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064af421 | 1 | /* |
07d2723a | 2 | * Copyright (c) 2008, 2009, 2010, 2012, 2013, 2015 Nicira, Inc. |
064af421 | 3 | * |
a14bc59f BP |
4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
5 | * you may not use this file except in compliance with the License. | |
6 | * You may obtain a copy of the License at: | |
064af421 | 7 | * |
a14bc59f BP |
8 | * http://www.apache.org/licenses/LICENSE-2.0 |
9 | * | |
10 | * Unless required by applicable law or agreed to in writing, software | |
11 | * distributed under the License is distributed on an "AS IS" BASIS, | |
12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
13 | * See the License for the specific language governing permissions and | |
14 | * limitations under the License. | |
064af421 BP |
15 | */ |
16 | ||
17 | #include <config.h> | |
ee89ea7b | 18 | #include "openvswitch/hmap.h" |
064af421 | 19 | #include <stdint.h> |
f3099647 | 20 | #include <string.h> |
064af421 | 21 | #include "coverage.h" |
f2f7be86 | 22 | #include "random.h" |
064af421 | 23 | #include "util.h" |
e6211adc | 24 | #include "openvswitch/vlog.h" |
0c5e05bf BP |
25 | |
26 | VLOG_DEFINE_THIS_MODULE(hmap); | |
064af421 | 27 | |
d76f09ea BP |
28 | COVERAGE_DEFINE(hmap_pathological); |
29 | COVERAGE_DEFINE(hmap_expand); | |
30 | COVERAGE_DEFINE(hmap_shrink); | |
31 | COVERAGE_DEFINE(hmap_reserve); | |
32 | ||
064af421 BP |
33 | /* Initializes 'hmap' as an empty hash table. */ |
34 | void | |
35 | hmap_init(struct hmap *hmap) | |
36 | { | |
37 | hmap->buckets = &hmap->one; | |
38 | hmap->one = NULL; | |
39 | hmap->mask = 0; | |
40 | hmap->n = 0; | |
41 | } | |
42 | ||
43 | /* Frees memory reserved by 'hmap'. It is the client's responsibility to free | |
44 | * the nodes themselves, if necessary. */ | |
45 | void | |
46 | hmap_destroy(struct hmap *hmap) | |
47 | { | |
48 | if (hmap && hmap->buckets != &hmap->one) { | |
49 | free(hmap->buckets); | |
50 | } | |
51 | } | |
52 | ||
f3099647 BP |
53 | /* Removes all node from 'hmap', leaving it ready to accept more nodes. Does |
54 | * not free memory allocated for 'hmap'. | |
55 | * | |
56 | * This function is appropriate when 'hmap' will soon have about as many | |
07d2723a BP |
57 | * elements as it did before. If 'hmap' will likely have fewer elements than |
58 | * before, use hmap_destroy() followed by hmap_init() to save memory and | |
f3099647 BP |
59 | * iteration time. */ |
60 | void | |
61 | hmap_clear(struct hmap *hmap) | |
62 | { | |
63 | if (hmap->n > 0) { | |
64 | hmap->n = 0; | |
65 | memset(hmap->buckets, 0, (hmap->mask + 1) * sizeof *hmap->buckets); | |
66 | } | |
67 | } | |
68 | ||
064af421 BP |
69 | /* Exchanges hash maps 'a' and 'b'. */ |
70 | void | |
71 | hmap_swap(struct hmap *a, struct hmap *b) | |
72 | { | |
73 | struct hmap tmp = *a; | |
74 | *a = *b; | |
75 | *b = tmp; | |
baa8f41b BP |
76 | hmap_moved(a); |
77 | hmap_moved(b); | |
78 | } | |
79 | ||
80 | /* Adjusts 'hmap' to compensate for having moved position in memory (e.g. due | |
81 | * to realloc()). */ | |
82 | void | |
83 | hmap_moved(struct hmap *hmap) | |
84 | { | |
85 | if (!hmap->mask) { | |
86 | hmap->buckets = &hmap->one; | |
064af421 BP |
87 | } |
88 | } | |
89 | ||
90 | static void | |
0c5e05bf | 91 | resize(struct hmap *hmap, size_t new_mask, const char *where) |
064af421 BP |
92 | { |
93 | struct hmap tmp; | |
94 | size_t i; | |
95 | ||
34a78b18 | 96 | ovs_assert(is_pow2(new_mask + 1)); |
064af421 BP |
97 | |
98 | hmap_init(&tmp); | |
99 | if (new_mask) { | |
