Line data Source code
1 : /* SPDX-License-Identifier: GPL-2.0-only */
2 : /*
3 : * Fast and scalable bitmaps.
4 : *
5 : * Copyright (C) 2016 Facebook
6 : * Copyright (C) 2013-2014 Jens Axboe
7 : */
8 :
9 : #ifndef __LINUX_SCALE_BITMAP_H
10 : #define __LINUX_SCALE_BITMAP_H
11 :
12 : #include <linux/atomic.h>
13 : #include <linux/bitops.h>
14 : #include <linux/cache.h>
15 : #include <linux/list.h>
16 : #include <linux/log2.h>
17 : #include <linux/minmax.h>
18 : #include <linux/percpu.h>
19 : #include <linux/slab.h>
20 : #include <linux/smp.h>
21 : #include <linux/types.h>
22 : #include <linux/wait.h>
23 :
24 : struct seq_file;
25 :
26 : /**
27 : * struct sbitmap_word - Word in a &struct sbitmap.
28 : */
29 : struct sbitmap_word {
30 : /**
31 : * @word: word holding free bits
32 : */
33 : unsigned long word;
34 :
35 : /**
36 : * @cleared: word holding cleared bits
37 : */
38 : unsigned long cleared ____cacheline_aligned_in_smp;
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 : * @round_robin: Allocate bits in strict round-robin order.
65 : */
66 : bool round_robin;
67 :
68 : /**
69 : * @map: Allocated bitmap.
70 : */
71 : struct sbitmap_word *map;
72 :
73 : /*
74 : * @alloc_hint: Cache of last successfully allocated or freed bit.
75 : *
76 : * This is per-cpu, which allows multiple users to stick to different
77 : * cachelines until the map is exhausted.
78 : */
79 : unsigned int __percpu *alloc_hint;
80 : };
81 :
82 : #define SBQ_WAIT_QUEUES 8
83 : #define SBQ_WAKE_BATCH 8
84 :
85 : /**
86 : * struct sbq_wait_state - Wait queue in a &struct sbitmap_queue.
87 : */
88 : struct sbq_wait_state {
89 : /**
90 : * @wait_cnt: Number of frees remaining before we wake up.
91 : */
92 : atomic_t wait_cnt;
93 :
94 : /**
95 : * @wait: Wait queue.
96 : */
97 : wait_queue_head_t wait;
98 : } ____cacheline_aligned_in_smp;
99 :
100 : /**
101 : * struct sbitmap_queue - Scalable bitmap with the added ability to wait on free
102 : * bits.
103 : *
104 : * A &struct sbitmap_queue uses multiple wait queues and rolling wakeups to
105 : * avoid contention on the wait queue spinlock. This ensures that we don't hit a
106 : * scalability wall when we run out of free bits and have to start putting tasks
107 : * to sleep.
108 : */
109 : struct sbitmap_queue {
110 : /**
111 : * @sb: Scalable bitmap.
112 : */
113 : struct sbitmap sb;
114 :
115 : /**
116 : * @wake_batch: Number of bits which must be freed before we wake up any
117 : * waiters.
118 : */
119 : unsigned int wake_batch;
120 :
121 : /**
122 : * @wake_index: Next wait queue in @ws to wake up.
123 : */
124 : atomic_t wake_index;
125 :
126 : /**
127 : * @ws: Wait queues.
128 : */
129 : struct sbq_wait_state *ws;
130 :
131 : /*
132 : * @ws_active: count of currently active ws waitqueues
133 : */
134 : atomic_t ws_active;
135 :
136 : /**
137 : * @min_shallow_depth: The minimum shallow depth which may be passed to
138 : * sbitmap_queue_get_shallow()
139 : */
140 : unsigned int min_shallow_depth;
141 : };
142 :
143 : /**
144 : * sbitmap_init_node() - Initialize a &struct sbitmap on a specific memory node.
145 : * @sb: Bitmap to initialize.
146 : * @depth: Number of bits to allocate.
147 : * @shift: Use 2^@shift bits per word in the bitmap; if a negative number if
148 : * given, a good default is chosen.
149 : * @flags: Allocation flags.
150 : * @node: Memory node to allocate on.
151 : * @round_robin: If true, be stricter about allocation order; always allocate
152 : * starting from the last allocated bit. This is less efficient
153 : * than the default behavior (false).
154 : * @alloc_hint: If true, apply percpu hint for where to start searching for
155 : * a free bit.
156 : *
157 : * Return: Zero on success or negative errno on failure.
