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0875b58f | 1 | /* -*-c-*- |
2 | * | |
8656dc50 | 3 | * $Id: sub.c,v 1.9 2004/04/08 01:36:13 mdw Exp $ |
0875b58f | 4 | * |
5 | * Allocation of known-size blocks | |
6 | * | |
7 | * (c) 1998 Straylight/Edgeware | |
8 | */ | |
9 | ||
d4efbcd9 | 10 | /*----- Licensing notice --------------------------------------------------* |
0875b58f | 11 | * |
12 | * This file is part of the mLib utilities library. | |
13 | * | |
14 | * mLib is free software; you can redistribute it and/or modify | |
c846879c | 15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the | |
17 | * License, or (at your option) any later version. | |
d4efbcd9 | 18 | * |
0875b58f | 19 | * mLib is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
c846879c | 22 | * GNU Library General Public License for more details. |
d4efbcd9 | 23 | * |
c846879c | 24 | * You should have received a copy of the GNU Library General Public |
0bd98442 | 25 | * License along with mLib; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
27 | * MA 02111-1307, USA. | |
0875b58f | 28 | */ |
29 | ||
0875b58f | 30 | /*----- The big idea ------------------------------------------------------* |
31 | * | |
32 | * This file provides an extra layer over @malloc@. It provides fast | |
8c6d948b | 33 | * turnover for small blocks, and tries to minimize the per-block overhead. |
0875b58f | 34 | * |
35 | * To do its job, @alloc@ must place an extra restriction on you: you must | |
36 | * know the size of a block when you free it. Usually you'll have this | |
37 | * information encoded in some way either in the block or in the thing that | |
38 | * referenced it, so this isn't a hardship. | |
39 | * | |
40 | * It works fairly simply. If a request for a big block (as defined by the | |
41 | * constants below) comes in, it gets sent on to @malloc@ unmolested. For | |
42 | * small blocks, it goes straight to a `bin' -- a list containing free blocks | |
43 | * of exactly that size, or the nearest bigger size we can manage. If the | |
44 | * bin is empty, a `chunk' is allocated from @malloc@: this has enough room | |
45 | * for lots of blocks of the requested size, so it ets split up and each | |
46 | * individual small block is added to the bin list. The first block in the | |
47 | * bin list is then removed and given to the caller. In this way, @malloc@ | |
48 | * only stores its information once for lots of little blocks, so we save | |
49 | * memory. Because I know where the correct bin is just from the block size, | |
50 | * and I don't need to do any searching at all in the usual case (because the | |
51 | * list isn't empty) I can get a speed advantage too. | |
52 | * | |
53 | * This code is almost certainly not ANSI conformant, although I'm not | |
54 | * actually sure. If some kind soul would let me know how seriously I've | |
55 | * violated the standard, and whether this is easily fixable, I'd be | |
56 | * grateful. | |
57 | */ | |
58 | ||
59 | /*----- Header files ------------------------------------------------------*/ | |
60 | ||
61 | /* --- ANSI headers --- */ | |
62 | ||
