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,
134 int *count, int maxcount);
135 static daddr_t blst_meta_alloc(blmeta_t *scan, daddr_t cursor, int *count,
136 int maxcount, u_daddr_t radix);
137 static void blst_leaf_free(blmeta_t *scan, daddr_t relblk, int count);
138 static void blst_meta_free(blmeta_t *scan, daddr_t freeBlk, daddr_t count,
140 static void blst_copy(blmeta_t *scan, daddr_t blk, daddr_t radix,
141 blist_t dest, daddr_t count);
142 static daddr_t blst_leaf_fill(blmeta_t *scan, daddr_t blk, int count);
143 static daddr_t blst_meta_fill(blmeta_t *scan, daddr_t allocBlk, daddr_t count,
146 static void blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t radix,
151 static MALLOC_DEFINE(M_SWAP, "SWAP", "Swap space");
154 _Static_assert(BLIST_BMAP_RADIX % BLIST_META_RADIX == 0,
155 "radix divisibility error");
156 #define BLIST_BMAP_MASK (BLIST_BMAP_RADIX - 1)
157 #define BLIST_META_MASK (BLIST_META_RADIX - 1)
160 * For a subtree that can represent the state of up to 'radix' blocks, the
161 * number of leaf nodes of the subtree is L=radix/BLIST_BMAP_RADIX. If 'm'
162 * is short for BLIST_META_RADIX, then for a tree of height h with L=m**h
163 * leaf nodes, the total number of tree nodes is 1 + m + m**2 + ... + m**h,
164 * or, equivalently, (m**(h+1)-1)/(m-1). This quantity is called 'skip'
165 * in the 'meta' functions that process subtrees. Since integer division
166 * discards remainders, we can express this computation as
167 * skip = (m * m**h) / (m - 1)
168 * skip = (m * (radix / BLIST_BMAP_RADIX)) / (m - 1)
169 * and since m divides BLIST_BMAP_RADIX, we can simplify further to
170 * skip = (radix / (BLIST_BMAP_RADIX / m)) / (m - 1)
171 * skip = radix / ((BLIST_BMAP_RADIX / m) * (m - 1))
172 * so that simple integer division by a constant can safely be used for the
175 static inline daddr_t
176 radix_to_skip(daddr_t radix)
180 ((BLIST_BMAP_RADIX / BLIST_META_RADIX) * BLIST_META_MASK));
184 * Provide a mask with count bits set, starting as position n.
186 static inline u_daddr_t
187 bitrange(int n, int count)
190 return (((u_daddr_t)-1 << n) &
191 ((u_daddr_t)-1 >> (BLIST_BMAP_RADIX - (n + count))));
196 * Find the first bit set in a u_daddr_t.
199 generic_bitpos(u_daddr_t mask)
204 hi = BLIST_BMAP_RADIX;
205 while (lo + 1 < hi) {
206 mid = (lo + hi) >> 1;
207 if (mask & bitrange(0, mid))
216 bitpos(u_daddr_t mask)
219 switch (sizeof(mask)) {
220 #ifdef HAVE_INLINE_FFSLL
221 case sizeof(long long):
222 return (ffsll(mask) - 1);
224 #ifdef HAVE_INLINE_FFS
226 return (ffs(mask) - 1);
229 return (generic_bitpos(mask));
234 * blist_create() - create a blist capable of handling up to the specified
237 * blocks - must be greater than 0
238 * flags - malloc flags
240 * The smallest blist consists of a single leaf node capable of
241 * managing BLIST_BMAP_RADIX blocks.
244 blist_create(daddr_t blocks, int flags)
247 u_daddr_t nodes, radix;
249 KASSERT(blocks > 0, ("invalid block count"));
252 * Calculate the radix and node count used for scanning.
