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0875b58f | 1 | /* -*-c-*- |
0875b58f | 2 | * |
3 | * Allocation of known-size blocks | |
4 | * | |
5 | * (c) 1998 Straylight/Edgeware | |
6 | */ | |
7 | ||
d4efbcd9 | 8 | /*----- Licensing notice --------------------------------------------------* |
0875b58f | 9 | * |
10 | * This file is part of the mLib utilities library. | |
11 | * | |
12 | * mLib is free software; you can redistribute it and/or modify | |
c846879c | 13 | * it under the terms of the GNU Library General Public License as |
14 | * published by the Free Software Foundation; either version 2 of the | |
15 | * License, or (at your option) any later version. | |
d4efbcd9 | 16 | * |
0875b58f | 17 | * mLib is distributed in the hope that it will be useful, |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
c846879c | 20 | * GNU Library General Public License for more details. |
d4efbcd9 | 21 | * |
c846879c | 22 | * You should have received a copy of the GNU Library General Public |
0bd98442 | 23 | * License along with mLib; if not, write to the Free |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
25 | * MA 02111-1307, USA. | |
0875b58f | 26 | */ |
27 | ||
0875b58f | 28 | /*----- The big idea ------------------------------------------------------* |
29 | * | |
30 | * This file provides an extra layer over @malloc@. It provides fast | |
8c6d948b | 31 | * turnover for small blocks, and tries to minimize the per-block overhead. |
0875b58f | 32 | * |
33 | * To do its job, @alloc@ must place an extra restriction on you: you must | |
34 | * know the size of a block when you free it. Usually you'll have this | |
35 | * information encoded in some way either in the block or in the thing that | |
36 | * referenced it, so this isn't a hardship. | |
37 | * | |
38 | * It works fairly simply. If a request for a big block (as defined by the | |
39 | * constants below) comes in, it gets sent on to @malloc@ unmolested. For | |
40 | * small blocks, it goes straight to a `bin' -- a list containing free blocks | |
41 | * of exactly that size, or the nearest bigger size we can manage. If the | |
42 | * bin is empty, a `chunk' is allocated from @malloc@: this has enough room | |
43 | * for lots of blocks of the requested size, so it ets split up and each | |
44 | * individual small block is added to the bin list. The first block in the | |
45 | * bin list is then removed and given to the caller. In this way, @malloc@ | |
46 | * only stores its information once for lots of little blocks, so we save | |
47 | * memory. Because I know where the correct bin is just from the block size, | |
48 | * and I don't need to do any searching at all in the usual case (because the | |
49 | * list isn't empty) I can get a speed advantage too. | |
50 | * | |
51 | * This code is almost certainly not ANSI conformant, although I'm not | |
52 | * actually sure. If some kind soul would let me know how seriously I've | |
53 | * violated the standard, and whether this is easily fixable, I'd be | |
54 | * grateful. | |
55 | */ | |
56 | ||
57 | /*----- Header files ------------------------------------------------------*/ | |
