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 | |
4c38e0a4 | 5 | Copyright (C) 1999, 2000, 2002, 2003, 2007, 2008, 2009, 2010 |
9b254dd1 | 6 | Free Software Foundation, Inc. |
c906108c | 7 | |
c5aa993b | 8 | This file is part of GDB. |
c906108c | 9 | |
c5aa993b JM |
10 | This program is free software; you can redistribute it and/or modify |
11 | it under the terms of the GNU General Public License as published by | |
a9762ec7 | 12 | the Free Software Foundation; either version 3 of the License, or |
c5aa993b | 13 | (at your option) any later version. |
c906108c | 14 | |
c5aa993b JM |
15 | This program is distributed in the hope that it will be useful, |
16 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
18 | GNU General Public License for more details. | |
c906108c | 19 | |
c5aa993b | 20 | You should have received a copy of the GNU General Public License |
a9762ec7 | 21 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
c906108c SS |
22 | |
23 | #include "defs.h" | |
04ea0df1 | 24 | #include "gdb_obstack.h" |
c906108c SS |
25 | #include "bcache.h" |
26 | #include "gdb_string.h" /* For memcpy declaration */ | |
2160782c | 27 | #include "gdb_assert.h" |
c906108c | 28 | |
2c7ef074 AC |
29 | #include <stddef.h> |
30 | #include <stdlib.h> | |
31 | ||
af5f3db6 AC |
32 | /* The type used to hold a single bcache string. The user data is |
33 | stored in d.data. Since it can be any type, it needs to have the | |
34 | same alignment as the most strict alignment of any type on the host | |
35 | machine. I don't know of any really correct way to do this in | |
36 | stock ANSI C, so just do it the same way obstack.h does. */ | |
37 | ||
38 | struct bstring | |
39 | { | |
49df298f | 40 | /* Hash chain. */ |
af5f3db6 | 41 | struct bstring *next; |
49df298f AC |
42 | /* Assume the data length is no more than 64k. */ |
43 | unsigned short length; | |
44 | /* The half hash hack. This contains the upper 16 bits of the hash | |
45 | value and is used as a pre-check when comparing two strings and | |
46 | avoids the need to do length or memcmp calls. It proves to be | |
47 | roughly 100% effective. */ | |
48 | unsigned short half_hash; | |
af5f3db6 AC |
49 | |
50 | union | |
51 | { | |
52 | char data[1]; | |
53 | double dummy; | |
54 | } | |
55 | d; | |
56 | }; | |
57 | ||
58 | ||
59 | /* The structure for a bcache itself. The bcache is initialized, in | |
60 | bcache_xmalloc(), by filling it with zeros and then setting the | |
61 | corresponding obstack's malloc() and free() methods. */ | |
62 | ||
63 | struct bcache | |
64 | { | |
65 | /* All the bstrings are allocated here. */ | |
66 | struct obstack cache; | |
67 | ||
68 | /* How many hash buckets we're using. */ | |
69 | unsigned int num_buckets; | |
70 | ||
71 | /* Hash buckets. This table is allocated using malloc, so when we | |
72 | grow the table we can return the old table to the system. */ | |
73 | struct bstring **bucket; | |
74 | ||
75 | /* Statistics. */ | |
76 | unsigned long unique_count; /* number of unique strings */ | |
77 | long total_count; /* total number of strings cached, including dups */ | |
78 | long unique_size; /* size of unique strings, in bytes */ | |
79 | long total_size; /* total number of bytes cached, including dups */ | |
80 | long structure_size; /* total size of bcache, including infrastructure */ | |
