Start
[exim.git] / src / src / store.c
CommitLineData
059ec3d9
PH
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
11implementation there was a lot of mallocing and freeing of small bits of store.
12The 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
14need to do any garbage collection, but the stack concept allows quick resetting
15in places where this seems sensible.
16
17Obviously the long-running processes (the daemon, the queue runner, and eximon)
18must take care not to eat store.
19
20The 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
47how to get an alignment factor in general. In the current world, a value of 8
48is 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
50is a constant, the compiler should optimize it to a simple constant wherever it
51appears (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
57must be a multiple of the alignment. We assume that 8192 is going to be
58suitably aligned. */
59
60#define STORE_BLOCK_SIZE 8192
61
62/* store_reset() will not free the following block if the last used block has
63less than this much left in it. */
64
65#define STOREPOOL_MIN_SIZE 256
66
67/* Structure describing the beginning of each big block. */
68
69typedef 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
75length that is not a multiple of the alignment, set up a macro for the padded
76length. */
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
82is held in store_pool, which is global so that it can be changed from outside.
83Setting the initial length values to -1 forces a malloc for the first call,
84even if the length is zero (which is used for getting a point to reset to). */
85
86int store_pool = POOL_PERM;
87
88static storeblock *chainbase[3] = { NULL, NULL, NULL };
89static storeblock *current_block[3] = { NULL, NULL, NULL };
90static void *next_yield[3] = { NULL, NULL, NULL };
91static int yield_length[3] = { -1, -1, -1 };
92
93/* pool_malloc holds the amount of memory used by the store pools; this goes up
94and down as store is reset or released. nonpool_malloc is the total got by
95malloc from other calls; this doesn't go down because it is just freed by
96pointer. */
97
98static int pool_malloc = 0;
99static int nonpool_malloc = 0;
100
101/* This variable is set by store_get() to its yield, and by store_reset() to
102NULL. This enables string_cat() to optimize its store handling for very long
103strings. That's why the variable is global. */
104
105void *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
114macro store_get(). It passes back a block of store within the current big
115block, getting a new one if necessary. The address is saved in
116store_last_was_get.
117
118Arguments:
119 size amount wanted
120 filename source file from which called
121 linenumber line number in source file.
122
123Returns: pointer to store (panic on malloc failure)
124*/
125
126void *
127store_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
130messy statement, because "alignment" is a constant expression, the compiler can
131do a reasonable job of optimizing, especially if the value of "alignment" is a
132power of two. I checked this with -O2, and gcc did very well, compiling it to 4
133instructions on a Sparc (alignment = 8). */
134
135if (size % alignment != 0) size += alignment - (size % alignment);
136
137/* If there isn't room in the current block, get a new one. The minimum
138size is STORE_BLOCK_SIZE, and we would expect this to be the norm, since
139these functions are mostly called for small amounts of store. */
140
141if (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
181pointer. */
182
183store_last_get[store_pool] = next_yield[store_pool];
184
185/* Cut out the debugging stuff for utilities, but stop picky compilers from
186giving warnings. */
187
188#ifdef COMPILE_UTILITY
189filename = filename;
190linenumber = linenumber;
191#else
192DEBUG(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
204next_yield[store_pool] = (void *)((char *)next_yield[store_pool] + size);
205yield_length[store_pool] -= size;
206
207return 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
217be obtained.
218
219Arguments:
220 size amount wanted
221 filename source file from which called
222 linenumber line number in source file.
223
224Returns: pointer to store (panic on malloc failure)
225*/
226
227void *
228store_get_perm_3(int size, const char *filename, int linenumber)
229{
230void *yield;
231int old_pool = store_pool;
232store_pool = POOL_PERM;
233yield = store_get_3(size, filename, linenumber);
234store_pool = old_pool;
235return 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
245string is being read into the block at the top of the stack. If it needs to be
246extended, it is more efficient just to extend the top block rather than
247allocate a new block and then have to copy the data. This function is provided
248for the use of string_cat(), but of course can be used elsewhere too.
