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 | |
2160782c | 5 | Copyright 1999, 2000, 2002, 2003 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 | |
11 | the Free Software Foundation; either version 2 of the License, or | |
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 JM |
19 | You should have received a copy of the GNU General Public License |
20 | along with this program; if not, write to the Free Software | |
21 | Foundation, Inc., 59 Temple Place - Suite 330, | |
22 | Boston, MA 02111-1307, USA. */ | |
c906108c SS |
23 | |
24 | #include "defs.h" | |
04ea0df1 | 25 | #include "gdb_obstack.h" |
c906108c SS |
26 | #include "bcache.h" |
27 | #include "gdb_string.h" /* For memcpy declaration */ | |
2160782c | 28 | #include "gdb_assert.h" |
c906108c | 29 | |
2c7ef074 AC |
30 | #include <stddef.h> |
31 | #include <stdlib.h> | |
32 | ||
af5f3db6 AC |
33 | /* The type used to hold a single bcache string. The user data is |
34 | stored in d.data. Since it can be any type, it needs to have the | |
35 | same alignment as the most strict alignment of any type on the host | |
36 | machine. I don't know of any really correct way to do this in | |
37 | stock ANSI C, so just do it the same way obstack.h does. */ | |
38 | ||
39 | struct bstring | |
40 | { | |
41 | struct bstring *next; | |
42 | size_t length; | |
43 | ||
44 | union | |
45 | { | |
46 | char data[1]; | |
47 | double dummy; | |
48 | } | |
49 | d; | |
50 | }; | |
51 | ||
52 | ||
53 | /* The structure for a bcache itself. The bcache is initialized, in | |
54 | bcache_xmalloc(), by filling it with zeros and then setting the | |
55 | corresponding obstack's malloc() and free() methods. */ | |
56 | ||
57 | struct bcache | |
58 | { | |
59 | /* All the bstrings are allocated here. */ | |
60 | struct obstack cache; | |
61 | ||
62 | /* How many hash buckets we're using. */ | |
63 | unsigned int num_buckets; | |
64 | ||
65 | /* Hash buckets. This table is allocated using malloc, so when we | |
66 | grow the table we can return the old table to the system. */ | |
67 | struct bstring **bucket; | |
68 | ||
69 | /* Statistics. */ | |
70 | unsigned long unique_count; /* number of unique strings */ | |
71 | long total_count; /* total number of strings cached, including dups */ | |
72 | long unique_size; /* size of unique strings, in bytes */ | |
73 | long total_size; /* total number of bytes cached, including dups */ | |
74 | long structure_size; /* total size of bcache, including infrastructure */ | |
2160782c AC |
75 | /* Number of times that the hash table is expanded and hence |
76 | re-built, and the corresponding number of times that a string is | |
77 | [re]hashed as part of entering it into the expanded table. The | |
78 | total number of hashes can be computed by adding TOTAL_COUNT to | |
79 | expand_hash_count. */ | |
80 | unsigned long expand_count; | |
81 | unsigned long expand_hash_count; | |
af5f3db6 AC |
82 | }; |
83 | ||
357e46e7 DB |
84 | /* The old hash function was stolen from SDBM. This is what DB 3.0 uses now, |
85 | * and is better than the old one. | |
86 | */ | |
c2d11a7d | 87 | \f |
c2d11a7d | 88 | unsigned long |
d85a5daf | 89 | hash(const void *addr, int length) |
c2d11a7d | 90 | { |
357e46e7 DB |
91 | const unsigned char *k, *e; |
92 | unsigned long h; | |
93 | ||
94 | k = (const unsigned char *)addr; | |
95 | e = k+length; | |
96 | for (h=0; k< e;++k) | |
97 | { | |
98 | h *=16777619; | |
99 | h ^= *k; | |
100 | } | |
101 | return (h); | |
c906108c | 102 | } |
c2d11a7d JM |
103 | \f |
104 | /* Growing the bcache's hash table. */ | |
105 | ||
106 | /* If the average chain length grows beyond this, then we want to | |
107 | resize our hash table. */ | |
108 | #define CHAIN_LENGTH_THRESHOLD (5) | |
