summaryrefslogtreecommitdiffstats
path: root/lib/sbitmap.c
blob: 2cecf05c82fd832ce0c1a49cfffdc8f547ea5eb0 (plain) (blame)
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
/*
 * 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/>.
 */

#include <linux/random.h>
#include <linux/sbitmap.h>

int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
		      gfp_t flags, int node)
{
	unsigned int bits_per_word;
	unsigned int i;

	if (shift < 0) {
		shift = ilog2(BITS_PER_LONG);
		/*
		 * If the bitmap is small, shrink the number of bits per word so
		 * we spread over a few cachelines, at least. If less than 4
		 * bits, just forget about it, it's not going to work optimally
		 * anyway.
		 */
		if (depth >= 4) {
			while ((4U << shift) > depth)
				shift--;
		}
	}
	bits_per_word = 1U << shift;
	if (bits_per_word > BITS_PER_LONG)
		return -EINVAL;

	sb->shift = shift;
	sb->depth = depth;
	sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);

	if (depth == 0) {
		sb->map = NULL;
		return 0;
	}

	sb->map = kzalloc_node(sb->map_nr * sizeof(*sb->map), flags, node);
	if (!sb->map)
		return -ENOMEM;

	for (i = 0; i < sb->map_nr; i++) {
		sb->map[i].depth = min(depth, bits_per_word);
		depth -= sb->map[i].depth;
	}
	return 0;
}
EXPORT_SYMBOL_GPL(sbitmap_init_node);

void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
{
	unsigned int bits_per_word = 1U << sb->shift;
	unsigned int i;

	sb->depth = depth;
	sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);

	for (i = 0; i < sb->map_nr; i++) {
		sb->map[i].depth = min(depth, bits_per_word);
		depth -= sb->map[i].depth;
	}
}
EXPORT_SYMBOL_GPL(sbitmap_resize);

static int __sbitmap_get_word(struct sbitmap_word *word, unsigned int hint,
			      bool wrap)
{
	unsigned int orig_hint = hint;
	int nr;

	while (1) {
		nr = find_next_zero_bit(&word->word, word->depth, hint);
		if (unlikely(nr >= word->depth)) {
			/*
			 * We started with an offset, and we didn't reset the
			 * offset to 0 in a failure case, so start from 0 to
			 * exhaust the map.
			 */
			if (orig_hint && hint && wrap) {
				hint = orig_hint = 0;
				continue;
			}
			return -1;
		}

		if (!test_and_set_bit(nr, &word->word))
			break;

		hint = nr + 1;
		if (hint >= word->depth - 1)
			hint = 0;
	}

	return nr;
}

int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin)
{
	unsigned int i, index;
	int nr = -1;

	index = SB_NR_TO_INDEX(sb, alloc_hint);

	for (i = 0; i < sb->map_nr; i++) {
		nr = __sbitmap_get_word(&sb->map[index],
					SB_NR_TO_BIT(sb, alloc_hint),
					!round_robin);
		if (nr != -1) {
			nr += index << sb->shift;
			break;
		}

		/* Jump to next index. */
		index++;
		alloc_hint = index << sb->shift;

		if (index >= sb->map_nr) {
			index = 0;
			alloc_hint = 0;
		}
	}

	return nr;
}
EXPORT_SYMBOL_GPL(sbitmap_get);

bool sbitmap_any_bit_set(const struct sbitmap *sb)
{
	unsigned int i;

	for (i = 0; i < sb->map_nr; i++) {
		if (sb->map[i].word)
			return true;
	}
	return false;
}
EXPORT_SYMBOL_GPL(sbitmap_any_bit_set);

bool sbitmap_any_bit_clear(const struct sbitmap *sb)
{
	unsigned int i;

	for (i = 0; i < sb->map_nr; i++) {
		const struct sbitmap_word *word = &sb->map[i];
		unsigned long ret;

		ret = find_first_zero_bit(&word->word, word->depth);
		if (ret < word->depth)
			return true;
	}
	return false;
}
EXPORT_SYMBOL_GPL(sbitmap_any_bit_clear);

unsigned int sbitmap_weight(const struct sbitmap *sb)
{
	unsigned int i, weight = 0;

	for (i = 0; i < sb->map_nr; i++) {
		const struct sbitmap_word *word = &sb->map[i];

		weight += bitmap_weight(&word->word, word->depth);
	}
	return weight;
}
EXPORT_SYMBOL_GPL(sbitmap_weight);

static unsigned int sbq_calc_wake_batch(unsigned int depth)
{
	unsigned int wake_batch;

