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memory pool 的高效實現(xiàn)（代碼）
     作者: 發(fā)表日期: 2009年10月23日 

http://nark.cc/p/?p=85

mpool.h

 

C++
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#ifndef __febird_c_mpool_h__
#define __febird_c_mpool_h__
#ifdef __cplusplus
extern "C" {
#endif
//------------------------------------------------------------------------------------------
typedef void* (*chunk_alloc_ft)(struct chunk_allocator* self, size_t size);
typedef void* (*chunk_realloc_ft)(struct chunk_allocator* self, void* block, size_t olc_size, size_t new_size);
typedef void  (*chunk_free_ft)(struct chunk_allocator* self, void* block, size_t size);
struct chunk_allocator
{
void* (*chunk_alloc)(struct chunk_allocator* self, size_t size);
void* (*chunk_realloc)(struct chunk_allocator* self, void* block, size_t olc_size, size_t new_size);
void  (*chunk_free)(struct chunk_allocator* self, void* block, size_t size);
};
struct fixed_mpool
{
struct chunk_allocator* ca;
struct mpool_chunk* pChunks;
struct mpool_cell*  head;
size_t iNextChunk;
size_t nChunks;
size_t cell_size;
size_t chunk_size;
size_t used_cells;
// size_t free_cells;
};
// 是否允許 mpool 分配超出 max_cell_size 的內(nèi)存塊
//#define FEBIRD_MPOOL_ALLOW_BIG_BLOCK
#ifdef FEBIRD_MPOOL_ALLOW_BIG_BLOCK
struct big_block_header
{
struct big_block_header *next, *prev;
};
#endif
struct mpool
{
//------------------------------------------------------------------------------------------
/// export a chunk_allocator interface
void* (*chunk_alloc)(struct chunk_allocator* self, size_t size);
void* (*chunk_realloc)(struct chunk_allocator* self, void* block, size_t olc_size, size_t new_size);
void  (*chunk_free)(struct chunk_allocator* self, void* block, size_t size);
//------------------------------------------------------------------------------------------
/// chunk_allocator for this mpool self
struct chunk_allocator* ca;
struct fixed_mpool* fixed;
size_t max_cell_size;
size_t chunk_size;
#ifdef FEBIRD_MPOOL_ALLOW_BIG_BLOCK
size_t big_blocks; // size > max_cell_size, use malloc, this is rare case
struct big_block_header big_list;
#endif
};
void fixed_mpool_init(struct fixed_mpool* mpf);
void fixed_mpool_destroy(struct fixed_mpool* mpf);
void* fixed_mpool_alloc(struct fixed_mpool* mpf);
void fixed_mpool_free(struct fixed_mpool* mpf, void* ptr);
void mpool_init(struct mpool* mp);
void mpool_destroy(struct mpool* mp);
void* mpool_alloc(struct mpool* mp, size_t size);
void mpool_free(struct mpool* mp, void* ptr, size_t size);
size_t mpool_used_cells(const struct mpool* mp);
size_t mpool_used_bytes(const struct mpool* mp);
#ifdef __cplusplus
}
#endif
#endif // __febird_c_mpool_h__

 

mpool.c

 