255 radix = BLIST_BMAP_RADIX;
256 while (radix <= blocks) {
257 nodes += 1 + (blocks - 1) / radix;
258 radix *= BLIST_META_RADIX;
261 bl = malloc(offsetof(struct blist, bl_root[nodes]), M_SWAP, flags |
266 bl->bl_blocks = blocks;
267 bl->bl_radix = radix;
269 #if defined(BLIST_DEBUG)
271 "BLIST representing %lld blocks (%lld MB of swap)"
272 ", requiring %lldK of ram\n",
273 (long long)bl->bl_blocks,
274 (long long)bl->bl_blocks * 4 / 1024,
275 (long long)(nodes * sizeof(blmeta_t) + 1023) / 1024
277 printf("BLIST raw radix tree contains %lld records\n",
285 blist_destroy(blist_t bl)
292 * blist_alloc() - reserve space in the block bitmap. Return the base
293 * of a contiguous region or SWAPBLK_NONE if space could
297 blist_alloc(blist_t bl, int *count, int maxcount)
301 KASSERT(*count <= maxcount,
302 ("invalid parameters %d > %d", *count, maxcount));
303 KASSERT(maxcount <= BLIST_MAX_ALLOC,
304 ("allocation too large: %d", maxcount));
307 * This loop iterates at most twice. An allocation failure in the
308 * first iteration leads to a second iteration only if the cursor was
309 * non-zero. When the cursor is zero, an allocation failure will
310 * stop further iterations.
312 for (cursor = bl->bl_cursor;; cursor = 0) {
313 blk = blst_meta_alloc(bl->bl_root, cursor, count, maxcount,
315 if (blk != SWAPBLK_NONE) {
316 bl->bl_avail -= *count;
317 bl->bl_cursor = blk + *count;
318 if (bl->bl_cursor == bl->bl_blocks)
323 return (SWAPBLK_NONE);
328 * blist_avail() - return the number of free blocks.
331 blist_avail(blist_t bl)
334 return (bl->bl_avail);
338 * blist_free() - free up space in the block bitmap. Return the base
339 * of a contiguous region.
342 blist_free(blist_t bl, daddr_t blkno, daddr_t count)
345 KASSERT(blkno >= 0 && blkno + count <= bl->bl_blocks,
346 ("freeing invalid range: blkno %jx, count %d, blocks %jd",
347 (uintmax_t)blkno, (int)count, (uintmax_t)bl->bl_blocks));
348 blst_meta_free(bl->bl_root, blkno, count, bl->bl_radix);
349 bl->bl_avail += count;
353 * blist_fill() - mark a region in the block bitmap as off-limits
354 * to the allocator (i.e. allocate it), ignoring any
355 * existing allocations. Return the number of blocks
356 * actually filled that were free before the call.
359 blist_fill(blist_t bl, daddr_t blkno, daddr_t count)
363 KASSERT(blkno >= 0 && blkno + count <= bl->bl_blocks,
364 ("filling invalid range: blkno %jx, count %d, blocks %jd",
365 (uintmax_t)blkno, (int)count, (uintmax_t)bl->bl_blocks));
366 filled = blst_meta_fill(bl->bl_root, blkno, count, bl->bl_radix);
367 bl->bl_avail -= filled;
372 * blist_resize() - resize an existing radix tree to handle the
373 * specified number of blocks. This will reallocate
374 * the tree and transfer the previous bitmap to the new
375 * one. When extending the tree you can specify whether
376 * the new blocks are to left allocated or freed.
379 blist_resize(blist_t *pbl, daddr_t count, int freenew, int flags)
381 blist_t newbl = blist_create(count, flags);
385 if (count > save->bl_blocks)
386 count = save->bl_blocks;
387 blst_copy(save->bl_root, 0, save->bl_radix, newbl, count);
390 * If resizing upwards, should we free the new space or not?
392 if (freenew && count < newbl->bl_blocks) {
393 blist_free(newbl, count, newbl->bl_blocks - count);
401 * blist_print() - dump radix tree
404 blist_print(blist_t bl)
406 printf("BLIST avail = %jd, cursor = %08jx {\n",
407 (uintmax_t)bl->bl_avail, (uintmax_t)bl->bl_cursor);
409 if (bl->bl_root->bm_bitmap != 0)
410 blst_radix_print(bl->bl_root, 0, bl->bl_radix, 4);
416 static const u_daddr_t fib[] = {
417 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584,
418 4181, 6765, 10946, 17711, 28657, 46368, 75025, 121393, 196418, 317811,
419 514229, 832040, 1346269, 2178309, 3524578,
423 * Use 'gap' to describe a maximal range of unallocated blocks/bits.
