Memblock Overview¶

Memblock is a method of managing memory regions during the earlyboot period when the usual kernel memory allocators are not up andrunning.

Memblock views the system memory as collections of contiguousregions. There are several types of these collections:

• memory - describes the physical memory available to thekernel; this may differ from the actual physical memory installedin the system, for instance when the memory is restricted withmem= command line parameter
• reserved - describes the regions that were allocated
• physmem - describes the actual physical memory available duringboot regardless of the possible restrictions and memory hot(un)plug;thephysmem type is only available on some architectures.

Each region is represented bystructmemblock_region thatdefines the region extents, its attributes and NUMA node id on NUMAsystems. Every memory type is described by thestructmemblock_type which contains an array of memory regions along withthe allocator metadata. The “memory” and “reserved” types are nicelywrapped withstructmemblock. This structure is staticallyinitialized at build time. The region arrays are initially sized toINIT_MEMBLOCK_REGIONS for “memory” andINIT_MEMBLOCK_RESERVED_REGIONSfor “reserved”. The region array for “physmem” is initially sized toINIT_PHYSMEM_REGIONS.The memblock_allow_resize() enables automatic resizing of the regionarrays during addition of new regions. This feature should be usedwith care so that memory allocated for the region array will notoverlap with areas that should be reserved, for example initrd.

The early architecture setup should tell memblock what the physicalmemory layout is by usingmemblock_add() ormemblock_add_node()functions. The first function does not assign the region to a NUMAnode and it is appropriate for UMA systems. Yet, it is possible touse it on NUMA systems as well and assign the region to a NUMA nodelater in the setup process usingmemblock_set_node(). Thememblock_add_node() performs such an assignment directly.

Once memblock is setup the memory can be allocated using one of theAPI variants:

• memblock_phys_alloc*() - these functions return thephysicaladdress of the allocated memory
• memblock_alloc*() - these functions return thevirtual addressof the allocated memory.

Note, that both API variants use implicit assumptions about allowedmemory ranges and the fallback methods. Consult the documentationofmemblock_alloc_internal() andmemblock_alloc_range_nid()functions for more elaborate description.

As the system boot progresses, the architecture specific mem_init()function frees all the memory to the buddy page allocator.

Unless an architecture enablesCONFIG_ARCH_KEEP_MEMBLOCK, thememblock data structures (except “physmem”) will be discarded after thesystem initialization completes.

Functions and structures¶

Here is the description of memblock data structures, functions andmacros. Some of them are actually internal, but since they aredocumented it would be silly to omit them. Besides, reading thedescriptions for the internal functions can help to understand whatreally happens under the hood.

enummemblock_flags¶

definition of memory region attributes

Constants

MEMBLOCK_NONE

no special request

MEMBLOCK_HOTPLUG

hotpluggable region

MEMBLOCK_MIRROR

mirrored region

MEMBLOCK_NOMAP

don’t add to kernel direct mapping

structmemblock_region¶

represents a memory region

Definition

struct memblock_region {  phys_addr_t base;  phys_addr_t size;  enum memblock_flags flags;#ifdef CONFIG_NEED_MULTIPLE_NODES;  int nid;#endif;};

Members

base

base address of the region

size

size of the region

flags

memory region attributes

nid

NUMA node id

structmemblock_type¶

collection of memory regions of certain type

Definition

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

Members

cnt

number of regions

max

size of the allocated array

total_size

size of all regions

regions

array of regions

name

the memory type symbolic name

structmemblock¶

memblock allocator metadata

Definition

struct memblock {  bool bottom_up;  phys_addr_t current_limit;  struct memblock_type memory;  struct memblock_type reserved;};

Members

bottom_up

is bottom up direction?

current_limit

physical address of the current allocation limit

memory

usable memory regions

reserved

reserved memory regions

for_each_physmem_range(i,type,p_start,p_end)¶

iterate through physmem areas not included in type.

Parameters

i

u64 used as loop variable

type

ptr to memblock_type which excludes from the iteration, can beNULL

p_start

ptr to phys_addr_t for start address of the range, can beNULL

p_end

ptr to phys_addr_t for end address of the range, can beNULL

for_each_mem_range(i,type_a,type_b,nid,flags,p_start,p_end,p_nid)¶

iterate through memblock areas from type_a and not included in type_b. Or just type_a if type_b is NULL.

