1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1998 Matthew Dillon. All Rights Reserved. 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS 18 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE 23 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 24 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 25 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 26 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 27 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 */ 29 /* 30 * BLIST.C - Bitmap allocator/deallocator, using a radix tree with hinting 31 * 32 * This module implements a general bitmap allocator/deallocator. The 33 * allocator eats around 2 bits per 'block'. The module does not 34 * try to interpret the meaning of a 'block' other than to return 35 * SWAPBLK_NONE on an allocation failure. 36 * 37 * A radix tree controls access to pieces of the bitmap, and includes 38 * auxiliary information at each interior node about the availabilty of 39 * contiguous free blocks in the subtree rooted at that node. Two radix 40 * constants are involved: one for the size of the bitmaps contained in the 41 * leaf nodes (BLIST_BMAP_RADIX), and one for the number of descendents of 42 * each of the meta (interior) nodes (BLIST_META_RADIX). Each subtree is 43 * associated with a range of blocks. The root of any subtree stores a 44 * hint field that defines an upper bound on the size of the largest 45 * allocation that can begin in the associated block range. A hint is an 46 * upper bound on a potential allocation, but not necessarily a tight upper 47 * bound. 48 * 49 * The bitmap field in each node directs the search for available blocks. 50 * For a leaf node, a bit is set if the corresponding block is free. For a 51 * meta node, a bit is set if the corresponding subtree contains a free 52 * block somewhere within it. The search at a meta node considers only 53 * children of that node that represent a range that includes a free block. 54 * 55 * The hinting greatly increases code efficiency for allocations while 56 * the general radix structure optimizes both allocations and frees. The 57 * radix tree should be able to operate well no matter how much 58 * fragmentation there is and no matter how large a bitmap is used. 59 * 60 * The blist code wires all necessary memory at creation time. Neither 61 * allocations nor frees require interaction with the memory subsystem. 62 * The non-blocking nature of allocations and frees is required by swap 63 * code (vm/swap_pager.c). 64 * 65 * LAYOUT: The radix tree is laid out recursively using a linear array. 66 * Each meta node is immediately followed (laid out sequentially in 67 * memory) by BLIST_META_RADIX lower level nodes. This is a recursive 68 * structure but one that can be easily scanned through a very simple 69 * 'skip' calculation. The memory allocation is only large enough to 70 * cover the number of blocks requested at creation time. Nodes that 71 * represent blocks beyond that limit, nodes that would never be read 72 * or written, are not allocated, so that the last of the 73 * BLIST_META_RADIX lower level nodes of a some nodes may not be 74 * allocated. 75 * 76 * NOTE: the allocator cannot currently allocate more than 77 * BLIST_BMAP_RADIX blocks per call. It will panic with 'allocation too 78 * large' if you try. This is an area that could use improvement. The 79 * radix is large enough that this restriction does not effect the swap 80 * system, though. Currently only the allocation code is affected by 81 * this algorithmic unfeature. The freeing code can handle arbitrary 82 * ranges. 83 * 84 * This code can be compiled stand-alone for debugging. 