freebsd-dev/sys/kern/subr_blist.c
Mateusz Guzik 3ff65f71cb Remove duplicated empty lines from kern/*.c
No functional changes.
2020-01-30 20:05:05 +00:00

1198 lines
32 KiB
C

/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 1998 Matthew Dillon. All Rights Reserved.
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* BLIST.C - Bitmap allocator/deallocator, using a radix tree with hinting
*
* This module implements a general bitmap allocator/deallocator. The
* allocator eats around 2 bits per 'block'. The module does not
* try to interpret the meaning of a 'block' other than to return
* SWAPBLK_NONE on an allocation failure.
*
* A radix tree controls access to pieces of the bitmap, and includes
* auxiliary information at each interior node about the availabilty of
* contiguous free blocks in the subtree rooted at that node. Two radix
* constants are involved: one for the size of the bitmaps contained in the
* leaf nodes (BLIST_BMAP_RADIX), and one for the number of descendents of
* each of the meta (interior) nodes (BLIST_META_RADIX). Each subtree is
* associated with a range of blocks. The root of any subtree stores a
* hint field that defines an upper bound on the size of the largest
* allocation that can begin in the associated block range. A hint is an
* upper bound on a potential allocation, but not necessarily a tight upper
* bound.
*
* The bitmap field in each node directs the search for available blocks.
* For a leaf node, a bit is set if the corresponding block is free. For a
* meta node, a bit is set if the corresponding subtree contains a free
* block somewhere within it. The search at a meta node considers only
* children of that node that represent a range that includes a free block.
*
* The hinting greatly increases code efficiency for allocations while
* the general radix structure optimizes both allocations and frees. The
* radix tree should be able to operate well no matter how much
* fragmentation there is and no matter how large a bitmap is used.
*
* The blist code wires all necessary memory at creation time. Neither
* allocations nor frees require interaction with the memory subsystem.
* The non-blocking nature of allocations and frees is required by swap
* code (vm/swap_pager.c).
*
* LAYOUT: The radix tree is laid out recursively using a linear array.
* Each meta node is immediately followed (laid out sequentially in
* memory) by BLIST_META_RADIX lower level nodes. This is a recursive
* structure but one that can be easily scanned through a very simple
* 'skip' calculation. The memory allocation is only large enough to
* cover the number of blocks requested at creation time. Nodes that
* represent blocks beyond that limit, nodes that would never be read
* or written, are not allocated, so that the last of the
* BLIST_META_RADIX lower level nodes of a some nodes may not be
* allocated.
*
* NOTE: the allocator cannot currently allocate more than
* BLIST_BMAP_RADIX blocks per call. It will panic with 'allocation too
* large' if you try. This is an area that could use improvement. The
* radix is large enough that this restriction does not effect the swap
* system, though. Currently only the allocation code is affected by
* this algorithmic unfeature. The freeing code can handle arbitrary
* ranges.
*
* This code can be compiled stand-alone for debugging.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#ifdef _KERNEL
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/kernel.h>
#include <sys/blist.h>
#include <sys/malloc.h>
#include <sys/sbuf.h>
#include <sys/proc.h>
#include <sys/mutex.h>
#else
#ifndef BLIST_NO_DEBUG
#define BLIST_DEBUG
#endif
#include <sys/errno.h>
#include <sys/types.h>
#include <sys/malloc.h>
#include <sys/sbuf.h>
#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdarg.h>
#include <stdbool.h>
#define bitcount64(x) __bitcount64((uint64_t)(x))
#define malloc(a,b,c) calloc(a, 1)
#define free(a,b) free(a)
#define ummin(a,b) ((a) < (b) ? (a) : (b))
#define imin(a,b) ((a) < (b) ? (a) : (b))
#define KASSERT(a,b) assert(a)
#include <sys/blist.h>
#endif
/*
* static support functions
*/
static daddr_t blst_leaf_alloc(blmeta_t *scan, daddr_t blk,
int *count, int maxcount);
static daddr_t blst_meta_alloc(blmeta_t *scan, daddr_t cursor, int *count,
int maxcount, u_daddr_t radix);
static void blst_leaf_free(blmeta_t *scan, daddr_t relblk, int count);
static void blst_meta_free(blmeta_t *scan, daddr_t freeBlk, daddr_t count,
u_daddr_t radix);
static void blst_copy(blmeta_t *scan, daddr_t blk, daddr_t radix,
blist_t dest, daddr_t count);
static daddr_t blst_leaf_fill(blmeta_t *scan, daddr_t blk, int count);
static daddr_t blst_meta_fill(blmeta_t *scan, daddr_t allocBlk, daddr_t count,
u_daddr_t radix);
#ifndef _KERNEL
static void blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t radix,
int tab);
#endif
#ifdef _KERNEL
static MALLOC_DEFINE(M_SWAP, "SWAP", "Swap space");
#endif
_Static_assert(BLIST_BMAP_RADIX % BLIST_META_RADIX == 0,
"radix divisibility error");
#define BLIST_BMAP_MASK (BLIST_BMAP_RADIX - 1)
#define BLIST_META_MASK (BLIST_META_RADIX - 1)
/*
* For a subtree that can represent the state of up to 'radix' blocks, the
* number of leaf nodes of the subtree is L=radix/BLIST_BMAP_RADIX. If 'm'
* is short for BLIST_META_RADIX, then for a tree of height h with L=m**h
* leaf nodes, the total number of tree nodes is 1 + m + m**2 + ... + m**h,
* or, equivalently, (m**(h+1)-1)/(m-1). This quantity is called 'skip'
* in the 'meta' functions that process subtrees. Since integer division
* discards remainders, we can express this computation as
* skip = (m * m**h) / (m - 1)
* skip = (m * (radix / BLIST_BMAP_RADIX)) / (m - 1)
* and since m divides BLIST_BMAP_RADIX, we can simplify further to
* skip = (radix / (BLIST_BMAP_RADIX / m)) / (m - 1)
* skip = radix / ((BLIST_BMAP_RADIX / m) * (m - 1))
* so that simple integer division by a constant can safely be used for the
* calculation.
