Mark its start
	 * as MEMBLOCK_NOMAP if it isn't
	 */
	for_each_memblock(memory, reg) {
		if (!memblock_is_nomap(reg)) {
			if (!IS_ALIGNED(reg->base, PMD_SIZE)) {
				phys_addr_t len;

				len = round_up(reg->base, PMD_SIZE) - reg->base;
				memblock_mark_nomap(reg->base, len);
			}
			break;
		}
	}

	for_each_memblock(memory, reg) {
		phys_addr_t block_start = reg->base;
		phys_addr_t block_end = reg->base + reg->size;

		if (memblock_is_nomap(reg))
			continue;

		if (reg->base < vmalloc_limit) {
			if (block_end > lowmem_limit)
				/*
				 * Compare as u64 to ensure vmalloc_limit does
				 * not get truncated. block_end should always
				 * fit in phys_addr_t so there should be no
				 * issue with assignment.
				 */
				lowmem_limit = min_t(u64,
							 vmalloc_limit,
							 block_end);

			/*
			 * Find the first non-pmd-aligned page, and point
			 * memblock_limit at it. This relies on rounding the
			 * limit down to be pmd-aligned, which happens at the
			 * end of this function.
			 *
			 * With this algorithm, the start or end of almost any
			 * bank can be non-pmd-aligned. The only exception is
			 * that the start of the bank 0 must be section-
			 * aligned, since otherwise memory would need to be
			 * allocated when mapping the start of bank 0, which
			 * occurs before any free memory is mapped.
			 */
			if (!memblock_limit) {
				if (!IS_ALIGNED(block_start, PMD_SIZE))
					memblock_limit = block_start;
				else if (!IS_ALIGNED(block_end, PMD_SIZE))
					memblock_limit = lowmem_limit;
			}

		}
	}

	arm_lowmem_limit = lowmem_limit;

	high_memory = __va(arm_lowmem_limit - 1) + 1;

	if (!memblock_limit)
		memblock_limit = arm_lowmem_limit;

	/*
	 * Round the memblock limit down to a pmd size.  This
	 * helps to ensure that we will allocate memory from the
	 * last full pmd, which should be mapped.
	 */
	memblock_limit = round_down(memblock_limit, PMD_SIZE);

	if (!IS_ENABLED(CONFIG_HIGHMEM) || cache_is_vipt_aliasing()) {
		if (memblock_end_of_DRAM() > arm_lowmem_limit) {
			phys_addr_t end = memblock_end_of_DRAM();

			pr_notice("Ignoring RAM at %pa-%pa\n",
				  &memblock_limit, &end);
			pr_notice("Consider using a HIGHMEM enabled kernel.\n");

			memblock_remove(memblock_limit, end - memblock_limit);
		}
	}

	memblock_set_current_limit(memblock_limit);
}

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    以从小到大方向为例，看一下可用内存查找过程：

    static phys_addr_t __init_memblock
__memblock_find_range_bottom_up(phys_addr_t start, phys_addr_t end,
				phys_addr_t size, phys_addr_t align, int nid,
				enum memblock_flags flags)
{
	phys_addr_t this_start, this_end, cand;
	u64 i;

	for_each_free_mem_range(i, nid, flags, &this_start, &this_end, NULL) {
		this_start = clamp(this_start, start, end);
		this_end = clamp(this_end, start, end);

		cand = round_up(this_start, align);
		if (cand < this_end && this_end - cand >= size)
			return cand;
	}

	return 0;
}

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    for_each_free_mem_range 是查找在memory中，但是没有在reserved中的内存，然后判断内存大小是否够用。

    #define for_each_free_mem_range(i, nid, flags, p_start, p_end, p_nid)	\
	for_each_mem_range(i, &memblock.memory, &memblock.reserved,	\
			   nid, flags, p_start, p_end, p_nid)

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    for_each_mem_range是遍历在type_a中，但是不在type_b中的内存。