85 */ 86 87 #include <sys/cdefs.h> 88 __FBSDID("$FreeBSD$"); 89 90 #ifdef _KERNEL 91 92 #include <sys/param.h> 93 #include <sys/systm.h> 94 #include <sys/lock.h> 95 #include <sys/kernel.h> 96 #include <sys/blist.h> 97 #include <sys/malloc.h> 98 #include <sys/sbuf.h> 99 #include <sys/proc.h> 100 #include <sys/mutex.h> 101 102 #else 103 104 #ifndef BLIST_NO_DEBUG 105 #define BLIST_DEBUG 106 #endif 107 108 #include <sys/errno.h> 109 #include <sys/types.h> 110 #include <sys/malloc.h> 111 #include <sys/sbuf.h> 112 #include <stdio.h> 113 #include <string.h> 114 #include <stddef.h> 115 #include <stdlib.h> 116 #include <stdarg.h> 117 #include <stdbool.h> 118 119 #define bitcount64(x) __bitcount64((uint64_t)(x)) 120 #define malloc(a,b,c) calloc(a, 1) 121 #define free(a,b) free(a) 122 #define ummin(a,b) ((a) < (b) ? (a) : (b)) 123 124 #include <sys/blist.h> 125 126 void panic(const char *ctl, ...); 127 128 #endif 129 130 /* 131 * static support functions 132 */ 133 static daddr_t blst_leaf_alloc(blmeta_t *scan, daddr_t blk, int count); 134 static daddr_t blst_meta_alloc(blmeta_t *scan, daddr_t cursor, daddr_t count, 135 u_daddr_t radix); 136 static void blst_leaf_free(blmeta_t *scan, daddr_t relblk, int count); 137 static void blst_meta_free(blmeta_t *scan, daddr_t freeBlk, daddr_t count, 138 u_daddr_t radix); 139 static void blst_copy(blmeta_t *scan, daddr_t blk, daddr_t radix, 140 blist_t dest, daddr_t count); 141 static daddr_t blst_leaf_fill(blmeta_t *scan, daddr_t blk, int count); 142 static daddr_t blst_meta_fill(blmeta_t *scan, daddr_t allocBlk, daddr_t count, 143 u_daddr_t radix); 144 #ifndef _KERNEL 145 static void blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t radix, 146 int tab); 147 #endif 148 149 #ifdef _KERNEL 150 static MALLOC_DEFINE(M_SWAP, "SWAP", "Swap space"); 151 #endif 152 153 _Static_assert(BLIST_BMAP_RADIX % BLIST_META_RADIX == 0, 154 "radix divisibility error"); 155 #define BLIST_BMAP_MASK (BLIST_BMAP_RADIX - 1) 156 #define BLIST_META_MASK (BLIST_META_RADIX - 1) 157 158 /* 159 * For a subtree that can represent the state of up to 'radix' blocks, the 160 * number of leaf nodes of the subtree is L=radix/BLIST_BMAP_RADIX. If 'm' 161 * is short for BLIST_META_RADIX, then for a tree of height h with L=m**h 162 * leaf nodes, the total number of tree nodes is 1 + m + m**2 + ... + m**h, 163 * or, equivalently, (m**(h+1)-1)/(m-1). This quantity is called 'skip' 164 * in the 'meta' functions that process subtrees. Since integer division 165 * discards remainders, we can express this computation as 166 * skip = (m * m**h) / (m - 1) 167 * skip = (m * (radix / BLIST_BMAP_RADIX)) / (m - 1) 168 * and since m divides BLIST_BMAP_RADIX, we can simplify further to 169 * skip = (radix / (BLIST_BMAP_RADIX / m)) / (m - 1) 170 * skip = radix / ((BLIST_BMAP_RADIX / m) * (m - 1)) 171 * so that simple integer division by a constant can safely be used for the 172 * calculation. 173 */ 174 static inline daddr_t 175 radix_to_skip(daddr_t radix) 176 { 177 178 return (radix / 179 ((BLIST_BMAP_RADIX / BLIST_META_RADIX) * BLIST_META_MASK)); 180 } 181 182 /* 183 * Provide a mask with count bits set, starting as position n. 184 */ 185 static inline u_daddr_t 186 bitrange(int n, int count) 187 { 188 189 return (((u_daddr_t)-1 << n) & 190 ((u_daddr_t)-1 >> (BLIST_BMAP_RADIX - (n + count)))); 191 } 192 193 194 /* 195 * Use binary search, or a faster method, to find the 1 bit in a u_daddr_t. 196 * Assumes that the argument has only one bit set. 197 */ 198 static inline int 199 bitpos(u_daddr_t mask) 200 { 201 int hi, lo, mid; 202 203 switch (sizeof(mask)) { 204 #ifdef HAVE_INLINE_FFSLL 205 case sizeof(long long): 206 return (ffsll(mask) - 1); 207 #endif 208 default: 209 lo = 0; 210 hi = BLIST_BMAP_RADIX; 211 while (lo + 1 < hi) { 212 mid = (lo + hi) >> 1; 213 if ((mask >> mid) != 0) 214 lo = mid; 215 else 216 hi = mid; 217 } 218 return (lo); 219 } 220 } 221 222 /* 223 * blist_create() - create a blist capable of handling up to the specified 224 * number of blocks 225 * 226 * blocks - must be greater than 0 227 * flags - malloc flags 228 * 229 * The smallest blist consists of a single leaf node capable of 230 * managing BLIST_BMAP_RADIX blocks. 231 */ 232 blist_t 233 blist_create(daddr_t blocks, int flags) 234 { 235 blist_t bl; 236 u_daddr_t nodes, radix; 237 238 if (blocks == 0) 239 panic("invalid block count"); 240 241 /* 242 * Calculate the radix and node count used for scanning. 