Commit | Line | Data |
---|---|---|
c906108c | 1 | /* Implement a cached obstack. |
c2d11a7d JM |
2 | Written by Fred Fish <fnf@cygnus.com> |
3 | Rewritten by Jim Blandy <jimb@cygnus.com> | |
2c7ef074 | 4 | |
6aba47ca | 5 | Copyright (C) 1999, 2000, 2002, 2003, 2007 Free Software Foundation, Inc. |
c906108c | 6 | |
c5aa993b | 7 | This file is part of GDB. |
c906108c | 8 | |
c5aa993b JM |
9 | This program is free software; you can redistribute it and/or modify |
10 | it under the terms of the GNU General Public License as published by | |
a9762ec7 | 11 | the Free Software Foundation; either version 3 of the License, or |
c5aa993b | 12 | (at your option) any later version. |
c906108c | 13 | |
c5aa993b JM |
14 | This program is distributed in the hope that it will be useful, |
15 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
17 | GNU General Public License for more details. | |
c906108c | 18 | |
c5aa993b | 19 | You should have received a copy of the GNU General Public License |
a9762ec7 | 20 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
c906108c SS |
21 | |
22 | #include "defs.h" | |
04ea0df1 | 23 | #include "gdb_obstack.h" |
c906108c SS |
24 | #include "bcache.h" |
25 | #include "gdb_string.h" /* For memcpy declaration */ | |
2160782c | 26 | #include "gdb_assert.h" |
c906108c | 27 | |
2c7ef074 AC |
28 | #include <stddef.h> |
29 | #include <stdlib.h> | |
30 | ||
af5f3db6 AC |
31 | /* The type used to hold a single bcache string. The user data is |
32 | stored in d.data. Since it can be any type, it needs to have the | |
33 | same alignment as the most strict alignment of any type on the host | |
34 | machine. I don't know of any really correct way to do this in | |
35 | stock ANSI C, so just do it the same way obstack.h does. */ | |
36 | ||
37 | struct bstring | |
38 | { | |
49df298f | 39 | /* Hash chain. */ |
af5f3db6 | 40 | struct bstring *next; |
49df298f AC |
41 | /* Assume the data length is no more than 64k. */ |
42 | unsigned short length; | |
43 | /* The half hash hack. This contains the upper 16 bits of the hash | |
44 | value and is used as a pre-check when comparing two strings and | |
45 | avoids the need to do length or memcmp calls. It proves to be | |
46 | roughly 100% effective. */ | |
47 | unsigned short half_hash; | |
af5f3db6 AC |
48 | |
49 | union | |
50 | { | |
51 | char data[1]; | |
52 | double dummy; | |
53 | } | |
54 | d; | |
55 | }; | |
56 | ||
57 | ||
58 | /* The structure for a bcache itself. The bcache is initialized, in | |
59 | bcache_xmalloc(), by filling it with zeros and then setting the | |
60 | corresponding obstack's malloc() and free() methods. */ | |
61 | ||
62 | struct bcache | |
63 | { | |
64 | /* All the bstrings are allocated here. */ | |
65 | struct obstack cache; | |
66 | ||
67 | /* How many hash buckets we're using. */ | |
68 | unsigned int num_buckets; | |
69 | ||
70 | /* Hash buckets. This table is allocated using malloc, so when we | |
71 | grow the table we can return the old table to the system. */ | |
72 | struct bstring **bucket; | |
73 | ||
74 | /* Statistics. */ | |
75 | unsigned long unique_count; /* number of unique strings */ | |
76 | long total_count; /* total number of strings cached, including dups */ | |
77 | long unique_size; /* size of unique strings, in bytes */ | |
78 | long total_size; /* total number of bytes cached, including dups */ | |
79 | long structure_size; /* total size of bcache, including infrastructure */ | |
2160782c AC |
80 | /* Number of times that the hash table is expanded and hence |
