Home Home > GIT Browse
summaryrefslogtreecommitdiff
blob: a1904aadbc45004ba18c8db06f184a164908cd46 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
/*
 * Fast and scalable bitmaps.
 *
 * Copyright (C) 2016 Facebook
 * Copyright (C) 2013-2014 Jens Axboe
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#ifndef __LINUX_SCALE_BITMAP_H
#define __LINUX_SCALE_BITMAP_H

#include <linux/kernel.h>
#include <linux/slab.h>

/**
 * struct sbitmap_word - Word in a &struct sbitmap.
 */
struct sbitmap_word {
	/**
	 * @word: The bitmap word itself.
	 */
	unsigned long word;

	/**
	 * @depth: Number of bits being used in @word.
	 */
	unsigned long depth;
} ____cacheline_aligned_in_smp;

/**
 * struct sbitmap - Scalable bitmap.
 *
 * A &struct sbitmap is spread over multiple cachelines to avoid ping-pong. This
 * trades off higher memory usage for better scalability.
 */
struct sbitmap {
	/**
	 * @depth: Number of bits used in the whole bitmap.
	 */
	unsigned int depth;

	/**
	 * @shift: log2(number of bits used per word)
	 */
	unsigned int shift;

	/**
	 * @map_nr: Number of words (cachelines) being used for the bitmap.
	 */
	unsigned int map_nr;

	/**
	 * @map: Allocated bitmap.
	 */
	struct sbitmap_word *map;
};

#define SBQ_WAIT_QUEUES 8
#define SBQ_WAKE_BATCH 8

/**
 * struct sbq_wait_state - Wait queue in a &struct sbitmap_queue.
 */
struct sbq_wait_state {
	/**
	 * @wait_cnt: Number of frees remaining before we wake up.
	 */
	atomic_t wait_cnt;

	/**
	 * @wait: Wait queue.
	 */
	wait_queue_head_t wait;
} ____cacheline_aligned_in_smp;

/**
 * struct sbitmap_queue - Scalable bitmap with the added ability to wait on free
 * bits.
 *
 * A &struct sbitmap_queue uses multiple wait queues and rolling wakeups to
 * avoid contention on the wait queue spinlock. This ensures that we don't hit a
 * scalability wall when we run out of free bits and have to start putting tasks
 * to sleep.
 */
struct sbitmap_queue {
	/**
	 * @sb: Scalable bitmap.
	 */
	struct sbitmap sb;

	/*
	 * @alloc_hint: Cache of last successfully allocated or freed bit.
	 *
	 * This is per-cpu, which allows multiple users to stick to different
	 * cachelines until the map is exhausted.
	 */
	unsigned int __percpu *alloc_hint;

	/**
	 * @wake_batch: Number of bits which must be freed before we wake up any
	 * waiters.
	 */
	unsigned int wake_batch;

	/**
	 * @wake_index: Next wait queue in @ws to wake up.
	 */
	atomic_t wake_index;

	/**
	 * @ws: Wait queues.
	 */
	struct sbq_wait_state *ws;

	/**
	 * @round_robin: Allocate bits in strict round-robin order.
	 */
	bool round_robin;
};

/**
 * sbitmap_init_node() - Initialize a &struct sbitmap on a specific memory node.
 * @sb: Bitmap to initialize.
 * @depth: Number of bits to allocate.
 * @shift: Use 2^@shift bits per word in the bitmap; if a negative number if
 *         given, a good default is chosen.
 * @flags: Allocation flags.
 * @node: Memory node to allocate on.
 *
 * Return: Zero on success or negative errno on failure.
 */
int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
		      gfp_t flags, int node);

/**
 * sbitmap_free() - Free memory used by a &struct sbitmap.
 * @sb: Bitmap to free.
 */
static inline void sbitmap_free(struct sbitmap *sb)
{
	kfree(sb->map);
	sb->map = NULL;
}

/**
 * sbitmap_resize() - Resize a &struct sbitmap.
 * @sb: Bitmap to resize.
 * @depth: New number of bits to resize to.
 *
 * Doesn't reallocate anything. It's up to the caller to ensure that the new
 * depth doesn't exceed the depth that the sb was initialized with.
 */
void sbitmap_resize(struct sbitmap *sb, unsigned int depth);

