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064af421 | 1 | /* |
6a7bceaa | 2 | * Copyright (c) 2008, 2009, 2010, 2012, 2013, 2015, 2019 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 | } | |
6a7bceaa BP |
106 | int n_big_buckets = 0; |
107 | int biggest_count = 0; | |
108 | int n_biggest_buckets = 0; | |
064af421 BP |
109 | for (i = 0; i <= hmap->mask; i++) { |
110 | struct hmap_node *node, *next; | |
111 | int count = 0; | |
112 | for (node = hmap->buckets[i]; node; node = next) { | |
113 | next = node->next; | |
114 | hmap_insert_fast(&tmp, node, node->hash); | |
115 | count++; | |
116 | } | |
117 | if (count > 5) { | |
6a7bceaa BP |
118 | n_big_buckets++; |
119 | if (count > biggest_count) { | |
120 | biggest_count = count; | |
121 | n_biggest_buckets = 1; | |
122 | } else if (count == biggest_count) { | |
123 | n_biggest_buckets++; | |
124 | } | |
064af421 BP |
125 | } |
126 | } | |
127 | hmap_swap(hmap, &tmp); | |
128 | hmap_destroy(&tmp); | |
6a7bceaa BP |
129 | |
130 | if (n_big_buckets) { | |
131 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(10, 10); | |
132 | COVERAGE_INC(hmap_pathological); | |
133 | VLOG_DBG_RL(&rl, "%s: %d bucket%s with 6+ nodes, " | |
134 | "including %d bucket%s with %d nodes " | |
135 | "(%"PRIuSIZE" nodes total across %"PRIuSIZE" buckets)", | |
136 | where, | |
137 | n_big_buckets, n_big_buckets > 1 ? "s" : "", | |
138 | n_biggest_buckets, n_biggest_buckets > 1 ? "s" : "", | |
139 | biggest_count, | |
140 | hmap->n, hmap->mask + 1); | |
141 | } | |
064af421 BP |
142 | } |
143 | ||
144 | static size_t | |
145 | calc_mask(size_t capacity) | |
146 | { | |
147 | size_t mask = capacity / 2; | |
148 | mask |= mask >> 1; | |
149 | mask |= mask >> 2; | |
150 | mask |= mask >> 4; | |
151 | mask |= mask >> 8; | |
152 | mask |= mask >> 16; | |
153 | #if SIZE_MAX > UINT32_MAX | |
154 | mask |= mask >> 32; | |
155 | #endif | |
156 | ||
157 | /* If we need to dynamically allocate buckets we might as well allocate at | |
158 | * least 4 of them. */ | |
159 | mask |= (mask & 1) << 1; | |
160 | ||
161 | return mask; | |
162 | } | |
163 | ||
0c5e05bf BP |
164 | /* Expands 'hmap', if necessary, to optimize the performance of searches. |
165 | * | |
166 | * ('where' is used in debug logging. Commonly one would use hmap_expand() to | |
167 | * automatically provide the caller's source file and line number for | |
168 | * 'where'.) */ | |
064af421 | 169 | void |
0c5e05bf | 170 | hmap_expand_at(struct hmap *hmap, const char *where) |
064af421 BP |
171 | { |
172 | size_t new_mask = calc_mask(hmap->n); | |
173 | if (new_mask > hmap->mask) { | |
174 | COVERAGE_INC(hmap_expand); | |
0c5e05bf | 175 | resize(hmap, new_mask, where); |
064af421 BP |
176 | } |
177 | } | |
178 | ||
0c5e05bf BP |
179 | /* Shrinks 'hmap', if necessary, to optimize the performance of iteration. |
180 | * | |
181 | * ('where' is used in debug logging. Commonly one would use hmap_shrink() to | |
182 | * automatically provide the caller's source file and line number for | |
183 | * 'where'.) */ | |
064af421 | 184 | void |
0c5e05bf | 185 | hmap_shrink_at(struct hmap *hmap, const char *where) |
064af421 BP |
186 | { |
187 | size_t new_mask = calc_mask(hmap->n); | |
188 | if (new_mask < hmap->mask) { | |
189 | COVERAGE_INC(hmap_shrink); | |
0c5e05bf | 190 | resize(hmap, new_mask, where); |
064af421 BP |
191 | } |
192 | } | |
193 | ||
194 | /* Expands 'hmap', if necessary, to optimize the performance of searches when | |
195 | * it has up to 'n' elements. (But iteration will be slow in a hash map whose | |
0c5e05bf BP |
196 | * allocated capacity is much higher than its current number of nodes.) |
197 | * | |
198 | * ('where' is used in debug logging. Commonly one would use hmap_reserve() to | |
199 | * automatically provide the caller's source file and line number for | |
200 | * 'where'.) */ | |
064af421 | 201 | void |
