OpenCores
URL https://opencores.org/ocsvn/or1k/or1k/trunk

Subversion Repositories or1k

[/] [or1k/] [trunk/] [insight/] [gdb/] [bcache.c] - Blame information for rev 1771

Go to most recent revision | Details | Compare with Previous | View Log

Line No. Rev Author Line
1 578 markom
/* Implement a cached obstack.
2
   Written by Fred Fish <fnf@cygnus.com>
3
   Rewritten by Jim Blandy <jimb@cygnus.com>
4
   Copyright 1999, 2000 Free Software Foundation, Inc.
5
 
6
   This file is part of GDB.
7
 
8
   This program is free software; you can redistribute it and/or modify
9
   it under the terms of the GNU General Public License as published by
10
   the Free Software Foundation; either version 2 of the License, or
11
   (at your option) any later version.
12
 
13
   This program is distributed in the hope that it will be useful,
14
   but WITHOUT ANY WARRANTY; without even the implied warranty of
15
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16
   GNU General Public License for more details.
17
 
18
   You should have received a copy of the GNU General Public License
19
   along with this program; if not, write to the Free Software
20
   Foundation, Inc., 59 Temple Place - Suite 330,
21
   Boston, MA 02111-1307, USA.  */
22
 
23
#include <stddef.h>
24
#include <stdlib.h>
25
 
26
#include "defs.h"
27
#include "obstack.h"
28
#include "bcache.h"
29
#include "gdb_string.h"         /* For memcpy declaration */
30
 
31
/* The old hash function was stolen from SDBM. This is what DB 3.0 uses now,
32
 * and is better than the old one.
33
 */
34
 
35
unsigned long
36
hash(void *addr, int length)
37
{
38
                const unsigned char *k, *e;
39
                unsigned long h;
40
 
41
                k = (const unsigned char *)addr;
42
                e = k+length;
43
                for (h=0; k< e;++k)
44
                {
45
                                h *=16777619;
46
                                h ^= *k;
47
                }
48
                return (h);
49
}
50
 
51
/* Growing the bcache's hash table.  */
52
 
53
/* If the average chain length grows beyond this, then we want to
54
   resize our hash table.  */
55
#define CHAIN_LENGTH_THRESHOLD (5)
56
 
57
static void
58
expand_hash_table (struct bcache *bcache)
59
{
60
  /* A table of good hash table sizes.  Whenever we grow, we pick the
61
     next larger size from this table.  sizes[i] is close to 1 << (i+10),
62
     so we roughly double the table size each time.  After we fall off
63
     the end of this table, we just double.  Don't laugh --- there have
64
     been executables sighted with a gigabyte of debug info.  */
65
  static unsigned long sizes[] = {
66
    1021, 2053, 4099, 8191, 16381, 32771,
67
    65537, 131071, 262144, 524287, 1048573, 2097143,
68
    4194301, 8388617, 16777213, 33554467, 67108859, 134217757,
69
    268435459, 536870923, 1073741827, 2147483659UL
70
  };
71
  unsigned int new_num_buckets;
72
  struct bstring **new_buckets;
73
  unsigned int i;
74
 
75
  /* Find the next size.  */
76
  new_num_buckets = bcache->num_buckets * 2;
77
  for (i = 0; i < (sizeof (sizes) / sizeof (sizes[0])); i++)
78
    if (sizes[i] > bcache->num_buckets)
79
      {
80
        new_num_buckets = sizes[i];
81
        break;
82
      }
83
 
84
  /* Allocate the new table.  */
85
  {
86
    size_t new_size = new_num_buckets * sizeof (new_buckets[0]);
87
    new_buckets = (struct bstring **) xmalloc (new_size);
88
    memset (new_buckets, 0, new_size);
89
 
90
    bcache->structure_size -= (bcache->num_buckets
91
                               * sizeof (bcache->bucket[0]));
92
    bcache->structure_size += new_size;
93
  }
94
 
95
  /* Rehash all existing strings.  */
96
  for (i = 0; i < bcache->num_buckets; i++)
97
    {
98
      struct bstring *s, *next;
99
 
100
      for (s = bcache->bucket[i]; s; s = next)
101
        {
102
          struct bstring **new_bucket;
103
          next = s->next;
104
 
105
          new_bucket = &new_buckets[(hash (&s->d.data, s->length)
106
                                     % new_num_buckets)];
107
          s->next = *new_bucket;
108
          *new_bucket = s;
109
        }
110
    }
111
 
112
  /* Plug in the new table.  */
113
  if (bcache->bucket)
114
    xfree (bcache->bucket);
115
  bcache->bucket = new_buckets;
116
  bcache->num_buckets = new_num_buckets;
117
}
118
 
119
 
120
/* Looking up things in the bcache.  */
121
 
122
/* The number of bytes needed to allocate a struct bstring whose data
123
   is N bytes long.  */
124
#define BSTRING_SIZE(n) (offsetof (struct bstring, d.data) + (n))
125
 
126
/* Find a copy of the LENGTH bytes at ADDR in BCACHE.  If BCACHE has
127
   never seen those bytes before, add a copy of them to BCACHE.  In
128
   either case, return a pointer to BCACHE's copy of that string.  */
129
void *
130
bcache (void *addr, int length, struct bcache *bcache)
131
{
132
  int hash_index;
133
  struct bstring *s;
134
 
135
  /* If our average chain length is too high, expand the hash table.  */
136
  if (bcache->unique_count >= bcache->num_buckets * CHAIN_LENGTH_THRESHOLD)
137
    expand_hash_table (bcache);
138
 