    /**
 * for_each_mem_range - iterate through memblock areas from type_a and not
 * included in type_b. Or just type_a if type_b is NULL.
 * @i: u64 used as loop variable
 * @type_a: ptr to memblock_type to iterate
 * @type_b: ptr to memblock_type which excludes from the iteration
 * @nid: node selector, %NUMA_NO_NODE for all nodes
 * @flags: pick from blocks based on memory attributes
 * @p_start: ptr to phys_addr_t for start address of the range, can be %NULL
 * @p_end: ptr to phys_addr_t for end address of the range, can be %NULL
 * @p_nid: ptr to int for nid of the range, can be %NULL
 */
#define for_each_mem_range(i, type_a, type_b, nid, flags,		\
			   p_start, p_end, p_nid)			\
	for (i = 0, __next_mem_range(&i, nid, flags, type_a, type_b,	\
				     p_start, p_end, p_nid);		\
	     i != (u64)ULLONG_MAX;					\
	     __next_mem_range(&i, nid, flags, type_a, type_b,		\
			      p_start, p_end, p_nid))

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    2）找到可用内存后，加入reserved队列。

    memblock_reserve函数：

    int __init_memblock memblock_reserve(phys_addr_t base, phys_addr_t size)
{
	phys_addr_t end = base + size - 1;

	memblock_dbg("memblock_reserve: [%pa-%pa] %pF\n",
		     &base, &end, (void *)_RET_IP_);

	return memblock_add_range(&memblock.reserved, base, size, MAX_NUMNODES, 0);
}

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    free

    从reserved链表中移除

    int __init_memblock memblock_free(phys_addr_t base, phys_addr_t size)
{
	phys_addr_t end = base + size - 1;

	memblock_dbg("   memblock_free: [%pa-%pa] %pF\n",
		     &base, &end, (void *)_RET_IP_);

	kmemleak_free_part_phys(base, size);
	return memblock_remove_range(&memblock.reserved, base, size);
}

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    memblock_remove_range:

    1）memblock_isolate_range：将要释放的区域隔离出来，即若释放区域不是刚好的region对齐，而是一头一尾处在某个region中间，则新建两个region节点，把这两个头尾两个节点切割成两半，使得要释放的区域刚好占n个region。

    2）memblock_remove_region：从region数组中删除对应的节点，后续的region节点前移。

    static int __init_memblock memblock_remove_range(struct memblock_type *type,
					  phys_addr_t base, phys_addr_t size)
{
	int start_rgn, end_rgn;
	int i, ret;

	ret = memblock_isolate_range(type, base, size, &start_rgn, &end_rgn);
	if (ret)
		return ret;

	for (i = end_rgn - 1; i >= start_rgn; i--)
		memblock_remove_region(type, i);
	return 0;
}

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    exit

    在初始化好伙伴系统后，memblock内存管理器要退出，将空闲内存加速伙伴系统管理(页框分配器)，并将内存管理权交给伙伴系统。

    linux源码 早期版本
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    mem_init中：

    • free_unused_memmap

      释放memblock的memory中的空洞内存。

    • free_all_bootmem

      释放memblock未使用的内存。memory中出去resev

    void __init mem_init(void)
{
#ifdef CONFIG_HAVE_TCM
	/* These pointers are filled in on TCM detection */
	extern u32 dtcm_end;
	extern u32 itcm_end;
#endif

	set_max_mapnr(pfn_to_page(max_pfn) - mem_map);

	/* this will put all unused low memory onto the freelists */
	free_unused_memmap();
	free_all_bootmem();

#ifdef CONFIG_SA1111
	/* now that our DMA memory is actually so designated, we can free it */
	free_reserved_area(__va(PHYS_OFFSET), swapper_pg_dir, -1, NULL);
#endif

	free_highpages();

	mem_init_print_info(NULL);

#define MLK(b, t) b, t, ((t) - (b)) >> 10
#define MLM(b, t) b, t, ((t) - (b)) >> 20
#define MLK_ROUNDUP(b, t) b, t, DIV_ROUND_UP(((t) - (b)), SZ_1K)

	pr_notice("Virtual kernel memory layout:\n"
			"    vector  : 0x%08lx - 0x%08lx   (%4ld kB)\n"
#ifdef CONFIG_HAVE_TCM
			"    DTCM    : 0x%08lx - 0x%08lx   (%4ld kB)\n"
			"    ITCM    : 0x%08lx - 0x%08lx   (%4ld kB)\n"
#endif
			"    fixmap  : 0x%08lx - 0x%08lx   (%4ld kB)\n"
			"    vmalloc : 0x%08lx - 0x%08lx   (%4ld MB)\n"
			"    lowmem  : 0x%08lx - 0x%08lx   (%4ld MB)\n"
#ifdef CONFIG_HIGHMEM
			"    pkmap   : 0x%08lx - 0x%08lx   (%4ld MB)\n"
#endif
#ifdef CONFIG_MODULES
			"    modules : 0x%08lx - 0x%08lx   (%4ld MB)\n"
#endif
			"      .text : 0x%p" " - 0x%p" "   (%4td kB)\n"
			"      .init : 0x%p" " - 0x%p" "   (%4td kB)\n"
			"      .data : 0x%p" " - 0x%p" "   (%4td kB)\n"
			"       .bss : 0x%p" " - 0x%p" "   (%4td kB)\n",