Parameters

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 beNULL

p_end

ptr to phys_addr_t for end address of the range, can beNULL

p_nid

ptr to int for nid of the range, can beNULL

for_each_mem_range_rev(i,type_a,type_b,nid,flags,p_start,p_end,p_nid)¶

reverse iterate through memblock areas from type_a and not included in type_b. Or just type_a if type_b is NULL.

Parameters

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 beNULL

p_end

ptr to phys_addr_t for end address of the range, can beNULL

p_nid

ptr to int for nid of the range, can beNULL

for_each_reserved_mem_region(i,p_start,p_end)¶

iterate over all reserved memblock areas

Parameters

i

u64 used as loop variable

p_start

ptr to phys_addr_t for start address of the range, can beNULL

p_end

ptr to phys_addr_t for end address of the range, can beNULL

Description

Walks over reserved areas of memblock. Available as soon as memblockis initialized.

for_each_mem_pfn_range(i,nid,p_start,p_end,p_nid)¶

early memory pfn range iterator

Parameters

i

an integer used as loop variable

nid

node selector,MAX_NUMNODES for all nodes

p_start

ptr to ulong for start pfn of the range, can beNULL

p_end

ptr to ulong for end pfn of the range, can beNULL

p_nid

ptr to int for nid of the range, can beNULL

Description

Walks over configured memory ranges.

for_each_free_mem_pfn_range_in_zone(i,zone,p_start,p_end)¶

iterate through zone specific free memblock areas

Parameters

i

u64 used as loop variable

zone

zone in which all of the memory blocks reside

p_start

ptr to phys_addr_t for start address of the range, can beNULL

p_end

ptr to phys_addr_t for end address of the range, can beNULL

Description

Walks over free (memory && !reserved) areas of memblock in a specificzone. Available once memblock and an empty zone is initialized. The mainassumption is that the zone start, end, and pgdat have been associated.This way we can use the zone to determine NUMA node, and if a given partof the memblock is valid for the zone.

for_each_free_mem_pfn_range_in_zone_from(i,zone,p_start,p_end)¶

iterate through zone specific free memblock areas from a given point

Parameters

i

u64 used as loop variable

zone

zone in which all of the memory blocks reside

p_start

ptr to phys_addr_t for start address of the range, can beNULL

p_end

ptr to phys_addr_t for end address of the range, can beNULL

Description

Walks over free (memory && !reserved) areas of memblock in a specificzone, continuing from current position. Available as soon as memblock isinitialized.

for_each_free_mem_range(i,nid,flags,p_start,p_end,p_nid)¶

iterate through free memblock areas

Parameters

i

u64 used as loop variable

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 beNULL

p_end

ptr to phys_addr_t for end address of the range, can beNULL

p_nid

ptr to int for nid of the range, can beNULL

Description

Walks over free (memory && !reserved) areas of memblock. Available assoon as memblock is initialized.

for_each_free_mem_range_reverse(i,nid,flags,p_start,p_end,p_nid)¶

rev-iterate through free memblock areas

Parameters

i

u64 used as loop variable

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 beNULL

p_end

ptr to phys_addr_t for end address of the range, can beNULL

p_nid

ptr to int for nid of the range, can beNULL

Description

Walks over free (memory && !reserved) areas of memblock in reverseorder. Available as soon as memblock is initialized.

voidmemblock_set_current_limit(phys_addr_t limit)¶

Set the current allocation limit to allow limiting allocations to what is currently accessible during boot

