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b79f4fa9 DF |
1 | /* |
2 | * Copyright (c) 1980 Regents of the University of California. | |
3 | * All rights reserved. The Berkeley software License Agreement | |
4 | * specifies the terms and conditions for redistribution. | |
5 | */ | |
6 | ||
3fb44be6 | 7 | #ifndef lint |
e15a1cd8 | 8 | static char sccsid[] = "@(#)alloc.c 5.2 (Berkeley) %G%"; |
b79f4fa9 | 9 | #endif not lint |
3fb44be6 KL |
10 | |
11 | /* | |
12 | * malloc.c (Caltech) 2/21/82 | |
13 | * Chris Kingsley, kingsley@cit-20. | |
14 | * | |
15 | * This is a very fast storage allocator. It allocates blocks of a small | |
16 | * number of different sizes, and keeps free lists of each size. Blocks that | |
17 | * don't exactly fit are passed up to the next larger size. In this | |
18 | * implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long. | |
19 | * This is designed for use in a program that uses vast quantities of memory, | |
20 | * but bombs when it runs out. | |
21 | */ | |
22 | ||
23 | #include <sys/types.h> | |
24 | ||
25 | #define NULL 0 | |
26 | ||
27 | /* | |
28 | * The overhead on a block is at least 4 bytes. When free, this space | |
29 | * contains a pointer to the next free block, and the bottom two bits must | |
30 | * be zero. When in use, the first byte is set to MAGIC, and the second | |
31 | * byte is the size index. The remaining bytes are for alignment. | |
32 | * If range checking is enabled and the size of the block fits | |
33 | * in two bytes, then the top two bytes hold the size of the requested block | |
34 | * plus the range checking words, and the header word MINUS ONE. | |
35 | */ | |
36 | union overhead { | |
37 | union overhead *ov_next; /* when free */ | |
38 | struct { | |
39 | u_char ovu_magic; /* magic number */ | |
40 | u_char ovu_index; /* bucket # */ | |
41 | #ifdef RCHECK | |
42 | u_short ovu_size; /* actual block size */ | |
43 | u_int ovu_rmagic; /* range magic number */ | |
44 | #endif | |
45 | } ovu; | |
46 | #define ov_magic ovu.ovu_magic | |
47 | #define ov_index ovu.ovu_index | |
48 | #define ov_size ovu.ovu_size | |
49 | #define ov_rmagic ovu.ovu_rmagic | |
50 | }; | |
51 | ||
52 | #define MAGIC 0xff /* magic # on accounting info */ | |
53 | #define RMAGIC 0x55555555 /* magic # on range info */ | |
54 | #ifdef RCHECK | |
55 | #define RSLOP sizeof (u_int) | |
56 | #else | |
57 | #define RSLOP 0 | |
58 | #endif | |
59 | ||
60 | /* | |
61 | * nextf[i] is the pointer to the next free block of size 2^(i+3). The | |
62 | * smallest allocatable block is 8 bytes. The overhead information | |
63 | * precedes the data area returned to the user. | |
64 | */ | |
65 | #define NBUCKETS 30 | |
66 | static union overhead *nextf[NBUCKETS]; | |
67 | extern char *sbrk(); | |
68 | ||
3fb44be6 KL |
69 | /* |
70 | * nmalloc[i] is the difference between the number of mallocs and frees | |
71 | * for a given block size. | |
72 | */ | |
73 | static u_int nmalloc[NBUCKETS]; | |
fc71ebc6 | 74 | |
fc71ebc6 | 75 | #ifdef debug |
3fb44be6 KL |
76 | #define ASSERT(p) if (!(p)) botch("p"); else |
77 | static | |
fc71ebc6 BJ |
78 | botch(s) |
79 | char *s; | |
80 | { | |
81 | printf("assertion botched: %s\n",s); | |
82 | abort(); | |
83 | } | |
84 | #else | |
3fb44be6 | 85 | #define ASSERT(p) |
fc71ebc6 BJ |
86 | #endif |
87 | ||
fc71ebc6 BJ |
88 | char * |
89 | malloc(nbytes) | |
3fb44be6 | 90 | register unsigned nbytes; |
fc71ebc6 | 91 | { |
3fb44be6 KL |
92 | register union overhead *p; |
93 | register int bucket = 0; | |
94 | register unsigned shiftr; | |
95 | ||
96 | /* | |
97 | * Convert amount of memory requested into | |
98 | * closest block size stored in hash buckets | |
99 | * which satisfies request. Account for | |
100 | * space used per block for accounting. | |
101 | */ | |
102 | nbytes += sizeof (union overhead) + RSLOP; | |
103 | nbytes = (nbytes + 3) &~ 3; | |