81 | re-built, and the corresponding number of times that a string is | |
82 | [re]hashed as part of entering it into the expanded table. The | |
83 | total number of hashes can be computed by adding TOTAL_COUNT to | |
84 | expand_hash_count. */ | |
85 | unsigned long expand_count; | |
86 | unsigned long expand_hash_count; | |
49df298f AC |
87 | /* Number of times that the half-hash compare hit (compare the upper |
88 | 16 bits of hash values) hit, but the corresponding combined | |
89 | length/data compare missed. */ | |
90 | unsigned long half_hash_miss_count; | |
af5f3db6 AC |
91 | }; |
92 | ||
357e46e7 DB |
93 | /* The old hash function was stolen from SDBM. This is what DB 3.0 uses now, |
94 | * and is better than the old one. | |
95 | */ | |
c2d11a7d | 96 | \f |
c2d11a7d | 97 | unsigned long |
d85a5daf | 98 | hash(const void *addr, int length) |
c2d11a7d | 99 | { |
357e46e7 DB |
100 | const unsigned char *k, *e; |
101 | unsigned long h; | |
102 | ||
103 | k = (const unsigned char *)addr; | |
104 | e = k+length; | |
105 | for (h=0; k< e;++k) | |
106 | { | |
107 | h *=16777619; | |
108 | h ^= *k; | |
109 | } | |
110 | return (h); | |
c906108c | 111 | } |
c2d11a7d JM |
112 | \f |
113 | /* Growing the bcache's hash table. */ | |
114 | ||
115 | /* If the average chain length grows beyond this, then we want to | |
116 | resize our hash table. */ | |
117 | #define CHAIN_LENGTH_THRESHOLD (5) | |
118 | ||
119 | static void | |
120 | expand_hash_table (struct bcache *bcache) | |
c906108c | 121 | { |
c2d11a7d JM |
122 | /* A table of good hash table sizes. Whenever we grow, we pick the |
123 | next larger size from this table. sizes[i] is close to 1 << (i+10), | |
124 | so we roughly double the table size each time. After we fall off | |
125 | the end of this table, we just double. Don't laugh --- there have | |
126 | been executables sighted with a gigabyte of debug info. */ | |
127 | static unsigned long sizes[] = { | |
128 | 1021, 2053, 4099, 8191, 16381, 32771, | |
129 | 65537, 131071, 262144, 524287, 1048573, 2097143, | |
130 | 4194301, 8388617, 16777213, 33554467, 67108859, 134217757, | |
131 | 268435459, 536870923, 1073741827, 2147483659UL | |
132 | }; | |
745b8ca0 | 133 | unsigned int new_num_buckets; |
c2d11a7d | 134 | struct bstring **new_buckets; |
745b8ca0 | 135 | unsigned int i; |
c2d11a7d | 136 | |
2160782c AC |
137 | /* Count the stats. Every unique item needs to be re-hashed and |
138 | re-entered. */ | |
139 | bcache->expand_count++; | |
140 | bcache->expand_hash_count += bcache->unique_count; | |
141 | ||
c2d11a7d | 142 | /* Find the next size. */ |
745b8ca0 | 143 | new_num_buckets = bcache->num_buckets * 2; |
c2d11a7d JM |
144 | for (i = 0; i < (sizeof (sizes) / sizeof (sizes[0])); i++) |
145 | if (sizes[i] > bcache->num_buckets) | |
146 | { | |
147 | new_num_buckets = sizes[i]; | |
148 | break; | |
149 | } | |
c2d11a7d JM |
150 | |
151 | /* Allocate the new table. */ | |
152 | { | |
153 | size_t new_size = new_num_buckets * sizeof (new_buckets[0]); | |
154 | new_buckets = (struct bstring **) xmalloc (new_size); | |
155 | memset (new_buckets, 0, new_size); | |
156 | ||
157 | bcache->structure_size -= (bcache->num_buckets | |
158 | * sizeof (bcache->bucket[0])); | |
159 | bcache->structure_size += new_size; | |
160 | } | |
c906108c | 161 | |
c2d11a7d JM |
162 | /* Rehash all existing strings. */ |
163 | for (i = 0; i < bcache->num_buckets; i++) | |
c906108c | 164 | { |
c2d11a7d JM |
165 | struct bstring *s, *next; |
166 | ||
167 | for (s = bcache->bucket[i]; s; s = next) | |
c906108c | 168 | { |
c2d11a7d JM |