			MLK(VECTORS_BASE, VECTORS_BASE + PAGE_SIZE),
#ifdef CONFIG_HAVE_TCM
			MLK(DTCM_OFFSET, (unsigned long) dtcm_end),
			MLK(ITCM_OFFSET, (unsigned long) itcm_end),
#endif
			MLK(FIXADDR_START, FIXADDR_END),
			MLM(VMALLOC_START, VMALLOC_END),
			MLM(PAGE_OFFSET, (unsigned long)high_memory),
#ifdef CONFIG_HIGHMEM
			MLM(PKMAP_BASE, (PKMAP_BASE) + (LAST_PKMAP) *
				(PAGE_SIZE)),
#endif
#ifdef CONFIG_MODULES
			MLM(MODULES_VADDR, MODULES_END),
#endif

			MLK_ROUNDUP(_text, _etext),
			MLK_ROUNDUP(__init_begin, __init_end),
			MLK_ROUNDUP(_sdata, _edata),
			MLK_ROUNDUP(__bss_start, __bss_stop));

#undef MLK
#undef MLM
#undef MLK_ROUNDUP

	/*
	 * Check boundaries twice: Some fundamental inconsistencies can
	 * be detected at build time already.
	 */
#ifdef CONFIG_MMU
	BUILD_BUG_ON(TASK_SIZE				> MODULES_VADDR);
	BUG_ON(TASK_SIZE 				> MODULES_VADDR);
#endif

#ifdef CONFIG_HIGHMEM
	BUILD_BUG_ON(PKMAP_BASE + LAST_PKMAP * PAGE_SIZE > PAGE_OFFSET);
	BUG_ON(PKMAP_BASE + LAST_PKMAP * PAGE_SIZE	> PAGE_OFFSET);
#endif
}

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    另外，mem_init中会打印启动内存信息，如：

    在这里插入图片描述

    • free_unused_memmap

    遍历memblock的memory节点，释放pre_end和start之间的内存，即空洞内存。

    static void __init free_unused_memmap(void)
{
	unsigned long start, prev_end = 0;
	struct memblock_region *reg;

	/*
	 * This relies on each bank being in address order.
	 * The banks are sorted previously in bootmem_init().
	 */
	for_each_memblock(memory, reg) {
		start = memblock_region_memory_base_pfn(reg);

#ifdef CONFIG_SPARSEMEM
		/*
		 * Take care not to free memmap entries that don't exist
		 * due to SPARSEMEM sections which aren't present.
		 */
		start = min(start,
				 ALIGN(prev_end, PAGES_PER_SECTION));
#else
		/*
		 * Align down here since the VM subsystem insists that the
		 * memmap entries are valid from the bank start aligned to
		 * MAX_ORDER_NR_PAGES.
		 */
		start = round_down(start, MAX_ORDER_NR_PAGES);
#endif
		/*
		 * If we had a previous bank, and there is a space
		 * between the current bank and the previous, free it.
		 */
		if (prev_end && prev_end < start)
			free_memmap(prev_end, start);

		/*
		 * Align up here since the VM subsystem insists that the
		 * memmap entries are valid from the bank end aligned to
		 * MAX_ORDER_NR_PAGES.
		 */
		prev_end = ALIGN(memblock_region_memory_end_pfn(reg),
				 MAX_ORDER_NR_PAGES);
	}

#ifdef CONFIG_SPARSEMEM
	if (!IS_ALIGNED(prev_end, PAGES_PER_SECTION))
		free_memmap(prev_end,
			    ALIGN(prev_end, PAGES_PER_SECTION));
#endif
}