426 daddr_t start; /* current gap start, or SWAPBLK_NONE */
427 daddr_t num; /* number of gaps observed */
428 daddr_t max; /* largest gap size */
429 daddr_t avg; /* average gap size */
430 daddr_t err; /* sum - num * avg */
431 daddr_t histo[nitems(fib)]; /* # gaps in each size range */
432 int max_bucket; /* last histo elt with nonzero val */
436 * gap_stats_counting() - is the state 'counting 1 bits'?
437 * or 'skipping 0 bits'?
440 gap_stats_counting(const struct gap_stats *stats)
443 return (stats->start != SWAPBLK_NONE);
447 * init_gap_stats() - initialize stats on gap sizes
450 init_gap_stats(struct gap_stats *stats)
453 bzero(stats, sizeof(*stats));
454 stats->start = SWAPBLK_NONE;
458 * update_gap_stats() - update stats on gap sizes
461 update_gap_stats(struct gap_stats *stats, daddr_t posn)
466 if (!gap_stats_counting(stats)) {
470 size = posn - stats->start;
471 stats->start = SWAPBLK_NONE;
472 if (size > stats->max)
476 * Find the fibonacci range that contains size,
477 * expecting to find it in an early range.
481 while (hi < nitems(fib) && fib[hi] <= size) {
485 if (hi >= nitems(fib))
487 while (lo + 1 != hi) {
488 mid = (lo + hi) >> 1;
489 if (fib[mid] <= size)
495 if (lo > stats->max_bucket)
496 stats->max_bucket = lo;
497 stats->err += size - stats->avg;
499 stats->avg += stats->err / stats->num;
500 stats->err %= stats->num;
504 * dump_gap_stats() - print stats on gap sizes
507 dump_gap_stats(const struct gap_stats *stats, struct sbuf *s)
511 sbuf_printf(s, "number of maximal free ranges: %jd\n",
512 (intmax_t)stats->num);
513 sbuf_printf(s, "largest free range: %jd\n", (intmax_t)stats->max);
514 sbuf_printf(s, "average maximal free range size: %jd\n",
515 (intmax_t)stats->avg);
516 sbuf_printf(s, "number of maximal free ranges of different sizes:\n");
517 sbuf_printf(s, " count | size range\n");
518 sbuf_printf(s, " ----- | ----------\n");
519 for (i = 0; i < stats->max_bucket; i++) {
520 if (stats->histo[i] != 0) {
521 sbuf_printf(s, "%20jd | ",
522 (intmax_t)stats->histo[i]);
523 if (fib[i] != fib[i + 1] - 1)
524 sbuf_printf(s, "%jd to %jd\n", (intmax_t)fib[i],
525 (intmax_t)fib[i + 1] - 1);
527 sbuf_printf(s, "%jd\n", (intmax_t)fib[i]);
530 sbuf_printf(s, "%20jd | ", (intmax_t)stats->histo[i]);
531 if (stats->histo[i] > 1)
532 sbuf_printf(s, "%jd to %jd\n", (intmax_t)fib[i],
533 (intmax_t)stats->max);
535 sbuf_printf(s, "%jd\n", (intmax_t)stats->max);
539 * blist_stats() - dump radix tree stats
542 blist_stats(blist_t bl, struct sbuf *s)
544 struct gap_stats gstats;
545 struct gap_stats *stats = &gstats;
546 daddr_t i, nodes, radix;
547 u_daddr_t diff, mask;
550 init_gap_stats(stats);
553 while (i < bl->bl_radix + bl->bl_blocks) {
555 * Find max size subtree starting at i.
557 radix = BLIST_BMAP_RADIX;
558 while (((i / radix) & BLIST_META_MASK) == 0)
559 radix *= BLIST_META_RADIX;
562 * Check for skippable subtrees starting at i.