2160782c AC |
81 | /* Number of times that the hash table is expanded and hence |
82 | re-built, and the corresponding number of times that a string is | |
83 | [re]hashed as part of entering it into the expanded table. The | |
84 | total number of hashes can be computed by adding TOTAL_COUNT to | |
85 | expand_hash_count. */ | |
86 | unsigned long expand_count; | |
87 | unsigned long expand_hash_count; | |
49df298f AC |
88 | /* Number of times that the half-hash compare hit (compare the upper |
89 | 16 bits of hash values) hit, but the corresponding combined | |
90 | length/data compare missed. */ | |
91 | unsigned long half_hash_miss_count; | |
cbd70537 SW |
92 | |
93 | /* Hash function to be used for this bcache object. */ | |
94 | unsigned long (*hash_function)(const void *addr, int length); | |
95 | ||
96 | /* Compare function to be used for this bcache object. */ | |
97 | int (*compare_function)(const void *, const void *, int length); | |
af5f3db6 AC |
98 | }; |
99 | ||
357e46e7 DB |
100 | /* The old hash function was stolen from SDBM. This is what DB 3.0 uses now, |
101 | * and is better than the old one. | |
102 | */ | |
c2d11a7d | 103 | \f |
c2d11a7d | 104 | unsigned long |
d85a5daf | 105 | hash(const void *addr, int length) |
cbd70537 SW |
106 | { |
107 | return hash_continue (addr, length, 0); | |
108 | } | |
109 | ||
110 | /* Continue the calculation of the hash H at the given address. */ | |
111 | ||
112 | unsigned long | |
113 | hash_continue (const void *addr, int length, unsigned long h) | |
c2d11a7d | 114 | { |
b6de9da4 | 115 | const unsigned char *k, *e; |
b6de9da4 MS |
116 | |
117 | k = (const unsigned char *)addr; | |
118 | e = k+length; | |
cbd70537 | 119 | for (; k< e;++k) |
b6de9da4 MS |
120 | { |
121 | h *=16777619; | |
122 | h ^= *k; | |
123 | } | |
124 | return (h); | |
c906108c | 125 | } |
c2d11a7d JM |
126 | \f |
127 | /* Growing the bcache's hash table. */ | |
128 | ||
129 | /* If the average chain length grows beyond this, then we want to | |
130 | resize our hash table. */ | |
131 | #define CHAIN_LENGTH_THRESHOLD (5) | |
132 | ||
133 | static void | |
134 | expand_hash_table (struct bcache *bcache) | |
c906108c | 135 | { |
c2d11a7d JM |
136 | /* A table of good hash table sizes. Whenever we grow, we pick the |
137 | next larger size from this table. sizes[i] is close to 1 << (i+10), | |
138 | so we roughly double the table size each time. After we fall off | |
139 | the end of this table, we just double. Don't laugh --- there have | |
140 | been executables sighted with a gigabyte of debug info. */ | |
141 | static unsigned long sizes[] = { | |
142 | 1021, 2053, 4099, 8191, 16381, 32771, | |
143 | 65537, 131071, 262144, 524287, 1048573, 2097143, | |
144 | 4194301, 8388617, 16777213, 33554467, 67108859, 134217757, | |
145 | 268435459, 536870923, 1073741827, 2147483659UL | |
146 | }; | |
745b8ca0 | 147 | unsigned int new_num_buckets; |
c2d11a7d | 148 | struct bstring **new_buckets; |
745b8ca0 | 149 | unsigned int i; |
c2d11a7d | 150 | |
2160782c AC |
151 | /* Count the stats. Every unique item needs to be re-hashed and |
152 | re-entered. */ | |
153 | bcache->expand_count++; | |
154 | bcache->expand_hash_count += bcache->unique_count; | |
155 | ||
c2d11a7d | 156 | /* Find the next size. */ |
745b8ca0 | 157 | new_num_buckets = bcache->num_buckets * 2; |
c2d11a7d JM |