169 | struct bstring **new_bucket; |
170 | next = s->next; | |
171 | ||
172 | new_bucket = &new_buckets[(hash (&s->d.data, s->length) | |
173 | % new_num_buckets)]; | |
174 | s->next = *new_bucket; | |
175 | *new_bucket = s; | |
c906108c SS |
176 | } |
177 | } | |
c2d11a7d JM |
178 | |
179 | /* Plug in the new table. */ | |
180 | if (bcache->bucket) | |
b8c9b27d | 181 | xfree (bcache->bucket); |
c2d11a7d JM |
182 | bcache->bucket = new_buckets; |
183 | bcache->num_buckets = new_num_buckets; | |
c906108c SS |
184 | } |
185 | ||
c2d11a7d JM |
186 | \f |
187 | /* Looking up things in the bcache. */ | |
188 | ||
189 | /* The number of bytes needed to allocate a struct bstring whose data | |
190 | is N bytes long. */ | |
191 | #define BSTRING_SIZE(n) (offsetof (struct bstring, d.data) + (n)) | |
192 | ||
193 | /* Find a copy of the LENGTH bytes at ADDR in BCACHE. If BCACHE has | |
194 | never seen those bytes before, add a copy of them to BCACHE. In | |
195 | either case, return a pointer to BCACHE's copy of that string. */ | |
3a16a68c AC |
196 | static void * |
197 | bcache_data (const void *addr, int length, struct bcache *bcache) | |
c906108c | 198 | { |
49df298f AC |
199 | unsigned long full_hash; |
200 | unsigned short half_hash; | |
c2d11a7d JM |
201 | int hash_index; |
202 | struct bstring *s; | |
c906108c | 203 | |
c2d11a7d JM |
204 | /* If our average chain length is too high, expand the hash table. */ |
205 | if (bcache->unique_count >= bcache->num_buckets * CHAIN_LENGTH_THRESHOLD) | |
206 | expand_hash_table (bcache); | |
207 | ||
208 | bcache->total_count++; | |
209 | bcache->total_size += length; | |
210 | ||
49df298f AC |
211 | full_hash = hash (addr, length); |
212 | half_hash = (full_hash >> 16); | |
213 | hash_index = full_hash % bcache->num_buckets; | |
c2d11a7d | 214 | |
49df298f AC |
215 | /* Search the hash bucket for a string identical to the caller's. |
216 | As a short-circuit first compare the upper part of each hash | |
217 | values. */ | |
c2d11a7d | 218 | for (s = bcache->bucket[hash_index]; s; s = s->next) |
49df298f AC |
219 | { |
220 | if (s->half_hash == half_hash) | |
221 | { | |
222 | if (s->length == length | |
223 | && ! memcmp (&s->d.data, addr, length)) | |
224 | return &s->d.data; | |
225 | else | |
226 | bcache->half_hash_miss_count++; | |
227 | } | |
228 | } | |
c2d11a7d JM |
229 | |
230 | /* The user's string isn't in the list. Insert it after *ps. */ | |
231 | { | |
232 | struct bstring *new | |
233 | = obstack_alloc (&bcache->cache, BSTRING_SIZE (length)); | |
234 | memcpy (&new->d.data, addr, length); | |
235 | new->length = length; | |
236 | new->next = bcache->bucket[hash_index]; | |
49df298f | 237 | new->half_hash = half_hash; |
c2d11a7d JM |
238 | bcache->bucket[hash_index] = new; |
239 | ||
240 | bcache->unique_count++; | |
241 | bcache->unique_size += length; | |
242 | bcache->structure_size += BSTRING_SIZE (length); | |
243 | ||
244 | return &new->d.data; | |
245 | } | |
c906108c SS |
246 | } |
247 | ||
3a16a68c AC |
248 | void * |
249 | deprecated_bcache (const void *addr, int length, struct bcache *bcache) | |
250 | { | |
251 | return bcache_data (addr, length, bcache); | |
252 | } | |
253 | ||
254 | const void * | |
255 | bcache (const void *addr, int length, struct bcache *bcache) | |
256 | { | |
257 | return bcache_data (addr, length, bcache); | |
258 | } | |
c2d11a7d | 259 | \f |
af5f3db6 AC |
260 | /* Allocating and freeing bcaches. */ |
261 | ||
262 | struct bcache * | |
263 | bcache_xmalloc (void) | |
264 | { | |
265 | /* Allocate the bcache pre-zeroed. */ | |