158 : */
159 : int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
160 : gfp_t flags, int node, bool round_robin, bool alloc_hint);
161 :
162 : /* sbitmap internal helper */
163 : static inline unsigned int __map_depth(const struct sbitmap *sb, int index)
164 : {
165 0 : if (index == sb->map_nr - 1)
166 0 : return sb->depth - (index << sb->shift);
167 0 : return 1U << sb->shift;
168 : }
169 :
170 : /**
171 : * sbitmap_free() - Free memory used by a &struct sbitmap.
172 : * @sb: Bitmap to free.
173 : */
174 : static inline void sbitmap_free(struct sbitmap *sb)
175 : {
176 0 : free_percpu(sb->alloc_hint);
177 0 : kvfree(sb->map);
178 0 : sb->map = NULL;
179 : }
180 :
181 : /**
182 : * sbitmap_resize() - Resize a &struct sbitmap.
183 : * @sb: Bitmap to resize.
184 : * @depth: New number of bits to resize to.
185 : *
186 : * Doesn't reallocate anything. It's up to the caller to ensure that the new
187 : * depth doesn't exceed the depth that the sb was initialized with.
188 : */
189 : void sbitmap_resize(struct sbitmap *sb, unsigned int depth);
190 :
191 : /**
192 : * sbitmap_get() - Try to allocate a free bit from a &struct sbitmap.
193 : * @sb: Bitmap to allocate from.
194 : *
195 : * This operation provides acquire barrier semantics if it succeeds.
196 : *
197 : * Return: Non-negative allocated bit number if successful, -1 otherwise.
198 : */
199 : int sbitmap_get(struct sbitmap *sb);
200 :
201 : /**
202 : * sbitmap_get_shallow() - Try to allocate a free bit from a &struct sbitmap,
203 : * limiting the depth used from each word.
204 : * @sb: Bitmap to allocate from.
205 : * @shallow_depth: The maximum number of bits to allocate from a single word.
206 : *
207 : * This rather specific operation allows for having multiple users with
208 : * different allocation limits. E.g., there can be a high-priority class that
209 : * uses sbitmap_get() and a low-priority class that uses sbitmap_get_shallow()
210 : * with a @shallow_depth of (1 << (@sb->shift - 1)). Then, the low-priority
211 : * class can only allocate half of the total bits in the bitmap, preventing it
212 : * from starving out the high-priority class.
213 : *
214 : * Return: Non-negative allocated bit number if successful, -1 otherwise.
215 : */
216 : int sbitmap_get_shallow(struct sbitmap *sb, unsigned long shallow_depth);
217 :
218 : /**
219 : * sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap.
220 : * @sb: Bitmap to check.
221 : *
222 : * Return: true if any bit in the bitmap is set, false otherwise.
223 : */
224 : bool sbitmap_any_bit_set(const struct sbitmap *sb);
225 :
226 : #define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift)
227 : #define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U))
228 :
229 : typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *);
230 :
231 : /**
232 : * __sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
233 : * @start: Where to start the iteration.
234 : * @sb: Bitmap to iterate over.
235 : * @fn: Callback. Should return true to continue or false to break early.
236 : * @data: Pointer to pass to callback.
237 : *
238 : * This is inline even though it's non-trivial so that the function calls to the
239 : * callback will hopefully get optimized away.
240 : */
241 0 : static inline void __sbitmap_for_each_set(struct sbitmap *sb,
242 : unsigned int start,
243 : sb_for_each_fn fn, void *data)
244 : {
245 : unsigned int index;
246 : unsigned int nr;
247 0 : unsigned int scanned = 0;
248 :
249 0 : if (start >= sb->depth)
250 0 : start = 0;
251 0 : index = SB_NR_TO_INDEX(sb, start);
252 0 : nr = SB_NR_TO_BIT(sb, start);
253 :
254 0 : while (scanned < sb->depth) {
255 : unsigned long word;
256 0 : unsigned int depth = min_t(unsigned int,
257 : __map_depth(sb, index) - nr,
258 : sb->depth - scanned);
259 :
260 0 : scanned += depth;
261 0 : word = sb->map[index].word & ~sb->map[index].cleared;
262 0 : if (!word)
263 : goto next;
264 :
265 : /*
266 : * On the first iteration of the outer loop, we need to add the
267 : * bit offset back to the size of the word for find_next_bit().
268 : * On all other iterations, nr is zero, so this is a noop.