109 | ||
110 | static void | |
111 | expand_hash_table (struct bcache *bcache) | |
c906108c | 112 | { |
c2d11a7d JM |
113 | /* A table of good hash table sizes. Whenever we grow, we pick the |
114 | next larger size from this table. sizes[i] is close to 1 << (i+10), | |
115 | so we roughly double the table size each time. After we fall off | |
116 | the end of this table, we just double. Don't laugh --- there have | |
117 | been executables sighted with a gigabyte of debug info. */ | |
118 | static unsigned long sizes[] = { | |
119 | 1021, 2053, 4099, 8191, 16381, 32771, | |
120 | 65537, 131071, 262144, 524287, 1048573, 2097143, | |
121 | 4194301, 8388617, 16777213, 33554467, 67108859, 134217757, | |
122 | 268435459, 536870923, 1073741827, 2147483659UL | |
123 | }; | |
745b8ca0 | 124 | unsigned int new_num_buckets; |
c2d11a7d | 125 | struct bstring **new_buckets; |
745b8ca0 | 126 | unsigned int i; |
c2d11a7d | 127 | |
2160782c AC |
128 | /* Count the stats. Every unique item needs to be re-hashed and |
129 | re-entered. */ | |
130 | bcache->expand_count++; | |
131 | bcache->expand_hash_count += bcache->unique_count; | |
132 | ||
c2d11a7d | 133 | /* Find the next size. */ |
745b8ca0 | 134 | new_num_buckets = bcache->num_buckets * 2; |
c2d11a7d JM |
135 | for (i = 0; i < (sizeof (sizes) / sizeof (sizes[0])); i++) |
136 | if (sizes[i] > bcache->num_buckets) | |
137 | { | |
138 | new_num_buckets = sizes[i]; | |
139 | break; | |
140 | } | |
c2d11a7d JM |
141 | |
142 | /* Allocate the new table. */ | |
143 | { | |
144 | size_t new_size = new_num_buckets * sizeof (new_buckets[0]); | |
145 | new_buckets = (struct bstring **) xmalloc (new_size); | |
146 | memset (new_buckets, 0, new_size); | |
147 | ||
148 | bcache->structure_size -= (bcache->num_buckets | |
149 | * sizeof (bcache->bucket[0])); | |
150 | bcache->structure_size += new_size; | |
151 | } | |
c906108c | 152 | |
c2d11a7d JM |
153 | /* Rehash all existing strings. */ |
154 | for (i = 0; i < bcache->num_buckets; i++) | |
c906108c | 155 | { |
c2d11a7d JM |
156 | struct bstring *s, *next; |
157 | ||
158 | for (s = bcache->bucket[i]; s; s = next) | |
c906108c | 159 | { |
c2d11a7d JM |
160 | struct bstring **new_bucket; |
161 | next = s->next; | |
162 | ||
163 | new_bucket = &new_buckets[(hash (&s->d.data, s->length) | |
164 | % new_num_buckets)]; | |
165 | s->next = *new_bucket; | |
166 | *new_bucket = s; | |
c906108c SS |
167 | } |
168 | } | |
c2d11a7d JM |
169 | |
170 | /* Plug in the new table. */ | |
171 | if (bcache->bucket) | |
b8c9b27d | 172 | xfree (bcache->bucket); |
c2d11a7d JM |
173 | bcache->bucket = new_buckets; |
174 | bcache->num_buckets = new_num_buckets; | |
c906108c SS |
175 | } |
176 | ||
c2d11a7d JM |
177 | \f |
178 | /* Looking up things in the bcache. */ | |
179 | ||
180 | /* The number of bytes needed to allocate a struct bstring whose data | |
181 | is N bytes long. */ | |
182 | #define BSTRING_SIZE(n) (offsetof (struct bstring, d.data) + (n)) | |
183 | ||
184 | /* Find a copy of the LENGTH bytes at ADDR in BCACHE. If BCACHE has | |
185 | never seen those bytes before, add a copy of them to BCACHE. In | |
186 | either case, return a pointer to BCACHE's copy of that string. */ | |
c906108c | 187 | void * |
d85a5daf | 188 | bcache (const void *addr, int length, struct bcache *bcache) |
c906108c | 189 | { |
c2d11a7d JM |
190 | int hash_index; |
191 | struct bstring *s; | |
c906108c | 192 | |
c2d11a7d JM |
193 | /* If our average chain length is too high, expand the hash table. */ |
194 | if (bcache->unique_count >= bcache->num_buckets * CHAIN_LENGTH_THRESHOLD) | |
195 | expand_hash_table (bcache); | |
196 | ||
197 | bcache->total_count++; | |
198 | bcache->total_size += length; | |
199 | ||