249
250Arguments:
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
257Returns: 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
262BOOL
263store_extend_3(void *ptr, int oldsize, int newsize, const char *filename,
264 int linenumber)
265{
266int inc = newsize - oldsize;
267int rounded_oldsize = oldsize;
268
269if (rounded_oldsize % alignment != 0)
270 rounded_oldsize += alignment - (rounded_oldsize % alignment);
271
272if ((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
277giving warnings. */
278
279#ifdef COMPILE_UTILITY
280filename = filename;
281linenumber = linenumber;
282#else
283DEBUG(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
293if (newsize % alignment != 0) newsize += alignment - (newsize % alignment);
294next_yield[store_pool] = (char *)ptr + newsize;
295yield_length[store_pool] -= newsize - rounded_oldsize;
296return 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
307that are now unused. Normally it is given a pointer that was the yield of a
308call to store_get, and is therefore aligned, but it may be given an offset
309after such a pointer in order to release the end of a block and anything that
310follows.
311
312Arguments:
313 ptr place to back up to
314 filename source file from which called
315 linenumber line number in source file
316
317Returns: nothing
318*/
319
320void
321store_reset_3(void *ptr, const char *filename, int linenumber)
322{
323storeblock *bb;
324storeblock *b = current_block[store_pool];
325char *bc = (char *)b + ALIGNED_SIZEOF_STOREBLOCK;
326int newlength;
327
328/* Last store operation was not a get */
329
330store_last_get[store_pool] = NULL;
331
332/* See if the place is in the current block - as it often will be. Otherwise,
333search for the block in which it lies. */
334
335if ((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
348the released memory. */
349
350newlength = bc + b->length - (char *)ptr;
351#ifndef COMPILE_UTILITY
352if (running_in_test_harness) memset(ptr, 0xF0, newlength);
353#endif
354yield_length[store_pool] = newlength - (newlength % alignment);
355next_yield[store_pool] = (char *)ptr + (newlength % alignment);
356current_block[store_pool] = b;
357
358/* Free any subsequent block. Do NOT free the first successor, if our
359current block has less than 256 bytes left. This should prevent us from
360flapping memory. However, keep this block only when it has the default size. */
361
362if (yield_length[store_pool] < STOREPOOL_MIN_SIZE &&
363 b->next != NULL &&
364 b->next->length == STORE_BLOCK_SIZE)
365 b = b->next;
366
367bb = b->next;
368b->next = NULL;
369
370while (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
379giving warnings. */
380
381#ifdef COMPILE_UTILITY
382filename = filename;
383linenumber = linenumber;
384#else
385DEBUG(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
405long strings, e.g. header lines. When the string gets longer than a
406complete block, it gets copied to a new block. It is helpful to free
407the old block iff the previous copy of the string is at its start,
408and therefore the only thing in it. Otherwise, for very long strings,
409dead store can pile up somewhat disastrously. This function checks that
410the pointer it is given is the first thing in a block, and if so,
411releases that block.
412
413Arguments:
414 block block of store to consider
415 filename source file from which called
416 linenumber line number in source file
417
418Returns: nothing
419*/
420
421void
422store_release_3(void *block, const char *filename, int linenumber)
423{
424storeblock *b;
425
426/* It will never be the first block, so no need to check that. */
427
428for (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
469do not run happily on very small sizes, nor do they document this fact. This
470function is called via the macro store_malloc().
471
472Arguments:
473 size amount of store wanted
474 filename source file from which called
475 linenumber line number in source file
476
477Returns: pointer to gotten store (panic on failure)
478*/
479
480void *
481store_malloc_3(int size, const char *filename, int linenumber)
482{
483void *yield;
484
485if (size < 16) size = 16;
486yield = malloc((size_t)size);
487
488if (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
492nonpool_malloc += size;
493
494/* Cut out the debugging stuff for utilities, but stop picky compilers from
495giving warnings. */
496
497#ifdef COMPILE_UTILITY
498filename = filename;
499linenumber = linenumber;
500#else
501
502/* If running in test harness, spend time making sure all the new store
503is not filled with zeros so as to catch problems. */
504
505if (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 }
511else
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
518return yield;
519}
520
521
522/************************************************
523* Free store *
524************************************************/
525
526/* This function is called by the macro store_free().
527
528Arguments:
529 block block of store to free
530 filename source file from which called
531 linenumber line number in source file
532
533Returns: nothing
534*/
535
536void
537store_free_3(void *block, const char *filename, int linenumber)
538{
539#ifdef COMPILE_UTILITY
540filename = filename;
541linenumber = linenumber;
542#else
543DEBUG(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 */
551free(block);
552}
553
554/* End of store.c */