ba1916b5 | 63 | #include <assert.h> |
0875b58f | 64 | #include <stdio.h> |
65 | #include <stdlib.h> | |
66 | #include <string.h> | |
67 | ||
68 | /* --- Local headers --- */ | |
69 | ||
0fd574c3 | 70 | #include "arena.h" |
71 | #include "exc.h" | |
72 | #include "sub.h" | |
0875b58f | 73 | |
ba1916b5 | 74 | /*----- Configuration tweaks ----------------------------------------------*/ |
75 | ||
76 | /* #define SUBARENA_TRIVIAL */ | |
77 | ||
0fd574c3 | 78 | /*----- Static variables --------------------------------------------------*/ |
0875b58f | 79 | |
0fd574c3 | 80 | static size_t sizes[SUB_BINS]; |
0875b58f | 81 | |
0fd574c3 | 82 | /*----- Global variables --------------------------------------------------*/ |
0875b58f | 83 | |
0fd574c3 | 84 | subarena sub_global; |
0875b58f | 85 | |
ba1916b5 | 86 | #ifdef SUBARENA_TRIVIAL |
87 | ||
88 | typedef struct sub_link { | |
89 | struct sub_link *next; | |
90 | void *p; | |
91 | size_t sz; | |
92 | } sub_link; | |
93 | ||
94 | #endif | |
95 | ||
0fd574c3 | 96 | /*----- Main code ---------------------------------------------------------*/ |
0875b58f | 97 | |
0fd574c3 | 98 | /* --- @subarena_create@ --- * |
0875b58f | 99 | * |
0fd574c3 | 100 | * Arguments: @subarena *s@ = pointer to arena to initialize |
101 | * @arena *a@ = pointer to underlying arena block | |
0875b58f | 102 | * |
0fd574c3 | 103 | * Returns: --- |
104 | * | |
105 | * Use: Initialize a suballocation arena based on an underlying large | |
106 | * blocks arena. | |
0875b58f | 107 | */ |
108 | ||
0fd574c3 | 109 | void subarena_create(subarena *s, arena *a) |
110 | { | |
ba1916b5 | 111 | #ifdef SUBARENA_TRIVIAL |
112 | s->bin[0] = 0; | |
113 | #else | |
0fd574c3 | 114 | size_t i; |
115 | if (!sizes[1]) | |
116 | sub_init(); | |
117 | for (i = 0; i < SUB_BINS; i++) | |
118 | s->bin[i] = 0; | |
ba1916b5 | 119 | #endif |
0fd574c3 | 120 | s->a = a; |
121 | } | |
0875b58f | 122 | |
0fd574c3 | 123 | /* --- @subarena_destroy@ --- * |
0875b58f | 124 | * |
0fd574c3 | 125 | * Arguments: @subarena *s@ = pointer to arena to destroy |
126 | * | |
127 | * Returns: --- | |
128 | * | |
129 | * Use: Destroys a suballocation arena, freeing all of the memory it | |
130 | * contains back to the underlying large blocks arena. | |
0875b58f | 131 | */ |
132 | ||
0fd574c3 | 133 | void subarena_destroy(subarena *s) |
134 | { | |
ba1916b5 | 135 | #ifdef SUBARENA_TRIVIAL |
136 | ||
137 | sub_link *l, *ll; | |
138 | ||
139 | for (l = s->bin[0]; l; l = ll) { | |
140 | ll = l; | |
141 | a_free(s->a, l->p); | |
142 | a_free(s->a, l); | |
143 | } | |
144 | s->bin[0] = 0; | |
145 | ||
146 | #else | |
147 | ||
0fd574c3 | 148 | size_t i; |
149 | for (i = 0; i < SUB_BINS; i++) { | |
150 | void *p = s->bin[i]; | |
151 | while (p) { | |
152 | void *q = p; | |
153 | p = *(void **)q; | |
154 | A_FREE(s->a, q); | |
155 | } | |
c5775f49 | 156 | s->bin[i] = 0; |
0fd574c3 | 157 | } |
ba1916b5 | 158 | |
159 | #endif | |
0fd574c3 | 160 | } |
0875b58f | 161 | |
0fd574c3 | 162 | /* --- @subarena_alloc@ --- * |
0875b58f | 163 | * |
d4efbcd9 | 164 | * Arguments: @subarena *s@ = pointer to arena |
