2 * SPDX-License-Identifier: BSD-3-Clause
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
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.
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.
30 * BLIST.C - Bitmap allocator/deallocator, using a radix tree with hinting
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.
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
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.
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.
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).
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
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
84 * This code can be compiled stand-alone for debugging.
87 #include <sys/cdefs.h>
88 __FBSDID("$FreeBSD$");
92 #include <sys/param.h>
93 #include <sys/systm.h>
95 #include <sys/kernel.h>
96 #include <sys/blist.h>
97 #include <sys/malloc.h>
100 #include <sys/mutex.h>
104 #ifndef BLIST_NO_DEBUG
108 #include <sys/errno.h>
109 #include <sys/types.h>
110 #include <sys/malloc.h>
111 #include <sys/sbuf.h>
120 #define bitcount64(x) __bitcount64((uint64_t)(x))
121 #define malloc(a,b,c) calloc(a, 1)
122 #define free(a,b) free(a)
123 #define ummin(a,b) ((a) < (b) ? (a) : (b))
124 #define KASSERT(a,b) assert(a)
126 #include <sys/blist.h>
131 * static support functions
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,
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,
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,
145 static void blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t radix,
150 static MALLOC_DEFINE(M_SWAP, "SWAP", "Swap space");
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)
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
174 static inline daddr_t
175 radix_to_skip(daddr_t radix)
179 ((BLIST_BMAP_RADIX / BLIST_META_RADIX) * BLIST_META_MASK));
183 * Provide a mask with count bits set, starting as position n.
185 static inline u_daddr_t
186 bitrange(int n, int count)
189 return (((u_daddr_t)-1 << n) &
190 ((u_daddr_t)-1 >> (BLIST_BMAP_RADIX - (n + count))));
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.
199 bitpos(u_daddr_t mask)
203 switch (sizeof(mask)) {
204 #ifdef HAVE_INLINE_FFSLL
205 case sizeof(long long):
206 return (ffsll(mask) - 1);
210 hi = BLIST_BMAP_RADIX;
211 while (lo + 1 < hi) {
212 mid = (lo + hi) >> 1;
213 if ((mask >> mid) != 0)
223 * blist_create() - create a blist capable of handling up to the specified
226 * blocks - must be greater than 0
227 * flags - malloc flags
229 * The smallest blist consists of a single leaf node capable of
230 * managing BLIST_BMAP_RADIX blocks.
233 blist_create(daddr_t blocks, int flags)
236 u_daddr_t nodes, radix;
238 KASSERT(blocks > 0, ("invalid block count"));
241 * Calculate the radix and node count used for scanning.
244 radix = BLIST_BMAP_RADIX;
245 while (radix <= blocks) {
246 nodes += 1 + (blocks - 1) / radix;
247 radix *= BLIST_META_RADIX;
250 bl = malloc(offsetof(struct blist, bl_root[nodes]), M_SWAP, flags |
255 bl->bl_blocks = blocks;
256 bl->bl_radix = radix;
258 #if defined(BLIST_DEBUG)
260 "BLIST representing %lld blocks (%lld MB of swap)"
261 ", requiring %lldK of ram\n",
262 (long long)bl->bl_blocks,
263 (long long)bl->bl_blocks * 4 / 1024,
264 (long long)(nodes * sizeof(blmeta_t) + 1023) / 1024
266 printf("BLIST raw radix tree contains %lld records\n",
274 blist_destroy(blist_t bl)
281 * blist_alloc() - reserve space in the block bitmap. Return the base
282 * of a contiguous region or SWAPBLK_NONE if space could
286 blist_alloc(blist_t bl, daddr_t count)
290 KASSERT(count <= BLIST_MAX_ALLOC,
291 ("allocation too large: %d", (int)count));
294 * This loop iterates at most twice. An allocation failure in the
295 * first iteration leads to a second iteration only if the cursor was
296 * non-zero. When the cursor is zero, an allocation failure will
297 * stop further iterations.
