2 * Copyright (c) 1983 Regents of the University of California.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 #if defined(LIBC_SCCS) && !defined(lint)
35 /*static char *sccsid = "from: @(#)malloc.c 5.11 (Berkeley) 2/23/91";*/
36 static char *rcsid = "$FreeBSD$";
37 #endif /* LIBC_SCCS and not lint */
40 * malloc.c (Caltech) 2/21/82
41 * Chris Kingsley, kingsley@cit-20.
43 * This is a very fast storage allocator. It allocates blocks of a small
44 * number of different sizes, and keeps free lists of each size. Blocks that
45 * don't exactly fit are passed up to the next larger size. In this
46 * implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long.
47 * This is designed for use in a virtual memory environment.
50 #include <sys/types.h>
56 #include <sys/param.h>
59 #define MAP_COPY MAP_PRIVATE
64 #ifndef BSD /* Need do better than this */
65 #define NEED_DEV_ZERO 1
70 static void morecore();
71 static int findbucket();
74 * Pre-allocate mmap'ed pages
76 #define NPOOLPAGES (32*1024/pagesz)
77 static caddr_t pagepool_start, pagepool_end;
78 static int morepages();
81 * The overhead on a block is at least 4 bytes. When free, this space
82 * contains a pointer to the next free block, and the bottom two bits must
83 * be zero. When in use, the first byte is set to MAGIC, and the second
84 * byte is the size index. The remaining bytes are for alignment.
85 * If range checking is enabled then a second word holds the size of the
86 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
87 * The order of elements is critical: ov_magic must overlay the low order
88 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
91 union overhead *ov_next; /* when free */
93 u_char ovu_magic; /* magic number */
94 u_char ovu_index; /* bucket # */
96 u_short ovu_rmagic; /* range magic number */
97 u_int ovu_size; /* actual block size */
100 #define ov_magic ovu.ovu_magic
101 #define ov_index ovu.ovu_index
102 #define ov_rmagic ovu.ovu_rmagic
103 #define ov_size ovu.ovu_size
106 #define MAGIC 0xef /* magic # on accounting info */
107 #define RMAGIC 0x5555 /* magic # on range info */
110 #define RSLOP sizeof (u_short)
116 * nextf[i] is the pointer to the next free block of size 2^(i+3). The
117 * smallest allocatable block is 8 bytes. The overhead information
118 * precedes the data area returned to the user.
121 static union overhead *nextf[NBUCKETS];
123 static int pagesz; /* page size */
124 static int pagebucket; /* page size bucket */
128 * nmalloc[i] is the difference between the number of mallocs and frees
129 * for a given block size.
131 static u_int nmalloc[NBUCKETS];
135 #if defined(MALLOC_DEBUG) || defined(RCHECK)
136 #define ASSERT(p) if (!(p)) botch("p")
142 fprintf(stderr, "\r\nassertion botched: %s\r\n", s);
143 (void) fflush(stderr); /* just in case user buffered it */
150 /* Debugging stuff */
151 extern void xprintf(const char *, ...);
152 #define TRACE() xprintf("TRACE %s:%d\n", __FILE__, __LINE__)
158 register union overhead *op;
161 register unsigned amt;
164 * First time malloc is called, setup page size and
165 * align break pointer so all data will be page aligned.
168 pagesz = n = getpagesize();
169 if (morepages(NPOOLPAGES) == 0)
171 op = (union overhead *)(pagepool_start);
172 n = n - sizeof (*op) - ((long)op & (n - 1));
180 while (pagesz > amt) {
187 * Convert amount of memory requested into closest block size
188 * stored in hash buckets which satisfies request.
189 * Account for space used per block for accounting.
191 if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) {
193 amt = 8; /* size of first bucket */
196 amt = 16; /* size of first bucket */
199 n = -(sizeof (*op) + RSLOP);
204 while (nbytes > amt + n) {
211 * If nothing in hash bucket right now,
212 * request more memory from the system.
214 if ((op = nextf[bucket]) == NULL) {
216 if ((op = nextf[bucket]) == NULL)
219 /* remove from linked list */
220 nextf[bucket] = op->ov_next;
221 op->ov_magic = MAGIC;
222 op->ov_index = bucket;
228 * Record allocated size of block and
229 * bound space with magic numbers.
231 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
232 op->ov_rmagic = RMAGIC;
233 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
235 return ((char *)(op + 1));
239 * Allocate more memory to the indicated bucket.