104 | shiftr = (nbytes - 1) >> 2; | |
105 | /* apart from this loop, this is O(1) */ | |
106 | while (shiftr >>= 1) | |
107 | bucket++; | |
108 | /* | |
109 | * If nothing in hash bucket right now, | |
110 | * request more memory from the system. | |
111 | */ | |
112 | if (nextf[bucket] == NULL) | |
113 | morecore(bucket); | |
114 | if ((p = (union overhead *)nextf[bucket]) == NULL) | |
115 | return (NULL); | |
116 | /* remove from linked list */ | |
117 | nextf[bucket] = nextf[bucket]->ov_next; | |
118 | p->ov_magic = MAGIC; | |
119 | p->ov_index= bucket; | |
3fb44be6 | 120 | nmalloc[bucket]++; |
3fb44be6 KL |
121 | #ifdef RCHECK |
122 | /* | |
123 | * Record allocated size of block and | |
124 | * bound space with magic numbers. | |
125 | */ | |
126 | if (nbytes <= 0x10000) | |
127 | p->ov_size = nbytes - 1; | |
128 | p->ov_rmagic = RMAGIC; | |
129 | *((u_int *)((caddr_t)p + nbytes - RSLOP)) = RMAGIC; | |
130 | #endif | |
131 | return ((char *)(p + 1)); | |
fc71ebc6 BJ |
132 | } |
133 | ||
3fb44be6 KL |
134 | /* |
135 | * Allocate more memory to the indicated bucket. | |
136 | */ | |
137 | static | |
138 | morecore(bucket) | |
139 | register bucket; | |
fc71ebc6 | 140 | { |
3fb44be6 KL |
141 | register union overhead *op; |
142 | register int rnu; /* 2^rnu bytes will be requested */ | |
143 | register int nblks; /* become nblks blocks of the desired size */ | |
144 | register int siz; | |
145 | ||
146 | if (nextf[bucket]) | |
147 | return; | |
148 | /* | |
149 | * Insure memory is allocated | |
150 | * on a page boundary. Should | |
151 | * make getpageize call? | |
152 | */ | |
153 | op = (union overhead *)sbrk(0); | |
154 | if ((int)op & 0x3ff) | |
35371dec | 155 | (void) sbrk(1024 - ((int)op & 0x3ff)); |
3fb44be6 KL |
156 | /* take 2k unless the block is bigger than that */ |
157 | rnu = (bucket <= 8) ? 11 : bucket + 3; | |
158 | nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */ | |
159 | if (rnu < bucket) | |
160 | rnu = bucket; | |
161 | op = (union overhead *)sbrk(1 << rnu); | |
162 | /* no more room! */ | |
163 | if ((int)op == -1) | |
164 | return; | |
165 | /* | |
166 | * Round up to minimum allocation size boundary | |
167 | * and deduct from block count to reflect. | |
168 | */ | |
169 | if ((int)op & 7) { | |
170 | op = (union overhead *)(((int)op + 8) &~ 7); | |
171 | nblks--; | |
172 | } | |
173 | /* | |
174 | * Add new memory allocated to that on | |
175 | * free list for this hash bucket. | |
176 | */ | |
177 | nextf[bucket] = op; | |
178 | siz = 1 << (bucket + 3); | |
179 | while (--nblks > 0) { | |
180 | op->ov_next = (union overhead *)((caddr_t)op + siz); | |
181 | op = (union overhead *)((caddr_t)op + siz); | |
182 | } | |
fc71ebc6 BJ |
183 | } |
184 | ||
3fb44be6 KL |
185 | free(cp) |
186 | char *cp; | |
187 | { | |
188 | register int size; | |
189 | register union overhead *op; | |
fc71ebc6 | 190 | |
3fb44be6 KL |
191 | if (cp == NULL) |
192 | return; | |
193 | op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); | |
194 | ||
195 | /* | |
196 | ** The following botch is because csh tries to free a free block | |
197 | ** when processing the =~ or !~ operators. -- layer@ucbmonet | |
198 | */ | |
199 | #ifdef CSHbotch /* was debug */ | |
200 | ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ | |
fc71ebc6 | 201 | #else |
3fb44be6 KL |
202 | if (op->ov_magic != MAGIC) |
203 | return; /* sanity */ | |
fc71ebc6 | 204 | #endif |
fc71ebc6 | 205 | |
3fb44be6 KL |
206 | #ifdef RCHECK |
207 | ASSERT(op->ov_rmagic == RMAGIC); | |
208 | if (op->ov_index <= 13) | |
209 | ASSERT(*(u_int *)((caddr_t)op + op->ov_size + 1 - RSLOP) == RMAGIC); | |
210 | #endif | |
211 | ASSERT(op->ov_index < NBUCKETS); | |
212 | size = op->ov_index; | |
213 | op->ov_next = nextf[size]; | |
214 | nextf[size] = op; | |
3fb44be6 | 215 | nmalloc[size]--; |
fc71ebc6 | 216 | } |
3fb44be6 KL |
217 | |
218 | /* | |