299 cursor = bl->bl_cursor;
301 blk = blst_meta_alloc(bl->bl_root, cursor, count,
303 if (blk != SWAPBLK_NONE) {
304 bl->bl_avail -= count;
305 bl->bl_cursor = blk + count;
306 if (bl->bl_cursor == bl->bl_blocks)
309 } else if (cursor == 0)
310 return (SWAPBLK_NONE);
316 * blist_avail() - return the number of free blocks.
319 blist_avail(blist_t bl)
322 return (bl->bl_avail);
326 * blist_free() - free up space in the block bitmap. Return the base
327 * of a contiguous region.
330 blist_free(blist_t bl, daddr_t blkno, daddr_t count)
333 KASSERT(blkno >= 0 && blkno + count <= bl->bl_blocks,
334 ("freeing invalid range: blkno %jx, count %d, blocks %jd",
335 (uintmax_t)blkno, (int)count, (uintmax_t)bl->bl_blocks));
336 blst_meta_free(bl->bl_root, blkno, count, bl->bl_radix);
337 bl->bl_avail += count;
341 * blist_fill() - mark a region in the block bitmap as off-limits
342 * to the allocator (i.e. allocate it), ignoring any
343 * existing allocations. Return the number of blocks
344 * actually filled that were free before the call.
347 blist_fill(blist_t bl, daddr_t blkno, daddr_t count)
351 KASSERT(blkno >= 0 && blkno + count <= bl->bl_blocks,
352 ("filling invalid range: blkno %jx, count %d, blocks %jd",
353 (uintmax_t)blkno, (int)count, (uintmax_t)bl->bl_blocks));
354 filled = blst_meta_fill(bl->bl_root, blkno, count, bl->bl_radix);
355 bl->bl_avail -= filled;
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.
367 blist_resize(blist_t *pbl, daddr_t count, int freenew, int flags)
369 blist_t newbl = blist_create(count, flags);
373 if (count > save->bl_blocks)
374 count = save->bl_blocks;
375 blst_copy(save->bl_root, 0, save->bl_radix, newbl, count);
378 * If resizing upwards, should we free the new space or not?
380 if (freenew && count < newbl->bl_blocks) {
381 blist_free(newbl, count, newbl->bl_blocks - count);
389 * blist_print() - dump radix tree
392 blist_print(blist_t bl)
394 printf("BLIST avail = %jd, cursor = %08jx {\n",
395 (uintmax_t)bl->bl_avail, (uintmax_t)bl->bl_cursor);
397 if (bl->bl_root->bm_bitmap != 0)
398 blst_radix_print(bl->bl_root, 0, bl->bl_radix, 4);
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,
411 * Use 'gap' to describe a maximal range of unallocated blocks/bits.
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 */
424 * gap_stats_counting() - is the state 'counting 1 bits'?
425 * or 'skipping 0 bits'?
428 gap_stats_counting(const struct gap_stats *stats)
431 return (stats->start != SWAPBLK_NONE);
435 * init_gap_stats() - initialize stats on gap sizes
438 init_gap_stats(struct gap_stats *stats)
441 bzero(stats, sizeof(*stats));
442 stats->start = SWAPBLK_NONE;
446 * update_gap_stats() - update stats on gap sizes
449 update_gap_stats(struct gap_stats *stats, daddr_t posn)
454 if (!gap_stats_counting(stats)) {
458 size = posn - stats->start;
459 stats->start = SWAPBLK_NONE;
460 if (size > stats->max)
464 * Find the fibonacci range that contains size,
465 * expecting to find it in an early range.
