2 * tc.alloc.c (Caltech) 2/21/82
3 * Chris Kingsley, kingsley@cit-20.
5 * This is a very fast storage allocator. It allocates blocks of a small
6 * number of different sizes, and keeps free lists of each size. Blocks that
7 * don't exactly fit are passed up to the next larger size. In this
8 * implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long.
9 * This is designed for use in a program that uses vast quantities of memory,
10 * but bombs when it runs out.
13 * Copyright (c) 1980, 1991 The Regents of the University of California.
14 * All rights reserved.
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
19 * 1. Redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer.
21 * 2. Redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution.
24 * 3. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
44 #if defined(HAVE_SBRK) && !defined(__APPLE__)
51 static char *memtop = NULL; /* PWP: top of current memory */
52 static char *membot = NULL; /* PWP: bottom of allocatable memory */
57 # define malloc fmalloc
59 # define calloc fcalloc
60 # define realloc frealloc
61 #endif /* WINNT_NATIVE */
63 #if !defined(DEBUG) || defined(SYSMALLOC)
67 static const char msg[] = "Out of memory\n";
69 TCSH_IGNORE(write(didfds ? 2 : SHDIAG, msg, strlen(msg)));
80 * Lots of os routines are busted and try to free invalid pointers.
81 * Although our free routine is smart enough and it will pick bad
82 * pointers most of the time, in cases where we know we are going to get
83 * a bad pointer, we'd rather leak.
90 typedef unsigned char U_char; /* we don't really have signed chars */
91 typedef unsigned int U_int;
92 typedef unsigned short U_short;
93 typedef unsigned long U_long;
97 * The overhead on a block is at least 4 bytes. When free, this space
98 * contains a pointer to the next free block, and the bottom two bits must
99 * be zero. When in use, the first byte is set to MAGIC, and the second
100 * byte is the size index. The remaining bytes are for alignment.
101 * If range checking is enabled and the size of the block fits
102 * in two bytes, then the top two bytes hold the size of the requested block
103 * plus the range checking words, and the header word MINUS ONE.
107 #define MEMALIGN(a) (((a) + ROUNDUP) & ~ROUNDUP)
110 union overhead *ov_next; /* when free */
112 U_char ovu_magic; /* magic number */
113 U_char ovu_index; /* bucket # */
115 U_short ovu_size; /* actual block size */
116 U_int ovu_rmagic; /* range magic number */
119 #define ov_magic ovu.ovu_magic
120 #define ov_index ovu.ovu_index
121 #define ov_size ovu.ovu_size
122 #define ov_rmagic ovu.ovu_rmagic
125 #define MAGIC 0xfd /* magic # on accounting info */
126 #define RMAGIC 0x55555555 /* magic # on range info */
128 #define RSLOP sizeof (U_int)
141 * nextf[i] is the pointer to the next free block of size 2^(i+3). The
142 * smallest allocatable block is 8 bytes. The overhead information
143 * precedes the data area returned to the user.
145 #define NBUCKETS ((sizeof(long) << 3) - 3)
146 static union overhead *nextf[NBUCKETS] IZERO_STRUCT;
149 * nmalloc[i] is the difference between the number of mallocs and frees
150 * for a given block size.
152 static U_int nmalloc[NBUCKETS] IZERO_STRUCT;
155 static int findbucket (union overhead *, int);
156 static void morecore (int);
161 # define CHECK(a, str, p) \
164 xprintf(" (memtop = %p membot = %p)\n", memtop, membot); \
168 # define CHECK(a, str, p) \
171 xprintf(" (memtop = %p membot = %p)\n", memtop, membot); \
177 malloc(size_t nbytes)
185 * Convert amount of memory requested into closest block size stored in
186 * hash buckets which satisfies request. Account for space used per block
191 * SunOS localtime() overwrites the 9th byte on an 8 byte malloc()....
192 * so we get one more...
193 * From Michael Schroeder: This is not true. It depends on the
194 * timezone string. In Europe it can overwrite the 13th byte on a
196 * So we punt and we always allocate an extra byte.
201 nbytes = MEMALIGN(MEMALIGN(sizeof(union overhead)) + nbytes + RSLOP);
202 shiftr = (nbytes - 1) >> 2;
204 /* apart from this loop, this is O(1) */
205 while ((shiftr >>= 1) != 0)
208 * If nothing in hash bucket right now, request more memory from the
211 if (nextf[bucket] == NULL)
213 if ((p = nextf[bucket]) == NULL) {
219 xprintf(CGETS(19, 1, "nbytes=%zu: Out of memory\n"), nbytes);
223 return ((memalign_t) 0);
225 /* remove from linked list */
226 nextf[bucket] = nextf[bucket]->ov_next;
228 p->ov_index = bucket;
232 * Record allocated size of block and bound space with magic numbers.
234 p->ov_size = (p->ov_index <= 13) ? (U_short)nbytes - 1 : 0;
235 p->ov_rmagic = RMAGIC;
236 *((U_int *) (((caddr_t) p) + nbytes - RSLOP)) = RMAGIC;
238 return ((memalign_t) (((caddr_t) p) + MEMALIGN(sizeof(union overhead))));
241 return ((memalign_t) 0);
243 return ((memalign_t) 0);
249 * Allocate more memory to the indicated bucket.