200 | hash_index = hash (addr, length) % bcache->num_buckets; | |
201 | ||
202 | /* Search the hash bucket for a string identical to the caller's. */ | |
203 | for (s = bcache->bucket[hash_index]; s; s = s->next) | |
204 | if (s->length == length | |
205 | && ! memcmp (&s->d.data, addr, length)) | |
206 | return &s->d.data; | |
207 | ||
208 | /* The user's string isn't in the list. Insert it after *ps. */ | |
209 | { | |
210 | struct bstring *new | |
211 | = obstack_alloc (&bcache->cache, BSTRING_SIZE (length)); | |
212 | memcpy (&new->d.data, addr, length); | |
213 | new->length = length; | |
214 | new->next = bcache->bucket[hash_index]; | |
215 | bcache->bucket[hash_index] = new; | |
216 | ||
217 | bcache->unique_count++; | |
218 | bcache->unique_size += length; | |
219 | bcache->structure_size += BSTRING_SIZE (length); | |
220 | ||
221 | return &new->d.data; | |
222 | } | |
c906108c SS |
223 | } |
224 | ||
c2d11a7d | 225 | \f |
af5f3db6 AC |
226 | /* Allocating and freeing bcaches. */ |
227 | ||
228 | struct bcache * | |
229 | bcache_xmalloc (void) | |
230 | { | |
231 | /* Allocate the bcache pre-zeroed. */ | |
232 | struct bcache *b = XCALLOC (1, struct bcache); | |
233 | obstack_specify_allocation (&b->cache, 0, 0, xmalloc, xfree); | |
234 | return b; | |
235 | } | |
c2d11a7d JM |
236 | |
237 | /* Free all the storage associated with BCACHE. */ | |
c906108c | 238 | void |
af5f3db6 | 239 | bcache_xfree (struct bcache *bcache) |
c906108c | 240 | { |
af5f3db6 AC |
241 | if (bcache == NULL) |
242 | return; | |
c2d11a7d | 243 | obstack_free (&bcache->cache, 0); |
af5f3db6 AC |
244 | xfree (bcache->bucket); |
245 | xfree (bcache); | |
c2d11a7d JM |
246 | } |
247 | ||
248 | ||
249 | \f | |
250 | /* Printing statistics. */ | |
251 | ||
252 | static int | |
253 | compare_ints (const void *ap, const void *bp) | |
254 | { | |
255 | /* Because we know we're comparing two ints which are positive, | |
256 | there's no danger of overflow here. */ | |
257 | return * (int *) ap - * (int *) bp; | |
258 | } | |
259 | ||
260 | ||
261 | static void | |
262 | print_percentage (int portion, int total) | |
263 | { | |
264 | if (total == 0) | |
265 | printf_filtered ("(not applicable)\n"); | |
c906108c | 266 | else |
c2d11a7d JM |
267 | printf_filtered ("%3d%%\n", portion * 100 / total); |
268 | } | |
269 | ||
270 | ||
271 | /* Print statistics on BCACHE's memory usage and efficacity at | |
272 | eliminating duplication. NAME should describe the kind of data | |
273 | BCACHE holds. Statistics are printed using `printf_filtered' and | |
274 | its ilk. */ | |
275 | void | |
276 | print_bcache_statistics (struct bcache *c, char *type) | |
277 | { | |
278 | int occupied_buckets; | |
279 | int max_chain_length; | |
280 | int median_chain_length; | |
2160782c AC |
281 | int max_entry_size; |
282 | int median_entry_size; | |
c2d11a7d | 283 | |
2160782c AC |
284 | /* Count the number of occupied buckets, tally the various string |
285 | lengths, and measure chain lengths. */ | |
c2d11a7d | 286 | { |
745b8ca0 | 287 | unsigned int b; |
2160782c AC |
288 | int *chain_length = XCALLOC (c->num_buckets + 1, int); |
289 | int *entry_size = XCALLOC (c->unique_count + 1, int); | |
290 | int stringi = 0; | |
c2d11a7d JM |
291 | |
292 | occupied_buckets = 0; | |
293 | ||
294 | for (b = 0; b < c->num_buckets; b++) | |
295 | { | |
296 | struct bstring *s = c->bucket[b]; | |
297 | ||
298 | chain_length[b] = 0; | |
299 | ||
300 | if (s) | |
301 | { | |
302 | occupied_buckets++; | |
303 | ||
304 | while (s) | |
305 | { | |
2160782c | 306 | gdb_assert (b < c->num_buckets); |
c2d11a7d | 307 | chain_length[b]++; |
2160782c AC |
308 | gdb_assert (stringi < c->unique_count); |
309 | entry_size[stringi++] = s->length; | |
c2d11a7d JM |