243 */ 244 nodes = 1; 245 radix = BLIST_BMAP_RADIX; 246 while (radix <= blocks) { 247 nodes += 1 + (blocks - 1) / radix; 248 radix *= BLIST_META_RADIX; 249 } 250 251 bl = malloc(offsetof(struct blist, bl_root[nodes]), M_SWAP, flags | 252 M_ZERO); 253 if (bl == NULL) 254 return (NULL); 255 256 bl->bl_blocks = blocks; 257 bl->bl_radix = radix; 258 259 #if defined(BLIST_DEBUG) 260 printf( 261 "BLIST representing %lld blocks (%lld MB of swap)" 262 ", requiring %lldK of ram\n", 263 (long long)bl->bl_blocks, 264 (long long)bl->bl_blocks * 4 / 1024, 265 (long long)(nodes * sizeof(blmeta_t) + 1023) / 1024 266 ); 267 printf("BLIST raw radix tree contains %lld records\n", 268 (long long)nodes); 269 #endif 270 271 return (bl); 272 } 273 274 void 275 blist_destroy(blist_t bl) 276 { 277 278 free(bl, M_SWAP); 279 } 280 281 /* 282 * blist_alloc() - reserve space in the block bitmap. Return the base 283 * of a contiguous region or SWAPBLK_NONE if space could 284 * not be allocated. 285 */ 286 daddr_t 287 blist_alloc(blist_t bl, daddr_t count) 288 { 289 daddr_t blk, cursor; 290 291 if (count > BLIST_MAX_ALLOC) 292 panic("allocation too large"); 293 294 /* 295 * This loop iterates at most twice. An allocation failure in the 296 * first iteration leads to a second iteration only if the cursor was 297 * non-zero. When the cursor is zero, an allocation failure will 298 * stop further iterations. 299 */ 300 cursor = bl->bl_cursor; 301 for (;;) { 302 blk = blst_meta_alloc(bl->bl_root, cursor, count, 303 bl->bl_radix); 304 if (blk != SWAPBLK_NONE) { 305 bl->bl_avail -= count; 306 bl->bl_cursor = blk + count; 307 if (bl->bl_cursor == bl->bl_blocks) 308 bl->bl_cursor = 0; 309 return (blk); 310 } else if (cursor == 0) 311 return (SWAPBLK_NONE); 312 cursor = 0; 313 } 314 } 315 316 /* 317 * blist_avail() - return the number of free blocks. 318 */ 319 daddr_t 320 blist_avail(blist_t bl) 321 { 322 323 return (bl->bl_avail); 324 } 325 326 /* 327 * blist_free() - free up space in the block bitmap. Return the base 328 * of a contiguous region. Panic if an inconsistancy is 329 * found. 330 */ 331 void 332 blist_free(blist_t bl, daddr_t blkno, daddr_t count) 333 { 334 335 if (blkno < 0 || blkno + count > bl->bl_blocks) 336 panic("freeing invalid range"); 337 blst_meta_free(bl->bl_root, blkno, count, bl->bl_radix); 338 bl->bl_avail += count; 339 } 340 341 /* 342 * blist_fill() - mark a region in the block bitmap as off-limits 343 * to the allocator (i.e. allocate it), ignoring any 344 * existing allocations. Return the number of blocks 345 * actually filled that were free before the call. 346 */ 347 daddr_t 348 blist_fill(blist_t bl, daddr_t blkno, daddr_t count) 349 { 350 daddr_t filled; 351 352 if (blkno < 0 || blkno + count > bl->bl_blocks) 353 panic("filling invalid range"); 354 filled = blst_meta_fill(bl->bl_root, blkno, count, bl->bl_radix); 355 bl->bl_avail -= filled; 356 return (filled); 357 } 358 359 /* 360 * blist_resize() - resize an existing radix tree to handle the 361 * specified number of blocks. This will reallocate 362 * the tree and transfer the previous bitmap to the new 363 * one. When extending the tree you can specify whether 364 * the new blocks are to left allocated or freed. 365 */ 366 void 367 blist_resize(blist_t *pbl, daddr_t count, int freenew, int flags) 368 { 369 blist_t newbl = blist_create(count, flags); 370 blist_t save = *pbl; 371 372 *pbl = newbl; 373 if (count > save->bl_blocks) 374 count = save->bl_blocks; 375 blst_copy(save->bl_root, 0, save->bl_radix, newbl, count); 376 377 /* 378 * If resizing upwards, should we free the new space or not? 379 */ 380 if (freenew && count < newbl->bl_blocks) { 381 blist_free(newbl, count, newbl->bl_blocks - count); 382 } 383 blist_destroy(save); 384 } 385 386 #ifdef BLIST_DEBUG 387 388 /* 389 * blist_print() - dump radix tree 390 */ 391 void 392 blist_print(blist_t bl) 393 { 394 printf("BLIST avail = %jd, cursor = %08jx {\n", 395 (uintmax_t)bl->bl_avail, (uintmax_t)bl->bl_cursor); 396 397 if (bl->bl_root->bm_bitmap != 0) 398 blst_radix_print(bl->bl_root, 0, bl->bl_radix, 4); 399 printf("}\n"); 400 } 401 402 #endif 403 404 static const u_daddr_t fib[] = { 405 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 406 4181, 6765, 10946, 17711, 28657, 46368, 