	/*
	 * For each batch, we wake up one queue. We need to make sure that our
	 * batch size is small enough that the full depth of the bitmap is
	 * enough to wake up all of the queues.
	 */
	wake_batch = SBQ_WAKE_BATCH;
	if (wake_batch > depth / SBQ_WAIT_QUEUES)
		wake_batch = max(1U, depth / SBQ_WAIT_QUEUES);

	return wake_batch;
}

int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
			    int shift, bool round_robin, gfp_t flags, int node)
{
	int ret;
	int i;

	ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node);
	if (ret)
		return ret;

	sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
	if (!sbq->alloc_hint) {
		sbitmap_free(&sbq->sb);
		return -ENOMEM;
	}

	if (depth && !round_robin) {
		for_each_possible_cpu(i)
			*per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
	}

	sbq->wake_batch = sbq_calc_wake_batch(depth);
	atomic_set(&sbq->wake_index, 0);

	sbq->ws = kzalloc_node(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags, node);
	if (!sbq->ws) {
		free_percpu(sbq->alloc_hint);
		sbitmap_free(&sbq->sb);
		return -ENOMEM;
	}

	for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
		init_waitqueue_head(&sbq->ws[i].wait);
		atomic_set(&sbq->ws[i].wait_cnt, sbq->wake_batch);
	}

	sbq->round_robin = round_robin;
	return 0;
}
EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);

void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)
{
	sbq->wake_batch = sbq_calc_wake_batch(depth);
	sbitmap_resize(&sbq->sb, depth);
}
EXPORT_SYMBOL_GPL(sbitmap_queue_resize);

int __sbitmap_queue_get(struct sbitmap_queue *sbq)
{
	unsigned int hint, depth;
	int nr;

	hint = this_cpu_read(*sbq->alloc_hint);
	depth = READ_ONCE(sbq->sb.depth);
	if (unlikely(hint >= depth)) {
		hint = depth ? prandom_u32() % depth : 0;
		this_cpu_write(*sbq->alloc_hint, hint);
	}
	nr = sbitmap_get(&sbq->sb, hint, sbq->round_robin);

	if (nr == -1) {
		/* If the map is full, a hint won't do us much good. */
		this_cpu_write(*sbq->alloc_hint, 0);
	} else if (nr == hint || unlikely(sbq->round_robin)) {
		/* Only update the hint if we used it. */
		hint = nr + 1;
		if (hint >= depth - 1)
			hint = 0;
		this_cpu_write(*sbq->alloc_hint, hint);
	}

	return nr;
}
EXPORT_SYMBOL_GPL(__sbitmap_queue_get);

static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq)
{
	int i, wake_index;

	wake_index = atomic_read(&sbq->wake_index);
	for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
		struct sbq_wait_state *ws = &sbq->ws[wake_index];

		if (waitqueue_active(&ws->wait)) {
			int o = atomic_read(&sbq->wake_index);

			if (wake_index != o)
				atomic_cmpxchg(&sbq->wake_index, o, wake_index);
			return ws;
		}

		wake_index = sbq_index_inc(wake_index);
	}

	return NULL;
}

static void sbq_wake_up(struct sbitmap_queue *sbq)
{
	struct sbq_wait_state *ws;
	int wait_cnt;

	/* Ensure that the wait list checks occur after clear_bit(). */
	smp_mb();

	ws = sbq_wake_ptr(sbq);
	if (!ws)
		return;

	wait_cnt = atomic_dec_return(&ws->wait_cnt);
	if (unlikely(wait_cnt < 0))
		wait_cnt = atomic_inc_return(&ws->wait_cnt);
	if (wait_cnt == 0) {
		atomic_add(sbq->wake_batch, &ws->wait_cnt);
		sbq_index_atomic_inc(&sbq->wake_index);
		wake_up(&ws->wait);
	}
}

void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
			 unsigned int cpu)
{
	sbitmap_clear_bit(&sbq->sb, nr);
	sbq_wake_up(sbq);
	if (likely(!sbq->round_robin && nr < sbq->sb.depth))
		*per_cpu_ptr(sbq->alloc_hint, cpu) = nr;
}
EXPORT_SYMBOL_GPL(sbitmap_queue_clear);

void sbitmap_queue_wake_all(struct sbitmap_queue *sbq)
{
	int i, wake_index;

	/*
	 * Make sure all changes prior to this are visible from other CPUs.
	 */
	smp_mb();
	wake_index = atomic_read(&sbq->wake_index);
	for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
		struct sbq_wait_state *ws = &sbq->ws[wake_index];

		if (waitqueue_active(&ws->wait))
			wake_up(&ws->wait);

		wake_index = sbq_index_inc(wake_index);
	}
}
EXPORT_SYMBOL_GPL(sbitmap_queue_wake_all);