src/src/store.c

   1 /* $Cambridge: exim/src/src/store.c,v 1.1 2004/10/07 10:39:01 ph10 Exp $ */
   2
   3 /*************************************************
   4 *     Exim - an Internet mail transport agent    *
   5 *************************************************/
   6
   7 /* Copyright (c) University of Cambridge 1995 - 2004 */
   8 /* See the file NOTICE for conditions of use and distribution. */
   9
  10 /* Exim gets and frees all its store through these functions. In the original
  11 implementation there was a lot of mallocing and freeing of small bits of store.
  12 The philosophy has now changed to a scheme which includes the concept of
  13 "stacking pools" of store. For the short-lived processes, there isn't any real
  14 need to do any garbage collection, but the stack concept allows quick resetting
  15 in places where this seems sensible.
  16
  17 Obviously the long-running processes (the daemon, the queue runner, and eximon)
  18 must take care not to eat store.
  19
  20 The following different types of store are recognized:
  21
  22 . Long-lived, large blocks: This is implemented by retaining the original
  23   malloc/free functions, and it used for permanent working buffers and for
  24   getting blocks to cut up for the other types.
  25
  26 . Long-lived, small blocks: This is used for blocks that have to survive until
  27   the process exits. It is implemented as a stacking pool (POOL_PERM). This is
  28   functionally the same as store_malloc(), except that the store can't be
  29   freed, but I expect it to be more efficient for handling small blocks.
  30
  31 . Short-lived, short blocks: Most of the dynamic store falls into this
  32   category. It is implemented as a stacking pool (POOL_MAIN) which is reset
  33   after accepting a message when multiple messages are received by a single
  34   process. Resetting happens at some other times as well, usually fairly
  35   locally after some specific processing that needs working store.
  36
  37 . There is a separate pool (POOL_SEARCH) that is used only for lookup storage.
  38   This means it can be freed when search_tidyup() is called to close down all
  39   the lookup caching.
  40 */
  41
  42
  43 #include "exim.h"
  44
  45
  46 /* We need to know how to align blocks of data for general use. I'm not sure
  47 how to get an alignment factor in general. In the current world, a value of 8
  48 is probably right, and this is sizeof(double) on some systems and sizeof(void
  49 *) on others, so take the larger of those. Since everything in this expression
  50 is a constant, the compiler should optimize it to a simple constant wherever it
  51 appears (I checked that gcc does do this). */
  52
  53 #define alignment \
  54   ((sizeof(void *) > sizeof(double))? sizeof(void *) : sizeof(double))
  55
  56 /* Size of block to get from malloc to carve up into smaller ones. This
  57 must be a multiple of the alignment. We assume that 8192 is going to be
  58 suitably aligned. */
  59
  60 #define STORE_BLOCK_SIZE 8192
  61
  62 /* store_reset() will not free the following block if the last used block has
  63 less than this much left in it. */
  64
  65 #define STOREPOOL_MIN_SIZE 256
  66
  67 /* Structure describing the beginning of each big block. */
  68
  69 typedef struct storeblock {
  70   struct storeblock *next;
  71   size_t length;
  72 } storeblock;
  73
  74 /* Just in case we find ourselves on a system where the structure above has a
  75 length that is not a multiple of the alignment, set up a macro for the padded
  76 length. */
  77
  78 #define ALIGNED_SIZEOF_STOREBLOCK \
  79   (((sizeof(storeblock) + alignment - 1) / alignment) * alignment)
  80
  81 /* Variables holding data for the local pools of store. The current pool number
  82 is held in store_pool, which is global so that it can be changed from outside.