75025, 121393, 196418, 317811, 407 514229, 832040, 1346269, 2178309, 3524578, 408 }; 409 410 /* 411 * Use 'gap' to describe a maximal range of unallocated blocks/bits. 412 */ 413 struct gap_stats { 414 daddr_t start; /* current gap start, or SWAPBLK_NONE */ 415 daddr_t num; /* number of gaps observed */ 416 daddr_t max; /* largest gap size */ 417 daddr_t avg; /* average gap size */ 418 daddr_t err; /* sum - num * avg */ 419 daddr_t histo[nitems(fib)]; /* # gaps in each size range */ 420 int max_bucket; /* last histo elt with nonzero val */ 421 }; 422 423 /* 424 * gap_stats_counting() - is the state 'counting 1 bits'? 425 * or 'skipping 0 bits'? 426 */ 427 static inline bool 428 gap_stats_counting(const struct gap_stats *stats) 429 { 430 431 return (stats->start != SWAPBLK_NONE); 432 } 433 434 /* 435 * init_gap_stats() - initialize stats on gap sizes 436 */ 437 static inline void 438 init_gap_stats(struct gap_stats *stats) 439 { 440 441 bzero(stats, sizeof(*stats)); 442 stats->start = SWAPBLK_NONE; 443 } 444 445 /* 446 * update_gap_stats() - update stats on gap sizes 447 */ 448 static void 449 update_gap_stats(struct gap_stats *stats, daddr_t posn) 450 { 451 daddr_t size; 452 int hi, lo, mid; 453 454 if (!gap_stats_counting(stats)) { 455 stats->start = posn; 456 return; 457 } 458 size = posn - stats->start; 459 stats->start = SWAPBLK_NONE; 460 if (size > stats->max) 461 stats->max = size; 462 463 /* 464 * Find the fibonacci range that contains size, 465 * expecting to find it in an early range. 466 */ 467 lo = 0; 468 hi = 1; 469 while (hi < nitems(fib) && fib[hi] <= size) { 470 lo = hi; 471 hi *= 2; 472 } 473 if (hi >= nitems(fib)) 474 hi = nitems(fib); 475 while (lo + 1 != hi) { 476 mid = (lo + hi) >> 1; 477 if (fib[mid] <= size) 478 lo = mid; 479 else 480 hi = mid; 481 } 482 stats->histo[lo]++; 483 if (lo > stats->max_bucket) 484 stats->max_bucket = lo; 485 stats->err += size - stats->avg; 486 stats->num++; 487 stats->avg += stats->err / stats->num; 488 stats->err %= stats->num; 489 } 490 491 /* 492 * dump_gap_stats() - print stats on gap sizes 493 */ 494 static inline void 495 dump_gap_stats(const struct gap_stats *stats, struct sbuf *s) 496 { 497 int i; 498 499 sbuf_printf(s, "number of maximal free ranges: %jd\n", 500 (intmax_t)stats->num); 501 sbuf_printf(s, "largest free range: %jd\n", (intmax_t)stats->max); 502 sbuf_printf(s, "average maximal free range size: %jd\n", 503 (intmax_t)stats->avg); 504 sbuf_printf(s, "number of maximal free ranges of different sizes:\n"); 505 sbuf_printf(s, " count | size range\n"); 506 sbuf_printf(s, " ----- | ----------\n"); 507 for (i = 0; i < stats->max_bucket; i++) { 508 if (stats->histo[i] != 0) { 509 sbuf_printf(s, "%20jd | ", 510 (intmax_t)stats->histo[i]); 511 if (fib[i] != fib[i + 1] - 1) 512 sbuf_printf(s, "%jd to %jd\n", (intmax_t)fib[i], 513 (intmax_t)fib[i + 1] - 1); 514 else 515 sbuf_printf(s, "%jd\n", (intmax_t)fib[i]); 516 } 517 } 518 sbuf_printf(s, "%20jd | ", (intmax_t)stats->histo[i]); 519 if (stats->histo[i] > 1) 520 sbuf_printf(s, "%jd to %jd\n", (intmax_t)fib[i], 521 (intmax_t)stats->max); 522 else 523 sbuf_printf(s, "%jd\n", (intmax_t)stats->max); 524 } 525 526 /* 527 * blist_stats() - dump radix tree stats 528 */ 529 void 530 blist_stats(blist_t bl, struct sbuf *s) 531 { 532 struct gap_stats gstats; 533 struct gap_stats *stats = &gstats; 534 daddr_t i, nodes, radix; 535 u_daddr_t bit, diff, mask; 536 537 init_gap_stats(stats); 538 nodes = 0; 539 i = bl->bl_radix; 540 while (i < bl->bl_radix + bl->bl_blocks) { 541 /* 542 * Find max size subtree starting at i. 543 */ 544 radix = BLIST_BMAP_RADIX; 545 while (((i / radix) & BLIST_META_MASK) == 0) 546 radix *= BLIST_META_RADIX; 547 548 /* 549 * Check for skippable subtrees starting at i. 550 */ 551 while (radix > BLIST_BMAP_RADIX) { 552 if (bl->bl_root[nodes].bm_bitmap == 0) { 553 if (gap_stats_counting(stats)) 554 update_gap_stats(stats, i); 555 break; 556 } 557 558 /* 559 * Skip subtree root. 560 */ 561 nodes++; 562 radix /= BLIST_META_RADIX; 563 } 564 if (radix == BLIST_BMAP_RADIX) { 565 /* 566 * Scan leaf. 567 */ 568 mask = bl->bl_root[nodes].bm_bitmap; 