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88459642 OS |
1 | /* |
2 | * Fast and scalable bitmaps. | |
3 | * | |
4 | * Copyright (C) 2016 Facebook | |
5 | * Copyright (C) 2013-2014 Jens Axboe | |
6 | * | |
7 | * This program is free software; you can redistribute it and/or | |
8 | * modify it under the terms of the GNU General Public | |
9 | * License v2 as published by the Free Software Foundation. | |
10 | * | |
11 | * This program is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | * General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU General Public License | |
17 | * along with this program. If not, see <https://www.gnu.org/licenses/>. | |
18 | */ | |
19 | ||
20 | #ifndef __LINUX_SCALE_BITMAP_H | |
21 | #define __LINUX_SCALE_BITMAP_H | |
22 | ||
23 | #include <linux/kernel.h> | |
24 | #include <linux/slab.h> | |
25 | ||
26 | /** | |
27 | * struct sbitmap_word - Word in a &struct sbitmap. | |
28 | */ | |
29 | struct sbitmap_word { | |
30 | /** | |
31 | * @word: The bitmap word itself. | |
32 | */ | |
33 | unsigned long word; | |
34 | ||
35 | /** | |
36 | * @depth: Number of bits being used in @word. | |
37 | */ | |
38 | unsigned long depth; | |
39 | } ____cacheline_aligned_in_smp; | |
40 | ||
41 | /** | |
42 | * struct sbitmap - Scalable bitmap. | |
43 | * | |
44 | * A &struct sbitmap is spread over multiple cachelines to avoid ping-pong. This | |
45 | * trades off higher memory usage for better scalability. | |
46 | */ | |
47 | struct sbitmap { | |
48 | /** | |
49 | * @depth: Number of bits used in the whole bitmap. | |
50 | */ | |
51 | unsigned int depth; | |
52 | ||
53 | /** | |
54 | * @shift: log2(number of bits used per word) | |
55 | */ | |
56 | unsigned int shift; | |
57 | ||
58 | /** | |
59 | * @map_nr: Number of words (cachelines) being used for the bitmap. | |
60 | */ | |
61 | unsigned int map_nr; | |
62 | ||
63 | /** | |
64 | * @map: Allocated bitmap. | |
65 | */ | |
66 | struct sbitmap_word *map; | |
67 | }; | |
68 | ||
69 | #define SBQ_WAIT_QUEUES 8 | |
70 | #define SBQ_WAKE_BATCH 8 | |
71 | ||
72 | /** | |
73 | * struct sbq_wait_state - Wait queue in a &struct sbitmap_queue. | |
74 | */ | |
75 | struct sbq_wait_state { | |
76 | /** | |
77 | * @wait_cnt: Number of frees remaining before we wake up. | |
78 | */ | |
79 | atomic_t wait_cnt; | |
80 | ||
81 | /** | |
82 | * @wait: Wait queue. | |
83 | */ | |
84 | wait_queue_head_t wait; | |
85 | } ____cacheline_aligned_in_smp; | |
86 | ||
87 | /** | |
88 | * struct sbitmap_queue - Scalable bitmap with the added ability to wait on free | |
89 | * bits. | |
90 | * | |
91 | * A &struct sbitmap_queue uses multiple wait queues and rolling wakeups to | |
92 | * avoid contention on the wait queue spinlock. This ensures that we don't hit a | |
93 | * scalability wall when we run out of free bits and have to start putting tasks | |
94 | * to sleep. | |
95 | */ | |
96 | struct sbitmap_queue { | |
97 | /** | |
98 | * @sb: Scalable bitmap. | |
99 | */ | |
100 | struct sbitmap sb; | |
101 | ||
40aabb67 OS |
102 | /* |
103 | * @alloc_hint: Cache of last successfully allocated or freed bit. | |
104 | * | |
105 | * This is per-cpu, which allows multiple users to stick to different | |
106 | * cachelines until the map is exhausted. | |
107 | */ | |
108 | unsigned int __percpu *alloc_hint; | |
109 | ||
88459642 OS |
110 | /** |
111 | * @wake_batch: Number of bits which must be freed before we wake up any | |
112 | * waiters. | |
113 | */ | |
114 | unsigned int wake_batch; | |
115 | ||
116 | /** | |
117 | * @wake_index: Next wait queue in @ws to wake up. | |
118 | */ | |
119 | atomic_t wake_index; | |
120 | ||
121 | /** | |
122 | * @ws: Wait queues. | |
123 | */ | |
124 | struct sbq_wait_state *ws; | |
f4a644db OS |
125 | |
126 | /** | |
127 | * @round_robin: Allocate bits in strict round-robin order. | |
128 | */ | |
129 | bool round_robin; | |
88459642 OS |
130 | }; |
131 | ||
132 | /** | |
133 | * sbitmap_init_node() - Initialize a &struct sbitmap on a specific memory node. | |
134 | * @sb: Bitmap to initialize. | |
135 | * @depth: Number of bits to allocate. | |
136 | * @shift: Use 2^@shift bits per word in the bitmap; if a negative number if | |
137 | * given, a good default is chosen. | |
138 | * @flags: Allocation flags. | |
139 | * @node: Memory node to allocate on. | |
140 | * | |