469 while (hi < nitems(fib) && fib[hi] <= size) {
473 if (hi >= nitems(fib))
475 while (lo + 1 != hi) {
476 mid = (lo + hi) >> 1;
477 if (fib[mid] <= size)
483 if (lo > stats->max_bucket)
484 stats->max_bucket = lo;
485 stats->err += size - stats->avg;
487 stats->avg += stats->err / stats->num;
488 stats->err %= stats->num;
492 * dump_gap_stats() - print stats on gap sizes
495 dump_gap_stats(const struct gap_stats *stats, struct sbuf *s)
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);
515 sbuf_printf(s, "%jd\n", (intmax_t)fib[i]);
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);
523 sbuf_printf(s, "%jd\n", (intmax_t)stats->max);
527 * blist_stats() - dump radix tree stats
530 blist_stats(blist_t bl, struct sbuf *s)
532 struct gap_stats gstats;
533 struct gap_stats *stats = &gstats;
534 daddr_t i, nodes, radix;
535 u_daddr_t bit, diff, mask;
537 init_gap_stats(stats);
540 while (i < bl->bl_radix + bl->bl_blocks) {
542 * Find max size subtree starting at i.
544 radix = BLIST_BMAP_RADIX;
545 while (((i / radix) & BLIST_META_MASK) == 0)
546 radix *= BLIST_META_RADIX;
549 * Check for skippable subtrees starting at i.
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);
562 radix /= BLIST_META_RADIX;
564 if (radix == BLIST_BMAP_RADIX) {
568 mask = bl->bl_root[nodes].bm_bitmap;
569 diff = mask ^ (mask << 1);
570 if (gap_stats_counting(stats))
574 update_gap_stats(stats, i + bitpos(bit));
578 nodes += radix_to_skip(radix);
581 update_gap_stats(stats, i);
582 dump_gap_stats(stats, s);
585 /************************************************************************
586 * ALLOCATION SUPPORT FUNCTIONS *
587 ************************************************************************
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.
596 * BLST_NEXT_LEAF_ALLOC() - allocate the first few blocks in the next leaf.
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.
607 blst_next_leaf_alloc(blmeta_t *scan, daddr_t blk, int count)
614 blk += BLIST_BMAP_RADIX;
615 radix = BLIST_BMAP_RADIX;
616 while ((digit = ((blk / radix) & BLIST_META_MASK)) == 0 &&
617 (next->bm_bitmap & 1) == 1) {
619 radix *= BLIST_META_RADIX;
621 if (((next->bm_bitmap + 1) & ~((u_daddr_t)-1 << count)) != 0) {
623 * The next leaf doesn't have enough free blocks at the
624 * beginning to complete the spanning allocation.
628 /* Clear the first 'count' bits in the next leaf to allocate. */
629 next->bm_bitmap &= (u_daddr_t)-1 << count;
632 * Update bitmaps of next-ancestors, up to least common ancestor.
634 while (next->bm_bitmap == 0) {
635 if (--next == scan) {
636 scan[-digit * radix_to_skip(radix)].bm_bitmap ^=
637 (u_daddr_t)1 << digit;
640 next->bm_bitmap ^= 1;
646 * Given a bitmask, flip all the bits from the least-significant 1-bit to the
647 * most significant bit. If the result is non-zero, then the least-significant
648 * 1-bit of the result is in the same position as the least-signification 0-bit
649 * in mask that is followed by a 1-bit.
651 static inline u_daddr_t
652 flip_hibits(u_daddr_t mask)
655 return (-mask & ~mask);
659 * BLST_LEAF_ALLOC() - allocate at a leaf in the radix tree (a bitmap).
661 * This function is the core of the allocator. Its execution time is
662 * proportional to log(count), plus height of the tree if the allocation
663 * crosses a leaf boundary.
666 blst_leaf_alloc(blmeta_t *scan, daddr_t blk, int count)
668 u_daddr_t cursor_mask, mask;
669 int count1, hi, lo, num_shifts, range1, range_ext;
673 num_shifts = fls(count1);
674 mask = scan->bm_bitmap;
675 while (flip_hibits(mask) != 0 && num_shifts > 0) {
677 * If bit i is set in mask, then bits in [i, i+range1] are set
678 * in scan->bm_bitmap. The value of range1 is equal to count1
679 * >> num_shifts. Grow range1 and reduce num_shifts to 0,
680 * while preserving these invariants. The updates to mask
681 * leave fewer bits set, but each bit that remains set
682 * represents a longer string of consecutive bits set in
683 * scan->bm_bitmap. If more updates to mask cannot clear more
684 * bits, because mask is partitioned with all 0 bits preceding
685 * all 1 bits, the loop terminates immediately.