569 diff = mask ^ (mask << 1); 570 if (gap_stats_counting(stats)) 571 diff ^= 1; 572 while (diff != 0) { 573 bit = diff & -diff; 574 update_gap_stats(stats, i + bitpos(bit)); 575 diff ^= bit; 576 } 577 } 578 nodes += radix_to_skip(radix); 579 i += radix; 580 } 581 update_gap_stats(stats, i); 582 dump_gap_stats(stats, s); 583 } 584 585 /************************************************************************ 586 * ALLOCATION SUPPORT FUNCTIONS * 587 ************************************************************************ 588 * 589 * These support functions do all the actual work. They may seem 590 * rather longish, but that's because I've commented them up. The 591 * actual code is straight forward. 592 * 593 */ 594 595 /* 596 * BLST_NEXT_LEAF_ALLOC() - allocate the first few blocks in the next leaf. 597 * 598 * 'scan' is a leaf node, associated with a block containing 'blk'. 599 * The next leaf node could be adjacent, or several nodes away if the 600 * least common ancestor of 'scan' and its neighbor is several levels 601 * up. Use 'blk' to determine how many meta-nodes lie between the 602 * leaves. If the next leaf has enough initial bits set, clear them 603 * and clear the bits in the meta nodes on the path up to the least 604 * common ancestor to mark any subtrees made completely empty. 605 */ 606 static int 607 blst_next_leaf_alloc(blmeta_t *scan, daddr_t blk, int count) 608 { 609 blmeta_t *next; 610 daddr_t skip; 611 u_daddr_t radix; 612 int digit; 613 614 next = scan + 1; 615 blk += BLIST_BMAP_RADIX; 616 radix = BLIST_BMAP_RADIX; 617 while ((digit = ((blk / radix) & BLIST_META_MASK)) == 0 && 618 (next->bm_bitmap & 1) == 1) { 619 next++; 620 radix *= BLIST_META_RADIX; 621 } 622 if (((next->bm_bitmap + 1) & ~((u_daddr_t)-1 << count)) != 0) { 623 /* 624 * The next leaf doesn't have enough free blocks at the 625 * beginning to complete the spanning allocation. 626 */ 627 return (ENOMEM); 628 } 629 /* Clear the first 'count' bits in the next leaf to allocate. */ 630 next->bm_bitmap &= (u_daddr_t)-1 << count; 631 632 /* 633 * Update bitmaps of next-ancestors, up to least common ancestor. 634 */ 635 skip = radix_to_skip(radix); 636 while (radix != BLIST_BMAP_RADIX && next->bm_bitmap == 0) { 637 (--next)->bm_bitmap ^= 1; 638 radix /= BLIST_META_RADIX; 639 } 640 if (next->bm_bitmap == 0) 641 scan[-digit * skip].bm_bitmap ^= (u_daddr_t)1 << digit; 642 return (0); 643 } 644 645 /* 646 * BLST_LEAF_ALLOC() - allocate at a leaf in the radix tree (a bitmap). 647 * 648 * This function is the core of the allocator. Its execution time is 649 * proportional to log(count), plus height of the tree if the allocation 650 * crosses a leaf boundary. 651 */ 652 static daddr_t 653 blst_leaf_alloc(blmeta_t *scan, daddr_t blk, int count) 654 { 655 u_daddr_t cursor_mask, mask; 656 int count1, hi, lo, num_shifts, range1, range_ext; 657 658 range1 = 0; 659 count1 = count - 1; 660 num_shifts = fls(count1); 661 mask = scan->bm_bitmap; 662 while ((-mask & ~mask) != 0 && num_shifts > 0) { 663 /* 664 * If bit i is set in mask, then bits in [i, i+range1] are set 665 * in scan->bm_bitmap. The value of range1 is equal to count1 666 * >> num_shifts. Grow range1 and reduce num_shifts to 0, 667 * while preserving these invariants. The updates to mask 668 * leave fewer bits set, but each bit that remains set 669 * represents a longer string of consecutive bits set in 670 * scan->bm_bitmap. If more updates to mask cannot clear more 671 * bits, because mask is partitioned with all 0 bits preceding 672 * all 1 bits, the loop terminates immediately. 