564 while (radix > BLIST_BMAP_RADIX) {
565 if (bl->bl_root[nodes].bm_bitmap == 0) {
566 if (gap_stats_counting(stats))
567 update_gap_stats(stats, i);
575 radix /= BLIST_META_RADIX;
577 if (radix == BLIST_BMAP_RADIX) {
581 mask = bl->bl_root[nodes].bm_bitmap;
582 diff = mask ^ (mask << 1);
583 if (gap_stats_counting(stats))
586 digit = bitpos(diff);
587 update_gap_stats(stats, i + digit);
588 diff ^= bitrange(digit, 1);
591 nodes += radix_to_skip(radix);
594 update_gap_stats(stats, i);
595 dump_gap_stats(stats, s);
598 /************************************************************************
599 * ALLOCATION SUPPORT FUNCTIONS *
600 ************************************************************************
602 * These support functions do all the actual work. They may seem
603 * rather longish, but that's because I've commented them up. The
604 * actual code is straight forward.
609 * BLST_NEXT_LEAF_ALLOC() - allocate the first few blocks in the next leaf.
611 * 'scan' is a leaf node, associated with a block containing 'blk'.
612 * The next leaf node could be adjacent, or several nodes away if the
613 * least common ancestor of 'scan' and its neighbor is several levels
614 * up. Use 'blk' to determine how many meta-nodes lie between the
615 * leaves. If the next leaf has enough initial bits set, clear them
616 * and clear the bits in the meta nodes on the path up to the least
617 * common ancestor to mark any subtrees made completely empty.
620 blst_next_leaf_alloc(blmeta_t *scan, daddr_t blk, int count, int maxcount)
627 blk += BLIST_BMAP_RADIX;
628 radix = BLIST_BMAP_RADIX;
629 while ((next->bm_bitmap & 1) == 1 &&
630 (digit = ((blk / radix) & BLIST_META_MASK)) == 0) {
632 radix *= BLIST_META_RADIX;
634 if ((next->bm_bitmap & 1) != 1)
636 avail = (~next->bm_bitmap != 0) ?
637 bitpos(~next->bm_bitmap) : BLIST_BMAP_RADIX;
640 * The next leaf doesn't have enough free blocks at the
641 * beginning to complete the spanning allocation.
645 count = imin(avail, maxcount);
646 /* Clear the first 'count' bits in the next leaf to allocate. */
647 next->bm_bitmap &= ~bitrange(0, count);
650 * Update bitmaps of next-ancestors, up to least common ancestor.
652 while (next->bm_bitmap == 0) {
653 if (--next == scan) {
654 scan[-digit * radix_to_skip(radix)].bm_bitmap ^=
655 (u_daddr_t)1 << digit;
658 next->bm_bitmap ^= 1;
664 * Given a bitmask, flip all the bits from the least-significant 1-bit to the
665 * most significant bit. If the result is non-zero, then the least-significant
666 * 1-bit of the result is in the same position as the least-signification 0-bit
667 * in mask that is followed by a 1-bit.
669 static inline u_daddr_t
670 flip_hibits(u_daddr_t mask)
673 return (-mask & ~mask);
677 * BLST_LEAF_ALLOC() - allocate at a leaf in the radix tree (a bitmap).
679 * This function is the core of the allocator. Its execution time is
680 * proportional to log(count), plus height of the tree if the allocation
681 * crosses a leaf boundary.
684 blst_leaf_alloc(blmeta_t *scan, daddr_t blk, int *count, int maxcount)
686 u_daddr_t cursor_mask, mask;
687 int count1, hi, lo, num_shifts, range1, range_ext;
691 num_shifts = fls(count1);
692 mask = scan->bm_bitmap;
693 while (flip_hibits(mask) != 0 && num_shifts > 0) {
695 * If bit i is set in mask, then bits in [i, i+range1] are set
696 * in scan->bm_bitmap. The value of range1 is equal to count1
697 * >> num_shifts. Grow range1 and reduce num_shifts to 0,
698 * while preserving these invariants. The updates to mask
699 * leave fewer bits set, but each bit that remains set
700 * represents a longer string of consecutive bits set in
701 * scan->bm_bitmap. If more updates to mask cannot clear more
702 * bits, because mask is partitioned with all 0 bits preceding
703 * all 1 bits, the loop terminates immediately.
