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memheap: dont alloc/memcpy when there is next node is enough for realloc 

When realloc a bigger space and the next node is free and big enough, we
should directly relocate the next node instead of doing alloc/memcpy.
The new method not only faster in this cases, it would avoid memory
fragment as well.
This commit is contained in:
Grissiom 2013-07-15 11:29:58 +08:00
parent f0f0e3dd9e
commit c3a39444da
1 changed files with 91 additions and 0 deletions
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91
src/memheap.c
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@ -26,6 +26,7 @@
* 2013-04-10 Bernard add rt_memheap_realloc function.
* 2013-05-24 Bernard fix the rt_memheap_realloc issue.
* 2013-07-11 Grissiom fix the memory block splitting issue.
* 2013-07-15 Grissiom optimize rt_memheap_realloc
*/
#include <rthw.h>
@ -318,6 +319,96 @@ void *rt_memheap_realloc(struct rt_memheap *heap, void *ptr, rt_size_t newsize)
if (newsize > oldsize)
{
void* new_ptr;
struct rt_memheap_item *next_ptr;
/* lock memheap */
result = rt_sem_take(&(heap->lock), RT_WAITING_FOREVER);
if (result != RT_EOK)
{
rt_set_errno(result);
return RT_NULL;
}
next_ptr = header_ptr->next;
/* header_ptr should not be the tail */
RT_ASSERT(next_ptr > header_ptr);
/* check whether the following free space is enough to expand */
if (!RT_MEMHEAP_IS_USED(next_ptr))
{
rt_int32_t nextsize;
nextsize = MEMITEM_SIZE(next_ptr);
RT_ASSERT(next_ptr > 0);
/* Here is the ASCII art of the situation that we can make use of
* the next free node without alloc/memcpy, |*| is the control
* block:
*
* oldsize free node
* |*|-----------|*|----------------------|*|
* newsize >= minialloc
* |*|----------------|*|-----------------|*|
*/
if (nextsize + oldsize > newsize + RT_MEMHEAP_MINIALLOC)
{
/* decrement the entire free size from the available bytes count. */
heap->available_size = heap->available_size - (newsize - oldsize);
if (heap->pool_size - heap->available_size > heap->max_used_size)
heap->max_used_size = heap->pool_size - heap->available_size;
/* remove next_ptr from free list */
RT_DEBUG_LOG(RT_DEBUG_MEMHEAP,
("remove block: block[0x%08x], next_free 0x%08x, prev_free 0x%08x",
next_ptr,
next_ptr->next_free,
next_ptr->prev_free));
next_ptr->next_free->prev_free = next_ptr->prev_free;
next_ptr->prev_free->next_free = next_ptr->next_free;
next_ptr->next->prev = next_ptr->prev;
next_ptr->prev->next = next_ptr->next;
/* build a new one on the right place */
next_ptr = (struct rt_memheap_item*)((char*)ptr + newsize);
RT_DEBUG_LOG(RT_DEBUG_MEMHEAP,
("new free block: block[0x%08x] nextm[0x%08x] prevm[0x%08x]",
next_ptr,
next_ptr->next,
next_ptr->prev));
/* mark the new block as a memory block and freed. */
next_ptr->magic = RT_MEMHEAP_MAGIC;
/* put the pool pointer into the new block. */
next_ptr->pool_ptr = heap;
next_ptr->prev = header_ptr;
next_ptr->next = header_ptr->next;
header_ptr->next->prev = next_ptr;
header_ptr->next = next_ptr;
/* insert next_ptr to free list */
next_ptr->next_free = heap->free_list->next_free;
next_ptr->prev_free = heap->free_list;
heap->free_list->next_free->prev_free = next_ptr;
heap->free_list->next_free = next_ptr;
RT_DEBUG_LOG(RT_DEBUG_MEMHEAP, ("new ptr: next_free 0x%08x, prev_free 0x%08x",
next_ptr->next_free,
next_ptr->prev_free));
/* release lock */
rt_sem_release(&(heap->lock));
return ptr;
}
}
/* release lock */
rt_sem_release(&(heap->lock));
/* re-allocate a memory block */
new_ptr = (void*)rt_memheap_alloc(heap, newsize);
if (new_ptr != RT_NULL)