673 */ 674 num_shifts--; 675 range_ext = range1 + ((count1 >> num_shifts) & 1); 676 /* 677 * mask is a signed quantity for the shift because when it is 678 * shifted right, the sign bit should copied; when the last 679 * block of the leaf is free, pretend, for a while, that all the 680 * blocks that follow it are also free. 681 */ 682 mask &= (daddr_t)mask >> range_ext; 683 range1 += range_ext; 684 } 685 if (mask == 0) { 686 /* 687 * Update bighint. There is no allocation bigger than range1 688 * starting in this leaf. 689 */ 690 scan->bm_bighint = range1; 691 return (SWAPBLK_NONE); 692 } 693 694 /* Discard any candidates that appear before blk. */ 695 if ((blk & BLIST_BMAP_MASK) != 0) { 696 cursor_mask = mask & bitrange(0, blk & BLIST_BMAP_MASK); 697 if (cursor_mask != 0) { 698 mask ^= cursor_mask; 699 if (mask == 0) 700 return (SWAPBLK_NONE); 701 702 /* 703 * Bighint change for last block allocation cannot 704 * assume that any other blocks are allocated, so the 705 * bighint cannot be reduced much. 706 */ 707 range1 = BLIST_MAX_ALLOC - 1; 708 } 709 blk &= ~BLIST_BMAP_MASK; 710 } 711 712 /* 713 * The least significant set bit in mask marks the start of the first 714 * available range of sufficient size. Clear all the bits but that one, 715 * and then find its position. 716 */ 717 mask &= -mask; 718 lo = bitpos(mask); 719 720 hi = lo + count; 721 if (hi > BLIST_BMAP_RADIX) { 722 /* 723 * An allocation within this leaf is impossible, so a successful 724 * allocation depends on the next leaf providing some of the blocks. 725 */ 726 if (blst_next_leaf_alloc(scan, blk, hi - BLIST_BMAP_RADIX) != 0) 727 /* 728 * The hint cannot be updated, because the same 729 * allocation request could be satisfied later, by this 730 * leaf, if the state of the next leaf changes, and 731 * without any changes to this leaf. 732 */ 733 return (SWAPBLK_NONE); 734 hi = BLIST_BMAP_RADIX; 735 } 736 737 /* Set the bits of mask at position 'lo' and higher. */ 738 mask = -mask; 739 if (hi == BLIST_BMAP_RADIX) { 740 /* 741 * Update bighint. There is no allocation bigger than range1 742 * available in this leaf after this allocation completes. 743 */ 744 scan->bm_bighint = range1; 745 } else { 746 /* Clear the bits of mask at position 'hi' and higher. */ 747 mask &= (u_daddr_t)-1 >> (BLIST_BMAP_RADIX - hi); 748 } 749 /* Clear the allocated bits from this leaf. */ 750 scan->bm_bitmap &= ~mask; 751 return (blk + lo); 752 } 753 754 /* 755 * blist_meta_alloc() - allocate at a meta in the radix tree. 756 * 757 * Attempt to allocate at a meta node. If we can't, we update 758 * bighint and return a failure. Updating bighint optimize future 759 * calls that hit this node. We have to check for our collapse cases 760 * and we have a few optimizations strewn in as well. 761 */ 762 static daddr_t 763 blst_meta_alloc(blmeta_t *scan, daddr_t cursor, daddr_t count, u_daddr_t radix) 764 { 765 daddr_t blk, i, r, skip; 766 u_daddr_t bit, mask; 767 bool scan_from_start; 768 int digit; 769 770 if (radix == BLIST_BMAP_RADIX) 771 return (blst_leaf_alloc(scan, cursor, count)); 772 blk = cursor & -radix; 773 scan_from_start = (cursor == blk); 774 radix /= BLIST_META_RADIX; 775 skip = radix_to_skip(radix); 776 mask = scan->bm_bitmap; 777 778 /* Discard any candidates that appear before cursor. */ 779 digit = (cursor / radix) & BLIST_META_MASK; 780 mask &= (u_daddr_t)-1 << digit; 781 if (mask == 0) 782 return (SWAPBLK_NONE); 783 784 /* 785 * If the first try is for a block that includes the cursor, pre-undo 786 * the digit * radix offset in the first call; otherwise, ignore the 787 * cursor entirely. 788 */ 789 if (((mask >> digit) & 1) == 1) 790 cursor -= digit * radix; 791 else 792 cursor = blk; 793 794 /* 795 * Examine the nonempty subtree associated with each bit set in mask. 796 */ 797 do { 798 bit = mask & -mask; 799 digit = bitpos(bit); 800 i = 1 + digit * skip; 801 if (count <= scan[i].bm_bighint) { 802 /* 803 * The allocation might fit beginning in the i'th subtree. 804 */ 805 r = blst_meta_alloc(&scan[i], cursor + digit * radix, 806 count, radix); 807 if (r != SWAPBLK_NONE) { 808 if (scan[i].bm_bitmap == 0) 809 scan->bm_bitmap ^= bit; 810 return (r); 811 } 812 } 813 cursor = blk; 814 } while ((mask ^= bit) != 0); 815 816 /* 817 * We couldn't allocate count in this subtree. If the whole tree was 818 * scanned, and the last tree node is allocated, update bighint. 819 */ 820 if (scan_from_start && !