内存池,简单的讲就是,内存不由系统管理,而由应用程序自己或另行委托第三者管理的内存空间。通俗点说就是,所谓内存池就是应用程序从系统那里批发来的内存空间。对于使用量较大且需要频繁申请和释放内存的应用程序来说,使用内存池会减少运行时间,而对于系统来讲,批发内存可以有效减少零售所带来的内存
内存池的结构体定义:
内存池的流程
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 | #include <stdlib.h> #include <stdio.h> #include <string.h> #include <unistd.h> #include <fcntl.h> #define MP_ALIGNMENT 32 #define MP_PAGE_SIZE 4096 #define MP_MAX_ALLOC_FROM_POOL (MP_PAGE_SIZE-1) #define mp_align(n, alignment) (((n)+(alignment-1)) & ~(alignment-1)) #define mp_align_ptr(p, alignment) (void *)((((size_t)p)+(alignment-1)) & ~(alignment-1)) struct mp_large_s { struct mp_large_s *next; void *alloc; }; struct mp_node_s { unsigned char *last; unsigned char *end; struct mp_node_s *next; size_t failed; }; struct mp_pool_s { size_t max; struct mp_node_s *current; struct mp_large_s *large; struct mp_node_s head[0]; }; struct mp_pool_s *mp_create_pool(size_t size); void mp_destory_pool(struct mp_pool_s *pool); void *mp_alloc(struct mp_pool_s *pool, size_t size); void *mp_nalloc(struct mp_pool_s *pool, size_t size); void *mp_calloc(struct mp_pool_s *pool, size_t size); void mp_free(struct mp_pool_s *pool, void *p); struct mp_pool_s *mp_create_pool(size_t size) { struct mp_pool_s *p; int ret = posix_memalign((void **)&p, MP_ALIGNMENT, size + sizeof(struct mp_pool_s) + sizeof(struct mp_node_s)); if (ret) { return NULL; } p->max = (size < MP_MAX_ALLOC_FROM_POOL) ? size : MP_MAX_ALLOC_FROM_POOL; p->current = p->head; p->large = NULL; p->head->last = (unsigned char *)p + sizeof(struct mp_pool_s) + sizeof(struct mp_node_s); p->head->end = p->head->last + size; p->head->failed = 0; return p; } void mp_destory_pool(struct mp_pool_s *pool) { struct mp_node_s *h, *n; struct mp_large_s *l; for (l = pool->large; l; l = l->next) { if (l->alloc) { free(l->alloc); } } h = pool->head->next; while (h) { n = h->next; free(h); h = n; } free(pool); } void mp_reset_pool(struct mp_pool_s *pool) { struct mp_node_s *h; struct mp_large_s *l; for (l = pool->large; l; l = l->next) { if (l->alloc) { free(l->alloc); } } pool->large = NULL; for (h = pool->head; h; h = h->next) { h->last = (unsigned char *)h + sizeof(struct mp_node_s); } } static void *mp_alloc_block(struct mp_pool_s *pool, size_t size) { unsigned char *m; struct mp_node_s *h = pool->head; size_t psize = (size_t)(h->end - (unsigned char *)h); int ret = posix_memalign((void **)&m, MP_ALIGNMENT, psize); if (ret) return NULL; struct mp_node_s *p, *new_node, *current; new_node = (struct mp_node_s*)m; new_node->end = m + psize; new_node->next = NULL; new_node->failed = 0; m += sizeof(struct mp_node_s); m = mp_align_ptr(m, MP_ALIGNMENT); new_node->last = m + size; current = pool->current; for (p = current; p->next; p = p->next) { if (p->failed++ > 4) { current = p->next; } } p->next = new_node; pool->current = current ? current : new_node; return m; } static void *mp_alloc_large(struct mp_pool_s *pool, size_t size) { void *p = malloc(size); if (p == NULL) return NULL; size_t n = 0; struct mp_large_s *large; for (large = pool->large; large; large = large->next) { if (large->alloc == NULL) { large->alloc = p; return p; } if (n ++ > 3) break; } large = mp_alloc(pool, sizeof(struct mp_large_s)); if (large == NULL) { free(p); return NULL; } large->alloc = p; large->next = pool->large; pool->large = large; return p; } void *mp_memalign(struct mp_pool_s *pool, size_t size, size_t alignment) { void *p; int ret = posix_memalign(&p, alignment, size); if (ret) { return NULL; } struct mp_large_s *large = mp_alloc(pool, sizeof(struct mp_large_s)); if (large == NULL) { free(p); return NULL; } large->alloc = p; large->next = pool->large; pool->large = large; return p; } void *mp_alloc(struct mp_pool_s *pool, size_t size) { unsigned char *m; struct mp_node_s *p; if (size <= pool->max) { p = pool->current; do { m = mp_align_ptr(p->last, MP_ALIGNMENT); if ((size_t)(p->end - m) >= size) { p->last = m + size; return m; } p = p->next; } while (p); return mp_alloc_block(pool, size); } return mp_alloc_large(pool, size); } void *mp_nalloc(struct mp_pool_s *pool, size_t size) { unsigned char *m; struct mp_node_s *p; if (size <= pool->max) { p = pool->current; do { m = p->last; if ((size_t)(p->end - m) >= size) { p->last = m+size; return m; } p = p->next; } while (p); return mp_alloc_block(pool, size); } return mp_alloc_large(pool, size); } void *mp_calloc(struct mp_pool_s *pool, size_t size) { void *p = mp_alloc(pool, size); if (p) { memset(p, 0, size); } return p; } void mp_free(struct mp_pool_s *pool, void *p) { struct mp_large_s *l; for (l = pool->large; l; l = l->next) { if (p == l->alloc) { free(l->alloc); l->alloc = NULL; return ; } } } int main(int argc, char *argv[]) { int size = 1 << 12; struct mp_pool_s *p = mp_create_pool(size); int i = 0; for (i = 0;i < 10;i ++) { void *mp = mp_alloc(p, 512); // mp_free(mp); } //printf("mp_create_pool: %ld\n", p->max); printf("mp_align(123, 32): %d, mp_align(17, 32): %d\n", mp_align(24, 32), mp_align(17, 32)); //printf("mp_align_ptr(p->current, 32): %lx, p->current: %lx, mp_align(p->large, 32): %lx, p->large: %lx\n", mp_align_ptr(p->current, 32), p->current, mp_align_ptr(p->large, 32), p->large); int j = 0; for (i = 0;i < 5;i ++) { char *pp = mp_calloc(p, 32); for (j = 0;j < 32;j ++) { if (pp[j]) { printf("calloc wrong\n"); } printf("calloc success\n"); } } //printf("mp_reset_pool\n"); for (i = 0;i < 5;i ++) { void *l = mp_alloc(p, 8192); mp_free(p, l); } mp_reset_pool(p); //printf("mp_destory_pool\n"); for (i = 0;i < 58;i ++) { mp_alloc(p, 256); } mp_destory_pool(p); return 0; } |