2 * Fast and scalable bitmaps.
4 * Copyright (C) 2016 Facebook
5 * Copyright (C) 2013-2014 Jens Axboe
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.
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.
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/>.
20 #ifndef __LINUX_SCALE_BITMAP_H
21 #define __LINUX_SCALE_BITMAP_H
23 #include <linux/kernel.h>
24 #include <linux/slab.h>
27 * struct sbitmap_word - Word in a &struct sbitmap.
31 * @word: The bitmap word itself.
36 * @depth: Number of bits being used in @word.
39 } ____cacheline_aligned_in_smp;
42 * struct sbitmap - Scalable bitmap.
44 * A &struct sbitmap is spread over multiple cachelines to avoid ping-pong. This
45 * trades off higher memory usage for better scalability.
49 * @depth: Number of bits used in the whole bitmap.
54 * @shift: log2(number of bits used per word)
59 * @map_nr: Number of words (cachelines) being used for the bitmap.
64 * @map: Allocated bitmap.
66 struct sbitmap_word *map;
69 #define SBQ_WAIT_QUEUES 8
70 #define SBQ_WAKE_BATCH 8
73 * struct sbq_wait_state - Wait queue in a &struct sbitmap_queue.
75 struct sbq_wait_state {
77 * @wait_cnt: Number of frees remaining before we wake up.
84 wait_queue_head_t wait;
85 } ____cacheline_aligned_in_smp;
88 * struct sbitmap_queue - Scalable bitmap with the added ability to wait on free
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
96 struct sbitmap_queue {
98 * @sb: Scalable bitmap.
103 * @wake_batch: Number of bits which must be freed before we wake up any
106 unsigned int wake_batch;
109 * @wake_index: Next wait queue in @ws to wake up.
116 struct sbq_wait_state *ws;
120 * sbitmap_init_node() - Initialize a &struct sbitmap on a specific memory node.
121 * @sb: Bitmap to initialize.
122 * @depth: Number of bits to allocate.
123 * @shift: Use 2^@shift bits per word in the bitmap; if a negative number if
124 * given, a good default is chosen.
125 * @flags: Allocation flags.
126 * @node: Memory node to allocate on.
128 * Return: Zero on success or negative errno on failure.
130 int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
131 gfp_t flags, int node);
134 * sbitmap_free() - Free memory used by a &struct sbitmap.
135 * @sb: Bitmap to free.
137 static inline void sbitmap_free(struct sbitmap *sb)
144 * sbitmap_resize() - Resize a &struct sbitmap.
145 * @sb: Bitmap to resize.
146 * @depth: New number of bits to resize to.
148 * Doesn't reallocate anything. It's up to the caller to ensure that the new
149 * depth doesn't exceed the depth that the sb was initialized with.
151 void sbitmap_resize(struct sbitmap *sb, unsigned int depth);
154 * sbitmap_get() - Try to allocate a free bit from a &struct sbitmap.
155 * @sb: Bitmap to allocate from.
156 * @alloc_hint: Hint for where to start searching for a free bit.
157 * @round_robin: If true, be stricter about allocation order; always allocate
158 * starting from the last allocated bit. This is less efficient
159 * than the default behavior (false).
161 * Return: Non-negative allocated bit number if successful, -1 otherwise.
163 int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin);
166 * sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap.
167 * @sb: Bitmap to check.
169 * Return: true if any bit in the bitmap is set, false otherwise.
171 bool sbitmap_any_bit_set(const struct sbitmap *sb);
174 * sbitmap_any_bit_clear() - Check for an unset bit in a &struct
176 * @sb: Bitmap to check.
178 * Return: true if any bit in the bitmap is clear, false otherwise.
180 bool sbitmap_any_bit_clear(const struct sbitmap *sb);
182 typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *);
185 * sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
186 * @sb: Bitmap to iterate over.
187 * @fn: Callback. Should return true to continue or false to break early.
188 * @data: Pointer to pass to callback.
190 * This is inline even though it's non-trivial so that the function calls to the
191 * callback will hopefully get optimized away.
193 static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn,
198 for (i = 0; i < sb->map_nr; i++) {
199 struct sbitmap_word *word = &sb->map[i];
200 unsigned int off, nr;
206 off = i << sb->shift;
208 nr = find_next_bit(&word->word, word->depth, nr);
209 if (nr >= word->depth)
212 if (!fn(sb, off + nr, data))
220 #define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift)
221 #define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U))
223 static inline unsigned long *__sbitmap_word(struct sbitmap *sb,
226 return &sb->map[SB_NR_TO_INDEX(sb, bitnr)].word;
229 /* Helpers equivalent to the operations in asm/bitops.h and linux/bitmap.h */
231 static inline void sbitmap_set_bit(struct sbitmap *sb, unsigned int bitnr)
233 set_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
236 static inline void sbitmap_clear_bit(struct sbitmap *sb, unsigned int bitnr)
238 clear_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
241 static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
243 return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
246 unsigned int sbitmap_weight(const struct sbitmap *sb);
249 * sbitmap_queue_init_node() - Initialize a &struct sbitmap_queue on a specific
251 * @sbq: Bitmap queue to initialize.
252 * @depth: See sbitmap_init_node().
253 * @shift: See sbitmap_init_node().
254 * @flags: Allocation flags.
255 * @node: Memory node to allocate on.
257 * Return: Zero on success or negative errno on failure.
259 int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
260 int shift, gfp_t flags, int node);
263 * sbitmap_queue_free() - Free memory used by a &struct sbitmap_queue.
265 * @sbq: Bitmap queue to free.
267 static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
270 sbitmap_free(&sbq->sb);
274 * sbitmap_queue_resize() - Resize a &struct sbitmap_queue.
275 * @sbq: Bitmap queue to resize.
276 * @depth: New number of bits to resize to.
278 * Like sbitmap_resize(), this doesn't reallocate anything. It has to do
279 * some extra work on the &struct sbitmap_queue, so it's not safe to just
280 * resize the underlying &struct sbitmap.
282 void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth);
285 * sbitmap_queue_clear() - Free an allocated bit and wake up waiters on a
286 * &struct sbitmap_queue.
287 * @sbq: Bitmap to free from.
288 * @nr: Bit number to free.
290 void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr);
292 static inline int sbq_index_inc(int index)
294 return (index + 1) & (SBQ_WAIT_QUEUES - 1);
297 static inline void sbq_index_atomic_inc(atomic_t *index)
299 int old = atomic_read(index);
300 int new = sbq_index_inc(old);
301 atomic_cmpxchg(index, old, new);
305 * sbq_wait_ptr() - Get the next wait queue to use for a &struct
307 * @sbq: Bitmap queue to wait on.
308 * @wait_index: A counter per "user" of @sbq.
310 static inline struct sbq_wait_state *sbq_wait_ptr(struct sbitmap_queue *sbq,
311 atomic_t *wait_index)
313 struct sbq_wait_state *ws;
315 ws = &sbq->ws[atomic_read(wait_index)];
316 sbq_index_atomic_inc(wait_index);
321 * sbitmap_queue_wake_all() - Wake up everything waiting on a &struct
323 * @sbq: Bitmap queue to wake up.
325 void sbitmap_queue_wake_all(struct sbitmap_queue *sbq);
327 #endif /* __LINUX_SCALE_BITMAP_H */