688 range_ext = range1 + ((count1 >> num_shifts) & 1);
690 * mask is a signed quantity for the shift because when it is
691 * shifted right, the sign bit should copied; when the last
692 * block of the leaf is free, pretend, for a while, that all the
693 * blocks that follow it are also free.
695 mask &= (daddr_t)mask >> range_ext;
700 * Update bighint. There is no allocation bigger than range1
701 * starting in this leaf.
703 scan->bm_bighint = range1;
704 return (SWAPBLK_NONE);
707 /* Discard any candidates that appear before blk. */
708 if ((blk & BLIST_BMAP_MASK) != 0) {
709 cursor_mask = mask & bitrange(0, blk & BLIST_BMAP_MASK);
710 if (cursor_mask != 0) {
713 return (SWAPBLK_NONE);
716 * Bighint change for last block allocation cannot
717 * assume that any other blocks are allocated, so the
718 * bighint cannot be reduced much.
720 range1 = BLIST_MAX_ALLOC - 1;
722 blk &= ~BLIST_BMAP_MASK;
726 * The least significant set bit in mask marks the start of the first
727 * available range of sufficient size. Clear all the bits but that one,
728 * and then find its position.
734 if (hi > BLIST_BMAP_RADIX) {
736 * An allocation within this leaf is impossible, so a successful
737 * allocation depends on the next leaf providing some of the blocks.
739 if (blst_next_leaf_alloc(scan, blk, hi - BLIST_BMAP_RADIX) != 0)
741 * The hint cannot be updated, because the same
742 * allocation request could be satisfied later, by this
743 * leaf, if the state of the next leaf changes, and
744 * without any changes to this leaf.
746 return (SWAPBLK_NONE);
747 hi = BLIST_BMAP_RADIX;
750 /* Set the bits of mask at position 'lo' and higher. */
752 if (hi == BLIST_BMAP_RADIX) {
754 * Update bighint. There is no allocation bigger than range1
755 * available in this leaf after this allocation completes.
757 scan->bm_bighint = range1;
759 /* Clear the bits of mask at position 'hi' and higher. */
760 mask &= (u_daddr_t)-1 >> (BLIST_BMAP_RADIX - hi);
762 /* Clear the allocated bits from this leaf. */
763 scan->bm_bitmap &= ~mask;
768 * blist_meta_alloc() - allocate at a meta in the radix tree.
770 * Attempt to allocate at a meta node. If we can't, we update
771 * bighint and return a failure. Updating bighint optimize future
772 * calls that hit this node. We have to check for our collapse cases
773 * and we have a few optimizations strewn in as well.
776 blst_meta_alloc(blmeta_t *scan, daddr_t cursor, daddr_t count, u_daddr_t radix)
778 daddr_t blk, i, r, skip;
780 bool scan_from_start;
783 if (radix == BLIST_BMAP_RADIX)
784 return (blst_leaf_alloc(scan, cursor, count));
785 blk = cursor & -radix;
786 scan_from_start = (cursor == blk);
787 radix /= BLIST_META_RADIX;
788 skip = radix_to_skip(radix);
789 mask = scan->bm_bitmap;
791 /* Discard any candidates that appear before cursor. */
792 digit = (cursor / radix) & BLIST_META_MASK;
793 mask &= (u_daddr_t)-1 << digit;
795 return (SWAPBLK_NONE);
798 * If the first try is for a block that includes the cursor, pre-undo
799 * the digit * radix offset in the first call; otherwise, ignore the
802 if (((mask >> digit) & 1) == 1)
803 cursor -= digit * radix;
808 * Examine the nonempty subtree associated with each bit set in mask.
813 i = 1 + digit * skip;
814 if (count <= scan[i].bm_bighint) {
816 * The allocation might fit beginning in the i'th subtree.