255 int rnu; /* 2^rnu bytes will be requested */
256 int nblks; /* become nblks blocks of the desired size */
262 * Insure memory is allocated on a page boundary. Should make getpageize
265 op = (union overhead *) sbrk(0);
266 memtop = (char *) op;
269 if ((long) op & 0x3ff) {
270 memtop = sbrk((int) (1024 - ((long) op & 0x3ff)));
271 memtop += (long) (1024 - ((long) op & 0x3ff));
274 /* take 2k unless the block is bigger than that */
275 rnu = (bucket <= 8) ? 11 : bucket + 3;
276 nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */
277 memtop = sbrk(1 << rnu); /* PWP */
278 op = (union overhead *) memtop;
282 memtop += (long) (1 << rnu);
284 * Round up to minimum allocation size boundary and deduct from block count
287 if (((U_long) op) & ROUNDUP) {
288 op = (union overhead *) (((U_long) op + (ROUNDUP + 1)) & ~ROUNDUP);
292 * Add new memory allocated to that on free list for this hash bucket.
295 siz = 1 << (bucket + 3);
296 while (--nblks > 0) {
297 op->ov_next = (union overhead *) (((caddr_t) op) + siz);
298 op = (union overhead *) (((caddr_t) op) + siz);
313 * the don't free flag is there so that we avoid os bugs in routines
314 * that free invalid pointers!
316 if (cp == NULL || dont_free)
318 CHECK(!memtop || !membot,
319 CGETS(19, 2, "free(%p) called before any allocations."), cp);
320 CHECK(cp > (ptr_t) memtop,
321 CGETS(19, 3, "free(%p) above top of memory."), cp);
322 CHECK(cp < (ptr_t) membot,
323 CGETS(19, 4, "free(%p) below bottom of memory."), cp);
324 op = (union overhead *) (((caddr_t) cp) - MEMALIGN(sizeof(union overhead)));
325 CHECK(op->ov_magic != MAGIC,
326 CGETS(19, 5, "free(%p) bad block."), cp);
329 if (op->ov_index <= 13)
330 CHECK(*(U_int *) ((caddr_t) op + op->ov_size + 1 - RSLOP) != RMAGIC,
331 CGETS(19, 6, "free(%p) bad range check."), cp);
333 CHECK(op->ov_index >= NBUCKETS,
334 CGETS(19, 7, "free(%p) bad block index."), cp);
336 op->ov_next = nextf[size];
348 calloc(size_t i, size_t j)
356 /* Stop gcc 5.x from optimizing malloc+memset = calloc */
360 return ((memalign_t) cp);
363 return ((memalign_t) 0);
365 return ((memalign_t) 0);
370 * When a program attempts "storage compaction" as mentioned in the
371 * old malloc man page, it realloc's an already freed block. Usually
372 * this is the last block it freed; occasionally it might be farther
373 * back. We have to search all the free lists for the block in order
374 * to determine its bucket: 1st we make one pass thru the lists
375 * checking only the first block in each; if that fails we search
376 * ``realloc_srchlen'' blocks in each list for a match (the variable
377 * is extern so the caller can modify it). If that fails we just copy
378 * however many bytes was given to realloc() and hope it's not huge.
381 /* 4 should be plenty, -1 =>'s whole list */
382 static int realloc_srchlen = 4;
386 realloc(ptr_t cp, size_t nbytes)
396 return (malloc(nbytes));
397 op = (union overhead *) (((caddr_t) cp) - MEMALIGN(sizeof(union overhead)));
398 if (op->ov_magic == MAGIC) {
404 * Already free, doing "compaction".
406 * Search for the old block of memory on the free list. First, check the
407 * most common case (last element free'd), then (this failing) the last
408 * ``realloc_srchlen'' items free'd. If all lookups fail, then assume
409 * the size of the memory block being realloc'd is the smallest
412 if ((i = findbucket(op, 1)) < 0 &&
413 (i = findbucket(op, realloc_srchlen)) < 0)
416 onb = MEMALIGN(nbytes + MEMALIGN(sizeof(union overhead)) + RSLOP);
418 /* avoid the copy if same size block */
419 if (was_alloced && (onb <= (U_int) (1 << (i + 3))) &&
420 (onb > (U_int) (1 << (i + 2)))) {
422 /* JMR: formerly this wasn't updated ! */
423 nbytes = MEMALIGN(MEMALIGN(sizeof(union overhead))+nbytes+RSLOP);
424 *((U_int *) (((caddr_t) op) + nbytes - RSLOP)) = RMAGIC;
425 op->ov_rmagic = RMAGIC;
426 op->ov_size = (op->ov_index <= 13) ? (U_short)nbytes - 1 : 0;
428 return ((memalign_t) cp);
430 if ((res = malloc(nbytes)) == NULL)
431 return ((memalign_t) NULL);
432 if (cp != res) { /* common optimization */
434 * christos: this used to copy nbytes! It should copy the
435 * smaller of the old and new size
437 onb = (1 << (i + 3)) - MEMALIGN(sizeof(union overhead)) - RSLOP;
438 (void) memmove(res, cp, onb < nbytes ? onb : nbytes);
442 return ((memalign_t) res);
445 return ((memalign_t) 0);
447 return ((memalign_t) 0);
452 * On linux, _nss_nis_setnetgrent() calls this function to determine
453 * the usable size of the pointer passed, but this is not a portable
454 * API, so we cannot use our malloc replacement without providing one.