158 | for (i = 0; i < (sizeof (sizes) / sizeof (sizes[0])); i++) |
159 | if (sizes[i] > bcache->num_buckets) | |
160 | { | |
161 | new_num_buckets = sizes[i]; | |
162 | break; | |
163 | } | |
c2d11a7d JM |
164 | |
165 | /* Allocate the new table. */ | |
166 | { | |
167 | size_t new_size = new_num_buckets * sizeof (new_buckets[0]); | |
b6de9da4 | 168 | |
c2d11a7d JM |
169 | new_buckets = (struct bstring **) xmalloc (new_size); |
170 | memset (new_buckets, 0, new_size); | |
171 | ||
172 | bcache->structure_size -= (bcache->num_buckets | |
173 | * sizeof (bcache->bucket[0])); | |
174 | bcache->structure_size += new_size; | |
175 | } | |
c906108c | 176 | |
c2d11a7d JM |
177 | /* Rehash all existing strings. */ |
178 | for (i = 0; i < bcache->num_buckets; i++) | |
c906108c | 179 | { |
c2d11a7d JM |
180 | struct bstring *s, *next; |
181 | ||
182 | for (s = bcache->bucket[i]; s; s = next) | |
c906108c | 183 | { |
c2d11a7d JM |
184 | struct bstring **new_bucket; |
185 | next = s->next; | |
186 | ||
d3aff959 TT |
187 | new_bucket = &new_buckets[(bcache->hash_function (&s->d.data, |
188 | s->length) | |
c2d11a7d JM |
189 | % new_num_buckets)]; |
190 | s->next = *new_bucket; | |
191 | *new_bucket = s; | |
c906108c SS |
192 | } |
193 | } | |
c2d11a7d JM |
194 | |
195 | /* Plug in the new table. */ | |
196 | if (bcache->bucket) | |
b8c9b27d | 197 | xfree (bcache->bucket); |
c2d11a7d JM |
198 | bcache->bucket = new_buckets; |
199 | bcache->num_buckets = new_num_buckets; | |
c906108c SS |
200 | } |
201 | ||
c2d11a7d JM |
202 | \f |
203 | /* Looking up things in the bcache. */ | |
204 | ||
205 | /* The number of bytes needed to allocate a struct bstring whose data | |
206 | is N bytes long. */ | |
207 | #define BSTRING_SIZE(n) (offsetof (struct bstring, d.data) + (n)) | |
208 | ||
209 | /* Find a copy of the LENGTH bytes at ADDR in BCACHE. If BCACHE has | |
210 | never seen those bytes before, add a copy of them to BCACHE. In | |
211 | either case, return a pointer to BCACHE's copy of that string. */ | |
2e618c13 AR |
212 | const void * |
213 | bcache (const void *addr, int length, struct bcache *bcache) | |
214 | { | |
11d31d94 | 215 | return bcache_full (addr, length, bcache, NULL); |
2e618c13 AR |
216 | } |
217 | ||
218 | /* Find a copy of the LENGTH bytes at ADDR in BCACHE. If BCACHE has | |
219 | never seen those bytes before, add a copy of them to BCACHE. In | |
220 | either case, return a pointer to BCACHE's copy of that string. If | |
221 | optional ADDED is not NULL, return 1 in case of new entry or 0 if | |
222 | returning an old entry. */ | |
223 | ||
11d31d94 TT |
224 | const void * |
225 | bcache_full (const void *addr, int length, struct bcache *bcache, int *added) | |
c906108c | 226 | { |
49df298f AC |
227 | unsigned long full_hash; |
228 | unsigned short half_hash; | |
c2d11a7d JM |
229 | int hash_index; |
230 | struct bstring *s; | |
c906108c | 231 | |
2e618c13 AR |
232 | if (added) |
233 | *added = 0; | |
234 | ||
e6ad058a TT |
235 | /* Lazily initialize the obstack. This can save quite a bit of |
236 | memory in some cases. */ | |
237 | if (bcache->total_count == 0) | |
238 | { | |
239 | /* We could use obstack_specify_allocation here instead, but | |
240 | gdb_obstack.h specifies the allocation/deallocation | |
241 | functions. */ | |
242 | obstack_init (&bcache->cache); | |