266 | struct bcache *b = XCALLOC (1, struct bcache); | |
1ab21617 EZ |
267 | /* We could use obstack_specify_allocation here instead, but |
268 | gdb_obstack.h specifies the allocation/deallocation | |
269 | functions. */ | |
270 | obstack_init (&b->cache); | |
af5f3db6 AC |
271 | return b; |
272 | } | |
c2d11a7d JM |
273 | |
274 | /* Free all the storage associated with BCACHE. */ | |
c906108c | 275 | void |
af5f3db6 | 276 | bcache_xfree (struct bcache *bcache) |
c906108c | 277 | { |
af5f3db6 AC |
278 | if (bcache == NULL) |
279 | return; | |
c2d11a7d | 280 | obstack_free (&bcache->cache, 0); |
af5f3db6 AC |
281 | xfree (bcache->bucket); |
282 | xfree (bcache); | |
c2d11a7d JM |
283 | } |
284 | ||
285 | ||
286 | \f | |
287 | /* Printing statistics. */ | |
288 | ||
289 | static int | |
290 | compare_ints (const void *ap, const void *bp) | |
291 | { | |
292 | /* Because we know we're comparing two ints which are positive, | |
293 | there's no danger of overflow here. */ | |
294 | return * (int *) ap - * (int *) bp; | |
295 | } | |
296 | ||
297 | ||
298 | static void | |
299 | print_percentage (int portion, int total) | |
300 | { | |
301 | if (total == 0) | |
3d263c1d BI |
302 | /* i18n: Like "Percentage of duplicates, by count: (not applicable)" */ |
303 | printf_filtered (_("(not applicable)\n")); | |
c906108c | 304 | else |
b2ba182e | 305 | printf_filtered ("%3d%%\n", (int) (portion * 100.0 / total)); |
c2d11a7d JM |
306 | } |
307 | ||
308 | ||
309 | /* Print statistics on BCACHE's memory usage and efficacity at | |
310 | eliminating duplication. NAME should describe the kind of data | |
311 | BCACHE holds. Statistics are printed using `printf_filtered' and | |
312 | its ilk. */ | |
313 | void | |
314 | print_bcache_statistics (struct bcache *c, char *type) | |
315 | { | |
316 | int occupied_buckets; | |
317 | int max_chain_length; | |
318 | int median_chain_length; | |
2160782c AC |
319 | int max_entry_size; |
320 | int median_entry_size; | |
c2d11a7d | 321 | |
2160782c AC |
322 | /* Count the number of occupied buckets, tally the various string |
323 | lengths, and measure chain lengths. */ | |
c2d11a7d | 324 | { |
745b8ca0 | 325 | unsigned int b; |
2160782c AC |
326 | int *chain_length = XCALLOC (c->num_buckets + 1, int); |
327 | int *entry_size = XCALLOC (c->unique_count + 1, int); | |
328 | int stringi = 0; | |
c2d11a7d JM |
329 | |
330 | occupied_buckets = 0; | |
331 | ||
332 | for (b = 0; b < c->num_buckets; b++) | |
333 | { | |
334 | struct bstring *s = c->bucket[b]; | |
335 | ||
336 | chain_length[b] = 0; | |
337 | ||
338 | if (s) | |
339 | { | |
340 | occupied_buckets++; | |
341 | ||
342 | while (s) | |
343 | { | |
2160782c | 344 | gdb_assert (b < c->num_buckets); |
c2d11a7d | 345 | chain_length[b]++; |
2160782c AC |
346 | gdb_assert (stringi < c->unique_count); |
347 | entry_size[stringi++] = s->length; | |
c2d11a7d JM |
348 | s = s->next; |
349 | } | |
350 | } | |
351 | } | |
352 | ||
353 | /* To compute the median, we need the set of chain lengths sorted. */ | |
354 | qsort (chain_length, c->num_buckets, sizeof (chain_length[0]), | |
355 | compare_ints); | |
2160782c AC |
356 | qsort (entry_size, c->unique_count, sizeof (entry_size[0]), |
357 | compare_ints); | |
c2d11a7d JM |
358 | |
359 | if (c->num_buckets > 0) | |
360 | { | |
361 | max_chain_length = chain_length[c->num_buckets - 1]; | |
362 | median_chain_length = chain_length[c->num_buckets / 2]; | |
363 | } | |
364 | else | |
365 | { | |
366 | max_chain_length = 0; | |
367 | median_chain_length = 0; | |
368 | } | |
2160782c AC |