310 | s = s->next; |
311 | } | |
312 | } | |
313 | } | |
314 | ||
315 | /* To compute the median, we need the set of chain lengths sorted. */ | |
316 | qsort (chain_length, c->num_buckets, sizeof (chain_length[0]), | |
317 | compare_ints); | |
2160782c AC |
318 | qsort (entry_size, c->unique_count, sizeof (entry_size[0]), |
319 | compare_ints); | |
c2d11a7d JM |
320 | |
321 | if (c->num_buckets > 0) | |
322 | { | |
323 | max_chain_length = chain_length[c->num_buckets - 1]; | |
324 | median_chain_length = chain_length[c->num_buckets / 2]; | |
325 | } | |
326 | else | |
327 | { | |
328 | max_chain_length = 0; | |
329 | median_chain_length = 0; | |
330 | } | |
2160782c AC |
331 | if (c->unique_count > 0) |
332 | { | |
333 | max_entry_size = entry_size[c->unique_count - 1]; | |
334 | median_entry_size = entry_size[c->unique_count / 2]; | |
335 | } | |
336 | else | |
337 | { | |
338 | max_entry_size = 0; | |
339 | median_entry_size = 0; | |
340 | } | |
341 | ||
342 | xfree (chain_length); | |
343 | xfree (entry_size); | |
c2d11a7d JM |
344 | } |
345 | ||
346 | printf_filtered (" Cached '%s' statistics:\n", type); | |
347 | printf_filtered (" Total object count: %ld\n", c->total_count); | |
745b8ca0 | 348 | printf_filtered (" Unique object count: %lu\n", c->unique_count); |
c2d11a7d JM |
349 | printf_filtered (" Percentage of duplicates, by count: "); |
350 | print_percentage (c->total_count - c->unique_count, c->total_count); | |
351 | printf_filtered ("\n"); | |
352 | ||
353 | printf_filtered (" Total object size: %ld\n", c->total_size); | |
354 | printf_filtered (" Unique object size: %ld\n", c->unique_size); | |
355 | printf_filtered (" Percentage of duplicates, by size: "); | |
356 | print_percentage (c->total_size - c->unique_size, c->total_size); | |
357 | printf_filtered ("\n"); | |
358 | ||
2160782c AC |
359 | printf_filtered (" Max entry size: %d\n", max_entry_size); |
360 | printf_filtered (" Average entry size: "); | |
361 | if (c->unique_count > 0) | |
362 | printf_filtered ("%ld\n", c->unique_size / c->unique_count); | |
363 | else | |
364 | printf_filtered ("(not applicable)\n"); | |
365 | printf_filtered (" Median entry size: %d\n", median_entry_size); | |
366 | printf_filtered ("\n"); | |
367 | ||
c2d11a7d JM |
368 | printf_filtered (" Total memory used by bcache, including overhead: %ld\n", |
369 | c->structure_size); | |
370 | printf_filtered (" Percentage memory overhead: "); | |
371 | print_percentage (c->structure_size - c->unique_size, c->unique_size); | |
372 | printf_filtered (" Net memory savings: "); | |
373 | print_percentage (c->total_size - c->structure_size, c->total_size); | |
374 | printf_filtered ("\n"); | |
375 | ||
376 | printf_filtered (" Hash table size: %3d\n", c->num_buckets); | |
2160782c AC |
377 | printf_filtered (" Hash table expands: %lu\n", |
378 | c->expand_count); | |
379 | printf_filtered (" Hash table hashes: %lu\n", | |
380 | c->total_count + c->expand_hash_count); | |
c2d11a7d JM |
381 | printf_filtered (" Hash table population: "); |
382 | print_percentage (occupied_buckets, c->num_buckets); | |
383 | printf_filtered (" Median hash chain length: %3d\n", | |
384 | median_chain_length); | |
385 | printf_filtered (" Average hash chain length: "); | |
386 | if (c->num_buckets > 0) | |
745b8ca0 | 387 | printf_filtered ("%3lu\n", c->unique_count / c->num_buckets); |
c906108c | 388 | else |
c2d11a7d JM |
389 | printf_filtered ("(not applicable)\n"); |
390 | printf_filtered (" Maximum hash chain length: %3d\n", max_chain_length); | |
391 | printf_filtered ("\n"); | |
c906108c | 392 | } |
af5f3db6 AC |
393 | |
394 | int | |
395 | bcache_memory_used (struct bcache *bcache) | |
396 | { | |
397 | return obstack_memory_used (&bcache->cache); | |
398 | } |