243 | } | |
244 | ||
c2d11a7d JM |
245 | /* If our average chain length is too high, expand the hash table. */ |
246 | if (bcache->unique_count >= bcache->num_buckets * CHAIN_LENGTH_THRESHOLD) | |
247 | expand_hash_table (bcache); | |
248 | ||
249 | bcache->total_count++; | |
250 | bcache->total_size += length; | |
251 | ||
cbd70537 SW |
252 | full_hash = bcache->hash_function (addr, length); |
253 | ||
49df298f AC |
254 | half_hash = (full_hash >> 16); |
255 | hash_index = full_hash % bcache->num_buckets; | |
c2d11a7d | 256 | |
49df298f AC |
257 | /* Search the hash bucket for a string identical to the caller's. |
258 | As a short-circuit first compare the upper part of each hash | |
259 | values. */ | |
c2d11a7d | 260 | for (s = bcache->bucket[hash_index]; s; s = s->next) |
49df298f AC |
261 | { |
262 | if (s->half_hash == half_hash) | |
263 | { | |
264 | if (s->length == length | |
cbd70537 | 265 | && bcache->compare_function (&s->d.data, addr, length)) |
49df298f AC |
266 | return &s->d.data; |
267 | else | |
268 | bcache->half_hash_miss_count++; | |
269 | } | |
270 | } | |
c2d11a7d JM |
271 | |
272 | /* The user's string isn't in the list. Insert it after *ps. */ | |
273 | { | |
274 | struct bstring *new | |
275 | = obstack_alloc (&bcache->cache, BSTRING_SIZE (length)); | |
b6de9da4 | 276 | |
c2d11a7d JM |
277 | memcpy (&new->d.data, addr, length); |
278 | new->length = length; | |
279 | new->next = bcache->bucket[hash_index]; | |
49df298f | 280 | new->half_hash = half_hash; |
c2d11a7d JM |
281 | bcache->bucket[hash_index] = new; |
282 | ||
283 | bcache->unique_count++; | |
284 | bcache->unique_size += length; | |
285 | bcache->structure_size += BSTRING_SIZE (length); | |
286 | ||
2e618c13 AR |
287 | if (added) |
288 | *added = 1; | |
289 | ||
c2d11a7d JM |
290 | return &new->d.data; |
291 | } | |
c906108c | 292 | } |
c2d11a7d | 293 | \f |
cbd70537 SW |
294 | |
295 | /* Compare the byte string at ADDR1 of lenght LENGHT to the | |
296 | string at ADDR2. Return 1 if they are equal. */ | |
297 | ||
298 | static int | |
299 | bcache_compare (const void *addr1, const void *addr2, int length) | |
300 | { | |
301 | return memcmp (addr1, addr2, length) == 0; | |
302 | } | |
303 | ||
af5f3db6 AC |
304 | /* Allocating and freeing bcaches. */ |
305 | ||
cbd70537 SW |
306 | /* Allocated a bcache. HASH_FUNCTION and COMPARE_FUNCTION can be used |
307 | to pass in custom hash, and compare functions to be used by this | |
308 | bcache. If HASH_FUNCTION is NULL hash() is used and if COMPARE_FUNCTION | |
309 | is NULL memcmp() is used. */ | |
310 | ||
af5f3db6 | 311 | struct bcache * |
cbd70537 SW |
312 | bcache_xmalloc (unsigned long (*hash_function)(const void *, int length), |
313 | int (*compare_function)(const void *, const void *, int length)) | |
af5f3db6 AC |
314 | { |
315 | /* Allocate the bcache pre-zeroed. */ | |
316 | struct bcache *b = XCALLOC (1, struct bcache); | |
b6de9da4 | 317 | |
cbd70537 SW |
318 | if (hash_function) |
319 | b->hash_function = hash_function; | |
320 | else | |
321 | b->hash_function = hash; | |
322 | ||
323 | if (compare_function) | |
324 | b->compare_function = compare_function; | |
325 | else | |
326 | b->compare_function = bcache_compare; | |
af5f3db6 AC |
327 | return b; |
328 | } | |
c2d11a7d JM |
329 | |
330 | /* Free all the storage associated with BCACHE. */ | |