706 range_ext = range1 + ((count1 >> num_shifts) & 1);
708 * mask is a signed quantity for the shift because when it is
709 * shifted right, the sign bit should copied; when the last
710 * block of the leaf is free, pretend, for a while, that all the
711 * blocks that follow it are also free.
713 mask &= (daddr_t)mask >> range_ext;
718 * Update bighint. There is no allocation bigger than range1
719 * starting in this leaf.
721 scan->bm_bighint = range1;
722 return (SWAPBLK_NONE);
725 /* Discard any candidates that appear before blk. */
726 if ((blk & BLIST_BMAP_MASK) != 0) {
727 cursor_mask = mask & bitrange(0, blk & BLIST_BMAP_MASK);
728 if (cursor_mask != 0) {
731 return (SWAPBLK_NONE);
734 * Bighint change for last block allocation cannot
735 * assume that any other blocks are allocated, so the
736 * bighint cannot be reduced much.
738 range1 = BLIST_MAX_ALLOC - 1;
740 blk &= ~BLIST_BMAP_MASK;
744 * The least significant set bit in mask marks the start of the first
745 * available range of sufficient size. Find its position.
750 * Find how much space is available starting at that position.
752 if (flip_hibits(mask) != 0) {
753 /* Count the 1 bits starting at position lo. */
754 hi = bitpos(flip_hibits(mask)) + count1;
755 if (maxcount < hi - lo)
758 mask = bitrange(lo, *count);
759 } else if (maxcount <= BLIST_BMAP_RADIX - lo) {
760 /* All the blocks we can use are available here. */
763 mask = bitrange(lo, *count);
765 /* Check next leaf for some of the blocks we want or need. */
766 count1 = *count - (BLIST_BMAP_RADIX - lo);
767 maxcount -= BLIST_BMAP_RADIX - lo;
768 hi = blst_next_leaf_alloc(scan, blk, count1, maxcount);
771 * The next leaf cannot supply enough blocks to reach
772 * the minimum required allocation. The hint cannot be
773 * updated, because the same allocation request could
774 * be satisfied later, by this leaf, if the state of
775 * the next leaf changes, and without any changes to
778 return (SWAPBLK_NONE);
779 *count = BLIST_BMAP_RADIX - lo + hi;
780 hi = BLIST_BMAP_RADIX;
783 if (hi == BLIST_BMAP_RADIX) {
785 * Update bighint. There is no allocation bigger than range1
786 * available in this leaf after this allocation completes.
788 scan->bm_bighint = range1;
790 /* Clear the allocated bits from this leaf. */
791 scan->bm_bitmap &= ~mask;
796 * blist_meta_alloc() - allocate at a meta in the radix tree.
798 * Attempt to allocate at a meta node. If we can't, we update
799 * bighint and return a failure. Updating bighint optimize future
800 * calls that hit this node. We have to check for our collapse cases
801 * and we have a few optimizations strewn in as well.
804 blst_meta_alloc(blmeta_t *scan, daddr_t cursor, int *count,
805 int maxcount, u_daddr_t radix)
807 daddr_t blk, i, r, skip;
809 bool scan_from_start;
812 if (radix == BLIST_BMAP_RADIX)
813 return (blst_leaf_alloc(scan, cursor, count, maxcount));
814 blk = cursor & -radix;
815 scan_from_start = (cursor == blk);
816 radix /= BLIST_META_RADIX;
817 skip = radix_to_skip(radix);
818 mask = scan->bm_bitmap;
820 /* Discard any candidates that appear before cursor. */
821 digit = (cursor / radix) & BLIST_META_MASK;
822 mask &= (u_daddr_t)-1 << digit;
824 return (SWAPBLK_NONE);
827 * If the first try is for a block that includes the cursor, pre-undo
828 * the digit * radix offset in the first call; otherwise, ignore the
831 if (((mask >> digit) & 1) == 1)
832 cursor -= digit * radix;
837 * Examine the nonempty subtree associated with each bit set in mask.
840 digit = bitpos(mask);
841 i = 1 + digit * skip;
842 if (*count <= scan[i].bm_bighint) {
844 * The allocation might fit beginning in the i'th subtree.