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#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "mpool.h"
/* must be power of 2 and greater than sizeof(void*) */
#define MPOOL_MIN_CELL 8
#define MPOOL_MIN_CHUNK 256
struct mpool_cell
{
struct mpool_cell* next;
};
struct mpool_chunk
{
struct mpool_cell* cell; // cell array
size_t size; // size in bytes;
};
/**********************************************************************************/
/**
* chunk_allocator use malloc/free
*/
static void*
chunk_malloc_alloc(struct chunk_allocator* , size_t size)
{
return malloc(size);
}
static void
chunk_malloc_free(struct chunk_allocator* , void* block, size_t size)
{
return free(block);
}
static void*
chunk_malloc_realloc(struct chunk_allocator* , void* block, size_t old_size, size_t new_size)
{
return realloc(block, new_size);
}
/**********************************************************************************/
void*
default_chunk_realloc(struct chunk_allocator* ca, void* ptr, size_t old_size, size_t new_size)
{
void* q = ca->chunk_alloc(ca, new_size);
assert(old_size > 0);
assert(new_size > 0);
if (NULL == q) return NULL;
memcpy(q, ptr, old_size < new_size ? old_size : new_size);
ca->chunk_free(ca, ptr, old_size);
return q;
}
static void
mpool_chunk_init(struct mpool_cell* cell, size_t cell_count, size_t cell_size)
{
size_t i;
struct mpool_cell* p = cell;
assert(cell_size % MPOOL_MIN_CELL == 0);
for (i = 0; i < cell_count-1; ++i)
p = p->next = (struct mpool_cell*)((char*)p + cell_size);
p->next = NULL;
}
/**********************************************************************************/
static struct chunk_allocator fal = {
&chunk_malloc_alloc,
&chunk_malloc_realloc,
&chunk_malloc_free
};
/**********************************************************************************/
/**
* require initialized fields:
* cell_size
* chunk_size
* ca [0 OR initialized]
*/
void fixed_mpool_init(struct fixed_mpool* mpf)
{
struct chunk_allocator* al;
if (NULL == mpf->ca)
al = mpf->ca = &fal;
else {
al = mpf->ca;
assert(NULL != al->chunk_alloc);
assert(NULL != al->chunk_free);
if (NULL == al->chunk_realloc)
al->chunk_realloc = &default_chunk_realloc;
}
assert(mpf->chunk_size > 0);
assert(mpf->cell_size > 0);
assert(mpf->cell_size < mpf->chunk_size);
mpf->cell_size = (mpf->cell_size + MPOOL_MIN_CELL - 1) / MPOOL_MIN_CELL * MPOOL_MIN_CELL;
mpf->chunk_size = (mpf->chunk_size + MPOOL_MIN_CHUNK - 1) / MPOOL_MIN_CHUNK * MPOOL_MIN_CHUNK;
mpf->head = NULL;
if (mpf->nChunks < MPOOL_MIN_CHUNK/sizeof(struct mpool_chunk))
mpf->nChunks = MPOOL_MIN_CHUNK/sizeof(struct mpool_chunk);
mpf->iNextChunk = 0;
mpf->pChunks = (struct mpool_chunk*)
al->chunk_alloc(al, sizeof(struct mpool_chunk) * mpf->nChunks);
if (NULL == mpf->pChunks) {
fprintf(stderr
, "fatal: febird.fixed_mpool_init failed, chunk[size=%zd, count=%zd]/n"
, mpf->chunk_size, mpf->nChunks);
abort();
}
mpf->used_cells = 0;
}
void fixed_mpool_destroy(struct fixed_mpool* mpf)
{
struct chunk_allocator* ca = mpf->ca;
long i;
for (i = mpf->iNextChunk - 1; i >= 0; --i)
ca->chunk_free(ca, mpf->pChunks[i].cell, mpf->pChunks[i].size);
ca->chunk_free(ca, mpf->pChunks, sizeof(struct mpool_chunk) * mpf->nChunks);
}
// 0 success, -1 fail
int fixed_mpool_add_chunk(struct fixed_mpool* mpf)
{
struct mpool_cell* cell;
assert(mpf->pChunks != NULL);
if (mpf->iNextChunk == mpf->nChunks) {
size_t old_size = sizeof(struct mpool_chunk) * mpf->nChunks;
size_t new_size = 2 * old_size;
// allocate new chunk array
struct mpool_chunk* c = (struct mpool_chunk*)
mpf->ca->chunk_realloc(mpf->ca, mpf->pChunks, old_size, new_size);
if (NULL == c) return -1;
mpf->pChunks = c;
mpf->nChunks *= 2;     // chunk array expanded 2
mpf->chunk_size *= 2;  // chunk_size  expanded 2 also
}
// allocate a new cell array
cell = (struct mpool_cell*)mpf->ca->chunk_alloc(mpf->ca, mpf->chunk_size);
if (NULL == cell) return -1;
mpf->pChunks[mpf->iNextChunk].cell = cell;
mpf->pChunks[mpf->iNextChunk].size = mpf->chunk_size;
mpf->iNextChunk++;
mpool_chunk_init(cell, mpf->chunk_size / mpf->cell_size, mpf->cell_size);
mpf->head = cell;
return 0;
}
void* fixed_mpool_alloc(struct fixed_mpool* mpf)
{
struct mpool_cell* cell;
if (NULL == mpf->head) {
// in most case it will not run this path