141 | * Return: Zero on success or negative errno on failure. | |
142 | */ | |
143 | int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift, | |
144 | gfp_t flags, int node); | |
145 | ||
146 | /** | |
147 | * sbitmap_free() - Free memory used by a &struct sbitmap. | |
148 | * @sb: Bitmap to free. | |
149 | */ | |
150 | static inline void sbitmap_free(struct sbitmap *sb) | |
151 | { | |
152 | kfree(sb->map); | |
153 | sb->map = NULL; | |
154 | } | |
155 | ||
156 | /** | |
157 | * sbitmap_resize() - Resize a &struct sbitmap. | |
158 | * @sb: Bitmap to resize. | |
159 | * @depth: New number of bits to resize to. | |
160 | * | |
161 | * Doesn't reallocate anything. It's up to the caller to ensure that the new | |
162 | * depth doesn't exceed the depth that the sb was initialized with. | |
163 | */ | |
164 | void sbitmap_resize(struct sbitmap *sb, unsigned int depth); | |
165 | ||
166 | /** | |
167 | * sbitmap_get() - Try to allocate a free bit from a &struct sbitmap. | |
168 | * @sb: Bitmap to allocate from. | |
169 | * @alloc_hint: Hint for where to start searching for a free bit. | |
170 | * @round_robin: If true, be stricter about allocation order; always allocate | |
171 | * starting from the last allocated bit. This is less efficient | |
172 | * than the default behavior (false). | |
173 | * | |
174 | * Return: Non-negative allocated bit number if successful, -1 otherwise. | |
175 | */ | |
176 | int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin); | |
177 | ||
178 | /** | |
179 | * sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap. | |
180 | * @sb: Bitmap to check. | |
181 | * | |
182 | * Return: true if any bit in the bitmap is set, false otherwise. | |
183 | */ | |
184 | bool sbitmap_any_bit_set(const struct sbitmap *sb); | |
185 | ||
186 | /** | |
187 | * sbitmap_any_bit_clear() - Check for an unset bit in a &struct | |
188 | * sbitmap. | |
189 | * @sb: Bitmap to check. | |
190 | * | |
191 | * Return: true if any bit in the bitmap is clear, false otherwise. | |
192 | */ | |
193 | bool sbitmap_any_bit_clear(const struct sbitmap *sb); | |
194 | ||
195 | typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *); | |
196 | ||
197 | /** | |
198 | * sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap. | |
199 | * @sb: Bitmap to iterate over. | |
200 | * @fn: Callback. Should return true to continue or false to break early. | |
201 | * @data: Pointer to pass to callback. | |
202 | * | |
203 | * This is inline even though it's non-trivial so that the function calls to the | |
204 | * callback will hopefully get optimized away. | |
205 | */ | |
206 | static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn, | |
207 | void *data) | |
208 | { | |
209 | unsigned int i; | |
210 | ||
211 | for (i = 0; i < sb->map_nr; i++) { | |
212 | struct sbitmap_word *word = &sb->map[i]; | |
213 | unsigned int off, nr; | |
214 | ||
215 | if (!word->word) | |
216 | continue; | |
217 | ||
218 | nr = 0; | |
219 | off = i << sb->shift; | |
220 | while (1) { | |
221 | nr = find_next_bit(&word->word, word->depth, nr); | |
222 | if (nr >= word->depth) | |
223 | break; | |
224 | ||
225 | if (!fn(sb, off + nr, data)) | |
226 | return; | |
227 | ||
228 | nr++; | |
229 | } | |
230 | } | |
231 | } | |
232 | ||
233 | #define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift) | |
234 | #define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U)) | |
235 | ||
236 | static inline unsigned long *__sbitmap_word(struct sbitmap *sb, | |
237 | unsigned int bitnr) | |
238 | { | |
239 | return &sb->map[SB_NR_TO_INDEX(sb, bitnr)].word; | |
240 | } | |
241 | ||
242 | /* Helpers equivalent to the operations in asm/bitops.h and linux/bitmap.h */ | |
243 | ||
244 | static inline void sbitmap_set_bit(struct sbitmap *sb, unsigned int bitnr) | |
245 | { | |
246 | set_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); | |
247 | } | |
248 | ||
249 | static inline void sbitmap_clear_bit(struct sbitmap *sb, unsigned int bitnr) | |
250 | { | |
251 | clear_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); | |
252 | } | |
253 | ||
254 | static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr) | |
255 | { | |
256 | return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); | |
257 | } | |
258 | ||
259 | unsigned int sbitmap_weight(const struct sbitmap *sb); | |