(digit == BLIST_META_RADIX - 1 && 821 scan[i].bm_bighint == BLIST_MAX_ALLOC)) 822 scan->bm_bighint = count - 1; 823 824 return (SWAPBLK_NONE); 825 } 826 827 /* 828 * BLST_LEAF_FREE() - free allocated block from leaf bitmap 829 * 830 */ 831 static void 832 blst_leaf_free(blmeta_t *scan, daddr_t blk, int count) 833 { 834 u_daddr_t mask; 835 836 /* 837 * free some data in this bitmap 838 * mask=0000111111111110000 839 * \_________/\__/ 840 * count n 841 */ 842 mask = bitrange(blk & BLIST_BMAP_MASK, count); 843 if (scan->bm_bitmap & mask) 844 panic("freeing free block"); 845 scan->bm_bitmap |= mask; 846 } 847 848 /* 849 * BLST_META_FREE() - free allocated blocks from radix tree meta info 850 * 851 * This support routine frees a range of blocks from the bitmap. 852 * The range must be entirely enclosed by this radix node. If a 853 * meta node, we break the range down recursively to free blocks 854 * in subnodes (which means that this code can free an arbitrary 855 * range whereas the allocation code cannot allocate an arbitrary 856 * range). 857 */ 858 static void 859 blst_meta_free(blmeta_t *scan, daddr_t freeBlk, daddr_t count, u_daddr_t radix) 860 { 861 daddr_t blk, endBlk, i, skip; 862 int digit, endDigit; 863 864 /* 865 * We could probably do a better job here. We are required to make 866 * bighint at least as large as the biggest allocable block of data. 867 * If we just shoehorn it, a little extra overhead will be incurred 868 * on the next allocation (but only that one typically). 869 */ 870 scan->bm_bighint = BLIST_MAX_ALLOC; 871 872 if (radix == BLIST_BMAP_RADIX) 873 return (blst_leaf_free(scan, freeBlk, count)); 874 875 endBlk = ummin(freeBlk + count, (freeBlk + radix) & -radix); 876 radix /= BLIST_META_RADIX; 877 skip = radix_to_skip(radix); 878 blk = freeBlk & -radix; 879 digit = (blk / radix) & BLIST_META_MASK; 880 endDigit = 1 + (((endBlk - 1) / radix) & BLIST_META_MASK); 881 scan->bm_bitmap |= bitrange(digit, endDigit - digit); 882 for (i = 1 + digit * skip; blk < endBlk; i += skip) { 883 blk += radix; 884 count = ummin(blk, endBlk) - freeBlk; 885 blst_meta_free(&scan[i], freeBlk, count, radix); 886 freeBlk = blk; 887 } 888 } 889 890 /* 891 * BLST_COPY() - copy one radix tree to another 892 * 893 * Locates free space in the source tree and frees it in the destination 894 * tree. The space may not already be free in the destination. 895 */ 896 static void 897 blst_copy(blmeta_t *scan, daddr_t blk, daddr_t radix, blist_t dest, 898 daddr_t count) 899 { 900 daddr_t endBlk, i, skip; 901 902 /* 903 * Leaf node 904 */ 905 906 if (radix == BLIST_BMAP_RADIX) { 907 u_daddr_t v = scan->bm_bitmap; 908 909 if (v == (u_daddr_t)-1) { 910 blist_free(dest, blk, count); 911 } else if (v != 0) { 912 int i; 913 914 for (i = 0; i < count; ++i) { 915 if (v & ((u_daddr_t)1 << i)) 916 blist_free(dest, blk + i, 1); 917 } 918 } 919 return; 920 } 921 922 /* 923 * Meta node 924 */ 925 926 if (scan->bm_bitmap == 0) { 927 /* 928 * Source all allocated, leave dest allocated 929 */ 930 return; 931 } 932 933 endBlk = blk + count; 934 radix /= BLIST_META_RADIX; 935 skip = radix_to_skip(radix); 936 for (i = 1; blk < endBlk; i += skip) { 937 blk += radix; 938 count = radix; 939 if (blk >= endBlk) 940 count -= blk - endBlk; 941 blst_copy(&scan[i], blk - radix, radix, dest, count); 942 } 943 } 944 945 /* 946 * BLST_LEAF_FILL() - allocate specific blocks in leaf bitmap 947 * 948 * This routine allocates all blocks in the specified range 949 * regardless of any existing allocations in that range. Returns 950 * the number of blocks allocated by the call. 951 */ 952 static daddr_t 953 blst_leaf_fill(blmeta_t *scan, daddr_t blk, int count) 954 { 955 daddr_t nblks; 956 u_daddr_t mask; 957 958 mask = bitrange(blk & BLIST_BMAP_MASK, count); 959 960 /* Count the number of blocks that we are allocating. */ 961 nblks = bitcount64(scan->bm_bitmap & mask); 962 963 scan->bm_bitmap &= ~mask; 964 return (nblks); 965 } 966 967 /* 968 * BLIST_META_FILL() - allocate specific blocks at a meta node 969 * 970 * This routine allocates the specified range of blocks, 971 * regardless of any existing allocations in the range. The 972 * range must be within the extent of this node. Returns the 973 * number of blocks allocated by the call. 974 */ 975 static daddr_t 976 blst_meta_fill(blmeta_t *scan, daddr_t allocBlk, daddr_t count, u_daddr_t radix) 977 { 978 daddr_t