58 | ||
59 | /* --- ANSI headers --- */ | |
60 | ||
ba1916b5 | 61 | #include <assert.h> |
0875b58f | 62 | #include <stdio.h> |
63 | #include <stdlib.h> | |
64 | #include <string.h> | |
65 | ||
66 | /* --- Local headers --- */ | |
67 | ||
0fd574c3 | 68 | #include "arena.h" |
69 | #include "exc.h" | |
70 | #include "sub.h" | |
0875b58f | 71 | |
ba1916b5 | 72 | /*----- Configuration tweaks ----------------------------------------------*/ |
73 | ||
74 | /* #define SUBARENA_TRIVIAL */ | |
75 | ||
0fd574c3 | 76 | /*----- Static variables --------------------------------------------------*/ |
0875b58f | 77 | |
0fd574c3 | 78 | static size_t sizes[SUB_BINS]; |
0875b58f | 79 | |
0fd574c3 | 80 | /*----- Global variables --------------------------------------------------*/ |
0875b58f | 81 | |
0fd574c3 | 82 | subarena sub_global; |
0875b58f | 83 | |
ba1916b5 | 84 | #ifdef SUBARENA_TRIVIAL |
85 | ||
86 | typedef struct sub_link { | |
87 | struct sub_link *next; | |
88 | void *p; | |
89 | size_t sz; | |
90 | } sub_link; | |
91 | ||
92 | #endif | |
93 | ||
0fd574c3 | 94 | /*----- Main code ---------------------------------------------------------*/ |
0875b58f | 95 | |
0fd574c3 | 96 | /* --- @subarena_create@ --- * |
0875b58f | 97 | * |
0fd574c3 | 98 | * Arguments: @subarena *s@ = pointer to arena to initialize |
99 | * @arena *a@ = pointer to underlying arena block | |
0875b58f | 100 | * |
0fd574c3 | 101 | * Returns: --- |
102 | * | |
103 | * Use: Initialize a suballocation arena based on an underlying large | |
104 | * blocks arena. | |
0875b58f | 105 | */ |
106 | ||
0fd574c3 | 107 | void subarena_create(subarena *s, arena *a) |
108 | { | |
ba1916b5 | 109 | #ifdef SUBARENA_TRIVIAL |
110 | s->bin[0] = 0; | |
111 | #else | |
0fd574c3 | 112 | size_t i; |
113 | if (!sizes[1]) | |
114 | sub_init(); | |
115 | for (i = 0; i < SUB_BINS; i++) | |
116 | s->bin[i] = 0; | |
ba1916b5 | 117 | #endif |
0fd574c3 | 118 | s->a = a; |
119 | } | |
0875b58f | 120 | |
0fd574c3 | 121 | /* --- @subarena_destroy@ --- * |
0875b58f | 122 | * |
0fd574c3 | 123 | * Arguments: @subarena *s@ = pointer to arena to destroy |
124 | * | |
125 | * Returns: --- | |
126 | * | |
127 | * Use: Destroys a suballocation arena, freeing all of the memory it | |
128 | * contains back to the underlying large blocks arena. | |
0875b58f | 129 | */ |
130 | ||
0fd574c3 | 131 | void subarena_destroy(subarena *s) |
132 | { | |
ba1916b5 | 133 | #ifdef SUBARENA_TRIVIAL |
134 | ||
135 | sub_link *l, *ll; | |
136 | ||
137 | for (l = s->bin[0]; l; l = ll) { | |
138 | ll = l; | |
139 | a_free(s->a, l->p); | |
140 | a_free(s->a, l); | |
141 | } | |
142 | s->bin[0] = 0; | |
143 | ||
144 | #else | |
145 | ||
0fd574c3 | 146 | size_t i; |
147 | for (i = 0; i < SUB_BINS; i++) { | |
148 | void *p = s->bin[i]; | |
149 | while (p) { | |
150 | void *q = p; | |
151 | p = *(void **)q; | |
152 | A_FREE(s->a, q); | |
153 | } | |
c5775f49 | 154 | s->bin[i] = 0; |
0fd574c3 | 155 | } |
ba1916b5 | 156 | |
157 | #endif | |
0fd574c3 | 158 | } |
0875b58f | 159 | |
0fd574c3 | 160 | /* --- @subarena_alloc@ --- * |
0875b58f | 161 | * |
d4efbcd9 | 162 | * Arguments: @subarena *s@ = pointer to arena |