100 | tmp.buckets = xmalloc(sizeof *tmp.buckets * (new_mask + 1)); | |
101 | tmp.mask = new_mask; | |
102 | for (i = 0; i <= tmp.mask; i++) { | |
103 | tmp.buckets[i] = NULL; | |
104 | } | |
105 | } | |
106 | for (i = 0; i <= hmap->mask; i++) { | |
107 | struct hmap_node *node, *next; | |
108 | int count = 0; | |
109 | for (node = hmap->buckets[i]; node; node = next) { | |
110 | next = node->next; | |
111 | hmap_insert_fast(&tmp, node, node->hash); | |
112 | count++; | |
113 | } | |
114 | if (count > 5) { | |
0c5e05bf | 115 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(10, 10); |
064af421 | 116 | COVERAGE_INC(hmap_pathological); |
34582733 | 117 | VLOG_DBG_RL(&rl, "%s: %d nodes in bucket (%"PRIuSIZE" nodes, %"PRIuSIZE" buckets)", |
0c5e05bf | 118 | where, count, hmap->n, hmap->mask + 1); |
064af421 BP |
119 | } |
120 | } | |
121 | hmap_swap(hmap, &tmp); | |
122 | hmap_destroy(&tmp); | |
123 | } | |
124 | ||
125 | static size_t | |
126 | calc_mask(size_t capacity) | |
127 | { | |
128 | size_t mask = capacity / 2; | |
129 | mask |= mask >> 1; | |
130 | mask |= mask >> 2; | |
131 | mask |= mask >> 4; | |
132 | mask |= mask >> 8; | |
133 | mask |= mask >> 16; | |
134 | #if SIZE_MAX > UINT32_MAX | |
135 | mask |= mask >> 32; | |
136 | #endif | |
137 | ||
138 | /* If we need to dynamically allocate buckets we might as well allocate at | |
139 | * least 4 of them. */ | |
140 | mask |= (mask & 1) << 1; | |
141 | ||
142 | return mask; | |
143 | } | |
144 | ||
0c5e05bf BP |
145 | /* Expands 'hmap', if necessary, to optimize the performance of searches. |
146 | * | |
147 | * ('where' is used in debug logging. Commonly one would use hmap_expand() to | |
148 | * automatically provide the caller's source file and line number for | |
149 | * 'where'.) */ | |
064af421 | 150 | void |
0c5e05bf | 151 | hmap_expand_at(struct hmap *hmap, const char *where) |
064af421 BP |
152 | { |
153 | size_t new_mask = calc_mask(hmap->n); | |
154 | if (new_mask > hmap->mask) { | |
155 | COVERAGE_INC(hmap_expand); | |
0c5e05bf | 156 | resize(hmap, new_mask, where); |
064af421 BP |
157 | } |
158 | } | |
159 | ||
0c5e05bf BP |
160 | /* Shrinks 'hmap', if necessary, to optimize the performance of iteration. |
161 | * | |
162 | * ('where' is used in debug logging. Commonly one would use hmap_shrink() to | |
163 | * automatically provide the caller's source file and line number for | |
164 | * 'where'.) */ | |
064af421 | 165 | void |
0c5e05bf | 166 | hmap_shrink_at(struct hmap *hmap, const char *where) |
064af421 BP |
167 | { |
168 | size_t new_mask = calc_mask(hmap->n); | |
169 | if (new_mask < hmap->mask) { | |
170 | COVERAGE_INC(hmap_shrink); | |
0c5e05bf | 171 | resize(hmap, new_mask, where); |
064af421 BP |
172 | } |
173 | } | |
174 | ||
175 | /* Expands 'hmap', if necessary, to optimize the performance of searches when | |
176 | * it has up to 'n' elements. (But iteration will be slow in a hash map whose | |
0c5e05bf BP |
177 | * allocated capacity is much higher than its current number of nodes.) |
178 | * | |
179 | * ('where' is used in debug logging. Commonly one would use hmap_reserve() to | |
180 | * automatically provide the caller's source file and line number for | |
181 | * 'where'.) */ | |
064af421 | 182 | void |
0c5e05bf | 183 | hmap_reserve_at(struct hmap *hmap, size_t n, const char *where) |
064af421 BP |
184 | { |
185 | size_t new_mask = calc_mask(n); | |
186 | if (new_mask > hmap->mask) { | |
187 | COVERAGE_INC(hmap_reserve); | |
0c5e05bf | 188 | resize(hmap, new_mask, where); |
064af421 BP |
189 | } |
190 | } | |
63e60b86 BP |
191 | |