blk, endBlk, i, nblks, skip; 979 int digit; 980 981 if (radix == BLIST_BMAP_RADIX) 982 return (blst_leaf_fill(scan, allocBlk, count)); 983 984 endBlk = ummin(allocBlk + count, (allocBlk + radix) & -radix); 985 radix /= BLIST_META_RADIX; 986 skip = radix_to_skip(radix); 987 blk = allocBlk & -radix; 988 nblks = 0; 989 while (blk < endBlk) { 990 digit = (blk / radix) & BLIST_META_MASK; 991 i = 1 + digit * skip; 992 blk += radix; 993 count = ummin(blk, endBlk) - allocBlk; 994 nblks += blst_meta_fill(&scan[i], allocBlk, count, radix); 995 if (scan[i].bm_bitmap == 0) 996 scan->bm_bitmap &= ~((u_daddr_t)1 << digit); 997 allocBlk = blk; 998 } 999 return (nblks); 1000 } 1001 1002 #ifdef BLIST_DEBUG 1003 1004 static void 1005 blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t radix, int tab) 1006 { 1007 daddr_t skip; 1008 u_daddr_t bit, mask; 1009 int digit; 1010 1011 if (radix == BLIST_BMAP_RADIX) { 1012 printf( 1013 "%*.*s(%08llx,%lld): bitmap %0*llx big=%lld\n", 1014 tab, tab, "", 1015 (long long)blk, (long long)radix, 1016 1 + (BLIST_BMAP_RADIX - 1) / 4, 1017 (long long)scan->bm_bitmap, 1018 (long long)scan->bm_bighint 1019 ); 1020 return; 1021 } 1022 1023 printf( 1024 "%*.*s(%08llx): subtree (%lld/%lld) bitmap %0*llx big=%lld {\n", 1025 tab, tab, "", 1026 (long long)blk, (long long)radix, 1027 (long long)radix, 1028 1 + (BLIST_META_RADIX - 1) / 4, 1029 (long long)scan->bm_bitmap, 1030 (long long)scan->bm_bighint 1031 ); 1032 1033 radix /= BLIST_META_RADIX; 1034 skip = radix_to_skip(radix); 1035 tab += 4; 1036 1037 mask = scan->bm_bitmap; 1038 /* Examine the nonempty subtree associated with each bit set in mask */ 1039 do { 1040 bit = mask & -mask; 1041 digit = bitpos(bit); 1042 blst_radix_print(&scan[1 + digit * skip], blk + digit * radix, 1043 radix, tab); 1044 } while ((mask ^= bit) != 0); 1045 tab -= 4; 1046 1047 printf( 1048 "%*.*s}\n", 1049 tab, tab, "" 1050 ); 1051 } 1052 1053 #endif 1054 1055 #ifdef BLIST_DEBUG 1056 1057 int 1058 main(int ac, char **av) 1059 { 1060 int size = BLIST_META_RADIX * BLIST_BMAP_RADIX; 1061 int i; 1062 blist_t bl; 1063 struct sbuf *s; 1064 1065 for (i = 1; i < ac; ++i) { 1066 const char *ptr = av[i]; 1067 if (*ptr != '-') { 1068 size = strtol(ptr, NULL, 0); 1069 continue; 1070 } 1071 ptr += 2; 1072 fprintf(stderr, "Bad option: %s\n", ptr - 2); 1073 exit(1); 1074 } 1075 bl = blist_create(size, M_WAITOK); 1076 blist_free(bl, 0, size); 1077 1078 for (;;) { 1079 char buf[1024]; 1080 long long da = 0; 1081 long long count = 0; 1082 1083 printf("%lld/%lld/%lld> ", (long long)blist_avail(bl), 1084 (long long)size, (long long)bl->bl_radix); 1085 fflush(stdout); 1086 if (fgets(buf, sizeof(buf), stdin) == NULL) 1087 break; 1088 switch(buf[0]) { 1089 case 'r': 1090 if (sscanf(buf + 1, "%lld", &count) == 1) { 1091 blist_resize(&bl, count, 1, M_WAITOK); 1092 } else { 1093 printf("?\n"); 1094 } 1095 case 'p': 1096 blist_print(bl); 1097 break; 1098 case 's': 1099 s = sbuf_new_auto(); 1100 blist_stats(bl, s); 1101 sbuf_finish(s); 1102 printf("%s", sbuf_data(s)); 1103 sbuf_delete(s); 1104 break; 1105 case 'a': 1106 if (sscanf(buf + 1, "%lld", &count) == 1) { 1107 daddr_t blk = blist_alloc(bl, count); 1108 printf(" R=%08llx\n", (long long)blk); 1109 } else { 1110 printf("?\n"); 1111 } 1112 break; 1113 case 'f': 1114 if (sscanf(buf + 1, "%llx %lld", &da, &count) == 2) { 1115 blist_free(bl, da, count); 1116 } else { 1117 printf("?\n"); 1118 } 1119 break; 1120 case 'l': 1121 if (sscanf(buf + 1, "%llx %lld", &da, &count) == 2) { 1122 printf(" n=%jd\n", 1123 (intmax_t)blist_fill(bl, da, count)); 1124 } else { 1125 printf("?\n"); 1126 } 1127 break; 1128 case '?': 1129 case 'h': 1130 puts( 1131 "p -print\n" 1132 "s -stats\n" 1133 "a %d -allocate\n" 1134 "f %x %d -free\n" 1135 "l %x %d -fill\n" 1136 "r %d -resize\n" 1137 "h/? -help" 1138 ); 1139 break; 1140 default: 1141 printf("?\n"); 1142 break; 1143 } 1144 } 1145 return(0); 1146 } 1147 1148 void 1149 panic(const char *ctl, ...) 1150 { 1151 va_list va; 1152 1153 va_start(va, ctl); 1154 vfprintf(stderr, ctl, va); 1155 fprintf(stderr, "\n"); 1156 va_end(va); 1157 exit(1); 1158 } 1159 1160 #endif 1161