846 r = blst_meta_alloc(&scan[i], cursor + digit * radix,
847 count, maxcount, radix);
848 if (r != SWAPBLK_NONE) {
849 if (scan[i].bm_bitmap == 0)
850 scan->bm_bitmap ^= bitrange(digit, 1);
855 } while ((mask ^= bitrange(digit, 1)) != 0);
858 * We couldn't allocate count in this subtree. If the whole tree was
859 * scanned, and the last tree node is allocated, update bighint.
861 if (scan_from_start && !(digit == BLIST_META_RADIX - 1 &&
862 scan[i].bm_bighint == BLIST_MAX_ALLOC))
863 scan->bm_bighint = *count - 1;
865 return (SWAPBLK_NONE);
869 * BLST_LEAF_FREE() - free allocated block from leaf bitmap
873 blst_leaf_free(blmeta_t *scan, daddr_t blk, int count)
878 * free some data in this bitmap
879 * mask=0000111111111110000
883 mask = bitrange(blk & BLIST_BMAP_MASK, count);
884 KASSERT((scan->bm_bitmap & mask) == 0,
885 ("freeing free block: %jx, size %d, mask %jx",
886 (uintmax_t)blk, count, (uintmax_t)scan->bm_bitmap & mask));
887 scan->bm_bitmap |= mask;
891 * BLST_META_FREE() - free allocated blocks from radix tree meta info
893 * This support routine frees a range of blocks from the bitmap.
894 * The range must be entirely enclosed by this radix node. If a
895 * meta node, we break the range down recursively to free blocks
896 * in subnodes (which means that this code can free an arbitrary
897 * range whereas the allocation code cannot allocate an arbitrary
901 blst_meta_free(blmeta_t *scan, daddr_t freeBlk, daddr_t count, u_daddr_t radix)
903 daddr_t blk, endBlk, i, skip;
907 * We could probably do a better job here. We are required to make
908 * bighint at least as large as the biggest allocable block of data.
909 * If we just shoehorn it, a little extra overhead will be incurred
910 * on the next allocation (but only that one typically).
912 scan->bm_bighint = BLIST_MAX_ALLOC;
914 if (radix == BLIST_BMAP_RADIX)
915 return (blst_leaf_free(scan, freeBlk, count));
917 endBlk = ummin(freeBlk + count, (freeBlk + radix) & -radix);
918 radix /= BLIST_META_RADIX;
919 skip = radix_to_skip(radix);
920 blk = freeBlk & -radix;
921 digit = (blk / radix) & BLIST_META_MASK;
922 endDigit = 1 + (((endBlk - 1) / radix) & BLIST_META_MASK);
923 scan->bm_bitmap |= bitrange(digit, endDigit - digit);
924 for (i = 1 + digit * skip; blk < endBlk; i += skip) {
926 count = ummin(blk, endBlk) - freeBlk;
927 blst_meta_free(&scan[i], freeBlk, count, radix);
933 * BLST_COPY() - copy one radix tree to another
935 * Locates free space in the source tree and frees it in the destination
936 * tree. The space may not already be free in the destination.
939 blst_copy(blmeta_t *scan, daddr_t blk, daddr_t radix, blist_t dest,
942 daddr_t endBlk, i, skip;
948 if (radix == BLIST_BMAP_RADIX) {
949 u_daddr_t v = scan->bm_bitmap;
951 if (v == (u_daddr_t)-1) {
952 blist_free(dest, blk, count);
956 for (i = 0; i < count; ++i) {
957 if (v & ((u_daddr_t)1 << i))
958 blist_free(dest, blk + i, 1);
968 if (scan->bm_bitmap == 0) {
970 * Source all allocated, leave dest allocated
975 endBlk = blk + count;
976 radix /= BLIST_META_RADIX;
977 skip = radix_to_skip(radix);
978 for (i = 1; blk < endBlk; i += skip) {
982 count -= blk - endBlk;
983 blst_copy(&scan[i], blk - radix, radix, dest, count);
988 * BLST_LEAF_FILL() - allocate specific blocks in leaf bitmap
990 * This routine allocates all blocks in the specified range
991 * regardless of any existing allocations in that range. Returns
992 * the number of blocks allocated by the call.