818 r = blst_meta_alloc(&scan[i], cursor + digit * radix,
820 if (r != SWAPBLK_NONE) {
821 if (scan[i].bm_bitmap == 0)
822 scan->bm_bitmap ^= bit;
827 } while ((mask ^= bit) != 0);
830 * We couldn't allocate count in this subtree. If the whole tree was
831 * scanned, and the last tree node is allocated, update bighint.
833 if (scan_from_start && !(digit == BLIST_META_RADIX - 1 &&
834 scan[i].bm_bighint == BLIST_MAX_ALLOC))
835 scan->bm_bighint = count - 1;
837 return (SWAPBLK_NONE);
841 * BLST_LEAF_FREE() - free allocated block from leaf bitmap
845 blst_leaf_free(blmeta_t *scan, daddr_t blk, int count)
850 * free some data in this bitmap
851 * mask=0000111111111110000
855 mask = bitrange(blk & BLIST_BMAP_MASK, count);
856 KASSERT((scan->bm_bitmap & mask) == 0,
857 ("freeing free block: %jx, size %d, mask %jx",
858 (uintmax_t)blk, count, (uintmax_t)scan->bm_bitmap & mask));
859 scan->bm_bitmap |= mask;
863 * BLST_META_FREE() - free allocated blocks from radix tree meta info
865 * This support routine frees a range of blocks from the bitmap.
866 * The range must be entirely enclosed by this radix node. If a
867 * meta node, we break the range down recursively to free blocks
868 * in subnodes (which means that this code can free an arbitrary
869 * range whereas the allocation code cannot allocate an arbitrary
873 blst_meta_free(blmeta_t *scan, daddr_t freeBlk, daddr_t count, u_daddr_t radix)
875 daddr_t blk, endBlk, i, skip;
879 * We could probably do a better job here. We are required to make
880 * bighint at least as large as the biggest allocable block of data.
881 * If we just shoehorn it, a little extra overhead will be incurred
882 * on the next allocation (but only that one typically).
884 scan->bm_bighint = BLIST_MAX_ALLOC;
886 if (radix == BLIST_BMAP_RADIX)
887 return (blst_leaf_free(scan, freeBlk, count));
889 endBlk = ummin(freeBlk + count, (freeBlk + radix) & -radix);
890 radix /= BLIST_META_RADIX;
891 skip = radix_to_skip(radix);
892 blk = freeBlk & -radix;
893 digit = (blk / radix) & BLIST_META_MASK;
894 endDigit = 1 + (((endBlk - 1) / radix) & BLIST_META_MASK);
895 scan->bm_bitmap |= bitrange(digit, endDigit - digit);
896 for (i = 1 + digit * skip; blk < endBlk; i += skip) {
898 count = ummin(blk, endBlk) - freeBlk;
899 blst_meta_free(&scan[i], freeBlk, count, radix);
905 * BLST_COPY() - copy one radix tree to another
907 * Locates free space in the source tree and frees it in the destination
908 * tree. The space may not already be free in the destination.
911 blst_copy(blmeta_t *scan, daddr_t blk, daddr_t radix, blist_t dest,
914 daddr_t endBlk, i, skip;
920 if (radix == BLIST_BMAP_RADIX) {
921 u_daddr_t v = scan->bm_bitmap;
923 if (v == (u_daddr_t)-1) {
924 blist_free(dest, blk, count);
928 for (i = 0; i < count; ++i) {
929 if (v & ((u_daddr_t)1 << i))
930 blist_free(dest, blk + i, 1);
940 if (scan->bm_bitmap == 0) {
942 * Source all allocated, leave dest allocated
947 endBlk = blk + count;
948 radix /= BLIST_META_RADIX;
949 skip = radix_to_skip(radix);
950 for (i = 1; blk < endBlk; i += skip) {
954 count -= blk - endBlk;
955 blst_copy(&scan[i], blk - radix, radix, dest, count);
960 * BLST_LEAF_FILL() - allocate specific blocks in leaf bitmap
962 * This routine allocates all blocks in the specified range
963 * regardless of any existing allocations in that range. Returns
964 * the number of blocks allocated by the call.