Parameters

phys_addr_tlimit

New limit value (physical address)

unsigned longmemblock_region_memory_base_pfn(const structmemblock_region * reg)¶

get the lowest pfn of the memory region

Parameters

conststructmemblock_region*reg

memblock_region structure

Return

the lowest pfn intersecting with the memory region

unsigned longmemblock_region_memory_end_pfn(const structmemblock_region * reg)¶

get the end pfn of the memory region

Parameters

conststructmemblock_region*reg

memblock_region structure

Return

the end_pfn of the reserved region

unsigned longmemblock_region_reserved_base_pfn(const structmemblock_region * reg)¶

get the lowest pfn of the reserved region

Parameters

conststructmemblock_region*reg

memblock_region structure

Return

the lowest pfn intersecting with the reserved region

unsigned longmemblock_region_reserved_end_pfn(const structmemblock_region * reg)¶

get the end pfn of the reserved region

Parameters

conststructmemblock_region*reg

memblock_region structure

Return

the end_pfn of the reserved region

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, enummemblock_flags flags)¶

find free area utility in bottom-up

Parameters

phys_addr_tstart

start of candidate range

phys_addr_tend

end of candidate range, can beMEMBLOCK_ALLOC_ANYWHERE orMEMBLOCK_ALLOC_ACCESSIBLE

phys_addr_tsize

size of free area to find

phys_addr_talign

alignment of free area to find

intnid

nid of the free area to find,NUMA_NO_NODE for any node

enummemblock_flagsflags

pick from blocks based on memory attributes

Description

Utility called frommemblock_find_in_range_node(), find free area bottom-up.

Return

Found address on success, 0 on failure.

phys_addr_t __init_memblock__memblock_find_range_top_down(phys_addr_t start, phys_addr_t end, phys_addr_t size, phys_addr_t align, int nid, enummemblock_flags flags)¶

find free area utility, in top-down

Parameters

phys_addr_tstart

start of candidate range

phys_addr_tend

end of candidate range, can beMEMBLOCK_ALLOC_ANYWHERE orMEMBLOCK_ALLOC_ACCESSIBLE

phys_addr_tsize

size of free area to find

phys_addr_talign

alignment of free area to find

intnid

nid of the free area to find,NUMA_NO_NODE for any node

enummemblock_flagsflags

pick from blocks based on memory attributes

Description

Utility called frommemblock_find_in_range_node(), find free area top-down.

Return

Found address on success, 0 on failure.

phys_addr_t __init_memblockmemblock_find_in_range_node(phys_addr_t size, phys_addr_t align, phys_addr_t start, phys_addr_t end, int nid, enummemblock_flags flags)¶

find free area in given range and node

Parameters

phys_addr_tsize

size of free area to find

phys_addr_talign

alignment of free area to find

phys_addr_tstart

start of candidate range

phys_addr_tend

end of candidate range, can beMEMBLOCK_ALLOC_ANYWHERE orMEMBLOCK_ALLOC_ACCESSIBLE

intnid

nid of the free area to find,NUMA_NO_NODE for any node

enummemblock_flagsflags

pick from blocks based on memory attributes

Description

Findsize free area aligned toalign in the specified range and node.

When allocation direction is bottom-up, thestart should be greaterthan the end of the kernel image. Otherwise, it will be trimmed. Thereason is that we want the bottom-up allocation just near the kernelimage so it is highly likely that the allocated memory and the kernelwill reside in the same node.

If bottom-up allocation failed, will try to allocate memory top-down.

Return

Found address on success, 0 on failure.

phys_addr_t __init_memblockmemblock_find_in_range(phys_addr_t start, phys_addr_t end, phys_addr_t size, phys_addr_t align)¶

find free area in given range

Parameters

phys_addr_tstart

start of candidate range

phys_addr_tend

end of candidate range, can beMEMBLOCK_ALLOC_ANYWHERE orMEMBLOCK_ALLOC_ACCESSIBLE

phys_addr_tsize

size of free area to find

phys_addr_talign

alignment of free area to find

Description

Findsize free area aligned toalign in the specified range.

Return

Found address on success, 0 on failure.

voidmemblock_discard(void)¶

discard memory and reserved arrays if they were allocated

Parameters

void

no arguments

int __init_memblockmemblock_double_array(structmemblock_type * type, phys_addr_t new_area_start, phys_addr_t new_area_size)¶

double the size of the memblock regions array

Parameters

structmemblock_type*type

memblock type of the regions array being doubled

phys_addr_tnew_area_start

starting address of memory range to avoid overlap with

phys_addr_tnew_area_size

size of memory range to avoid overlap with

Description

Double the size of thetype regions array. If memblock is being used toallocate memory for a new reserved regions array and there is a previouslyallocated memory range [new_area_start,new_area_start +new_area_size]waiting to be reserved, ensure the memory used by the new array doesnot overlap.