  83 Setting the initial length values to -1 forces a malloc for the first call,
  84 even if the length is zero (which is used for getting a point to reset to). */
  85
  86 int store_pool = POOL_PERM;
  87
  88 static storeblock *chainbase[3] = { NULL, NULL, NULL };
  89 static storeblock *current_block[3] = { NULL, NULL, NULL };
  90 static void *next_yield[3] = { NULL, NULL, NULL };
  91 static int yield_length[3] = { -1, -1, -1 };
  92
  93 /* pool_malloc holds the amount of memory used by the store pools; this goes up
  94 and down as store is reset or released. nonpool_malloc is the total got by
  95 malloc from other calls; this doesn't go down because it is just freed by
  96 pointer. */
  97
  98 static int pool_malloc = 0;
  99 static int nonpool_malloc = 0;
 100
 101 /* This variable is set by store_get() to its yield, and by store_reset() to
 102 NULL. This enables string_cat() to optimize its store handling for very long
 103 strings. That's why the variable is global. */
 104
 105 void *store_last_get[3] = { NULL, NULL, NULL };
 106
 107
 108
 109 /*************************************************
 110 *       Get a block from the current pool        *
 111 *************************************************/
 112
 113 /* Running out of store is a total disaster. This function is called via the
 114 macro store_get(). It passes back a block of store within the current big
 115 block, getting a new one if necessary. The address is saved in
 116 store_last_was_get.
 117
 118 Arguments:
 119   size        amount wanted
 120   filename    source file from which called
 121   linenumber  line number in source file.
 122
 123 Returns:      pointer to store (panic on malloc failure)
 124 */
 125
 126 void *
 127 store_get_3(int size, const char *filename, int linenumber)
 128 {
 129 /* Round up the size to a multiple of the alignment. Although this looks a
 130 messy statement, because "alignment" is a constant expression, the compiler can
 131 do a reasonable job of optimizing, especially if the value of "alignment" is a
 132 power of two. I checked this with -O2, and gcc did very well, compiling it to 4
 133 instructions on a Sparc (alignment = 8). */
 134
 135 if (size % alignment != 0) size += alignment - (size % alignment);
 136
 137 /* If there isn't room in the current block, get a new one. The minimum
 138 size is STORE_BLOCK_SIZE, and we would expect this to be the norm, since
 139 these functions are mostly called for small amounts of store. */
 140
 141 if (size > yield_length[store_pool])
 142   {
 143   int length = (size <= STORE_BLOCK_SIZE)? STORE_BLOCK_SIZE : size;
 144   int mlength = length + ALIGNED_SIZEOF_STOREBLOCK;
 145   storeblock *newblock = NULL;
 146
 147   /* Sometimes store_reset() may leave a block for us; check if we can use it */
 148
 149   if (current_block[store_pool] != NULL &&
 150       current_block[store_pool]->next != NULL)
 151     {
 152     newblock = current_block[store_pool]->next;
 153     if (newblock->length < length)
 154       {
 155       /* Give up on this block, because it's too small */
 156       store_free(newblock);
 157       newblock = NULL;
 158       }
 159     }
 160
 161   /* If there was no free block, get a new one */
 162
 163   if (newblock == NULL)
 164     {
 165     pool_malloc += mlength;           /* Used in pools */
 166     nonpool_malloc -= mlength;        /* Exclude from overall total */
 167     newblock = store_malloc(mlength);
 168     newblock->next = NULL;
 169     newblock->length = length;
 170     if (chainbase[store_pool] == NULL) chainbase[store_pool] = newblock;
 171       else current_block[store_pool]->next = newblock;
 172     }
 173
 174   current_block[store_pool] = newblock;
 175   yield_length[store_pool] = newblock->length;
 176   next_yield[store_pool] =
 177     (void *)((char *)current_block[store_pool] + ALIGNED_SIZEOF_STOREBLOCK);
 178   }
 179
 180 /* There's (now) enough room in the current block; the yield is the next
 181 pointer. */
 182
 183 store_last_get[store_pool] = next_yield[store_pool];
 184
 185 /* Cut out the debugging stuff for utilities, but stop picky compilers from
 186 giving warnings. */
 187
 188 #ifdef COMPILE_UTILITY
 189 filename = filename;
 190 linenumber = linenumber;
 191 #else
 192 DEBUG(D_memory)
 193   {
 194   if (running_in_test_harness)
 195     debug_printf("---%d Get %5d\n", store_pool, size);
 196   else
 197     debug_printf("---%d Get %6p %5d %-14s %4d\n", store_pool,
 198       store_last_get[store_pool], size, filename, linenumber);
 199   }
 200 #endif  /* COMPILE_UTILITY */
 201
 202 /* Update next pointer and number of bytes left in the current block. */
 203
 204 next_yield[store_pool] = (void *)((char *)next_yield[store_pool] + size);
 205 yield_length[store_pool] -= size;
 206
 207 return store_last_get[store_pool];
 208 }
 209
 210
 211
 212 /*************************************************
 213 *       Get a block from the PERM pool           *
 214 *************************************************/
 215
 216 /* This is just a convenience function, useful when just a single block is to
 217 be obtained.