/**
 * sbitmap_get() - Try to allocate a free bit from a &struct sbitmap.
 * @sb: Bitmap to allocate from.
 * @alloc_hint: Hint for where to start searching for a free bit.
 * @round_robin: If true, be stricter about allocation order; always allocate
 *               starting from the last allocated bit. This is less efficient
 *               than the default behavior (false).
 *
 * Return: Non-negative allocated bit number if successful, -1 otherwise.
 */
int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin);

/**
 * sbitmap_get_shallow() - Try to allocate a free bit from a &struct sbitmap,
 * limiting the depth used from each word.
 * @sb: Bitmap to allocate from.
 * @alloc_hint: Hint for where to start searching for a free bit.
 * @shallow_depth: The maximum number of bits to allocate from a single word.
 *
 * This rather specific operation allows for having multiple users with
 * different allocation limits. E.g., there can be a high-priority class that
 * uses sbitmap_get() and a low-priority class that uses sbitmap_get_shallow()
 * with a @shallow_depth of (1 << (@sb->shift - 1)). Then, the low-priority
 * class can only allocate half of the total bits in the bitmap, preventing it
 * from starving out the high-priority class.
 *
 * Return: Non-negative allocated bit number if successful, -1 otherwise.
 */
int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
			unsigned long shallow_depth);

/**
 * sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap.
 * @sb: Bitmap to check.
 *
 * Return: true if any bit in the bitmap is set, false otherwise.
 */
bool sbitmap_any_bit_set(const struct sbitmap *sb);

/**
 * sbitmap_any_bit_clear() - Check for an unset bit in a &struct
 * sbitmap.
 * @sb: Bitmap to check.
 *
 * Return: true if any bit in the bitmap is clear, false otherwise.
 */
bool sbitmap_any_bit_clear(const struct sbitmap *sb);

typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *);

/**
 * sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
 * @sb: Bitmap to iterate over.
 * @fn: Callback. Should return true to continue or false to break early.
 * @data: Pointer to pass to callback.
 *
 * This is inline even though it's non-trivial so that the function calls to the
 * callback will hopefully get optimized away.
 */
static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn,
					void *data)
{
	unsigned int i;

	for (i = 0; i < sb->map_nr; i++) {
		struct sbitmap_word *word = &sb->map[i];
		unsigned int off, nr;

		if (!word->word)
			continue;

		nr = 0;
		off = i << sb->shift;
		while (1) {
			nr = find_next_bit(&word->word, word->depth, nr);
			if (nr >= word->depth)
				break;

			if (!fn(sb, off + nr, data))
				return;

			nr++;
		}
	}
}

#define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift)
#define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U))

static inline unsigned long *__sbitmap_word(struct sbitmap *sb,
					    unsigned int bitnr)
{
	return &sb->map[SB_NR_TO_INDEX(sb, bitnr)].word;
}

/* Helpers equivalent to the operations in asm/bitops.h and linux/bitmap.h */

static inline void sbitmap_set_bit(struct sbitmap *sb, unsigned int bitnr)
{
	set_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
}

static inline void sbitmap_clear_bit(struct sbitmap *sb, unsigned int bitnr)
{
	clear_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
}

static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
{
	return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
}

unsigned int sbitmap_weight(const struct sbitmap *sb);

/**
 * sbitmap_show() - Dump &struct sbitmap information to a &struct seq_file.
 * @sb: Bitmap to show.
 * @m: struct seq_file to write to.
 *
 * This is intended for debugging. The format may change at any time.
 */
void sbitmap_show(struct sbitmap *sb, struct seq_file *m);

/**
 * sbitmap_bitmap_show() - Write a hex dump of a &struct sbitmap to a &struct
 * seq_file.
 * @sb: Bitmap to show.
 * @m: struct seq_file to write to.
 *
 * This is intended for debugging. The output isn't guaranteed to be internally
 * consistent.
 */
void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m);

/**
 * sbitmap_queue_init_node() - Initialize a &struct sbitmap_queue on a specific
 * memory node.
 * @sbq: Bitmap queue to initialize.
 * @depth: See sbitmap_init_node().
 * @shift: See sbitmap_init_node().
 * @round_robin: See sbitmap_get().
 * @flags: Allocation flags.
 * @node: Memory node to allocate on.
 *
 * Return: Zero on success or negative errno on failure.
 */
int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
			    int shift, bool round_robin, gfp_t flags, int node);