Return

0 on success, -1 on failure.

void __init_memblockmemblock_merge_regions(structmemblock_type * type)¶

merge neighboring compatible regions

Parameters

structmemblock_type*type

memblock type to scan

Description

Scantype and merge neighboring compatible regions.

void __init_memblockmemblock_insert_region(structmemblock_type * type, int idx, phys_addr_t base, phys_addr_t size, int nid, enummemblock_flags flags)¶

insert new memblock region

Parameters

structmemblock_type*type

memblock type to insert into

intidx

index for the insertion point

phys_addr_tbase

base address of the new region

phys_addr_tsize

size of the new region

intnid

node id of the new region

enummemblock_flagsflags

flags of the new region

Description

Insert new memblock region [base,base +size) intotype atidx.type must already have extra room to accommodate the new region.

int __init_memblockmemblock_add_range(structmemblock_type * type, phys_addr_t base, phys_addr_t size, int nid, enummemblock_flags flags)¶

add new memblock region

Parameters

structmemblock_type*type

memblock type to add new region into

phys_addr_tbase

base address of the new region

phys_addr_tsize

size of the new region

intnid

nid of the new region

enummemblock_flagsflags

flags of the new region

Description

Add new memblock region [base,base +size) intotype. The new regionis allowed to overlap with existing ones - overlaps don’t affect alreadyexisting regions.type is guaranteed to be minimal (all neighbouringcompatible regions are merged) after the addition.

Return

0 on success, -errno on failure.

int __init_memblockmemblock_add_node(phys_addr_t base, phys_addr_t size, int nid)¶

add new memblock region within a NUMA node

Parameters

phys_addr_tbase

base address of the new region

phys_addr_tsize

size of the new region

intnid

nid of the new region

Description

Add new memblock region [base,base +size) to the “memory”type. Seememblock_add_range() description for mode details

Return

0 on success, -errno on failure.

int __init_memblockmemblock_add(phys_addr_t base, phys_addr_t size)¶

add new memblock region

Parameters

phys_addr_tbase

base address of the new region

phys_addr_tsize

size of the new region

Description

Add new memblock region [base,base +size) to the “memory”type. Seememblock_add_range() description for mode details

Return

0 on success, -errno on failure.

int __init_memblockmemblock_isolate_range(structmemblock_type * type, phys_addr_t base, phys_addr_t size, int * start_rgn, int * end_rgn)¶

isolate given range into disjoint memblocks

Parameters

structmemblock_type*type

memblock type to isolate range for

phys_addr_tbase

base of range to isolate

phys_addr_tsize

size of range to isolate

int*start_rgn

out parameter for the start of isolated region

int*end_rgn

out parameter for the end of isolated region

Description

Walktype and ensure that regions don’t cross the boundaries defined by[base,base +size). Crossing regions are split at the boundaries,which may create at most two more regions. The index of the firstregion inside the range is returned in*start_rgn and end in*end_rgn.

Return

0 on success, -errno on failure.

int __init_memblockmemblock_free(phys_addr_t base, phys_addr_t size)¶

free boot memory block

Parameters

phys_addr_tbase

phys starting address of the boot memory block

phys_addr_tsize

size of the boot memory block in bytes

Description

Free boot memory block previously allocated by memblock_alloc_xx() API.The freeing memory will not be released to the buddy allocator.

int __init_memblockmemblock_setclr_flag(phys_addr_t base, phys_addr_t size, int set, int flag)¶

set or clear flag for a memory region

Parameters

phys_addr_tbase

base address of the region

phys_addr_tsize

size of the region

intset

set or clear the flag

intflag

the flag to udpate

Description

This function isolates region [base,base +size), and sets/clears flag

Return

0 on success, -errno on failure.

int __init_memblockmemblock_mark_hotplug(phys_addr_t base, phys_addr_t size)¶

Mark hotpluggable memory with flag MEMBLOCK_HOTPLUG.

