mem-pool: add life cycle management functions

Add initialization and discard functions to mem_pool type. As the
memory allocated by mem_pool can now be freed, we also track the large
allocations.

If the there are existing mp_blocks in the mem_poo's linked list of
mp_blocksl, then the mp_block for a large allocation is inserted
behind the head block. This is because only the head mp_block is considered
when searching for availble space. This results in the following
desirable properties:

1) The mp_block allocated for the large request will not be included
not included in the search for available in future requests, the large
mp_block is sized for the specific request and does not contain any
spare space.

2) The head mp_block will not bumped from considation for future
memory requests just because a request for a large chunk of memory
came in.

These changes are in preparation for a future commit that will utilize
creating and discarding memory pool.

Signed-off-by: Jameson Miller <jamill@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jameson Miller 2018-07-02 19:49:34 +00:00 коммит произвёл Junio C Hamano
Родитель 8fb8e3f636
Коммит 158dfeff3d
2 изменённых файлов: 61 добавлений и 8 удалений

Просмотреть файл

@ -5,20 +5,65 @@
#include "cache.h"
#include "mem-pool.h"
static struct mp_block *mem_pool_alloc_block(struct mem_pool *mem_pool, size_t block_alloc)
#define BLOCK_GROWTH_SIZE 1024*1024 - sizeof(struct mp_block);
/*
* Allocate a new mp_block and insert it after the block specified in
* `insert_after`. If `insert_after` is NULL, then insert block at the
* head of the linked list.
*/
static struct mp_block *mem_pool_alloc_block(struct mem_pool *mem_pool, size_t block_alloc, struct mp_block *insert_after)
{
struct mp_block *p;
mem_pool->pool_alloc += sizeof(struct mp_block) + block_alloc;
p = xmalloc(st_add(sizeof(struct mp_block), block_alloc));
p->next_block = mem_pool->mp_block;
p->next_free = (char *)p->space;
p->end = p->next_free + block_alloc;
mem_pool->mp_block = p;
if (insert_after) {
p->next_block = insert_after->next_block;
insert_after->next_block = p;
} else {
p->next_block = mem_pool->mp_block;
mem_pool->mp_block = p;
}
return p;
}
void mem_pool_init(struct mem_pool **mem_pool, size_t initial_size)
{
struct mem_pool *pool;
if (*mem_pool)
return;
pool = xcalloc(1, sizeof(*pool));
pool->block_alloc = BLOCK_GROWTH_SIZE;
if (initial_size > 0)
mem_pool_alloc_block(pool, initial_size, NULL);
*mem_pool = pool;
}
void mem_pool_discard(struct mem_pool *mem_pool)
{
struct mp_block *block, *block_to_free;
while ((block = mem_pool->mp_block))
{
block_to_free = block;
block = block->next_block;
free(block_to_free);
}
free(mem_pool);
}
void *mem_pool_alloc(struct mem_pool *mem_pool, size_t len)
{
struct mp_block *p = NULL;
@ -33,12 +78,10 @@ void *mem_pool_alloc(struct mem_pool *mem_pool, size_t len)
p = mem_pool->mp_block;
if (!p) {
if (len >= (mem_pool->block_alloc / 2)) {
mem_pool->pool_alloc += len;
return xmalloc(len);
}
if (len >= (mem_pool->block_alloc / 2))
return mem_pool_alloc_block(mem_pool, len, mem_pool->mp_block);
p = mem_pool_alloc_block(mem_pool, mem_pool->block_alloc);
p = mem_pool_alloc_block(mem_pool, mem_pool->block_alloc, NULL);
}
r = p->next_free;

Просмотреть файл

@ -21,6 +21,16 @@ struct mem_pool {
size_t pool_alloc;
};
/*
* Initialize mem_pool with specified initial size.
*/
void mem_pool_init(struct mem_pool **mem_pool, size_t initial_size);
/*
* Discard a memory pool and free all the memory it is responsible for.
*/
void mem_pool_discard(struct mem_pool *mem_pool);
/*
* Alloc memory from the mem_pool.
*/