0fd574c3 | 163 | * @size_t s@ = size of chunk wanted |
0875b58f | 164 | * |
d4efbcd9 | 165 | * Returns: Pointer to a block at least as large as the one wanted. |
0875b58f | 166 | * |
d4efbcd9 | 167 | * Use: Allocates a small block of memory from the given pool. The |
0fd574c3 | 168 | * exception @EXC_NOMEM@ is raised if the underlying arena is |
169 | * full. | |
0875b58f | 170 | */ |
171 | ||
0fd574c3 | 172 | void *subarena_alloc(subarena *s, size_t sz) |
0875b58f | 173 | { |
ba1916b5 | 174 | #ifdef SUBARENA_TRIVIAL |
175 | ||
176 | sub_link *l; | |
177 | void *p; | |
178 | ||
179 | if (!s->a) | |
180 | subarena_create(s, arena_global); | |
181 | ||
182 | if ((l = a_alloc(s->a, sizeof(*l))) == 0) | |
183 | return (0); | |
184 | if ((p = a_alloc(s->a, sz)) == 0) { | |
185 | a_free(s->a, l); | |
186 | return (0); | |
187 | } | |
188 | l->p = p; | |
189 | l->sz = sz; | |
190 | l->next = s->bin[0]; | |
191 | s->bin[0] = l; | |
192 | return (p); | |
193 | ||
194 | #else | |
195 | ||
0fd574c3 | 196 | int bin; |
0875b58f | 197 | void *p; |
198 | ||
0fd574c3 | 199 | /* --- Ensure that everything is initialized --- */ |
200 | ||
201 | if (!s->a) | |
202 | subarena_create(s, arena_global); | |
0fd574c3 | 203 | |
0875b58f | 204 | /* --- Handle oversize blocks --- */ |
205 | ||
ba1916b5 | 206 | bin = SUB_BIN(sz); |
0fd574c3 | 207 | if (bin >= SUB_BINS) { |
208 | void *p = A_ALLOC(s->a, sz); | |
209 | if (!p) | |
210 | THROW(EXC_NOMEM); | |
211 | return (p); | |
212 | } | |
0875b58f | 213 | |
214 | /* --- If the bin is empty, find some memory --- */ | |
215 | ||
0fd574c3 | 216 | if (!s->bin[bin]) { |
0875b58f | 217 | char *p, *q; |
218 | ||
0fd574c3 | 219 | p = A_ALLOC(s->a, sizes[bin]); |
220 | if (!p) | |
221 | THROW(EXC_NOMEM); | |
ff0f0220 | 222 | q = p + sizes[bin]; |
0875b58f | 223 | |
0fd574c3 | 224 | sz = SUB_BINSZ(bin); |
0875b58f | 225 | |
0fd574c3 | 226 | q -= sz; |
0875b58f | 227 | *(void **)q = 0; |
228 | ||
229 | while (q > p) { | |
0fd574c3 | 230 | q -= sz; |
231 | *(void **)q = q + sz; | |
0875b58f | 232 | } |
233 | ||
0fd574c3 | 234 | s->bin[bin] = p; |
0875b58f | 235 | } |
236 | ||
237 | /* --- Extract the first block in the list --- */ | |
238 | ||
0fd574c3 | 239 | p = s->bin[bin]; |
240 | s->bin[bin] = *(void **)p; | |
0875b58f | 241 | return (p); |
ba1916b5 | 242 | |
243 | #endif | |
0875b58f | 244 | } |
245 | ||
0fd574c3 | 246 | /* --- @subarena_free@ --- * |
0875b58f | 247 | * |
d4efbcd9 | 248 | * Arguments: @subarena *s@ = pointer to arena |
0fd574c3 | 249 | * @void *p@ = address of block to free |
d4efbcd9 | 250 | * @size_t s@ = size of block |
0875b58f | 251 | * |
d4efbcd9 | 252 | * Returns: --- |
0875b58f | 253 | * |
d4efbcd9 | 254 | * Use: Frees a block allocated by @subarena_alloc@. |
0875b58f | 255 | */ |
256 | ||
0fd574c3 | 257 | void subarena_free(subarena *s, void *p, size_t sz) |
0875b58f | 258 | { |
ba1916b5 | 259 | #ifdef SUBARENA_TRIVIAL |
260 | ||
261 | sub_link *lh = s->bin[0], **l, *ll; | |
262 | ||
263 | for (l = &lh; *l && (*l)->p != p; l = &(*l)->next) | |
264 | ; | |
265 | ll = *l; | |
266 | assert(ll); | |
267 | assert(ll->sz == sz); | |
