Memory Management

Collaboration diagram for Memory Management:

Data Structures
struct	rt_mempool

Functions
void *	rt_smem_alloc (rt_smem_t m, rt_size_t size)
void *	rt_smem_realloc (rt_smem_t m, void *rmem, rt_size_t newsize)
void	rt_smem_free (void *rmem)
rt_err_t	rt_mp_init (struct rt_mempool *mp, const char *name, void *start, rt_size_t size, rt_size_t block_size)
rt_err_t	rt_mp_detach (struct rt_mempool *mp)
rt_mp_t	rt_mp_create (const char *name, rt_size_t block_count, rt_size_t block_size)
rt_err_t	rt_mp_delete (rt_mp_t mp)
void *	rt_mp_alloc (rt_mp_t mp, rt_int32_t time)
void	rt_mp_free (void *block)
void	rt_system_heap_init (void *begin_addr, void *end_addr)
void	rt_system_heap_init_generic (void *begin_addr, void *end_addr)
void *	rt_malloc (rt_size_t size)
void	rt_free (void *ptr)
void *	rt_realloc (void *ptr, rt_size_t newsize)
void *	rt_calloc (rt_size_t count, rt_size_t size)
void *	rt_malloc_align (rt_size_t size, rt_size_t align)
void	rt_free_align (void *ptr)
void	rt_memory_info (rt_size_t *total, rt_size_t *used, rt_size_t *max_used)
rt_smem_t	rt_smem_init (const char *name, void *begin_addr, rt_size_t size)
rt_err_t	rt_smem_detach (rt_smem_t m)
void	rt_realloc_set_entry_hook (void(*hook)(void **ptr, rt_size_t size))
void	rt_realloc_set_exit_hook (void(*hook)(void **ptr, rt_size_t size))
void	rt_free_sethook (void(*hook)(void **ptr))

Detailed Description

memory management for memory pool and heap memory

RT-Thread operating system supports two types memory management:

• Static memory pool management
• Dynamic memory heap management.

The time to allocate a memory block from the memory pool is determinant. When the memory pool is empty, the allocated thread can be blocked (or immediately return, or waiting for sometime to return, which are determined by a timeout parameter). When other thread releases memory blocks to this memory pool, the blocked thread is wake up.

There are two methods in dynamic memory heap management, one is used for small memory, such as less than 1MB. Another is a SLAB like memory management, which is suitable for large memory system. All of them has no real-time character.

Function Documentation

rt_smem_alloc()

void * rt_smem_alloc	(	rt_smem_t	m,
		rt_size_t	size
	)

Allocate a block of memory with a minimum of 'size' bytes.

Parameters

m	the small memory management object.
size	is the minimum size of the requested block in bytes.

Returns

the pointer to allocated memory or NULL if no free memory was found.

rt_smem_realloc()

void * rt_smem_realloc	(	rt_smem_t	m,
		void *	rmem,
		rt_size_t	newsize
	)

This function will change the size of previously allocated memory block.

Parameters

m	the small memory management object.
rmem	is the pointer to memory allocated by rt_mem_alloc.
newsize	is the required new size.

Returns

the changed memory block address.

rt_smem_free()

void rt_smem_free

(

void *

rmem

)

This function will release the previously allocated memory block by rt_mem_alloc. The released memory block is taken back to system heap.

Parameters

rmem	the address of memory which will be released.

rt_mp_init()

rt_err_t rt_mp_init	(	struct rt_mempool *	mp,
		const char *	name,
		void *	start,
		rt_size_t	size,
		rt_size_t	block_size
	)

This function will initialize a memory pool object, normally which is used for static object.

Parameters

mp	is the memory pool object.
name	is the name of the memory pool.
start	is the start address of the memory pool.
size	is the total size of the memory pool.
block_size	is the size for each block..

Returns

RT_EOK

rt_mp_detach()

rt_err_t rt_mp_detach

(

struct rt_mempool *

mp

)

This function will detach a memory pool from system object management.

Parameters

mp	is the memory pool object.

Returns

RT_EOK

rt_mp_create()

rt_mp_t rt_mp_create	(	const char *	name,
		rt_size_t	block_count,
		rt_size_t	block_size
	)

This function will create a mempool object and allocate the memory pool from heap.

Parameters

name	is the name of memory pool.
block_count	is the count of blocks in memory pool.
block_size	is the size for each block.

Returns

the created mempool object

rt_mp_delete()

rt_err_t rt_mp_delete

(

rt_mp_t

mp

)

This function will delete a memory pool and release the object memory.