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    • free_all_bootmem

    free_all_bootmem 时遍历memory中没有reserved的，将其加入totlram_pages，归伙伴系统管理。

    /**
 * free_all_bootmem - release free pages to the buddy allocator
 *
 * Return: the number of pages actually released.
 */
unsigned long __init free_all_bootmem(void)
{
	unsigned long pages;

	reset_all_zones_managed_pages();

	pages = free_low_memory_core_early();
	totalram_pages += pages;

	return pages;
}

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    调用链：

    free_all_bootmem->free_low_memory_core_early->__free_memory_core->__free_pages_memory->__free_pages_bootmem->__free_pages_boot_core->__free_pages

page_zone(page)->managed_pages += nr_pages;

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    free_low_memory_core_early：

    static unsigned long __init free_low_memory_core_early(void)
{
	unsigned long count = 0;
	phys_addr_t start, end;
	u64 i;

	memblock_clear_hotplug(0, -1);

	for_each_reserved_mem_region(i, &start, &end)
		reserve_bootmem_region(start, end);

	/*
	 * We need to use NUMA_NO_NODE instead of NODE_DATA(0)->node_id
	 *  because in some case like Node0 doesn't have RAM installed
	 *  low ram will be on Node1
	 */
	for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end,
				NULL)
		count += __free_memory_core(start, end);

	return count;
}

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    启动阶段打印的reverved内存。

    mem_init_print_info：

    reserved内存：(physpages - totalram_pages - totalcma_pages) << (PAGE_SHIFT - 10)。

    void __init mem_init_print_info(const char *str)
{
	unsigned long physpages, codesize, datasize, rosize, bss_size;
	unsigned long init_code_size, init_data_size;

	physpages = get_num_physpages();
	codesize = _etext - _stext;
	datasize = _edata - _sdata;
	rosize = __end_rodata - __start_rodata;
	bss_size = __bss_stop - __bss_start;
	init_data_size = __init_end - __init_begin;
	init_code_size = _einittext - _sinittext;

	/*
	 * Detect special cases and adjust section sizes accordingly:
	 * 1) .init.* may be embedded into .data sections
	 * 2) .init.text.* may be out of [__init_begin, __init_end],
	 *    please refer to arch/tile/kernel/vmlinux.lds.S.
	 * 3) .rodata.* may be embedded into .text or .data sections.
	 */
#define adj_init_size(start, end, size, pos, adj) \
	do { \
		if (start <= pos && pos < end && size > adj) \
			size -= adj; \
	} while (0)

	adj_init_size(__init_begin, __init_end, init_data_size,
		     _sinittext, init_code_size);
	adj_init_size(_stext, _etext, codesize, _sinittext, init_code_size);
	adj_init_size(_sdata, _edata, datasize, __init_begin, init_data_size);
	adj_init_size(_stext, _etext, codesize, __start_rodata, rosize);
	adj_init_size(_sdata, _edata, datasize, __start_rodata, rosize);

#undef	adj_init_size

	pr_info("Memory: %luK/%luK available (%luK kernel code, %luK rwdata, %luK rodata, %luK init, %luK bss, %luK reserved, %luK cma-reserved"
#ifdef	CONFIG_HIGHMEM
		", %luK highmem"
#endif
		"%s%s)\n",
		nr_free_pages() << (PAGE_SHIFT - 10),
		physpages << (PAGE_SHIFT - 10),
		codesize >> 10, datasize >> 10, rosize >> 10,
		(init_data_size + init_code_size) >> 10, bss_size >> 10,
		(physpages - totalram_pages - totalcma_pages) << (PAGE_SHIFT - 10),
		totalcma_pages << (PAGE_SHIFT - 10),
#ifdef	CONFIG_HIGHMEM
		totalhigh_pages << (PAGE_SHIFT - 10),
#endif
		str ? ", " : "", str ? str : "");
}

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    debug

    • 启动阶段：打开log bootargs

      memblock=debug

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    • debugfs

    debugfs可以查看memblock的memory和reserved信息。

    使用

    • zero_page

      零页的分配，在paging_init调用。

    • create_mapping

    • early_pte_alloc

    • kmemleak_init

    参考

    https://www.iteye.com/blog/wx1568397608-2454954

    https://blog.csdn.net/u012489236/article/details/106796880

    https://zhuanlan.zhihu.com/p/44565320

    https://www.cnblogs.com/qinglan1210/p/14779073.html

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  • 原文地址：https://blog.csdn.net/qq_40036519/article/details/126087465