967 blst_leaf_fill(blmeta_t *scan, daddr_t blk, int count)
972 mask = bitrange(blk & BLIST_BMAP_MASK, count);
974 /* Count the number of blocks that we are allocating. */
975 nblks = bitcount64(scan->bm_bitmap & mask);
977 scan->bm_bitmap &= ~mask;
982 * BLIST_META_FILL() - allocate specific blocks at a meta node
984 * This routine allocates the specified range of blocks,
985 * regardless of any existing allocations in the range. The
986 * range must be within the extent of this node. Returns the
987 * number of blocks allocated by the call.
990 blst_meta_fill(blmeta_t *scan, daddr_t allocBlk, daddr_t count, u_daddr_t radix)
992 daddr_t blk, endBlk, i, nblks, skip;
995 if (radix == BLIST_BMAP_RADIX)
996 return (blst_leaf_fill(scan, allocBlk, count));
998 endBlk = ummin(allocBlk + count, (allocBlk + radix) & -radix);
999 radix /= BLIST_META_RADIX;
1000 skip = radix_to_skip(radix);
1001 blk = allocBlk & -radix;
1003 while (blk < endBlk) {
1004 digit = (blk / radix) & BLIST_META_MASK;
1005 i = 1 + digit * skip;
1007 count = ummin(blk, endBlk) - allocBlk;
1008 nblks += blst_meta_fill(&scan[i], allocBlk, count, radix);
1009 if (scan[i].bm_bitmap == 0)
1010 scan->bm_bitmap &= ~((u_daddr_t)1 << digit);
1019 blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t radix, int tab)
1022 u_daddr_t bit, mask;
1025 if (radix == BLIST_BMAP_RADIX) {
1027 "%*.*s(%08llx,%lld): bitmap %0*llx big=%lld\n",
1029 (long long)blk, (long long)radix,
1030 1 + (BLIST_BMAP_RADIX - 1) / 4,
1031 (long long)scan->bm_bitmap,
1032 (long long)scan->bm_bighint
1038 "%*.*s(%08llx): subtree (%lld/%lld) bitmap %0*llx big=%lld {\n",
1040 (long long)blk, (long long)radix,
1042 1 + (BLIST_META_RADIX - 1) / 4,
1043 (long long)scan->bm_bitmap,
1044 (long long)scan->bm_bighint
1047 radix /= BLIST_META_RADIX;
1048 skip = radix_to_skip(radix);
1051 mask = scan->bm_bitmap;
1052 /* Examine the nonempty subtree associated with each bit set in mask */
1055 digit = bitpos(bit);
1056 blst_radix_print(&scan[1 + digit * skip], blk + digit * radix,
1058 } while ((mask ^= bit) != 0);
1072 main(int ac, char **av)
1074 int size = BLIST_META_RADIX * BLIST_BMAP_RADIX;
1079 for (i = 1; i < ac; ++i) {
1080 const char *ptr = av[i];
1082 size = strtol(ptr, NULL, 0);
1086 fprintf(stderr, "Bad option: %s\n", ptr - 2);
1089 bl = blist_create(size, M_WAITOK);
1090 blist_free(bl, 0, size);
1095 long long count = 0;
1097 printf("%lld/%lld/%lld> ", (long long)blist_avail(bl),
1098 (long long)size, (long long)bl->bl_radix);
1100 if (fgets(buf, sizeof(buf), stdin) == NULL)
1104 if (sscanf(buf + 1, "%lld", &count) == 1) {
1105 blist_resize(&bl, count, 1, M_WAITOK);
1113 s = sbuf_new_auto();
1116 printf("%s", sbuf_data(s));
1120 if (sscanf(buf + 1, "%lld", &count) == 1) {
1121 daddr_t blk = blist_alloc(bl, count);
1122 printf(" R=%08llx\n", (long long)blk);
1128 if (sscanf(buf + 1, "%llx %lld", &da, &count) == 2) {
1129 blist_free(bl, da, count);
1135 if (sscanf(buf + 1, "%llx %lld", &da, &count) == 2) {
1137 (intmax_t)blist_fill(bl, da, count));