269 : */
270 0 : depth += nr;
271 : while (1) {
272 0 : nr = find_next_bit(&word, depth, nr);
273 0 : if (nr >= depth)
274 : break;
275 0 : if (!fn(sb, (index << sb->shift) + nr, data))
276 0 : return;
277 :
278 0 : nr++;
279 : }
280 : next:
281 0 : nr = 0;
282 0 : if (++index >= sb->map_nr)
283 0 : index = 0;
284 : }
285 : }
286 :
287 : /**
288 : * sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
289 : * @sb: Bitmap to iterate over.
290 : * @fn: Callback. Should return true to continue or false to break early.
291 : * @data: Pointer to pass to callback.
292 : */
293 : static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn,
294 : void *data)
295 : {
296 0 : __sbitmap_for_each_set(sb, 0, fn, data);
297 : }
298 :
299 : static inline unsigned long *__sbitmap_word(struct sbitmap *sb,
300 : unsigned int bitnr)
301 : {
302 0 : return &sb->map[SB_NR_TO_INDEX(sb, bitnr)].word;
303 : }
304 :
305 : /* Helpers equivalent to the operations in asm/bitops.h and linux/bitmap.h */
306 :
307 : static inline void sbitmap_set_bit(struct sbitmap *sb, unsigned int bitnr)
308 : {
309 0 : set_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
310 : }
311 :
312 : static inline void sbitmap_clear_bit(struct sbitmap *sb, unsigned int bitnr)
313 : {
314 0 : clear_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
315 : }
316 :
317 : /*
318 : * This one is special, since it doesn't actually clear the bit, rather it
319 : * sets the corresponding bit in the ->cleared mask instead. Paired with
320 : * the caller doing sbitmap_deferred_clear() if a given index is full, which
321 : * will clear the previously freed entries in the corresponding ->word.
322 : */
323 : static inline void sbitmap_deferred_clear_bit(struct sbitmap *sb, unsigned int bitnr)
324 : {
325 0 : unsigned long *addr = &sb->map[SB_NR_TO_INDEX(sb, bitnr)].cleared;
326 :
327 0 : set_bit(SB_NR_TO_BIT(sb, bitnr), addr);
328 : }
329 :
330 : /*
331 : * Pair of sbitmap_get, and this one applies both cleared bit and
332 : * allocation hint.
333 : */
334 : static inline void sbitmap_put(struct sbitmap *sb, unsigned int bitnr)
335 : {
336 : sbitmap_deferred_clear_bit(sb, bitnr);
337 :
338 : if (likely(sb->alloc_hint && !sb->round_robin && bitnr < sb->depth))
339 : *raw_cpu_ptr(sb->alloc_hint) = bitnr;
340 : }
341 :
342 : static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
343 : {
344 0 : return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
345 : }
346 :
347 : static inline int sbitmap_calculate_shift(unsigned int depth)
348 : {
349 0 : int shift = ilog2(BITS_PER_LONG);
350 :
351 : /*
352 : * If the bitmap is small, shrink the number of bits per word so
353 : * we spread over a few cachelines, at least. If less than 4
354 : * bits, just forget about it, it's not going to work optimally
355 : * anyway.
356 : */
357 0 : if (depth >= 4) {
358 0 : while ((4U << shift) > depth)
359 0 : shift--;
360 : }
361 :
362 : return shift;
363 : }
364 :
365 : /**
366 : * sbitmap_show() - Dump &struct sbitmap information to a &struct seq_file.
367 : * @sb: Bitmap to show.
368 : * @m: struct seq_file to write to.
369 : *
370 : * This is intended for debugging. The format may change at any time.
371 : */
372 : void sbitmap_show(struct sbitmap *sb, struct seq_file *m);
373 :
374 :
375 : /**
376 : * sbitmap_weight() - Return how many set and not cleared bits in a &struct
377 : * sbitmap.
378 : * @sb: Bitmap to check.
379 : *
380 : * Return: How many set and not cleared bits set
381 : */
382 : unsigned int sbitmap_weight(const struct sbitmap *sb);
383 :
384 : /**
385 : * sbitmap_bitmap_show() - Write a hex dump of a &struct sbitmap to a &struct
386 : * seq_file.
387 : * @sb: Bitmap to show.
388 : * @m: struct seq_file to write to.
389 : *
390 : * This is intended for debugging. The output isn't guaranteed to be internally
391 : * consistent.
392 : */
393 : void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m);
394 :
395 : /**
396 : * sbitmap_queue_init_node() - Initialize a &struct sbitmap_queue on a specific
397 : * memory node.
398 : * @sbq: Bitmap queue to initialize.
399 : * @depth: See sbitmap_init_node().
400 : * @shift: See sbitmap_init_node().