 218
 219 Arguments:
 220   size        amount wanted
 221   filename    source file from which called
 222   linenumber  line number in source file.
 223
 224 Returns:      pointer to store (panic on malloc failure)
 225 */
 226
 227 void *
 228 store_get_perm_3(int size, const char *filename, int linenumber)
 229 {
 230 void *yield;
 231 int old_pool = store_pool;
 232 store_pool = POOL_PERM;
 233 yield = store_get_3(size, filename, linenumber);
 234 store_pool = old_pool;
 235 return yield;
 236 }
 237
 238
 239
 240 /*************************************************
 241 *      Extend a block if it is at the top        *
 242 *************************************************/
 243
 244 /* While reading strings of unknown length, it is often the case that the
 245 string is being read into the block at the top of the stack. If it needs to be
 246 extended, it is more efficient just to extend the top block rather than
 247 allocate a new block and then have to copy the data. This function is provided
 248 for the use of string_cat(), but of course can be used elsewhere too.
 249
 250 Arguments:
 251   ptr        pointer to store block
 252   oldsize    current size of the block, as requested by user
 253   newsize    new size required
 254   filename   source file from which called
 255   linenumber line number in source file
 256
 257 Returns:     TRUE if the block is at the top of the stack and has been
 258              extended; FALSE if it isn't at the top of the stack, or cannot
 259              be extended
 260 */
 261
 262 BOOL
 263 store_extend_3(void *ptr, int oldsize, int newsize, const char *filename,
 264   int linenumber)
 265 {
 266 int inc = newsize - oldsize;
 267 int rounded_oldsize = oldsize;
 268
 269 if (rounded_oldsize % alignment != 0)
 270   rounded_oldsize += alignment - (rounded_oldsize % alignment);
 271
 272 if ((char *)ptr + rounded_oldsize != (char *)(next_yield[store_pool]) ||
 273     inc > yield_length[store_pool] + rounded_oldsize - oldsize)
 274   return FALSE;
 275
 276 /* Cut out the debugging stuff for utilities, but stop picky compilers from
 277 giving warnings. */
 278
 279 #ifdef COMPILE_UTILITY
 280 filename = filename;
 281 linenumber = linenumber;
 282 #else
 283 DEBUG(D_memory)
 284   {
 285   if (running_in_test_harness)
 286     debug_printf("---%d Ext %5d\n", store_pool, newsize);
 287   else
 288     debug_printf("---%d Ext %6p %5d %-14s %4d\n", store_pool, ptr, newsize,
 289       filename, linenumber);
 290   }
 291 #endif  /* COMPILE_UTILITY */
 292
 293 if (newsize % alignment != 0) newsize += alignment - (newsize % alignment);
 294 next_yield[store_pool] = (char *)ptr + newsize;
 295 yield_length[store_pool] -= newsize - rounded_oldsize;
 296 return TRUE;
 297 }
 298
 299
 300
 301
 302 /*************************************************
 303 *    Back up to a previous point on the stack    *
 304 *************************************************/
 305
 306 /* This function resets the next pointer, freeing any subsequent whole blocks
 307 that are now unused. Normally it is given a pointer that was the yield of a
 308 call to store_get, and is therefore aligned, but it may be given an offset
 309 after such a pointer in order to release the end of a block and anything that
 310 follows.