Parameters

phys_addr_tbase

the base phys addr of the region

phys_addr_tsize

the size of the region

Return

0 on success, -errno on failure.

int __init_memblockmemblock_clear_hotplug(phys_addr_t base, phys_addr_t size)¶

Clear flag MEMBLOCK_HOTPLUG for a specified region.

Parameters

phys_addr_tbase

the base phys addr of the region

phys_addr_tsize

the size of the region

Return

0 on success, -errno on failure.

int __init_memblockmemblock_mark_mirror(phys_addr_t base, phys_addr_t size)¶

Mark mirrored memory with flag MEMBLOCK_MIRROR.

Parameters

phys_addr_tbase

the base phys addr of the region

phys_addr_tsize

the size of the region

Return

0 on success, -errno on failure.

int __init_memblockmemblock_mark_nomap(phys_addr_t base, phys_addr_t size)¶

Mark a memory region with flag MEMBLOCK_NOMAP.

Parameters

phys_addr_tbase

the base phys addr of the region

phys_addr_tsize

the size of the region

Return

0 on success, -errno on failure.

int __init_memblockmemblock_clear_nomap(phys_addr_t base, phys_addr_t size)¶

Clear flag MEMBLOCK_NOMAP for a specified region.

Parameters

phys_addr_tbase

the base phys addr of the region

phys_addr_tsize

the size of the region

Return

0 on success, -errno on failure.

void __init_memblock__next_reserved_mem_region(u64 * idx, phys_addr_t * out_start, phys_addr_t * out_end)¶

next function for for_each_reserved_region()

Parameters

u64*idx

pointer to u64 loop variable

phys_addr_t*out_start

ptr to phys_addr_t for start address of the region, can beNULL

phys_addr_t*out_end

ptr to phys_addr_t for end address of the region, can beNULL

Description

Iterate over all reserved memory regions.

void__next_mem_range(u64 * idx, int nid, enummemblock_flags flags, structmemblock_type * type_a, structmemblock_type * type_b, phys_addr_t * out_start, phys_addr_t * out_end, int * out_nid)¶

next function forfor_each_free_mem_range() etc.

Parameters

u64*idx

pointer to u64 loop variable

intnid

node selector,NUMA_NO_NODE for all nodes

enummemblock_flagsflags

pick from blocks based on memory attributes

structmemblock_type*type_a

pointer to memblock_type from where the range is taken

structmemblock_type*type_b

pointer to memblock_type which excludes memory from being taken

phys_addr_t*out_start

ptr to phys_addr_t for start address of the range, can beNULL

phys_addr_t*out_end

ptr to phys_addr_t for end address of the range, can beNULL

int*out_nid

ptr to int for nid of the range, can beNULL

Description

Find the first area from*idx which matchesnid, fill the outparameters, and update*idx for the next iteration. The lower 32bit of*idx contains index into type_a and the upper 32bit indexes theareas before each region in type_b. For example, if type_b regionslook like the following,

0:[0-16), 1:[32-48), 2:[128-130)

The upper 32bit indexes the following regions.

0:[0-0), 1:[16-32), 2:[48-128), 3:[130-MAX)

As both region arrays are sorted, the function advances the two indicesin lockstep and returns each intersection.

void __init_memblock__next_mem_range_rev(u64 * idx, int nid, enummemblock_flags flags, structmemblock_type * type_a, structmemblock_type * type_b, phys_addr_t * out_start, phys_addr_t * out_end, int * out_nid)¶

generic next function for for_each_*_range_rev()

Parameters

u64*idx

pointer to u64 loop variable

intnid

node selector,NUMA_NO_NODE for all nodes

enummemblock_flagsflags

pick from blocks based on memory attributes

structmemblock_type*type_a

pointer to memblock_type from where the range is taken

structmemblock_type*type_b

pointer to memblock_type which excludes memory from being taken

phys_addr_t*out_start

ptr to phys_addr_t for start address of the range, can beNULL

phys_addr_t*out_end

ptr to phys_addr_t for end address of the range, can beNULL

int*out_nid

ptr to int for nid of the range, can beNULL

Description

Finds the next range from type_a which is not marked as unsuitablein type_b.