401 : * @round_robin: See sbitmap_get().
402 : * @flags: Allocation flags.
403 : * @node: Memory node to allocate on.
404 : *
405 : * Return: Zero on success or negative errno on failure.
406 : */
407 : int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
408 : int shift, bool round_robin, gfp_t flags, int node);
409 :
410 : /**
411 : * sbitmap_queue_free() - Free memory used by a &struct sbitmap_queue.
412 : *
413 : * @sbq: Bitmap queue to free.
414 : */
415 0 : static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
416 : {
417 0 : kfree(sbq->ws);
418 0 : sbitmap_free(&sbq->sb);
419 0 : }
420 :
421 : /**
422 : * sbitmap_queue_recalculate_wake_batch() - Recalculate wake batch
423 : * @sbq: Bitmap queue to recalculate wake batch.
424 : * @users: Number of shares.
425 : *
426 : * Like sbitmap_queue_update_wake_batch(), this will calculate wake batch
427 : * by depth. This interface is for HCTX shared tags or queue shared tags.
428 : */
429 : void sbitmap_queue_recalculate_wake_batch(struct sbitmap_queue *sbq,
430 : unsigned int users);
431 :
432 : /**
433 : * sbitmap_queue_resize() - Resize a &struct sbitmap_queue.
434 : * @sbq: Bitmap queue to resize.
435 : * @depth: New number of bits to resize to.
436 : *
437 : * Like sbitmap_resize(), this doesn't reallocate anything. It has to do
438 : * some extra work on the &struct sbitmap_queue, so it's not safe to just
439 : * resize the underlying &struct sbitmap.
440 : */
441 : void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth);
442 :
443 : /**
444 : * __sbitmap_queue_get() - Try to allocate a free bit from a &struct
445 : * sbitmap_queue with preemption already disabled.
446 : * @sbq: Bitmap queue to allocate from.
447 : *
448 : * Return: Non-negative allocated bit number if successful, -1 otherwise.
449 : */
450 : int __sbitmap_queue_get(struct sbitmap_queue *sbq);
451 :
452 : /**
453 : * __sbitmap_queue_get_batch() - Try to allocate a batch of free bits
454 : * @sbq: Bitmap queue to allocate from.
455 : * @nr_tags: number of tags requested
456 : * @offset: offset to add to returned bits
457 : *
458 : * Return: Mask of allocated tags, 0 if none are found. Each tag allocated is
459 : * a bit in the mask returned, and the caller must add @offset to the value to
460 : * get the absolute tag value.
461 : */
462 : unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags,
463 : unsigned int *offset);
464 :
465 : /**
466 : * sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct
467 : * sbitmap_queue, limiting the depth used from each word, with preemption
468 : * already disabled.
469 : * @sbq: Bitmap queue to allocate from.
470 : * @shallow_depth: The maximum number of bits to allocate from a single word.
471 : * See sbitmap_get_shallow().
472 : *
473 : * If you call this, make sure to call sbitmap_queue_min_shallow_depth() after
474 : * initializing @sbq.
475 : *
476 : * Return: Non-negative allocated bit number if successful, -1 otherwise.
477 : */
478 : int sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
479 : unsigned int shallow_depth);
480 :
481 : /**
482 : * sbitmap_queue_get() - Try to allocate a free bit from a &struct
483 : * sbitmap_queue.
484 : * @sbq: Bitmap queue to allocate from.
485 : * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to
486 : * sbitmap_queue_clear()).
487 : *
488 : * Return: Non-negative allocated bit number if successful, -1 otherwise.
489 : */
490 : static inline int sbitmap_queue_get(struct sbitmap_queue *sbq,
491 : unsigned int *cpu)
492 : {
493 : int nr;
494 :
495 : *cpu = get_cpu();
496 : nr = __sbitmap_queue_get(sbq);
497 : put_cpu();
498 : return nr;
499 : }
500 :
501 : /**
502 : * sbitmap_queue_min_shallow_depth() - Inform a &struct sbitmap_queue of the
503 : * minimum shallow depth that will be used.
504 : * @sbq: Bitmap queue in question.
505 : * @min_shallow_depth: The minimum shallow depth that will be passed to
506 : * sbitmap_queue_get_shallow() or __sbitmap_queue_get_shallow().
507 : *
508 : * sbitmap_queue_clear() batches wakeups as an optimization. The batch size
509 : * depends on the depth of the bitmap. Since the shallow allocation functions
510 : * effectively operate with a different depth, the shallow depth must be taken
511 : * into account when calculating the batch size. This function must be called
512 : * with the minimum shallow depth that will be used. Failure to do so can result
513 : * in missed wakeups.
