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
|
/* -*- Mode: C; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
* Hash table
*
*/
#include "config.h"
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <pthread.h>
#include "default_engine.h"
#define hashsize(n) ((uint32_t)1<<(n))
#define hashmask(n) (hashsize(n)-1)
ENGINE_ERROR_CODE assoc_init(struct default_engine *engine) {
engine->assoc.primary_hashtable = calloc(hashsize(engine->assoc.hashpower), sizeof(void *));
return (engine->assoc.primary_hashtable != NULL) ? ENGINE_SUCCESS : ENGINE_ENOMEM;
}
hash_item *assoc_find(struct default_engine *engine, uint32_t hash, const char *key, const size_t nkey) {
hash_item *it;
unsigned int oldbucket;
if (engine->assoc.expanding &&
(oldbucket = (hash & hashmask(engine->assoc.hashpower - 1))) >= engine->assoc.expand_bucket)
{
it = engine->assoc.old_hashtable[oldbucket];
} else {
it = engine->assoc.primary_hashtable[hash & hashmask(engine->assoc.hashpower)];
}
hash_item *ret = NULL;
int depth = 0;
while (it) {
if ((nkey == it->nkey) && (memcmp(key, item_get_key(it), nkey) == 0)) {
ret = it;
break;
}
it = it->h_next;
++depth;
}
MEMCACHED_ASSOC_FIND(key, nkey, depth);
return ret;
}
/* returns the address of the item pointer before the key. if *item == 0,
the item wasn't found */
static hash_item** _hashitem_before(struct default_engine *engine,
uint32_t hash,
const char *key,
const size_t nkey) {
hash_item **pos;
unsigned int oldbucket;
if (engine->assoc.expanding &&
(oldbucket = (hash & hashmask(engine->assoc.hashpower - 1))) >= engine->assoc.expand_bucket)
{
pos = &engine->assoc.old_hashtable[oldbucket];
} else {
pos = &engine->assoc.primary_hashtable[hash & hashmask(engine->assoc.hashpower)];
}
while (*pos && ((nkey != (*pos)->nkey) || memcmp(key, item_get_key(*pos), nkey))) {
pos = &(*pos)->h_next;
}
return pos;
}
static void *assoc_maintenance_thread(void *arg);
/* grows the hashtable to the next power of 2. */
static void assoc_expand(struct default_engine *engine) {
engine->assoc.old_hashtable = engine->assoc.primary_hashtable;
engine->assoc.primary_hashtable = calloc(hashsize(engine->assoc.hashpower + 1), sizeof(void *));
if (engine->assoc.primary_hashtable) {
engine->assoc.hashpower++;
engine->assoc.expanding = true;
engine->assoc.expand_bucket = 0;
/* start a thread to do the expansion */
int ret = 0;
pthread_t tid;
pthread_attr_t attr;
if (pthread_attr_init(&attr) != 0 ||
pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED) != 0 ||
(ret = pthread_create(&tid, &attr,
assoc_maintenance_thread, engine)) != 0)
{
fprintf(stderr, "Can't create thread: %s\n", strerror(ret));
engine->assoc.hashpower--;
engine->assoc.expanding = false;
free(engine->assoc.primary_hashtable);
engine->assoc.primary_hashtable =engine->assoc.old_hashtable;
}
} else {
engine->assoc.primary_hashtable = engine->assoc.old_hashtable;
/* Bad news, but we can keep running. */
}
}
/* Note: this isn't an assoc_update. The key must not already exist to call this */
int assoc_insert(struct default_engine *engine, uint32_t hash, hash_item *it) {
unsigned int oldbucket;
assert(assoc_find(engine, hash, item_get_key(it), it->nkey) == 0); /* shouldn't have duplicately named things defined */
if (engine->assoc.expanding &&
(oldbucket = (hash & hashmask(engine->assoc.hashpower - 1))) >= engine->assoc.expand_bucket)
{
it->h_next = engine->assoc.old_hashtable[oldbucket];
engine->assoc.old_hashtable[oldbucket] = it;
} else {
it->h_next = engine->assoc.primary_hashtable[hash & hashmask(engine->assoc.hashpower)];
engine->assoc.primary_hashtable[hash & hashmask(engine->assoc.hashpower)] = it;
}
engine->assoc.hash_items++;
if (! engine->assoc.expanding && engine->assoc.hash_items > (hashsize(engine->assoc.hashpower) * 3) / 2) {
assoc_expand(engine);
}
MEMCACHED_ASSOC_INSERT(item_get_key(it), it->nkey, engine->assoc.hash_items);
return 1;
}
void assoc_delete(struct default_engine *engine, uint32_t hash, const char *key, const size_t nkey) {
hash_item **before = _hashitem_before(engine, hash, key, nkey);
if (*before) {
hash_item *nxt;
engine->assoc.hash_items--;
/* The DTrace probe cannot be triggered as the last instruction
* due to possible tail-optimization by the compiler
*/
MEMCACHED_ASSOC_DELETE(key, nkey, engine->assoc.hash_items);
nxt = (*before)->h_next;
(*before)->h_next = 0; /* probably pointless, but whatever. */
*before = nxt;
return;
}
/* Note: we never actually get here. the callers don't delete things
they can't find. */
assert(*before != 0);
}
#define DEFAULT_HASH_BULK_MOVE 1
int hash_bulk_move = DEFAULT_HASH_BULK_MOVE;
static void *assoc_maintenance_thread(void *arg) {
struct default_engine *engine = arg;
bool done = false;
do {
int ii;
pthread_mutex_lock(&engine->cache_lock);
for (ii = 0; ii < hash_bulk_move && engine->assoc.expanding; ++ii) {
hash_item *it, *next;
int bucket;
for (it = engine->assoc.old_hashtable[engine->assoc.expand_bucket];
NULL != it; it = next) {
next = it->h_next;
bucket = engine->server.core->hash(item_get_key(it), it->nkey, 0)
& hashmask(engine->assoc.hashpower);
it->h_next = engine->assoc.primary_hashtable[bucket];
engine->assoc.primary_hashtable[bucket] = it;
}
engine->assoc.old_hashtable[engine->assoc.expand_bucket] = NULL;
engine->assoc.expand_bucket++;
if (engine->assoc.expand_bucket == hashsize(engine->assoc.hashpower - 1)) {
engine->assoc.expanding = false;
free(engine->assoc.old_hashtable);
if (engine->config.verbose > 1) {
fprintf(stderr, "Hash table expansion done\n");
}
}
}
if (!engine->assoc.expanding) {
done = true;
}
pthread_mutex_unlock(&engine->cache_lock);
} while (!done);
return NULL;
}
|