369 | if (c->unique_count > 0) |
370 | { | |
371 | max_entry_size = entry_size[c->unique_count - 1]; | |
372 | median_entry_size = entry_size[c->unique_count / 2]; | |
373 | } | |
374 | else | |
375 | { | |
376 | max_entry_size = 0; | |
377 | median_entry_size = 0; | |
378 | } | |
379 | ||
380 | xfree (chain_length); | |
381 | xfree (entry_size); | |
c2d11a7d JM |
382 | } |
383 | ||
3d263c1d BI |
384 | printf_filtered (_(" Cached '%s' statistics:\n"), type); |
385 | printf_filtered (_(" Total object count: %ld\n"), c->total_count); | |
386 | printf_filtered (_(" Unique object count: %lu\n"), c->unique_count); | |
387 | printf_filtered (_(" Percentage of duplicates, by count: ")); | |
c2d11a7d JM |
388 | print_percentage (c->total_count - c->unique_count, c->total_count); |
389 | printf_filtered ("\n"); | |
390 | ||
3d263c1d BI |
391 | printf_filtered (_(" Total object size: %ld\n"), c->total_size); |
392 | printf_filtered (_(" Unique object size: %ld\n"), c->unique_size); | |
393 | printf_filtered (_(" Percentage of duplicates, by size: ")); | |
c2d11a7d JM |
394 | print_percentage (c->total_size - c->unique_size, c->total_size); |
395 | printf_filtered ("\n"); | |
396 | ||
3d263c1d BI |
397 | printf_filtered (_(" Max entry size: %d\n"), max_entry_size); |
398 | printf_filtered (_(" Average entry size: ")); | |
2160782c AC |
399 | if (c->unique_count > 0) |
400 | printf_filtered ("%ld\n", c->unique_size / c->unique_count); | |
401 | else | |
3d263c1d BI |
402 | /* i18n: "Average entry size: (not applicable)" */ |
403 | printf_filtered (_("(not applicable)\n")); | |
404 | printf_filtered (_(" Median entry size: %d\n"), median_entry_size); | |
2160782c AC |
405 | printf_filtered ("\n"); |
406 | ||
3d263c1d | 407 | printf_filtered (_(" Total memory used by bcache, including overhead: %ld\n"), |
c2d11a7d | 408 | c->structure_size); |
3d263c1d | 409 | printf_filtered (_(" Percentage memory overhead: ")); |
c2d11a7d | 410 | print_percentage (c->structure_size - c->unique_size, c->unique_size); |
3d263c1d | 411 | printf_filtered (_(" Net memory savings: ")); |
c2d11a7d JM |
412 | print_percentage (c->total_size - c->structure_size, c->total_size); |
413 | printf_filtered ("\n"); | |
414 | ||
3d263c1d BI |
415 | printf_filtered (_(" Hash table size: %3d\n"), c->num_buckets); |
416 | printf_filtered (_(" Hash table expands: %lu\n"), | |
2160782c | 417 | c->expand_count); |
3d263c1d | 418 | printf_filtered (_(" Hash table hashes: %lu\n"), |
2160782c | 419 | c->total_count + c->expand_hash_count); |
3d263c1d | 420 | printf_filtered (_(" Half hash misses: %lu\n"), |
49df298f | 421 | c->half_hash_miss_count); |
3d263c1d | 422 | printf_filtered (_(" Hash table population: ")); |
c2d11a7d | 423 | print_percentage (occupied_buckets, c->num_buckets); |
3d263c1d | 424 | printf_filtered (_(" Median hash chain length: %3d\n"), |
c2d11a7d | 425 | median_chain_length); |
3d263c1d | 426 | printf_filtered (_(" Average hash chain length: ")); |
c2d11a7d | 427 | if (c->num_buckets > 0) |
745b8ca0 | 428 | printf_filtered ("%3lu\n", c->unique_count / c->num_buckets); |
c906108c | 429 | else |
3d263c1d BI |
430 | /* i18n: "Average hash chain length: (not applicable)" */ |
431 | printf_filtered (_("(not applicable)\n")); | |
432 | printf_filtered (_(" Maximum hash chain length: %3d\n"), max_chain_length); | |
c2d11a7d | 433 | printf_filtered ("\n"); |
c906108c | 434 | } |
af5f3db6 AC |
435 | |
436 | int | |
437 | bcache_memory_used (struct bcache *bcache) | |
438 | { | |
439 | return obstack_memory_used (&bcache->cache); | |
440 | } |