268 | *l = ll->next; | |
269 | a_free(s->a, ll); | |
270 | a_free(s->a, p); | |
271 | s->bin[0] = lh; | |
272 | ||
273 | #else | |
274 | ||
0fd574c3 | 275 | int bin = SUB_BIN(sz); |
0875b58f | 276 | |
277 | if (bin >= SUB_BINS) | |
0fd574c3 | 278 | A_FREE(s->a, p); |
0875b58f | 279 | else { |
0fd574c3 | 280 | *(void **)p = s->bin[bin]; |
281 | s->bin[bin] = p; | |
0875b58f | 282 | } |
ba1916b5 | 283 | |
284 | #endif | |
0875b58f | 285 | } |
286 | ||
0fd574c3 | 287 | /*----- Compatibility stuff -----------------------------------------------*/ |
288 | ||
289 | /* --- @sub_alloc@ --- * | |
290 | * | |
d4efbcd9 | 291 | * Arguments: @size_t s@ = size of chunk wanted |
0fd574c3 | 292 | * |
d4efbcd9 | 293 | * Returns: Pointer to a block at least as large as the one wanted. |
0fd574c3 | 294 | * |
d4efbcd9 | 295 | * Use: Allocates a small block of memory from the @sub_global@ pool. |
0fd574c3 | 296 | */ |
297 | ||
298 | void *(sub_alloc)(size_t sz) { return sub_alloc(sz); } | |
299 | ||
300 | /* --- @sub_free@ --- * | |
301 | * | |
d4efbcd9 MW |
302 | * Arguments: @void *p@ = address of block to free |
303 | * @size_t s@ = size of block | |
0fd574c3 | 304 | * |
d4efbcd9 | 305 | * Returns: --- |
0fd574c3 | 306 | * |
d4efbcd9 | 307 | * Use: Frees a block allocated by @sub_alloc@. |
0fd574c3 | 308 | */ |
309 | ||
310 | void (sub_free)(void *p, size_t sz) { sub_free(p, sz); } | |
311 | ||
0875b58f | 312 | /* --- @sub_init@ --- * |
313 | * | |
d4efbcd9 | 314 | * Arguments: --- |
0875b58f | 315 | * |
d4efbcd9 | 316 | * Returns: --- |
0875b58f | 317 | * |
d4efbcd9 | 318 | * Use: Initializes the magic allocator. |
0875b58f | 319 | */ |
320 | ||
321 | void sub_init(void) | |
322 | { | |
ba1916b5 | 323 | #ifndef SUBARENA_TRIVIAL |
0875b58f | 324 | int i; |
325 | ||
8c6d948b | 326 | /* --- Initialize the sizes bins --- */ |
0875b58f | 327 | |
328 | for (i = 1; i < SUB_BINS; i++) { | |
ff0f0220 | 329 | sizes[i] = ((SUB_CHUNK + SUB_BINSZ(i) - 1) / |
0875b58f | 330 | SUB_BINSZ(i) * SUB_BINSZ(i)); |
331 | } | |
ba1916b5 | 332 | #endif |
0875b58f | 333 | } |
334 | ||
335 | /*----- Debugging code ----------------------------------------------------*/ | |
336 | ||
337 | #ifdef TEST_RIG | |
338 | ||
339 | #define BLOCKS 1024 | |
340 | #define SIZE_MAX 2048 | |
341 | #define ITERATIONS 500000 | |
342 | ||
343 | int main(void) | |
344 | { | |
345 | static void *block[BLOCKS]; | |
346 | static size_t size[BLOCKS]; | |
347 | size_t allocced = 0; | |
348 | int i; | |
349 | long count; | |
350 | ||
351 | sub_init(); | |
352 | ||
353 | for (count = 0; count < ITERATIONS; count++) { | |
354 | i = rand() % BLOCKS; | |
355 | if (block[i]) { | |
356 | sub_free(block[i], size[i]); | |
357 | block[i] = 0; | |
358 | allocced -= size[i]; | |
359 | } else { | |
360 | block[i] = sub_alloc(size[i] = | |
361 | rand() % (SUB_MAXBIN - 128) + 128); | |
362 | allocced += size[i]; | |
363 | memset(block[i], 0, size[i]); /* trample allocated storage */ | |
364 | } | |
365 | } | |
366 | ||
367 | return (0); | |
368 | } | |
369 | ||
370 | #endif | |
371 | ||
372 | /*----- That's all, folks -------------------------------------------------*/ |