0fd574c3 | 165 | * @size_t s@ = size of chunk wanted |
0875b58f | 166 | * |
d4efbcd9 | 167 | * Returns: Pointer to a block at least as large as the one wanted. |
0875b58f | 168 | * |
d4efbcd9 | 169 | * Use: Allocates a small block of memory from the given pool. The |
0fd574c3 | 170 | * exception @EXC_NOMEM@ is raised if the underlying arena is |
171 | * full. | |
0875b58f | 172 | */ |
173 | ||
0fd574c3 | 174 | void *subarena_alloc(subarena *s, size_t sz) |
0875b58f | 175 | { |
ba1916b5 | 176 | #ifdef SUBARENA_TRIVIAL |
177 | ||
178 | sub_link *l; | |
179 | void *p; | |
180 | ||
181 | if (!s->a) | |
182 | subarena_create(s, arena_global); | |
183 | ||
184 | if ((l = a_alloc(s->a, sizeof(*l))) == 0) | |
185 | return (0); | |
186 | if ((p = a_alloc(s->a, sz)) == 0) { | |
187 | a_free(s->a, l); | |
188 | return (0); | |
189 | } | |
190 | l->p = p; | |
191 | l->sz = sz; | |
192 | l->next = s->bin[0]; | |
193 | s->bin[0] = l; | |
194 | return (p); | |
195 | ||
196 | #else | |
197 | ||
0fd574c3 | 198 | int bin; |
0875b58f | 199 | void *p; |
200 | ||
0fd574c3 | 201 | /* --- Ensure that everything is initialized --- */ |
202 | ||
203 | if (!s->a) | |
204 | subarena_create(s, arena_global); | |
0fd574c3 | 205 | |
0875b58f | 206 | /* --- Handle oversize blocks --- */ |
207 | ||
ba1916b5 | 208 | bin = SUB_BIN(sz); |
0fd574c3 | 209 | if (bin >= SUB_BINS) { |
210 | void *p = A_ALLOC(s->a, sz); | |
211 | if (!p) | |
212 | THROW(EXC_NOMEM); | |
213 | return (p); | |
214 | } | |
0875b58f | 215 | |
216 | /* --- If the bin is empty, find some memory --- */ | |
217 | ||
0fd574c3 | 218 | if (!s->bin[bin]) { |
0875b58f | 219 | char *p, *q; |
220 | ||
0fd574c3 | 221 | p = A_ALLOC(s->a, sizes[bin]); |
222 | if (!p) | |
223 | THROW(EXC_NOMEM); | |
ff0f0220 | 224 | q = p + sizes[bin]; |
0875b58f | 225 | |
0fd574c3 | 226 | sz = SUB_BINSZ(bin); |
0875b58f | 227 | |
0fd574c3 | 228 | q -= sz; |
0875b58f | 229 | *(void **)q = 0; |
230 | ||
231 | while (q > p) { | |
0fd574c3 | 232 | q -= sz; |
233 | *(void **)q = q + sz; | |
0875b58f | 234 | } |
235 | ||
0fd574c3 | 236 | s->bin[bin] = p; |
0875b58f | 237 | } |
238 | ||
239 | /* --- Extract the first block in the list --- */ | |
240 | ||
0fd574c3 | 241 | p = s->bin[bin]; |
242 | s->bin[bin] = *(void **)p; | |
0875b58f | 243 | return (p); |
ba1916b5 | 244 | |
245 | #endif | |
0875b58f | 246 | } |
247 | ||
0fd574c3 | 248 | /* --- @subarena_free@ --- * |
0875b58f | 249 | * |
d4efbcd9 | 250 | * Arguments: @subarena *s@ = pointer to arena |
0fd574c3 | 251 | * @void *p@ = address of block to free |
d4efbcd9 | 252 | * @size_t s@ = size of block |
0875b58f | 253 | * |
d4efbcd9 | 254 | * Returns: --- |
0875b58f | 255 | * |
d4efbcd9 | 256 | * Use: Frees a block allocated by @subarena_alloc@. |
0875b58f | 257 | */ |
258 | ||
0fd574c3 | 259 | void subarena_free(subarena *s, void *p, size_t sz) |
0875b58f | 260 | { |
ba1916b5 | 261 | #ifdef SUBARENA_TRIVIAL |
262 | ||
263 | sub_link *lh = s->bin[0], **l, *ll; | |
264 | ||
265 | for (l = &lh; *l && (*l)->p != p; l = &(*l)->next) | |
266 | ; | |
267 | ll = *l; | |
268 | assert(ll); | |
269 | assert(ll->sz == sz); | |
270 | *l = ll->next; | |