192 | /* Adjusts 'hmap' to compensate for 'old_node' having moved position in memory | |
193 | * to 'node' (e.g. due to realloc()). */ | |
194 | void | |
195 | hmap_node_moved(struct hmap *hmap, | |
196 | struct hmap_node *old_node, struct hmap_node *node) | |
197 | { | |
198 | struct hmap_node **bucket = &hmap->buckets[node->hash & hmap->mask]; | |
199 | while (*bucket != old_node) { | |
200 | bucket = &(*bucket)->next; | |
201 | } | |
202 | *bucket = node; | |
203 | } | |
204 | ||
f2f7be86 BP |
205 | /* Chooses and returns a randomly selected node from 'hmap', which must not be |
206 | * empty. | |
207 | * | |
208 | * I wouldn't depend on this algorithm to be fair, since I haven't analyzed it. | |
209 | * But it does at least ensure that any node in 'hmap' can be chosen. */ | |
210 | struct hmap_node * | |
211 | hmap_random_node(const struct hmap *hmap) | |
212 | { | |
213 | struct hmap_node *bucket, *node; | |
214 | size_t n, i; | |
215 | ||
216 | /* Choose a random non-empty bucket. */ | |
e58f91a1 YT |
217 | for (;;) { |
218 | bucket = hmap->buckets[random_uint32() & hmap->mask]; | |
f2f7be86 BP |
219 | if (bucket) { |
220 | break; | |
221 | } | |
222 | } | |
223 | ||
224 | /* Count nodes in bucket. */ | |
225 | n = 0; | |
226 | for (node = bucket; node; node = node->next) { | |
227 | n++; | |
228 | } | |
229 | ||
230 | /* Choose random node from bucket. */ | |
231 | i = random_range(n); | |
232 | for (node = bucket; i-- > 0; node = node->next) { | |
233 | continue; | |
234 | } | |
235 | return node; | |
236 | } | |
ee114c23 BP |
237 | |
238 | /* Returns the next node in 'hmap' in hash order, or NULL if no nodes remain in | |
bfbcebc2 DDP |
239 | * 'hmap'. Uses '*pos' to determine where to begin iteration, and updates |
240 | * '*pos' to pass on the next iteration into them before returning. | |
ee114c23 BP |
241 | * |
242 | * It's better to use plain HMAP_FOR_EACH and related functions, since they are | |
243 | * faster and better at dealing with hmaps that change during iteration. | |
244 | * | |
bfbcebc2 | 245 | * Before beginning iteration, set '*pos' to all zeros. */ |
ee114c23 BP |
246 | struct hmap_node * |
247 | hmap_at_position(const struct hmap *hmap, | |
bfbcebc2 | 248 | struct hmap_position *pos) |
ee114c23 BP |
249 | { |
250 | size_t offset; | |
251 | size_t b_idx; | |
252 | ||
bfbcebc2 DDP |
253 | offset = pos->offset; |
254 | for (b_idx = pos->bucket; b_idx <= hmap->mask; b_idx++) { | |
ee114c23 BP |
255 | struct hmap_node *node; |
256 | size_t n_idx; | |
257 | ||
258 | for (n_idx = 0, node = hmap->buckets[b_idx]; node != NULL; | |
259 | n_idx++, node = node->next) { | |
260 | if (n_idx == offset) { | |
261 | if (node->next) { | |
bfbcebc2 DDP |
262 | pos->bucket = node->hash & hmap->mask; |
263 | pos->offset = offset + 1; | |
ee114c23 | 264 | } else { |
bfbcebc2 DDP |
265 | pos->bucket = (node->hash & hmap->mask) + 1; |
266 | pos->offset = 0; | |
ee114c23 BP |
267 | } |
268 | return node; | |
269 | } | |
270 | } | |
271 | offset = 0; | |
272 | } | |
273 | ||
bfbcebc2 DDP |
274 | pos->bucket = 0; |
275 | pos->offset = 0; | |
ee114c23 BP |
276 | return NULL; |
277 | } | |
e39e5b9d BP |
278 | |
279 | /* Returns true if 'node' is in 'hmap', false otherwise. */ | |
280 | bool | |
281 | hmap_contains(const struct hmap *hmap, const struct hmap_node *node) | |
282 | { | |
283 | struct hmap_node *p; | |
284 | ||
285 | for (p = hmap_first_in_bucket(hmap, node->hash); p; p = p->next) { | |
286 | if (p == node) { | |
287 | return true; | |
288 | } | |
289 | } | |
290 | ||
291 | return false; | |
292 | } |