*/
static inline daddr_t
radix_to_skip(daddr_t radix)
{
return (radix /
((BLIST_BMAP_RADIX / BLIST_META_RADIX) * BLIST_META_MASK));
}
/*
* Provide a mask with count bits set, starting as position n.
*/
static inline u_daddr_t
bitrange(int n, int count)
{
return (((u_daddr_t)-1 << n) &
((u_daddr_t)-1 >> (BLIST_BMAP_RADIX - (n + count))));
}
/*
* Find the first bit set in a u_daddr_t.
*/
static inline int
generic_bitpos(u_daddr_t mask)
{
int hi, lo, mid;
lo = 0;
hi = BLIST_BMAP_RADIX;
while (lo + 1 < hi) {
mid = (lo + hi) >> 1;
if (mask & bitrange(0, mid))
hi = mid;
else
lo = mid;
}
return (lo);
}
static inline int
bitpos(u_daddr_t mask)
{
switch (sizeof(mask)) {
#ifdef HAVE_INLINE_FFSLL
case sizeof(long long):
return (ffsll(mask) - 1);
#endif
#ifdef HAVE_INLINE_FFS
case sizeof(int):
return (ffs(mask) - 1);
#endif
default:
return (generic_bitpos(mask));
}
}
/*
* blist_create() - create a blist capable of handling up to the specified
* number of blocks
*
* blocks - must be greater than 0
* flags - malloc flags
*
* The smallest blist consists of a single leaf node capable of
* managing BLIST_BMAP_RADIX blocks.
*/
blist_t
blist_create(daddr_t blocks, int flags)
{
blist_t bl;
u_daddr_t nodes, radix;
KASSERT(blocks > 0, ("invalid block count"));
/*
* Calculate the radix and node count used for scanning.
*/
nodes = 1;
radix = BLIST_BMAP_RADIX;
while (radix <= blocks) {
nodes += 1 + (blocks - 1) / radix;
radix *= BLIST_META_RADIX;
}
bl = malloc(offsetof(struct blist, bl_root[nodes]), M_SWAP, flags |
M_ZERO);
if (bl == NULL)
return (NULL);
bl->bl_blocks = blocks;
bl->bl_radix = radix;
#if defined(BLIST_DEBUG)
printf(
"BLIST representing %lld blocks (%lld MB of swap)"
", requiring %lldK of ram\n",
(long long)bl->bl_blocks,
(long long)bl->bl_blocks * 4 / 1024,
(long long)(nodes * sizeof(blmeta_t) + 1023) / 1024
);
printf("BLIST raw radix tree contains %lld records\n",
(long long)nodes);
#endif
return (bl);
}
void
blist_destroy(blist_t bl)
{
free(bl, M_SWAP);
}
/*
* blist_alloc() - reserve space in the block bitmap. Return the base
* of a contiguous region or SWAPBLK_NONE if space could
* not be allocated.
*/
daddr_t
blist_alloc(blist_t bl, int *count, int maxcount)
{
daddr_t blk, cursor;
KASSERT(*count <= maxcount,
("invalid parameters %d > %d", *count, maxcount));
KASSERT(*count <= BLIST_MAX_ALLOC,
("minimum allocation too large: %d", *count));
/*
* This loop iterates at most twice. An allocation failure in the
* first iteration leads to a second iteration only if the cursor was
* non-zero. When the cursor is zero, an allocation failure will
* stop further iterations.