c906108c | 331 | void |
af5f3db6 | 332 | bcache_xfree (struct bcache *bcache) |
c906108c | 333 | { |
af5f3db6 AC |
334 | if (bcache == NULL) |
335 | return; | |
e6ad058a TT |
336 | /* Only free the obstack if we actually initialized it. */ |
337 | if (bcache->total_count > 0) | |
338 | obstack_free (&bcache->cache, 0); | |
af5f3db6 AC |
339 | xfree (bcache->bucket); |
340 | xfree (bcache); | |
c2d11a7d JM |
341 | } |
342 | ||
343 | ||
344 | \f | |
345 | /* Printing statistics. */ | |
346 | ||
c2d11a7d JM |
347 | static void |
348 | print_percentage (int portion, int total) | |
349 | { | |
350 | if (total == 0) | |
3d263c1d BI |
351 | /* i18n: Like "Percentage of duplicates, by count: (not applicable)" */ |
352 | printf_filtered (_("(not applicable)\n")); | |
c906108c | 353 | else |
b2ba182e | 354 | printf_filtered ("%3d%%\n", (int) (portion * 100.0 / total)); |
c2d11a7d JM |
355 | } |
356 | ||
357 | ||
358 | /* Print statistics on BCACHE's memory usage and efficacity at | |
359 | eliminating duplication. NAME should describe the kind of data | |
360 | BCACHE holds. Statistics are printed using `printf_filtered' and | |
361 | its ilk. */ | |
362 | void | |
363 | print_bcache_statistics (struct bcache *c, char *type) | |
364 | { | |
365 | int occupied_buckets; | |
366 | int max_chain_length; | |
367 | int median_chain_length; | |
2160782c AC |
368 | int max_entry_size; |
369 | int median_entry_size; | |
c2d11a7d | 370 | |
2160782c AC |
371 | /* Count the number of occupied buckets, tally the various string |
372 | lengths, and measure chain lengths. */ | |
c2d11a7d | 373 | { |
745b8ca0 | 374 | unsigned int b; |
2160782c AC |
375 | int *chain_length = XCALLOC (c->num_buckets + 1, int); |
376 | int *entry_size = XCALLOC (c->unique_count + 1, int); | |
377 | int stringi = 0; | |
c2d11a7d JM |
378 | |
379 | occupied_buckets = 0; | |
380 | ||
381 | for (b = 0; b < c->num_buckets; b++) | |
382 | { | |
383 | struct bstring *s = c->bucket[b]; | |
384 | ||
385 | chain_length[b] = 0; | |
386 | ||
387 | if (s) | |
388 | { | |
389 | occupied_buckets++; | |
390 | ||
391 | while (s) | |
392 | { | |
2160782c | 393 | gdb_assert (b < c->num_buckets); |
c2d11a7d | 394 | chain_length[b]++; |
2160782c AC |
395 | gdb_assert (stringi < c->unique_count); |
396 | entry_size[stringi++] = s->length; | |
c2d11a7d JM |
397 | s = s->next; |
398 | } | |
399 | } | |
400 | } | |
401 | ||
402 | /* To compute the median, we need the set of chain lengths sorted. */ | |
403 | qsort (chain_length, c->num_buckets, sizeof (chain_length[0]), | |
dc146f7c | 404 | compare_positive_ints); |
2160782c | 405 | qsort (entry_size, c->unique_count, sizeof (entry_size[0]), |
dc146f7c | 406 | compare_positive_ints); |
c2d11a7d JM |
407 | |
408 | if (c->num_buckets > 0) | |
409 | { | |
410 | max_chain_length = chain_length[c->num_buckets - 1]; | |
411 | median_chain_length = chain_length[c->num_buckets / 2]; | |
412 | } | |
413 | else | |
414 | { | |
415 | max_chain_length = 0; | |
416 | median_chain_length = 0; | |
417 | } | |
2160782c AC |
418 | if (c->unique_count > 0) |
419 | { | |
420 | max_entry_size = entry_size[c->unique_count - 1]; | |
421 | median_entry_size = entry_size[c->unique_count / 2]; | |
422 | } | |
423 | else | |
424 | { | |
425 | max_entry_size = 0; | |
426 | median_entry_size = 0; | |
427 | } | |
428 | ||