Reverse of__next_mem_range().

int __init_memblockmemblock_set_node(phys_addr_t base, phys_addr_t size, structmemblock_type * type, int nid)¶

set node ID on memblock regions

Parameters

phys_addr_tbase

base of area to set node ID for

phys_addr_tsize

size of area to set node ID for

structmemblock_type*type

memblock type to set node ID for

intnid

node ID to set

Description

Set the nid of memblocktype regions in [base,base +size) tonid.Regions which cross the area boundaries are split as necessary.

Return

0 on success, -errno on failure.

void __init_memblock__next_mem_pfn_range_in_zone(u64 * idx, struct zone * zone, unsigned long * out_spfn, unsigned long * out_epfn)¶

iterator for for_each_*_range_in_zone()

Parameters

u64*idx

pointer to u64 loop variable

structzone*zone

zone in which all of the memory blocks reside

unsignedlong*out_spfn

ptr to ulong for start pfn of the range, can beNULL

unsignedlong*out_epfn

ptr to ulong for end pfn of the range, can beNULL

Description

This function is meant to be a zone/pfn specific wrapper for thefor_each_mem_range type iterators. Specifically they are used in thedeferred memory init routines and as such we were duplicating much ofthis logic throughout the code. So instead of having it in multiplelocations it seemed like it would make more sense to centralize this toone new iterator that does everything they need.

phys_addr_tmemblock_alloc_range_nid(phys_addr_t size, phys_addr_t align, phys_addr_t start, phys_addr_t end, int nid, bool exact_nid)¶

allocate boot memory block

Parameters

phys_addr_tsize

size of memory block to be allocated in bytes

phys_addr_talign

alignment of the region and block’s size

phys_addr_tstart

the lower bound of the memory region to allocate (phys address)

phys_addr_tend

the upper bound of the memory region to allocate (phys address)

intnid

nid of the free area to find,NUMA_NO_NODE for any node

boolexact_nid

control the allocation fall back to other nodes

Description

The allocation is performed from memory region limited bymemblock.current_limit ifend ==MEMBLOCK_ALLOC_ACCESSIBLE.

If the specified node can not hold the requested memory andexact_nidis false, the allocation falls back to any node in the system.

For systems with memory mirroring, the allocation is attempted firstfrom the regions with mirroring enabled and then retried from anymemory region.

In addition, function sets the min_count to 0 using kmemleak_alloc_phys forallocated boot memory block, so that it is never reported as leaks.

Return

Physical address of allocated memory block on success,0 on failure.

phys_addr_tmemblock_phys_alloc_range(phys_addr_t size, phys_addr_t align, phys_addr_t start, phys_addr_t end)¶

allocate a memory block inside specified range

Parameters

phys_addr_tsize

size of memory block to be allocated in bytes

phys_addr_talign

alignment of the region and block’s size

phys_addr_tstart

the lower bound of the memory region to allocate (physical address)

phys_addr_tend

the upper bound of the memory region to allocate (physical address)

Description

Allocatesize bytes in the betweenstart andend.

Return

physical address of the allocated memory block on success,0 on failure.

phys_addr_tmemblock_phys_alloc_try_nid(phys_addr_t size, phys_addr_t align, int nid)¶

allocate a memory block from specified MUMA node

Parameters

phys_addr_tsize

size of memory block to be allocated in bytes

phys_addr_talign

alignment of the region and block’s size

intnid

nid of the free area to find,NUMA_NO_NODE for any node

Description

Allocates memory block from the specified NUMA node. If the nodehas no available memory, attempts to allocated from any node in thesystem.

Return

physical address of the allocated memory block on success,0 on failure.

void *memblock_alloc_internal(phys_addr_t size, phys_addr_t align, phys_addr_t min_addr, phys_addr_t max_addr, int nid, bool exact_nid)¶

allocate boot memory block

Parameters

phys_addr_tsize

size of memory block to be allocated in bytes

phys_addr_talign

alignment of the region and block’s size

phys_addr_tmin_addr

the lower bound of the memory region to allocate (phys address)

phys_addr_tmax_addr

the upper bound of the memory region to allocate (phys address)

intnid

nid of the free area to find,NUMA_NO_NODE for any node

boolexact_nid

control the allocation fall back to other nodes

Description

Allocates memory block usingmemblock_alloc_range_nid() andconverts the returned physical address to virtual.