 311
 312 Arguments:
 313   ptr         place to back up to
 314   filename    source file from which called
 315   linenumber  line number in source file
 316
 317 Returns:      nothing
 318 */
 319
 320 void
 321 store_reset_3(void *ptr, const char *filename, int linenumber)
 322 {
 323 storeblock *bb;
 324 storeblock *b = current_block[store_pool];
 325 char *bc = (char *)b + ALIGNED_SIZEOF_STOREBLOCK;
 326 int newlength;
 327
 328 /* Last store operation was not a get */
 329
 330 store_last_get[store_pool] = NULL;
 331
 332 /* See if the place is in the current block - as it often will be. Otherwise,
 333 search for the block in which it lies. */
 334
 335 if ((char *)ptr < bc || (char *)ptr > bc + b->length)
 336   {
 337   for (b = chainbase[store_pool]; b != NULL; b = b->next)
 338     {
 339     bc = (char *)b + ALIGNED_SIZEOF_STOREBLOCK;
 340     if ((char *)ptr >= bc && (char *)ptr <= bc + b->length) break;
 341     }
 342   if (b == NULL)
 343     log_write(0, LOG_MAIN|LOG_PANIC_DIE, "internal error: store_reset(%d) "
 344       "failed: pool=%d %-14s %4d", ptr, store_pool, filename, linenumber);
 345   }
 346
 347 /* Back up, rounding to the alignment if necessary. When testing, flatten
 348 the released memory. */
 349
 350 newlength = bc + b->length - (char *)ptr;
 351 #ifndef COMPILE_UTILITY
 352 if (running_in_test_harness) memset(ptr, 0xF0, newlength);
 353 #endif
 354 yield_length[store_pool] = newlength - (newlength % alignment);
 355 next_yield[store_pool] = (char *)ptr + (newlength % alignment);
 356 current_block[store_pool] = b;
 357
 358 /* Free any subsequent block. Do NOT free the first successor, if our
 359 current block has less than 256 bytes left. This should prevent us from
 360 flapping memory. However, keep this block only when it has the default size. */
 361
 362 if (yield_length[store_pool] < STOREPOOL_MIN_SIZE &&
 363     b->next != NULL &&
 364     b->next->length == STORE_BLOCK_SIZE)
 365   b = b->next;
 366
 367 bb = b->next;
 368 b->next = NULL;
 369
 370 while (bb != NULL)
 371   {
 372   b = bb;
 373   bb = bb->next;
 374   pool_malloc -= b->length + ALIGNED_SIZEOF_STOREBLOCK;
 375   store_free_3(b, filename, linenumber);
 376   }
 377
 378 /* Cut out the debugging stuff for utilities, but stop picky compilers from
 379 giving warnings. */
 380
 381 #ifdef COMPILE_UTILITY
 382 filename = filename;
 383 linenumber = linenumber;
 384 #else
 385 DEBUG(D_memory)
 386   {
 387   if (running_in_test_harness)
 388     debug_printf("---%d Rst    ** %d\n", store_pool, pool_malloc);
 389   else
 390     debug_printf("---%d Rst %6p    ** %-14s %4d %d\n", store_pool, ptr,
 391       filename, linenumber, pool_malloc);
 392   }
 393 #endif  /* COMPILE_UTILITY */
 394 }
 395
 396
 397
 398
 399
 400 /************************************************
 401 *             Release store                     *
 402 ************************************************/
 403
 404 /* This function is specifically provided for use when reading very
 405 long strings, e.g. header lines. When the string gets longer than a
 406 complete block, it gets copied to a new block. It is helpful to free
 407 the old block iff the previous copy of the string is at its start,
 408 and therefore the only thing in it. Otherwise, for very long strings,
 409 dead store can pile up somewhat disastrously. This function checks that
 410 the pointer it is given is the first thing in a block, and if so,
 411 releases that block.