0c5e05bf | 202 | hmap_reserve_at(struct hmap *hmap, size_t n, const char *where) |
064af421 BP |
203 | { |
204 | size_t new_mask = calc_mask(n); | |
205 | if (new_mask > hmap->mask) { | |
206 | COVERAGE_INC(hmap_reserve); | |
0c5e05bf | 207 | resize(hmap, new_mask, where); |
064af421 BP |
208 | } |
209 | } | |
63e60b86 BP |
210 | |
211 | /* Adjusts 'hmap' to compensate for 'old_node' having moved position in memory | |
212 | * to 'node' (e.g. due to realloc()). */ | |
213 | void | |
214 | hmap_node_moved(struct hmap *hmap, | |
215 | struct hmap_node *old_node, struct hmap_node *node) | |
216 | { | |
217 | struct hmap_node **bucket = &hmap->buckets[node->hash & hmap->mask]; | |
218 | while (*bucket != old_node) { | |
219 | bucket = &(*bucket)->next; | |
220 | } | |
221 | *bucket = node; | |
222 | } | |
223 | ||
f2f7be86 BP |
224 | /* Chooses and returns a randomly selected node from 'hmap', which must not be |
225 | * empty. | |
226 | * | |
227 | * I wouldn't depend on this algorithm to be fair, since I haven't analyzed it. | |
228 | * But it does at least ensure that any node in 'hmap' can be chosen. */ | |
229 | struct hmap_node * | |
230 | hmap_random_node(const struct hmap *hmap) | |
231 | { | |
232 | struct hmap_node *bucket, *node; | |
233 | size_t n, i; | |
234 | ||
235 | /* Choose a random non-empty bucket. */ | |
e58f91a1 YT |
236 | for (;;) { |
237 | bucket = hmap->buckets[random_uint32() & hmap->mask]; | |
f2f7be86 BP |
238 | if (bucket) { |
239 | break; | |
240 | } | |
241 | } | |
242 | ||
243 | /* Count nodes in bucket. */ | |
244 | n = 0; | |
245 | for (node = bucket; node; node = node->next) { | |
246 | n++; | |
247 | } | |
248 | ||
249 | /* Choose random node from bucket. */ | |
250 | i = random_range(n); | |
251 | for (node = bucket; i-- > 0; node = node->next) { | |
252 | continue; | |
253 | } | |
254 | return node; | |
255 | } | |
ee114c23 BP |
256 | |
257 | /* Returns the next node in 'hmap' in hash order, or NULL if no nodes remain in | |
bfbcebc2 DDP |
258 | * 'hmap'. Uses '*pos' to determine where to begin iteration, and updates |
259 | * '*pos' to pass on the next iteration into them before returning. | |
ee114c23 BP |
260 | * |
261 | * It's better to use plain HMAP_FOR_EACH and related functions, since they are | |
262 | * faster and better at dealing with hmaps that change during iteration. | |
263 | * | |
bfbcebc2 | 264 | * Before beginning iteration, set '*pos' to all zeros. */ |
ee114c23 BP |
265 | struct hmap_node * |
266 | hmap_at_position(const struct hmap *hmap, | |
bfbcebc2 | 267 | struct hmap_position *pos) |
ee114c23 BP |
268 | { |
269 | size_t offset; | |
270 | size_t b_idx; | |
271 | ||
bfbcebc2 DDP |
272 | offset = pos->offset; |
273 | for (b_idx = pos->bucket; b_idx <= hmap->mask; b_idx++) { | |
ee114c23 BP |
274 | struct hmap_node *node; |
275 | size_t n_idx; | |
276 | ||
277 | for (n_idx = 0, node = hmap->buckets[b_idx]; node != NULL; | |
278 | n_idx++, node = node->next) { | |
279 | if (n_idx == offset) { | |
280 | if (node->next) { | |
bfbcebc2 DDP |
281 | pos->bucket = node->hash & hmap->mask; |
282 | pos->offset = offset + 1; | |
ee114c23 | 283 | } else { |
bfbcebc2 DDP |
284 | pos->bucket = (node->hash & hmap->mask) + 1; |
285 | pos->offset = 0; | |
ee114c23 BP |
286 | } |
287 | return node; | |
288 | } | |
289 | } | |
290 | offset = 0; | |
291 | } | |
292 | ||
bfbcebc2 DDP |
293 | pos->bucket = 0; |
294 | pos->offset = 0; | |
ee114c23 BP |
295 | return NULL; |
296 | } | |
e39e5b9d BP |
297 | |
298 | /* Returns true if 'node' is in 'hmap', false otherwise. */ | |
299 | bool | |
300 | hmap_contains(const struct hmap *hmap, const struct hmap_node *node) | |
301 | { | |
302 | struct hmap_node *p; | |
303 | ||
304 | for (p = hmap_first_in_bucket(hmap, node->hash); p; p = p->next) { | |
305 | if (p == node) { | |
306 | return true; | |
307 | } | |
308 | } | |
309 | ||
310 | return false; | |
311 | } |