if (fixed_mpool_add_chunk(mpf) != 0)
return NULL;
}
cell = mpf->head;
mpf->used_cells++;
mpf->head = mpf->head->next;
return cell;
}
void fixed_mpool_free(struct fixed_mpool* mpf, void* ptr)
{
struct mpool_cell* cell = (struct mpool_cell*)ptr;
cell->next = mpf->head;
mpf->used_cells--;
mpf->head = cell;
}
/**********************************************************************************/
/**
* require initialized fields:
*   max_cell_size
* chunk_size
* ca [0 OR initialized]
*/
void mpool_init(struct mpool* mp)
{
int i, nFixed;
struct chunk_allocator* al;
assert(mp->max_cell_size < mp->chunk_size);
if (NULL == mp->chunk_alloc)
al = mp->ca = &fal;
else {
al = mp->ca;
assert(NULL != al->chunk_alloc);
assert(NULL != al->chunk_free);
if (NULL == al->chunk_realloc)
al->chunk_realloc = &default_chunk_realloc;
}
mp->chunk_alloc = (chunk_alloc_ft)&mpool_alloc;
mp->chunk_free = (chunk_free_ft)&mpool_free;
mp->chunk_realloc = (chunk_realloc_ft)&default_chunk_realloc;
mp->max_cell_size = (mp->max_cell_size + MPOOL_MIN_CELL - 1) / MPOOL_MIN_CELL * MPOOL_MIN_CELL;
mp->chunk_size = (mp->chunk_size + MPOOL_MIN_CHUNK - 1) / MPOOL_MIN_CHUNK * MPOOL_MIN_CHUNK;
nFixed = mp->max_cell_size / MPOOL_MIN_CELL;
mp->fixed = (struct fixed_mpool*)al->chunk_alloc(al, sizeof(struct fixed_mpool) * nFixed);
if (NULL == mp->fixed) {
fprintf(stderr, "fatal: febird.mpool_init[max_cell_size=%zd, chunk_size=%zd]/n"
, mp->max_cell_size, mp->chunk_size);
abort();
}
for (i = 0; i < nFixed; ++i)
{
mp->fixed[i].cell_size = (i + 1) * MPOOL_MIN_CELL;
mp->fixed[i].chunk_size = mp->chunk_size;
mp->fixed[i].nChunks = 16;
mp->fixed[i].ca = mp->ca;
fixed_mpool_init(&mp->fixed[i]);
}
#ifdef FEBIRD_MPOOL_ALLOW_BIG_BLOCK
mp->big_blocks = 0;
mp->big_list.prev = mp->big_list.next = &mp->big_list;
#endif
}
void mpool_destroy(struct mpool* mp)
{
size_t i, nFixed;
#ifdef FEBIRD_MPOOL_ALLOW_BIG_BLOCK
struct big_block_header *p;
for (i = 0, p = mp->big_list.next; p != &mp->big_list; ++i)
{
struct big_block_header *q;
if (i > mp->big_blocks) {
fprintf(stderr, "fatal: febird.mpool_destroy/n");
abort();
}
q = p->next;
free(p);
p = q;
}
assert(i == mp->big_blocks);
#endif
nFixed = mp->max_cell_size / MPOOL_MIN_CELL;
for (i = 0; i < nFixed; ++i)
{
fixed_mpool_destroy(&mp->fixed[i]);
}
mp->ca->chunk_free(mp->ca, mp->fixed, sizeof(struct fixed_mpool) * nFixed);
}
void* mpool_alloc(struct mpool* mp, size_t size)
{
size_t idx;
struct fixed_mpool* mpf;
struct mpool_cell* cell;
#ifdef FEBIRD_MPOOL_ALLOW_BIG_BLOCK
if (size > mp->max_cell_size) {
// this is rare case
struct big_block_header *p, *h;
p = (struct big_block_header*)malloc(sizeof(struct big_block_header) + size);
if (p) {
h = &mp->big_list;
p->prev = h;
p->next = h->next;
h->next->prev = p;
h->next = p;
mp->big_blocks++;
return (p + 1);
} else
return NULL;
}
#else
assert(size <= mp->max_cell_size);
#endif
assert(size > 0);
idx = (size - 1) / MPOOL_MIN_CELL;
mpf = &mp->fixed[idx];
// same as fixed_mpool_alloc....
if (NULL == mpf->head) {
// in most case it will not run this path
if (fixed_mpool_add_chunk(mpf) != 0)
return NULL;
}
cell = mpf->head;
mpf->used_cells++;
mpf->head = mpf->head->next;
return cell;
}
void mpool_free(struct mpool* mp, void* ptr, size_t size)
{
size_t idx;
struct fixed_mpool* mpf;
struct mpool_cell* cell;
#ifdef FEBIRD_MPOOL_ALLOW_BIG_BLOCK
if (size > mp->max_cell_size) {
// this is rare case
struct big_block_header* bbh = (struct big_block_header*)ptr - 1;
bbh->prev->next = bbh->next;
bbh->next->prev = bbh->prev;
free(bbh);
mp->big_blocks--;
return;
}
#else
assert(size <= mp->max_cell_size);
#endif
assert(size > 0);
idx = (size - 1) / MPOOL_MIN_CELL;
mpf = &mp->fixed[idx];
// same as fixed_mpool_free...
cell = (struct mpool_cell*)ptr;
cell->next = mpf->head;
mpf->used_cells--;
mpf->head = cell;
}
size_t mpool_used_cells(const struct mpool* mp)
{
size_t i, n = mp->max_cell_size / MPOOL_MIN_CELL;
size_t used = 0;
for (i = 0; i < n; ++i)
used += mp->fixed[i].used_cells;
return used;
}
size_t mpool_used_bytes(const struct mpool* mp)
{
size_t i, n = mp->max_cell_size / MPOOL_MIN_CELL;
size_t used = 0;
for (i = 0; i < n; ++i)
used += mp->fixed[i].cell_size * mp->fixed[i].used_cells;
return used;
}

  

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