Parameters

mp	is the memory pool object.

Returns

RT_EOK

rt_mp_alloc()

void * rt_mp_alloc	(	rt_mp_t	mp,
		rt_int32_t	time
	)

This function will allocate a block from memory pool.

Parameters

mp	is the memory pool object.
time	is the maximum waiting time for allocating memory. 0 for not waiting, allocating memory immediately.

Returns

the allocated memory block or RT_NULL on allocated failed.

rt_mp_free()

void rt_mp_free

(

void *

block

)

This function will release a memory block.

Parameters

block

the address of memory block to be released.

rt_system_heap_init()

void rt_system_heap_init	(	void *	begin_addr,
		void *	end_addr
	)

This function will init system heap. User can override this API to complete other works, like heap sanitizer initialization.

Parameters

begin_addr	the beginning address of system page.
end_addr	the end address of system page.

rt_system_heap_init_generic()

void rt_system_heap_init_generic	(	void *	begin_addr,
		void *	end_addr
	)

This function will do the generic system heap initialization.

Parameters

begin_addr	the beginning address of system page.
end_addr	the end address of system page.

rt_malloc()

void* rt_malloc

(

rt_size_t

size

)

Allocate a block of memory with a minimum of 'size' bytes.

Parameters

size	is the minimum size of the requested block in bytes.

Returns

the pointer to allocated memory or NULL if no free memory was found.

rt_free()

void rt_free

(

void *

ptr

)

This function will release the previously allocated memory block by rt_malloc. The released memory block is taken back to system heap.

Parameters

ptr	the address of memory which will be released.

rt_realloc()

void* rt_realloc	(	void *	ptr,
		rt_size_t	newsize
	)

This function will change the size of previously allocated memory block.

Parameters

ptr	is the pointer to memory allocated by rt_malloc.
newsize	is the required new size.

Returns

the changed memory block address.

rt_calloc()

void* rt_calloc	(	rt_size_t	count,
		rt_size_t	size
	)

This function will contiguously allocate enough space for count objects that are size bytes of memory each and returns a pointer to the allocated memory.

Note

The allocated memory is filled with bytes of value zero.

Parameters

count	is the number of objects to allocate.
size	is the size of one object to allocate.

Returns

pointer to allocated memory / NULL pointer if there is an error.

rt_malloc_align()

void* rt_malloc_align	(	rt_size_t	size,
		rt_size_t	align
	)

This function allocates a memory block, which address is aligned to the specified alignment size.

Parameters

size	is the allocated memory block size.
align	is the alignment size.

Returns

The memory block address was returned successfully, otherwise it was returned empty RT_NULL.

rt_free_align()

void rt_free_align

(

void *

ptr

)

This function release the memory block, which is allocated by rt_malloc_align function and address is aligned.

Parameters

ptr	is the memory block pointer.

rt_memory_info()

void rt_memory_info	(	rt_size_t *	total,
		rt_size_t *	used,
		rt_size_t *	max_used
	)

This function will caculate the total memory, the used memory, and the max used memory.

Parameters

total	is a pointer to get the total size of the memory.
used	is a pointer to get the size of memory used.
max_used	is a pointer to get the maximum memory used.

rt_realloc_set_entry_hook()

void rt_realloc_set_entry_hook

(

void(*)(void **ptr, rt_size_t size)

hook

)

This function will set a hook function, which will be invoked when a memory block is allocated from heap memory.

Parameters

hook	the hook function.

rt_realloc_set_exit_hook()

void rt_realloc_set_exit_hook

(

void(*)(void **ptr, rt_size_t size)

hook

)

This function will set a hook function, which will be invoked when a memory block is allocated from heap memory.

Parameters

hook	the hook function.

rt_free_sethook()

void rt_free_sethook

(

void(*)(void **ptr)

hook

)

This function will set a hook function, which will be invoked when a memory block is released to heap memory.

Parameters

hook	the hook function

rt_smem_init()

rt_smem_t rt_smem_init	(	const char *	name,
		void *	begin_addr,
		rt_size_t	size
	)

This function will initialize small memory management algorithm.

small memory object interface

Parameters

name	is the name of the small memory management object.
begin_addr	the beginning address of memory.
size	is the size of the memory.

Returns

Return a pointer to the memory object. When the return value is RT_NULL, it means the init failed.

rt_smem_detach()

rt_err_t rt_smem_detach

(

rt_smem_t

m

)

This function will remove a small mem from the system.

Parameters

m	the small memory management object.

Returns

RT_EOK