260 | ||
261 | /** | |
262 | * sbitmap_queue_init_node() - Initialize a &struct sbitmap_queue on a specific | |
263 | * memory node. | |
264 | * @sbq: Bitmap queue to initialize. | |
265 | * @depth: See sbitmap_init_node(). | |
266 | * @shift: See sbitmap_init_node(). | |
f4a644db | 267 | * @round_robin: See sbitmap_get(). |
88459642 OS |
268 | * @flags: Allocation flags. |
269 | * @node: Memory node to allocate on. | |
270 | * | |
271 | * Return: Zero on success or negative errno on failure. | |
272 | */ | |
273 | int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, | |
f4a644db | 274 | int shift, bool round_robin, gfp_t flags, int node); |
88459642 OS |
275 | |
276 | /** | |
277 | * sbitmap_queue_free() - Free memory used by a &struct sbitmap_queue. | |
278 | * | |
279 | * @sbq: Bitmap queue to free. | |
280 | */ | |
281 | static inline void sbitmap_queue_free(struct sbitmap_queue *sbq) | |
282 | { | |
283 | kfree(sbq->ws); | |
40aabb67 | 284 | free_percpu(sbq->alloc_hint); |
88459642 OS |
285 | sbitmap_free(&sbq->sb); |
286 | } | |
287 | ||
288 | /** | |
289 | * sbitmap_queue_resize() - Resize a &struct sbitmap_queue. | |
290 | * @sbq: Bitmap queue to resize. | |
291 | * @depth: New number of bits to resize to. | |
292 | * | |
293 | * Like sbitmap_resize(), this doesn't reallocate anything. It has to do | |
294 | * some extra work on the &struct sbitmap_queue, so it's not safe to just | |
295 | * resize the underlying &struct sbitmap. | |
296 | */ | |
297 | void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth); | |
298 | ||
40aabb67 OS |
299 | /** |
300 | * __sbitmap_queue_get() - Try to allocate a free bit from a &struct | |
301 | * sbitmap_queue with preemption already disabled. | |
302 | * @sbq: Bitmap queue to allocate from. | |
40aabb67 OS |
303 | * |
304 | * Return: Non-negative allocated bit number if successful, -1 otherwise. | |
305 | */ | |
f4a644db | 306 | int __sbitmap_queue_get(struct sbitmap_queue *sbq); |
40aabb67 OS |
307 | |
308 | /** | |
309 | * sbitmap_queue_get() - Try to allocate a free bit from a &struct | |
310 | * sbitmap_queue. | |
311 | * @sbq: Bitmap queue to allocate from. | |
40aabb67 OS |
312 | * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to |
313 | * sbitmap_queue_clear()). | |
314 | * | |
315 | * Return: Non-negative allocated bit number if successful, -1 otherwise. | |
316 | */ | |
f4a644db | 317 | static inline int sbitmap_queue_get(struct sbitmap_queue *sbq, |
40aabb67 OS |
318 | unsigned int *cpu) |
319 | { | |
320 | int nr; | |
321 | ||
322 | *cpu = get_cpu(); | |
f4a644db | 323 | nr = __sbitmap_queue_get(sbq); |
40aabb67 OS |
324 | put_cpu(); |
325 | return nr; | |
326 | } | |
327 | ||
88459642 OS |
328 | /** |
329 | * sbitmap_queue_clear() - Free an allocated bit and wake up waiters on a | |
330 | * &struct sbitmap_queue. | |
331 | * @sbq: Bitmap to free from. | |
332 | * @nr: Bit number to free. | |
40aabb67 | 333 | * @cpu: CPU the bit was allocated on. |
88459642 | 334 | */ |
40aabb67 | 335 | void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr, |
f4a644db | 336 | unsigned int cpu); |
88459642 OS |
337 | |
338 | static inline int sbq_index_inc(int index) | |
339 | { | |
340 | return (index + 1) & (SBQ_WAIT_QUEUES - 1); | |
341 | } | |
342 | ||
343 | static inline void sbq_index_atomic_inc(atomic_t *index) | |
344 | { | |
345 | int old = atomic_read(index); | |
346 | int new = sbq_index_inc(old); | |
347 | atomic_cmpxchg(index, old, new); | |
348 | } | |
349 | ||
350 | /** | |
351 | * sbq_wait_ptr() - Get the next wait queue to use for a &struct | |
352 | * sbitmap_queue. | |
353 | * @sbq: Bitmap queue to wait on. | |
354 | * @wait_index: A counter per "user" of @sbq. | |
355 | */ | |
356 | static inline struct sbq_wait_state *sbq_wait_ptr(struct sbitmap_queue *sbq, | |
357 | atomic_t *wait_index) | |
358 | { | |
359 | struct sbq_wait_state *ws; | |
360 | ||
361 | ws = &sbq->ws[atomic_read(wait_index)]; | |
362 | sbq_index_atomic_inc(wait_index); | |
363 | return ws; | |
364 | } | |
365 | ||
366 | /** | |
367 | * sbitmap_queue_wake_all() - Wake up everything waiting on a &struct | |
368 | * sbitmap_queue. | |
369 | * @sbq: Bitmap queue to wake up. | |
370 | */ | |
371 | void sbitmap_queue_wake_all(struct sbitmap_queue *sbq); | |
372 | ||
373 | #endif /* __LINUX_SCALE_BITMAP_H */ |