Themin_addr limit is dropped if it can not be satisfied and the allocationwill fall back to memory belowmin_addr. Other constraints, suchas node and mirrored memory will be handled again inmemblock_alloc_range_nid().

Return

Virtual address of allocated memory block on success, NULL on failure.

void *memblock_alloc_exact_nid_raw(phys_addr_t size, phys_addr_t align, phys_addr_t min_addr, phys_addr_t max_addr, int nid)¶

allocate boot memory block on the exact node without zeroing memory

Parameters

phys_addr_tsize

size of memory block to be allocated in bytes

phys_addr_talign

alignment of the region and block’s size

phys_addr_tmin_addr

the lower bound of the memory region from where the allocationis preferred (phys address)

phys_addr_tmax_addr

the upper bound of the memory region from where the allocationis preferred (phys address), orMEMBLOCK_ALLOC_ACCESSIBLE toallocate only from memory limited by memblock.current_limit value

intnid

nid of the free area to find,NUMA_NO_NODE for any node

Description

Public function, provides additional debug information (including callerinfo), if enabled. Does not zero allocated memory.

Return

Virtual address of allocated memory block on success, NULL on failure.

void *memblock_alloc_try_nid_raw(phys_addr_t size, phys_addr_t align, phys_addr_t min_addr, phys_addr_t max_addr, int nid)¶

allocate boot memory block without zeroing memory and without panicking

Parameters

phys_addr_tsize

size of memory block to be allocated in bytes

phys_addr_talign

alignment of the region and block’s size

phys_addr_tmin_addr

the lower bound of the memory region from where the allocationis preferred (phys address)

phys_addr_tmax_addr

the upper bound of the memory region from where the allocationis preferred (phys address), orMEMBLOCK_ALLOC_ACCESSIBLE toallocate only from memory limited by memblock.current_limit value

intnid

nid of the free area to find,NUMA_NO_NODE for any node

Description

Public function, provides additional debug information (including callerinfo), if enabled. Does not zero allocated memory, does not panic if requestcannot be satisfied.

Return

Virtual address of allocated memory block on success, NULL on failure.

void *memblock_alloc_try_nid(phys_addr_t size, phys_addr_t align, phys_addr_t min_addr, phys_addr_t max_addr, int nid)¶

allocate boot memory block

Parameters

phys_addr_tsize

size of memory block to be allocated in bytes

phys_addr_talign

alignment of the region and block’s size

phys_addr_tmin_addr

the lower bound of the memory region from where the allocationis preferred (phys address)

phys_addr_tmax_addr

the upper bound of the memory region from where the allocationis preferred (phys address), orMEMBLOCK_ALLOC_ACCESSIBLE toallocate only from memory limited by memblock.current_limit value

intnid

nid of the free area to find,NUMA_NO_NODE for any node

Description

Public function, provides additional debug information (including callerinfo), if enabled. This function zeroes the allocated memory.

Return

Virtual address of allocated memory block on success, NULL on failure.

void__memblock_free_late(phys_addr_t base, phys_addr_t size)¶

free pages directly to buddy allocator

Parameters

phys_addr_tbase

phys starting address of the boot memory block

phys_addr_tsize

size of the boot memory block in bytes

Description

This is only useful when the memblock allocator has already been torndown, but we are still initializing the system. Pages are released directlyto the buddy allocator.

bool __init_memblockmemblock_is_region_memory(phys_addr_t base, phys_addr_t size)¶

check if a region is a subset of memory

Parameters

phys_addr_tbase

base of region to check

phys_addr_tsize

size of region to check

Description

Check if the region [base,base +size) is a subset of a memory block.

Return

0 if false, non-zero if true

bool __init_memblockmemblock_is_region_reserved(phys_addr_t base, phys_addr_t size)¶

check if a region intersects reserved memory

Parameters

phys_addr_tbase

base of region to check

phys_addr_tsize

size of region to check

Description

Check if the region [base,base +size) intersects a reservedmemory block.

Return

True if they intersect, false if not.

unsigned longmemblock_free_all(void)¶

release free pages to the buddy allocator

Parameters

void

no arguments

Return

the number of pages actually released.