139
  bcache->total_count++;
140
  bcache->total_size += length;
141
 
142
  hash_index = hash (addr, length) % bcache->num_buckets;
143
 
144
  /* Search the hash bucket for a string identical to the caller's.  */
145
  for (s = bcache->bucket[hash_index]; s; s = s->next)
146
    if (s->length == length
147
        && ! memcmp (&s->d.data, addr, length))
148
      return &s->d.data;
149
 
150
  /* The user's string isn't in the list.  Insert it after *ps.  */
151
  {
152
    struct bstring *new
153
      = obstack_alloc (&bcache->cache, BSTRING_SIZE (length));
154
    memcpy (&new->d.data, addr, length);
155
    new->length = length;
156
    new->next = bcache->bucket[hash_index];
157
    bcache->bucket[hash_index] = new;
158
 
159
    bcache->unique_count++;
160
    bcache->unique_size += length;
161
    bcache->structure_size += BSTRING_SIZE (length);
162
 
163
    return &new->d.data;
164
  }
165
}
166
 
167
 
168
/* Freeing bcaches.  */
169
 
170
/* Free all the storage associated with BCACHE.  */
171
void
172
free_bcache (struct bcache *bcache)
173
{
174
  obstack_free (&bcache->cache, 0);
175
  if (bcache->bucket)
176
    xfree (bcache->bucket);
177
 
178
  /* This isn't necessary, but at least the bcache is always in a
179
     consistent state.  */
180
  memset (bcache, 0, sizeof (*bcache));
181
}
182
 
183
 
184
 
185
/* Printing statistics.  */
186
 
187
static int
188
compare_ints (const void *ap, const void *bp)
189
{
190
  /* Because we know we're comparing two ints which are positive,
191
     there's no danger of overflow here.  */
192
  return * (int *) ap - * (int *) bp;
193
}
194
 
195
 
196
static void
197
print_percentage (int portion, int total)
198
{
199
  if (total == 0)
200
    printf_filtered ("(not applicable)\n");
201
  else
202
    printf_filtered ("%3d%%\n", portion * 100 / total);
203
}
204
 
205
 
206
/* Print statistics on BCACHE's memory usage and efficacity at
207
   eliminating duplication.  NAME should describe the kind of data
208
   BCACHE holds.  Statistics are printed using `printf_filtered' and
209
   its ilk.  */
210
void
211
print_bcache_statistics (struct bcache *c, char *type)
212
{
213
  int occupied_buckets;
214
  int max_chain_length;
215
  int median_chain_length;
216
 
217
  /* Count the number of occupied buckets, and measure chain lengths.  */
218
  {
219
    unsigned int b;
220
    int *chain_length
221
      = (int *) alloca (c->num_buckets * sizeof (*chain_length));
222
 
223
    occupied_buckets = 0;
224
 
225
    for (b = 0; b < c->num_buckets; b++)
226
      {
227
        struct bstring *s = c->bucket[b];
228
 
229
        chain_length[b] = 0;
230
 
231
        if (s)
232
          {
233
            occupied_buckets++;
234
 
235
            while (s)
236
              {
237
                chain_length[b]++;
238
                s = s->next;
239
              }
240
          }
241
      }
242
 
243
    /* To compute the median, we need the set of chain lengths sorted.  */
244
    qsort (chain_length, c->num_buckets, sizeof (chain_length[0]),
245
           compare_ints);
246
 
247
    if (c->num_buckets > 0)
248
      {
249
        max_chain_length = chain_length[c->num_buckets - 1];
250
        median_chain_length = chain_length[c->num_buckets / 2];
251
      }
252
    else
253
      {
254
        max_chain_length = 0;
255
        median_chain_length = 0;
256
      }
257
  }
258
 
259
  printf_filtered ("  Cached '%s' statistics:\n", type);
260
  printf_filtered ("    Total object count:  %ld\n", c->total_count);
261
  printf_filtered ("    Unique object count: %lu\n", c->unique_count);
262
  printf_filtered ("    Percentage of duplicates, by count: ");
263
  print_percentage (c->total_count - c->unique_count, c->total_count);
264
  printf_filtered ("\n");
265
 
266
  printf_filtered ("    Total object size:   %ld\n", c->total_size);
267
  printf_filtered ("    Unique object size:  %ld\n", c->unique_size);
268
  printf_filtered ("    Percentage of duplicates, by size:  ");
269
  print_percentage (c->total_size - c->unique_size, c->total_size);
270
  printf_filtered ("\n");
271
 
272
  printf_filtered ("    Total memory used by bcache, including overhead: %ld\n",
273
                   c->structure_size);
274
  printf_filtered ("    Percentage memory overhead: ");
275
  print_percentage (c->structure_size - c->unique_size, c->unique_size);
276
  printf_filtered ("    Net memory savings:         ");
277
  print_percentage (c->total_size - c->structure_size, c->total_size);
278
  printf_filtered ("\n");
279
 
280
  printf_filtered ("    Hash table size:           %3d\n", c->num_buckets);
281
  printf_filtered ("    Hash table population:     ");
282
  print_percentage (occupied_buckets, c->num_buckets);
283
  printf_filtered ("    Median hash chain length:  %3d\n",
284
                   median_chain_length);
285
  printf_filtered ("    Average hash chain length: ");
286
  if (c->num_buckets > 0)
287
    printf_filtered ("%3lu\n", c->unique_count / c->num_buckets);
288
  else
289
    printf_filtered ("(not applicable)\n");
290
  printf_filtered ("    Maximum hash chain length: %3d\n", max_chain_length);
291
  printf_filtered ("\n");
292
}

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.