514 : */
515 : void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq,
516 : unsigned int min_shallow_depth);
517 :
518 : /**
519 : * sbitmap_queue_clear() - Free an allocated bit and wake up waiters on a
520 : * &struct sbitmap_queue.
521 : * @sbq: Bitmap to free from.
522 : * @nr: Bit number to free.
523 : * @cpu: CPU the bit was allocated on.
524 : */
525 : void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
526 : unsigned int cpu);
527 :
528 : /**
529 : * sbitmap_queue_clear_batch() - Free a batch of allocated bits
530 : * &struct sbitmap_queue.
531 : * @sbq: Bitmap to free from.
532 : * @offset: offset for each tag in array
533 : * @tags: array of tags
534 : * @nr_tags: number of tags in array
535 : */
536 : void sbitmap_queue_clear_batch(struct sbitmap_queue *sbq, int offset,
537 : int *tags, int nr_tags);
538 :
539 : static inline int sbq_index_inc(int index)
540 : {
541 0 : return (index + 1) & (SBQ_WAIT_QUEUES - 1);
542 : }
543 :
544 : static inline void sbq_index_atomic_inc(atomic_t *index)
545 : {
546 0 : int old = atomic_read(index);
547 0 : int new = sbq_index_inc(old);
548 0 : atomic_cmpxchg(index, old, new);
549 : }
550 :
551 : /**
552 : * sbq_wait_ptr() - Get the next wait queue to use for a &struct
553 : * sbitmap_queue.
554 : * @sbq: Bitmap queue to wait on.
555 : * @wait_index: A counter per "user" of @sbq.
556 : */
557 : static inline struct sbq_wait_state *sbq_wait_ptr(struct sbitmap_queue *sbq,
558 : atomic_t *wait_index)
559 : {
560 : struct sbq_wait_state *ws;
561 :
562 0 : ws = &sbq->ws[atomic_read(wait_index)];
563 0 : sbq_index_atomic_inc(wait_index);
564 : return ws;
565 : }
566 :
567 : /**
568 : * sbitmap_queue_wake_all() - Wake up everything waiting on a &struct
569 : * sbitmap_queue.
570 : * @sbq: Bitmap queue to wake up.
571 : */
572 : void sbitmap_queue_wake_all(struct sbitmap_queue *sbq);
573 :
574 : /**
575 : * sbitmap_queue_wake_up() - Wake up some of waiters in one waitqueue
576 : * on a &struct sbitmap_queue.
577 : * @sbq: Bitmap queue to wake up.
578 : */
579 : void sbitmap_queue_wake_up(struct sbitmap_queue *sbq);
580 :
581 : /**
582 : * sbitmap_queue_show() - Dump &struct sbitmap_queue information to a &struct
583 : * seq_file.
584 : * @sbq: Bitmap queue to show.
585 : * @m: struct seq_file to write to.
586 : *
587 : * This is intended for debugging. The format may change at any time.
588 : */
589 : void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m);
590 :
591 : struct sbq_wait {
592 : struct sbitmap_queue *sbq; /* if set, sbq_wait is accounted */
593 : struct wait_queue_entry wait;
594 : };
595 :
596 : #define DEFINE_SBQ_WAIT(name) \
597 : struct sbq_wait name = { \
598 : .sbq = NULL, \
599 : .wait = { \
600 : .private = current, \
601 : .func = autoremove_wake_function, \
602 : .entry = LIST_HEAD_INIT((name).wait.entry), \
603 : } \
604 : }
605 :
606 : /*
607 : * Wrapper around prepare_to_wait_exclusive(), which maintains some extra
608 : * internal state.
609 : */
610 : void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq,
611 : struct sbq_wait_state *ws,
612 : struct sbq_wait *sbq_wait, int state);
613 :
614 : /*
615 : * Must be paired with sbitmap_prepare_to_wait().
616 : */
617 : void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws,
618 : struct sbq_wait *sbq_wait);
619 :
620 : /*
621 : * Wrapper around add_wait_queue(), which maintains some extra internal state
622 : */
623 : void sbitmap_add_wait_queue(struct sbitmap_queue *sbq,
624 : struct sbq_wait_state *ws,
625 : struct sbq_wait *sbq_wait);
626 :
627 : /*
628 : * Must be paired with sbitmap_add_wait_queue()
629 : */
630 : void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait);
631 :
632 : #endif /* __LINUX_SCALE_BITMAP_H */
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