429 | xfree (chain_length); | |
430 | xfree (entry_size); | |
c2d11a7d JM |
431 | } |
432 | ||
3d263c1d BI |
433 | printf_filtered (_(" Cached '%s' statistics:\n"), type); |
434 | printf_filtered (_(" Total object count: %ld\n"), c->total_count); | |
435 | printf_filtered (_(" Unique object count: %lu\n"), c->unique_count); | |
436 | printf_filtered (_(" Percentage of duplicates, by count: ")); | |
c2d11a7d JM |
437 | print_percentage (c->total_count - c->unique_count, c->total_count); |
438 | printf_filtered ("\n"); | |
439 | ||
3d263c1d BI |
440 | printf_filtered (_(" Total object size: %ld\n"), c->total_size); |
441 | printf_filtered (_(" Unique object size: %ld\n"), c->unique_size); | |
442 | printf_filtered (_(" Percentage of duplicates, by size: ")); | |
c2d11a7d JM |
443 | print_percentage (c->total_size - c->unique_size, c->total_size); |
444 | printf_filtered ("\n"); | |
445 | ||
3d263c1d BI |
446 | printf_filtered (_(" Max entry size: %d\n"), max_entry_size); |
447 | printf_filtered (_(" Average entry size: ")); | |
2160782c AC |
448 | if (c->unique_count > 0) |
449 | printf_filtered ("%ld\n", c->unique_size / c->unique_count); | |
450 | else | |
3d263c1d BI |
451 | /* i18n: "Average entry size: (not applicable)" */ |
452 | printf_filtered (_("(not applicable)\n")); | |
453 | printf_filtered (_(" Median entry size: %d\n"), median_entry_size); | |
2160782c AC |
454 | printf_filtered ("\n"); |
455 | ||
3d263c1d | 456 | printf_filtered (_(" Total memory used by bcache, including overhead: %ld\n"), |
c2d11a7d | 457 | c->structure_size); |
3d263c1d | 458 | printf_filtered (_(" Percentage memory overhead: ")); |
c2d11a7d | 459 | print_percentage (c->structure_size - c->unique_size, c->unique_size); |
3d263c1d | 460 | printf_filtered (_(" Net memory savings: ")); |
c2d11a7d JM |
461 | print_percentage (c->total_size - c->structure_size, c->total_size); |
462 | printf_filtered ("\n"); | |
463 | ||
3d263c1d BI |
464 | printf_filtered (_(" Hash table size: %3d\n"), c->num_buckets); |
465 | printf_filtered (_(" Hash table expands: %lu\n"), | |
2160782c | 466 | c->expand_count); |
3d263c1d | 467 | printf_filtered (_(" Hash table hashes: %lu\n"), |
2160782c | 468 | c->total_count + c->expand_hash_count); |
3d263c1d | 469 | printf_filtered (_(" Half hash misses: %lu\n"), |
49df298f | 470 | c->half_hash_miss_count); |
3d263c1d | 471 | printf_filtered (_(" Hash table population: ")); |
c2d11a7d | 472 | print_percentage (occupied_buckets, c->num_buckets); |
3d263c1d | 473 | printf_filtered (_(" Median hash chain length: %3d\n"), |
c2d11a7d | 474 | median_chain_length); |
3d263c1d | 475 | printf_filtered (_(" Average hash chain length: ")); |
c2d11a7d | 476 | if (c->num_buckets > 0) |
745b8ca0 | 477 | printf_filtered ("%3lu\n", c->unique_count / c->num_buckets); |
c906108c | 478 | else |
3d263c1d BI |
479 | /* i18n: "Average hash chain length: (not applicable)" */ |
480 | printf_filtered (_("(not applicable)\n")); | |
481 | printf_filtered (_(" Maximum hash chain length: %3d\n"), max_chain_length); | |
c2d11a7d | 482 | printf_filtered ("\n"); |
c906108c | 483 | } |
af5f3db6 AC |
484 | |
485 | int | |
486 | bcache_memory_used (struct bcache *bcache) | |
487 | { | |
e6ad058a TT |
488 | if (bcache->total_count == 0) |
489 | return 0; | |
af5f3db6 AC |
490 | return obstack_memory_used (&bcache->cache); |
491 | } |