1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
|
/* Implement a cached obstack.
Written by Fred Fish (fnf@cygnus.com)
Copyright 1995, 1998 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
#include "defs.h"
#include "obstack.h"
#include "bcache.h"
#include "gdb_string.h" /* For memcpy declaration */
/* Prototypes for local functions. */
static unsigned int hash PARAMS ((void *, int));
static void *lookup_cache PARAMS ((void *, int, int, struct bcache *));
/* FIXME: Incredibly simplistic hash generator. Probably way too expensive
(consider long strings) and unlikely to have good distribution across hash
values for typical input. */
static unsigned int
hash (bytes, count)
void *bytes;
int count;
{
unsigned int len;
unsigned long hashval;
unsigned int c;
const unsigned char *data = bytes;
hashval = 0;
len = 0;
while (count-- > 0)
{
c = *data++;
hashval += c + (c << 17);
hashval ^= hashval >> 2;
++len;
}
hashval += len + (len << 17);
hashval ^= hashval >> 2;
return (hashval % BCACHE_HASHSIZE);
}
static void *
lookup_cache (bytes, count, hashval, bcachep)
void *bytes;
int count;
int hashval;
struct bcache *bcachep;
{
void *location = NULL;
struct hashlink **hashtablep;
struct hashlink *linkp;
hashtablep = bcachep -> indextable[count];
if (hashtablep != NULL)
{
linkp = hashtablep[hashval];
while (linkp != NULL)
{
if (memcmp (BCACHE_DATA (linkp), bytes, count) == 0)
{
location = BCACHE_DATA (linkp);
break;
}
linkp = linkp -> next;
}
}
return (location);
}
void *
bcache (bytes, count, bcachep)
void *bytes;
int count;
struct bcache *bcachep;
{
int hashval;
void *location;
struct hashlink *newlink;
struct hashlink **linkpp;
struct hashlink ***hashtablepp;
if (count >= BCACHE_MAXLENGTH)
{
/* Rare enough to just stash unique copies */
location = (void *) obstack_alloc (&bcachep->cache, count);
bcachep -> cache_bytes += count;
memcpy (location, bytes, count);
bcachep -> bcache_overflows++;
}
else
{
hashval = hash (bytes, count);
location = lookup_cache (bytes, count, hashval, bcachep);
if (location != NULL)
{
bcachep -> cache_savings += count;
bcachep -> cache_hits++;
}
else
{
bcachep -> cache_misses++;
hashtablepp = &bcachep -> indextable[count];
if (*hashtablepp == NULL)
{
*hashtablepp = (struct hashlink **)
obstack_alloc (&bcachep->cache, BCACHE_HASHSIZE * sizeof (struct hashlink *));
bcachep -> cache_bytes += BCACHE_HASHSIZE * sizeof (struct hashlink *);
memset (*hashtablepp, 0, BCACHE_HASHSIZE * sizeof (struct hashlink *));
}
linkpp = &(*hashtablepp)[hashval];
newlink = (struct hashlink *)
obstack_alloc (&bcachep->cache, BCACHE_DATA_ALIGNMENT + count);
bcachep -> cache_bytes += BCACHE_DATA_ALIGNMENT + count;
memcpy (BCACHE_DATA (newlink), bytes, count);
newlink -> next = *linkpp;
*linkpp = newlink;
location = BCACHE_DATA (newlink);
}
}
return (location);
}
#if MAINTENANCE_CMDS
void
print_bcache_statistics (bcachep, id)
struct bcache *bcachep;
char *id;
{
struct hashlink **hashtablep;
struct hashlink *linkp;
int tidx, tcount, hidx, hcount, lcount, lmax, temp, lmaxt, lmaxh;
for (lmax = lcount = tcount = hcount = tidx = 0; tidx < BCACHE_MAXLENGTH; tidx++)
{
hashtablep = bcachep -> indextable[tidx];
if (hashtablep != NULL)
{
tcount++;
for (hidx = 0; hidx < BCACHE_HASHSIZE; hidx++)
{
linkp = hashtablep[hidx];
if (linkp != NULL)
{
hcount++;
for (temp = 0; linkp != NULL; linkp = linkp -> next)
{
lcount++;
temp++;
}
if (temp > lmax)
{
lmax = temp;
lmaxt = tidx;
lmaxh = hidx;
}
}
}
}
}
printf_filtered (" Cached '%s' statistics:\n", id);
printf_filtered (" Cache hits: %d\n", bcachep -> cache_hits);
printf_filtered (" Cache misses: %d\n", bcachep -> cache_misses);
printf_filtered (" Cache hit ratio: ");
if (bcachep -> cache_hits + bcachep -> cache_misses > 0)
{
printf_filtered ("%d%%\n", ((bcachep -> cache_hits) * 100) /
(bcachep -> cache_hits + bcachep -> cache_misses));
}
else
{
printf_filtered ("(not applicable)\n");
}
printf_filtered (" Space used for caching: %d\n", bcachep -> cache_bytes);
printf_filtered (" Space saved by cache hits: %d\n", bcachep -> cache_savings);
printf_filtered (" Number of bcache overflows: %d\n", bcachep -> bcache_overflows);
printf_filtered (" Number of index buckets used: %d\n", tcount);
printf_filtered (" Number of hash table buckets used: %d\n", hcount);
printf_filtered (" Number of chained items: %d\n", lcount);
printf_filtered (" Average hash table population: ");
if (tcount > 0)
{
printf_filtered ("%d%%\n", (hcount * 100) / (tcount * BCACHE_HASHSIZE));
}
else
{
printf_filtered ("(not applicable)\n");
}
printf_filtered (" Average chain length ");
if (hcount > 0)
{
printf_filtered ("%d\n", lcount / hcount);
}
else
{
printf_filtered ("(not applicable)\n");
}
printf_filtered (" Maximum chain length %d at %d:%d\n", lmax, lmaxt, lmaxh);
}
#endif /* MAINTENANCE_CMDS */
|