455 * Thanks a lot glibc!
462 size_t malloc_usable_size(M_U_S_CONST void *);
464 malloc_usable_size(M_U_S_CONST void *ptr)
466 const union overhead *op = (const union overhead *)
467 (((const char *) ptr) - MEMALIGN(sizeof(*op)));
468 if (op->ov_magic == MAGIC)
469 return 1 << (op->ov_index + 3);
477 * Search ``srchlen'' elements of each free list for a block whose
478 * header starts at ``freep''. If srchlen is -1 search the whole list.
479 * Return bucket number, or -1 if not found.
482 findbucket(union overhead *freep, int srchlen)
488 for (i = 0; i < NBUCKETS; i++) {
490 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
502 #else /* SYSMALLOC */
505 ** ``Protected versions'' of malloc, realloc, calloc, and free
509 ** 1. malloc(0) is bad
511 ** 3. realloc(0, n) is bad
512 ** 4. realloc(n, 0) is bad
514 ** Also we call our error routine if we run out of memory.
526 #endif /* USE_SBRK */
528 if ((ptr = malloc(n)) == NULL)
531 if (memtop < ((char *) ptr) + n)
532 memtop = ((char *) ptr) + n;
535 #endif /* !USE_SBRK */
536 return ((memalign_t) ptr);
540 srealloc(ptr_t p, size_t n)
549 #endif /* USE_SBRK */
551 if ((ptr = (p ? realloc(p, n) : malloc(n))) == NULL)
554 if (memtop < ((char *) ptr) + n)
555 memtop = ((char *) ptr) + n;
558 #endif /* !USE_SBRK */
559 return ((memalign_t) ptr);
563 scalloc(size_t s, size_t n)
573 #endif /* USE_SBRK */
575 if ((ptr = malloc(n)) == NULL)
581 if (memtop < ((char *) ptr) + n)
582 memtop = ((char *) ptr) + n;
585 #endif /* !USE_SBRK */
587 return ((memalign_t) ptr);
597 #endif /* SYSMALLOC */
600 * mstats - print out statistics about malloc
602 * Prints two lines of numbers, one showing the length of the free list
603 * for each size category, the second showing the number of mallocs -
604 * frees for each size category.
608 showall(Char **v, struct command *c)
613 int totfree = 0, totused = 0;
615 xprintf(CGETS(19, 8, "%s current memory allocation:\nfree:\t"), progname);
616 for (i = 0; i < NBUCKETS; i++) {
617 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
620 totfree += j * (1 << (i + 3));
622 xprintf("\n%s:\t", CGETS(19, 9, "used"));
623 for (i = 0; i < NBUCKETS; i++) {
624 xprintf(" %4d", nmalloc[i]);
625 totused += nmalloc[i] * (1 << (i + 3));
627 xprintf(CGETS(19, 10, "\n\tTotal in use: %d, total free: %d\n"),
629 xprintf(CGETS(19, 11,
630 "\tAllocated memory from 0x%lx to 0x%lx. Real top at 0x%lx\n"),
631 (unsigned long) membot, (unsigned long) memtop,
632 (unsigned long) sbrk(0));
633 #else /* SYSMALLOC */
634 #ifndef HAVE_MALLINFO
637 #endif /* USE_SBRK */
638 xprintf(CGETS(19, 12, "Allocated memory from 0x%lx to 0x%lx (%ld).\n"),
639 (unsigned long) membot, (unsigned long) memtop,
640 (unsigned long) (memtop - membot));
641 #else /* HAVE_MALLINFO */
645 xprintf(CGETS(19, 13, "%s current memory allocation:\n"), progname);
646 xprintf(CGETS(19, 14, "Total space allocated from system: %d\n"), mi.arena);
647 xprintf(CGETS(19, 15, "Number of non-inuse chunks: %d\n"), mi.ordblks);
648 xprintf(CGETS(19, 16, "Number of mmapped regions: %d\n"), mi.hblks);
649 xprintf(CGETS(19, 17, "Total space in mmapped regions: %d\n"), mi.hblkhd);
650 xprintf(CGETS(19, 18, "Total allocated space: %d\n"), mi.uordblks);
651 xprintf(CGETS(19, 19, "Total non-inuse space: %d\n"), mi.fordblks);
652 xprintf(CGETS(19, 20, "Top-most, releasable space: %d\n"), mi.keepcost);
653 #endif /* HAVE_MALLINFO */
654 #endif /* SYSMALLOC */