995 blst_leaf_fill(blmeta_t *scan, daddr_t blk, int count)
1000 mask = bitrange(blk & BLIST_BMAP_MASK, count);
1002 /* Count the number of blocks that we are allocating. */
1003 nblks = bitcount64(scan->bm_bitmap & mask);
1005 scan->bm_bitmap &= ~mask;
1010 * BLIST_META_FILL() - allocate specific blocks at a meta node
1012 * This routine allocates the specified range of blocks,
1013 * regardless of any existing allocations in the range. The
1014 * range must be within the extent of this node. Returns the
1015 * number of blocks allocated by the call.
1018 blst_meta_fill(blmeta_t *scan, daddr_t allocBlk, daddr_t count, u_daddr_t radix)
1020 daddr_t blk, endBlk, i, nblks, skip;
1023 if (radix == BLIST_BMAP_RADIX)
1024 return (blst_leaf_fill(scan, allocBlk, count));
1026 endBlk = ummin(allocBlk + count, (allocBlk + radix) & -radix);
1027 radix /= BLIST_META_RADIX;
1028 skip = radix_to_skip(radix);
1029 blk = allocBlk & -radix;
1031 while (blk < endBlk) {
1032 digit = (blk / radix) & BLIST_META_MASK;
1033 i = 1 + digit * skip;
1035 count = ummin(blk, endBlk) - allocBlk;
1036 nblks += blst_meta_fill(&scan[i], allocBlk, count, radix);
1037 if (scan[i].bm_bitmap == 0)
1038 scan->bm_bitmap &= ~((u_daddr_t)1 << digit);
1047 blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t radix, int tab)
1053 if (radix == BLIST_BMAP_RADIX) {
1055 "%*.*s(%08llx,%lld): bitmap %0*llx big=%lld\n",
1057 (long long)blk, (long long)radix,
1058 1 + (BLIST_BMAP_RADIX - 1) / 4,
1059 (long long)scan->bm_bitmap,
1060 (long long)scan->bm_bighint
1066 "%*.*s(%08llx): subtree (%lld/%lld) bitmap %0*llx big=%lld {\n",
1068 (long long)blk, (long long)radix,
1070 1 + (BLIST_META_RADIX - 1) / 4,
1071 (long long)scan->bm_bitmap,
1072 (long long)scan->bm_bighint
1075 radix /= BLIST_META_RADIX;
1076 skip = radix_to_skip(radix);
1079 mask = scan->bm_bitmap;
1080 /* Examine the nonempty subtree associated with each bit set in mask */
1082 digit = bitpos(mask);
1083 blst_radix_print(&scan[1 + digit * skip], blk + digit * radix,
1085 } while ((mask ^= bitrange(digit, 1)) != 0);
1099 main(int ac, char **av)
1101 int size = BLIST_META_RADIX * BLIST_BMAP_RADIX;
1106 for (i = 1; i < ac; ++i) {
1107 const char *ptr = av[i];
1109 size = strtol(ptr, NULL, 0);
1113 fprintf(stderr, "Bad option: %s\n", ptr - 2);
1116 bl = blist_create(size, M_WAITOK);
1117 blist_free(bl, 0, size);
1122 int count = 0, maxcount = 0;
1124 printf("%lld/%lld/%lld> ", (long long)blist_avail(bl),
1125 (long long)size, (long long)bl->bl_radix);
1127 if (fgets(buf, sizeof(buf), stdin) == NULL)
1131 if (sscanf(buf + 1, "%d", &count) == 1) {
1132 blist_resize(&bl, count, 1, M_WAITOK);
1140 s = sbuf_new_auto();
1143 printf("%s", sbuf_data(s));
1147 if (sscanf(buf + 1, "%d%d", &count, &maxcount) == 2) {
1148 daddr_t blk = blist_alloc(bl, &count, maxcount);
1149 printf(" R=%08llx, c=%08d\n",
1150 (long long)blk, count);
1156 if (sscanf(buf + 1, "%llx %d", &da, &count) == 2) {
1157 blist_free(bl, da, count);
1163 if (sscanf(buf + 1, "%llx %d", &da, &count) == 2) {
1165 (intmax_t)blist_fill(bl, da, count));
1175 "a %d %d -allocate\n"