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 if (index == sb->map_nr - 1) 166 return sb->depth - (index << sb->shift); 167 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 free_percpu(sb->alloc_hint); 177 kvfree(sb->map); 178 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 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 unsigned int scanned = 0; 248 249 if (start >= sb->depth) 250 start = 0; 251 index = SB_NR_TO_INDEX(sb, start); 252 nr = SB_NR_TO_BIT(sb, start); 253 254 while (scanned < sb->depth) { 255 unsigned long word; 256 unsigned int depth = min_t(unsigned int, 257 __map_depth(sb, index) - nr, 258 sb->depth - scanned); 259 260 scanned += depth; 261 word = sb->map[index].word & ~sb->map[index].cleared; 262 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 depth += nr; 271 while (1) { 272 nr = find_next_bit(&word, depth, nr); 273 if (nr >= depth) 274 break; 275 if (!fn(sb, (index << sb->shift) + nr, data)) 276 return; 277 278 nr++; 279 } 280 next: 281 nr = 0; 282 if (++index >= sb->map_nr) 283 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 __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 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 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 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 unsigned long *addr = &sb->map[SB_NR_TO_INDEX(sb, bitnr)].cleared; 326 327 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 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 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 if (depth >= 4) { 358 while ((4U << shift) > depth) 359 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 static inline void sbitmap_queue_free(struct sbitmap_queue *sbq) 416 { 417 kfree(sbq->ws); 418 sbitmap_free(&sbq->sb); 419 } 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 return (index + 1) & (SBQ_WAIT_QUEUES - 1); 542 } 543 544 static inline void sbq_index_atomic_inc(atomic_t *index) 545 { 546 int old = atomic_read(index); 547 int new = sbq_index_inc(old); 548 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 ws = &sbq->ws[atomic_read(wait_index)]; 563 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 * @nr: Number of bits cleared. 579 */ 580 void sbitmap_queue_wake_up(struct sbitmap_queue *sbq, int nr); 581 582 /** 583 * sbitmap_queue_show() - Dump &struct sbitmap_queue information to a &struct 584 * seq_file. 585 * @sbq: Bitmap queue to show. 586 * @m: struct seq_file to write to. 587 * 588 * This is intended for debugging. The format may change at any time. 589 */ 590 void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m); 591 592 struct sbq_wait { 593 struct sbitmap_queue *sbq; /* if set, sbq_wait is accounted */ 594 struct wait_queue_entry wait; 595 }; 596 597 #define DEFINE_SBQ_WAIT(name) \ 598 struct sbq_wait name = { \ 599 .sbq = NULL, \ 600 .wait = { \ 601 .private = current, \ 602 .func = autoremove_wake_function, \ 603 .entry = LIST_HEAD_INIT((name).wait.entry), \ 604 } \ 605 } 606 607 /* 608 * Wrapper around prepare_to_wait_exclusive(), which maintains some extra 609 * internal state. 610 */ 611 void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq, 612 struct sbq_wait_state *ws, 613 struct sbq_wait *sbq_wait, int state); 614 615 /* 616 * Must be paired with sbitmap_prepare_to_wait(). 617 */ 618 void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws, 619 struct sbq_wait *sbq_wait); 620 621 /* 622 * Wrapper around add_wait_queue(), which maintains some extra internal state 623 */ 624 void sbitmap_add_wait_queue(struct sbitmap_queue *sbq, 625 struct sbq_wait_state *ws, 626 struct sbq_wait *sbq_wait); 627 628 /* 629 * Must be paired with sbitmap_add_wait_queue() 630 */ 631 void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait); 632 633 #endif /* __LINUX_SCALE_BITMAP_H */ 634