219 | * When a program attempts "storage compaction" as mentioned in the | |
220 | * old malloc man page, it realloc's an already freed block. Usually | |
221 | * this is the last block it freed; occasionally it might be farther | |
222 | * back. We have to search all the free lists for the block in order | |
223 | * to determine its bucket: 1st we make one pass thru the lists | |
224 | * checking only the first block in each; if that fails we search | |
225 | * ``realloc_srchlen'' blocks in each list for a match (the variable | |
226 | * is extern so the caller can modify it). If that fails we just copy | |
227 | * however many bytes was given to realloc() and hope it's not huge. | |
228 | */ | |
229 | int realloc_srchlen = 4; /* 4 should be plenty. -1 means whole list */ | |
230 | ||
231 | char * | |
232 | realloc(cp, nbytes) | |
233 | char *cp; | |
234 | unsigned nbytes; | |
235 | { | |
236 | register u_int onb; | |
237 | union overhead *op; | |
238 | char *res; | |
239 | register int i; | |
240 | int was_alloced = 0; | |
241 | ||
242 | if (cp == NULL) | |
243 | return (malloc(nbytes)); | |
244 | op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); | |
245 | if (op->ov_magic == MAGIC) { | |
246 | was_alloced++; | |
247 | i = op->ov_index; | |
248 | } | |
249 | else { /* already free: he is doing "compaction" (tee hee) */ | |
250 | if ((i = findbucket(op, 1)) < 0 && | |
251 | (i = findbucket(op, realloc_srchlen)) < 0) | |
252 | i = 0; /* assume smallest possible */ | |
253 | } | |
254 | onb = (1 << (i + 3)) - sizeof (*op) - RSLOP; | |
255 | if (was_alloced && /* avoid the copy if same size block */ | |
256 | nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP) | |
257 | return(cp); | |
258 | if ((res = malloc(nbytes)) == NULL) | |
259 | return (NULL); | |
260 | if (cp != res) /* common optimization */ | |
261 | bcopy(cp, res, (nbytes < onb) ? nbytes : onb); | |
262 | if (was_alloced) | |
263 | free(cp); | |
264 | return (res); | |
265 | } | |
266 | ||
267 | /* | |
268 | * Search ``srchlen'' elements of each free list for a block whose | |
269 | * header starts at ``freep''. If srchlen is -1 search the whole list. | |
270 | * Return bucket number, or -1 if not found. | |
271 | */ | |
272 | static | |
273 | findbucket(freep, srchlen) | |
274 | union overhead *freep; | |
275 | int srchlen; | |
276 | { | |
277 | register union overhead *p; | |
278 | register int i, j; | |
279 | ||
280 | for (i = 0; i < NBUCKETS; i++) | |
281 | for (j = 0, p = nextf[i]; p && j != srchlen; j++, p = p->ov_next) | |
282 | if (p == freep) | |
283 | return (i); | |
284 | return (-1); | |
285 | } | |
fc71ebc6 | 286 | |
3fb44be6 KL |
287 | /* |
288 | * mstats - print out statistics about malloc | |
289 | * | |
290 | * Prints two lines of numbers, one showing the length of the free list | |
291 | * for each size category, the second showing the number of mallocs - | |
292 | * frees for each size category. | |
293 | */ | |
294 | showall(s) | |
35371dec | 295 | char **s; |
fc71ebc6 | 296 | { |
35371dec EW |
297 | register int i, j; |
298 | register union overhead *p; | |
299 | int totfree = 0, | |
300 | totused = 0; | |
3fb44be6 KL |
301 | |
302 | if (s[1]) | |
35371dec EW |
303 | printf("Memory allocation statistics %s\nfree:", s[1]); |
304 | for (i = 0; i < NBUCKETS; i++) { | |
305 | for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) | |
306 | ; | |
307 | ||
308 | if (s[1]) | |
309 | printf(" %d", j); | |
310 | totfree += j * (1 << (i + 3)); | |
311 | } | |
3fb44be6 | 312 | if (s[1]) |
35371dec EW |
313 | printf("\nused:"); |
314 | for (i = 0; i < NBUCKETS; i++) { | |
315 | if (s[1]) | |
316 | printf(" %d", nmalloc[i]); | |
317 | totused += nmalloc[i] * (1 << (i + 3)); | |
318 | } | |
3fb44be6 | 319 | if (s[1]) |
35371dec EW |
320 | printf("\n"); |
321 | printf("Total in use: %d, total free: %d\n", totused, totfree); | |
fc71ebc6 | 322 | } |