271 | a_free(s->a, ll); | |
272 | a_free(s->a, p); | |
273 | s->bin[0] = lh; | |
274 | ||
275 | #else | |
276 | ||
0fd574c3 | 277 | int bin = SUB_BIN(sz); |
0875b58f | 278 | |
279 | if (bin >= SUB_BINS) | |
0fd574c3 | 280 | A_FREE(s->a, p); |
0875b58f | 281 | else { |
0fd574c3 | 282 | *(void **)p = s->bin[bin]; |
283 | s->bin[bin] = p; | |
0875b58f | 284 | } |
ba1916b5 | 285 | |
286 | #endif | |
0875b58f | 287 | } |
288 | ||
0fd574c3 | 289 | /*----- Compatibility stuff -----------------------------------------------*/ |
290 | ||
291 | /* --- @sub_alloc@ --- * | |
292 | * | |
d4efbcd9 | 293 | * Arguments: @size_t s@ = size of chunk wanted |
0fd574c3 | 294 | * |
d4efbcd9 | 295 | * Returns: Pointer to a block at least as large as the one wanted. |
0fd574c3 | 296 | * |
d4efbcd9 | 297 | * Use: Allocates a small block of memory from the @sub_global@ pool. |
0fd574c3 | 298 | */ |
299 | ||
300 | void *(sub_alloc)(size_t sz) { return sub_alloc(sz); } | |
301 | ||
302 | /* --- @sub_free@ --- * | |
303 | * | |
d4efbcd9 MW |
304 | * Arguments: @void *p@ = address of block to free |
305 | * @size_t s@ = size of block | |
0fd574c3 | 306 | * |
d4efbcd9 | 307 | * Returns: --- |
0fd574c3 | 308 | * |
d4efbcd9 | 309 | * Use: Frees a block allocated by @sub_alloc@. |
0fd574c3 | 310 | */ |
311 | ||
312 | void (sub_free)(void *p, size_t sz) { sub_free(p, sz); } | |
313 | ||
0875b58f | 314 | /* --- @sub_init@ --- * |
315 | * | |
d4efbcd9 | 316 | * Arguments: --- |
0875b58f | 317 | * |
d4efbcd9 | 318 | * Returns: --- |
0875b58f | 319 | * |
d4efbcd9 | 320 | * Use: Initializes the magic allocator. |
0875b58f | 321 | */ |
322 | ||
323 | void sub_init(void) | |
324 | { | |
ba1916b5 | 325 | #ifndef SUBARENA_TRIVIAL |
0875b58f | 326 | int i; |
327 | ||
8c6d948b | 328 | /* --- Initialize the sizes bins --- */ |
0875b58f | 329 | |
330 | for (i = 1; i < SUB_BINS; i++) { | |
ff0f0220 | 331 | sizes[i] = ((SUB_CHUNK + SUB_BINSZ(i) - 1) / |
0875b58f | 332 | SUB_BINSZ(i) * SUB_BINSZ(i)); |
333 | } | |
ba1916b5 | 334 | #endif |
0875b58f | 335 | } |
336 | ||
337 | /*----- Debugging code ----------------------------------------------------*/ | |
338 | ||
339 | #ifdef TEST_RIG | |
340 | ||
341 | #define BLOCKS 1024 | |
342 | #define SIZE_MAX 2048 | |
343 | #define ITERATIONS 500000 | |
344 | ||
345 | int main(void) | |
346 | { | |
347 | static void *block[BLOCKS]; | |
348 | static size_t size[BLOCKS]; | |
349 | size_t allocced = 0; | |
350 | int i; | |
351 | long count; | |
352 | ||
353 | sub_init(); | |
354 | ||
355 | for (count = 0; count < ITERATIONS; count++) { | |
356 | i = rand() % BLOCKS; | |
357 | if (block[i]) { | |
358 | sub_free(block[i], size[i]); | |
359 | block[i] = 0; | |
360 | allocced -= size[i]; | |
361 | } else { | |
362 | block[i] = sub_alloc(size[i] = | |
363 | rand() % (SUB_MAXBIN - 128) + 128); | |
364 | allocced += size[i]; | |
365 | memset(block[i], 0, size[i]); /* trample allocated storage */ | |
366 | } | |
367 | } | |
368 | ||
369 | return (0); | |
370 | } | |
371 | ||
372 | #endif | |
373 | ||
374 | /*----- That's all, folks -------------------------------------------------*/ |