245 register union overhead *op;
246 register int sz; /* size of desired block */
247 int amt; /* amount to allocate */
248 int nblks; /* how many blocks we get */
251 * sbrk_size <= 0 only for big, FLUFFY, requests (about
252 * 2^30 bytes on a VAX, I think) or for a negative arg.
254 sz = 1 << (bucket + 3);
268 if (amt > pagepool_end - pagepool_start)
269 if (morepages(amt/pagesz + NPOOLPAGES) == 0)
271 op = (union overhead *)pagepool_start;
272 pagepool_start += amt;
275 * Add new memory allocated to that on
276 * free list for this hash bucket.
279 while (--nblks > 0) {
280 op->ov_next = (union overhead *)((caddr_t)op + sz);
281 op = (union overhead *)((caddr_t)op + sz);
290 register union overhead *op;
294 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
296 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
298 if (op->ov_magic != MAGIC)
302 ASSERT(op->ov_rmagic == RMAGIC);
303 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
306 ASSERT(size < NBUCKETS);
307 op->ov_next = nextf[size]; /* also clobbers ov_magic */
315 * When a program attempts "storage compaction" as mentioned in the
316 * old malloc man page, it realloc's an already freed block. Usually
317 * this is the last block it freed; occasionally it might be farther
318 * back. We have to search all the free lists for the block in order
319 * to determine its bucket: 1st we make one pass thru the lists
320 * checking only the first block in each; if that fails we search
321 * ``realloc_srchlen'' blocks in each list for a match (the variable
322 * is extern so the caller can modify it). If that fails we just copy
323 * however many bytes was given to realloc() and hope it's not huge.
325 int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
339 return (malloc(nbytes));
340 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
341 if (op->ov_magic == MAGIC) {
346 * Already free, doing "compaction".
348 * Search for the old block of memory on the
349 * free list. First, check the most common
350 * case (last element free'd), then (this failing)
351 * the last ``realloc_srchlen'' items free'd.
352 * If all lookups fail, then assume the size of
353 * the memory block being realloc'd is the
354 * largest possible (so that all "nbytes" of new
355 * memory are copied into). Note that this could cause
356 * a memory fault if the old area was tiny, and the moon
357 * is gibbous. However, that is very unlikely.
359 if ((i = findbucket(op, 1)) < 0 &&
360 (i = findbucket(op, realloc_srchlen)) < 0)
365 onb -= sizeof (*op) + RSLOP;
367 onb += pagesz - sizeof (*op) - RSLOP;
368 /* avoid the copy if same size block */
373 i -= sizeof (*op) + RSLOP;
375 i += pagesz - sizeof (*op) - RSLOP;
377 if (nbytes <= onb && nbytes > i) {
379 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
380 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
386 if ((res = malloc(nbytes)) == NULL)
388 if (cp != res) /* common optimization if "compacting" */
389 bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
394 * Search ``srchlen'' elements of each free list for a block whose
395 * header starts at ``freep''. If srchlen is -1 search the whole list.
396 * Return bucket number, or -1 if not found.
399 findbucket(freep, srchlen)
400 union overhead *freep;
403 register union overhead *p;
406 for (i = 0; i < NBUCKETS; i++) {
408 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
419 * mstats - print out statistics about malloc
421 * Prints two lines of numbers, one showing the length of the free list
422 * for each size category, the second showing the number of mallocs -
423 * frees for each size category.
429 register union overhead *p;
433 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
434 for (i = 0; i < NBUCKETS; i++) {
435 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
437 fprintf(stderr, " %d", j);
438 totfree += j * (1 << (i + 3));
440 fprintf(stderr, "\nused:\t");
441 for (i = 0; i < NBUCKETS; i++) {
442 fprintf(stderr, " %d", nmalloc[i]);
443 totused += nmalloc[i] * (1 << (i + 3));
445 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
459 fd = open(_PATH_DEVZERO, O_RDWR, 0);
461 perror(_PATH_DEVZERO);
464 if (pagepool_end - pagepool_start > pagesz) {
465 caddr_t addr = (caddr_t)
466 (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1));
467 if (munmap(addr, pagepool_end - addr) != 0)
468 warn("morepages: munmap %p", addr);
471 offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1));
473 if ((pagepool_start = mmap(0, n * pagesz,
474 PROT_READ|PROT_WRITE,
475 MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) {
476 xprintf("Cannot map anonymous memory");
479 pagepool_end = pagepool_start + n * pagesz;
480 pagepool_start += offset;