/**
 * sbitmap_queue_free() - Free memory used by a &struct sbitmap_queue.
 *
 * @sbq: Bitmap queue to free.
 */
static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
{
	kfree(sbq->ws);
	free_percpu(sbq->alloc_hint);
	sbitmap_free(&sbq->sb);
}

/**
 * sbitmap_queue_resize() - Resize a &struct sbitmap_queue.
 * @sbq: Bitmap queue to resize.
 * @depth: New number of bits to resize to.
 *
 * Like sbitmap_resize(), this doesn't reallocate anything. It has to do
 * some extra work on the &struct sbitmap_queue, so it's not safe to just
 * resize the underlying &struct sbitmap.
 */
void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth);

/**
 * __sbitmap_queue_get() - Try to allocate a free bit from a &struct
 * sbitmap_queue with preemption already disabled.
 * @sbq: Bitmap queue to allocate from.
 *
 * Return: Non-negative allocated bit number if successful, -1 otherwise.
 */
int __sbitmap_queue_get(struct sbitmap_queue *sbq);

/**
 * __sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct
 * sbitmap_queue, limiting the depth used from each word, with preemption
 * already disabled.
 * @sbq: Bitmap queue to allocate from.
 * @shallow_depth: The maximum number of bits to allocate from a single word.
 * See sbitmap_get_shallow().
 *
 * Return: Non-negative allocated bit number if successful, -1 otherwise.
 */
int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
				unsigned int shallow_depth);

/**
 * sbitmap_queue_get() - Try to allocate a free bit from a &struct
 * sbitmap_queue.
 * @sbq: Bitmap queue to allocate from.
 * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to
 *       sbitmap_queue_clear()).
 *
 * Return: Non-negative allocated bit number if successful, -1 otherwise.
 */
static inline int sbitmap_queue_get(struct sbitmap_queue *sbq,
				    unsigned int *cpu)
{
	int nr;

	*cpu = get_cpu();
	nr = __sbitmap_queue_get(sbq);
	put_cpu();
	return nr;
}

/**
 * sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct
 * sbitmap_queue, limiting the depth used from each word.
 * @sbq: Bitmap queue to allocate from.
 * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to
 *       sbitmap_queue_clear()).
 * @shallow_depth: The maximum number of bits to allocate from a single word.
 * See sbitmap_get_shallow().
 *
 * Return: Non-negative allocated bit number if successful, -1 otherwise.
 */
static inline int sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
					    unsigned int *cpu,
					    unsigned int shallow_depth)
{
	int nr;

	*cpu = get_cpu();
	nr = __sbitmap_queue_get_shallow(sbq, shallow_depth);
	put_cpu();
	return nr;
}

/**
 * sbitmap_queue_clear() - Free an allocated bit and wake up waiters on a
 * &struct sbitmap_queue.
 * @sbq: Bitmap to free from.
 * @nr: Bit number to free.
 * @cpu: CPU the bit was allocated on.
 */
void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
			 unsigned int cpu);

static inline int sbq_index_inc(int index)
{
	return (index + 1) & (SBQ_WAIT_QUEUES - 1);
}

static inline void sbq_index_atomic_inc(atomic_t *index)
{
	int old = atomic_read(index);
	int new = sbq_index_inc(old);
	atomic_cmpxchg(index, old, new);
}

/**
 * sbq_wait_ptr() - Get the next wait queue to use for a &struct
 * sbitmap_queue.
 * @sbq: Bitmap queue to wait on.
 * @wait_index: A counter per "user" of @sbq.
 */
static inline struct sbq_wait_state *sbq_wait_ptr(struct sbitmap_queue *sbq,
						  atomic_t *wait_index)
{
	struct sbq_wait_state *ws;

	ws = &sbq->ws[atomic_read(wait_index)];
	sbq_index_atomic_inc(wait_index);
	return ws;
}

/**
 * sbitmap_queue_wake_all() - Wake up everything waiting on a &struct
 * sbitmap_queue.
 * @sbq: Bitmap queue to wake up.
 */
void sbitmap_queue_wake_all(struct sbitmap_queue *sbq);

/**
 * sbitmap_queue_show() - Dump &struct sbitmap_queue information to a &struct
 * seq_file.
 * @sbq: Bitmap queue to show.
 * @m: struct seq_file to write to.
 *
 * This is intended for debugging. The format may change at any time.
 */
void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m);

#endif /* __LINUX_SCALE_BITMAP_H */