 412
 413 Arguments:
 414   block       block of store to consider
 415   filename    source file from which called
 416   linenumber  line number in source file
 417
 418 Returns:      nothing
 419 */
 420
 421 void
 422 store_release_3(void *block, const char *filename, int linenumber)
 423 {
 424 storeblock *b;
 425
 426 /* It will never be the first block, so no need to check that. */
 427
 428 for (b = chainbase[store_pool]; b != NULL; b = b->next)
 429   {
 430   storeblock *bb = b->next;
 431   if (bb != NULL && (char *)block == (char *)bb + ALIGNED_SIZEOF_STOREBLOCK)
 432     {
 433     b->next = bb->next;
 434     pool_malloc -= bb->length + ALIGNED_SIZEOF_STOREBLOCK;
 435
 436     /* Cut out the debugging stuff for utilities, but stop picky compilers
 437     from giving warnings. */
 438
 439     #ifdef COMPILE_UTILITY
 440     filename = filename;
 441     linenumber = linenumber;
 442     #else
 443     DEBUG(D_memory)
 444       {
 445       if (running_in_test_harness)
 446         debug_printf("-Release       %d\n", pool_malloc);
 447       else
 448         debug_printf("-Release %6p %-20s %4d %d\n", (void *)bb, filename,
 449           linenumber, pool_malloc);
 450       }
 451     if (running_in_test_harness)
 452       memset(bb, 0xF0, bb->length+ALIGNED_SIZEOF_STOREBLOCK);
 453     #endif  /* COMPILE_UTILITY */
 454
 455     free(bb);
 456     return;
 457     }
 458   }
 459 }
 460
 461
 462
 463
 464 /*************************************************
 465 *                Malloc store                    *
 466 *************************************************/
 467
 468 /* Running out of store is a total disaster for exim. Some malloc functions
 469 do not run happily on very small sizes, nor do they document this fact. This
 470 function is called via the macro store_malloc().
 471
 472 Arguments:
 473   size        amount of store wanted
 474   filename    source file from which called
 475   linenumber  line number in source file
 476
 477 Returns:      pointer to gotten store (panic on failure)
 478 */
 479
 480 void *
 481 store_malloc_3(int size, const char *filename, int linenumber)
 482 {
 483 void *yield;
 484
 485 if (size < 16) size = 16;
 486 yield = malloc((size_t)size);
 487
 488 if (yield == NULL)
 489   log_write(0, LOG_MAIN|LOG_PANIC_DIE, "failed to malloc %d bytes of memory: "
 490     "called from line %d of %s", size, linenumber, filename);
 491
 492 nonpool_malloc += size;
 493
 494 /* Cut out the debugging stuff for utilities, but stop picky compilers from
 495 giving warnings. */
 496
 497 #ifdef COMPILE_UTILITY
 498 filename = filename;
 499 linenumber = linenumber;
 500 #else
 501
 502 /* If running in test harness, spend time making sure all the new store
 503 is not filled with zeros so as to catch problems. */
 504
 505 if (running_in_test_harness)
 506   {
 507   memset(yield, 0xF0, (size_t)size);
 508   DEBUG(D_memory) debug_printf("--Malloc %5d %d %d\n", size, pool_malloc,
 509     nonpool_malloc);
 510   }
 511 else
 512   {
 513   DEBUG(D_memory) debug_printf("--Malloc %6p %5d %-14s %4d %d %d\n", yield,
 514     size, filename, linenumber, pool_malloc, nonpool_malloc);
 515   }
 516 #endif  /* COMPILE_UTILITY */
 517
 518 return yield;
 519 }
 520
 521
 522 /************************************************
 523 *             Free store                        *
 524 ************************************************/
 525
 526 /* This function is called by the macro store_free().
 527
 528 Arguments:
 529   block       block of store to free
 530   filename    source file from which called
 531   linenumber  line number in source file
 532
 533 Returns:      nothing
 534 */
 535
 536 void
 537 store_free_3(void *block, const char *filename, int linenumber)
 538 {
 539 #ifdef COMPILE_UTILITY
 540 filename = filename;
 541 linenumber = linenumber;
 542 #else
 543 DEBUG(D_memory)
 544   {
 545   if (running_in_test_harness)
 546     debug_printf("----Free\n");
 547   else
 548     debug_printf("----Free %6p %-20s %4d\n", block, filename, linenumber);
 549   }
 550 #endif  /* COMPILE_UTILITY */
 551 free(block);
 552 }
 553
 554 /* End of store.c */