Memory Management
[RT-Thread Kernel API]

Functions
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_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_mp_alloc_sethook (void(*hook)(void *block))
void	rt_mp_free_sethook (void(*hook)(void *block))
void *	rt_malloc (rt_size_t nbytes)
void	rt_free (void *ptr)
void *	rt_realloc (void *ptr, rt_size_t nbytes)
void	rt_free_sethook (void(*hook)(void *ptr))
void *	rt_calloc (rt_size_t count, rt_size_t size)

---

Detailed Description

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.

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Function Documentation

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.

The allocated memory is filled with bytes of value zero.

Parameters:

	count	number of objects to allocate
	size	size of the objects to allocate

Returns:

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

void rt_free

(

void *

rmem

)

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

Parameters:

rmem

the address of memory which will be released

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

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:

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

void * rt_mp_alloc	(	rt_mp_t	mp,
		rt_int32_t	time
	)

This function will allocate a block from memory pool

Parameters:

	mp	the memory pool object
	time	the waiting time

Returns:

the allocated memory block

void rt_mp_alloc_sethook

(

void(*)(void *block)

hook

)

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

Parameters:

hook

the hook function

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

Returns:

the created mempool object

rt_err_t rt_mp_delete

(

rt_mp_t

mp

)

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

Parameters:

mp

the memory pool object

Returns:

the operation status, RT_EOK on OK; -RT_ERROR on error

void rt_mp_free

(

void *

block

)

This function will release a memory block

Parameters:

block

the address of memory block to be released

void rt_mp_free_sethook

(

void(*)(void *block)

hook

)

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

Parameters:

hook

the hook function

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 mempool object, normally which is used for static object.

Parameters:

	mp	the mempool object
	name	the name of memory pool
	start	the star address of memory pool
	size	the total size of memory pool
	block_size	the size for each block

Returns:

the operation status, RT_EOK on OK; RT_ERROR on error

void * rt_realloc	(	void *	rmem,
		rt_size_t	newsize
	)

This function will change the previously allocated memory block.

Parameters:

	rmem	pointer to memory allocated by rt_malloc
	newsize	the required new size

Returns:

the changed memory block address