*/
for (cursor = bl->bl_cursor;; cursor = 0) {
blk = blst_meta_alloc(bl->bl_root, cursor, count, maxcount,
bl->bl_radix);
if (blk != SWAPBLK_NONE) {
bl->bl_avail -= *count;
bl->bl_cursor = blk + *count;
if (bl->bl_cursor == bl->bl_blocks)
bl->bl_cursor = 0;
return (blk);
}
if (cursor == 0)
return (SWAPBLK_NONE);
}
}
/*
* blist_avail() - return the number of free blocks.
*/
daddr_t
blist_avail(blist_t bl)
{
return (bl->bl_avail);
}
/*
* blist_free() - free up space in the block bitmap. Return the base
* of a contiguous region.
*/
void
blist_free(blist_t bl, daddr_t blkno, daddr_t count)
{
KASSERT(blkno >= 0 && blkno + count <= bl->bl_blocks,
("freeing invalid range: blkno %jx, count %d, blocks %jd",
(uintmax_t)blkno, (int)count, (uintmax_t)bl->bl_blocks));
blst_meta_free(bl->bl_root, blkno, count, bl->bl_radix);
bl->bl_avail += count;
}
/*
* blist_fill() - mark a region in the block bitmap as off-limits
* to the allocator (i.e. allocate it), ignoring any
* existing allocations. Return the number of blocks
* actually filled that were free before the call.
*/
daddr_t
blist_fill(blist_t bl, daddr_t blkno, daddr_t count)
{
daddr_t filled;
KASSERT(blkno >= 0 && blkno + count <= bl->bl_blocks,
("filling invalid range: blkno %jx, count %d, blocks %jd",
(uintmax_t)blkno, (int)count, (uintmax_t)bl->bl_blocks));
filled = blst_meta_fill(bl->bl_root, blkno, count, bl->bl_radix);
bl->bl_avail -= filled;
return (filled);
}
/*
* blist_resize() - resize an existing radix tree to handle the
* specified number of blocks. This will reallocate
* the tree and transfer the previous bitmap to the new
* one. When extending the tree you can specify whether
* the new blocks are to left allocated or freed.
*/
void
blist_resize(blist_t *pbl, daddr_t count, int freenew, int flags)
{
blist_t newbl = blist_create(count, flags);
blist_t save = *pbl;
*pbl = newbl;
if (count > save->bl_blocks)
count = save->bl_blocks;
blst_copy(save->bl_root, 0, save->bl_radix, newbl, count);
/*
* If resizing upwards, should we free the new space or not?
*/
if (freenew && count < newbl->bl_blocks) {
blist_free(newbl, count, newbl->bl_blocks - count);
}
blist_destroy(save);
}
#ifdef BLIST_DEBUG
/*
* blist_print() - dump radix tree
*/
void
blist_print(blist_t bl)
{
printf("BLIST avail = %jd, cursor = %08jx {\n",
(uintmax_t)bl->bl_avail, (uintmax_t)bl->bl_cursor);
if (bl->bl_root->bm_bitmap != 0)
blst_radix_print(bl->bl_root, 0, bl->bl_radix, 4);
printf("}\n");
}
#endif
static const u_daddr_t fib[] = {
1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584,
4181, 6765, 10946, 17711, 28657, 46368, 75025, 121393, 196418, 317811,
514229, 832040, 1346269, 2178309, 3524578,
};
/*
* Use 'gap' to describe a maximal range of unallocated blocks/bits.
*/
struct gap_stats {
daddr_t start; /* current gap start, or SWAPBLK_NONE */
daddr_t num; /* number of gaps observed */
daddr_t max; /* largest gap size */
daddr_t avg; /* average gap size */
daddr_t err; /* sum - num * avg */
daddr_t histo[nitems(fib)]; /* # gaps in each size range */
int max_bucket; /* last histo elt with nonzero val */
};
/*
* gap_stats_counting() - is the state 'counting 1 bits'?
* or 'skipping 0 bits'?
*/
static inline bool
gap_stats_counting(const struct gap_stats *stats)
{
return (stats->start != SWAPBLK_NONE);
}
/*
* init_gap_stats() - initialize stats on gap sizes
*/
static inline void
init_gap_stats(struct gap_stats *stats)
{
bzero(stats, sizeof(*stats));
stats->start = SWAPBLK_NONE;
}
/*
* update_gap_stats() - update stats on gap sizes
*/
static void
update_gap_stats(struct gap_stats *stats, daddr_t posn)
{
daddr_t size;
int hi, lo, mid;
if (!gap_stats_counting(stats)) {
stats->start = posn;
return;
}
size = posn - stats->start;
stats->start = SWAPBLK_NONE;
if (size > stats->max)
stats->max = size;
/*
* Find the fibonacci range that contains size,
* expecting to find it in an early range.
*/
lo = 0;
hi = 1;
while (hi < nitems(fib) && fib[hi] <= size) {
lo = hi;
hi *= 2;
}
if (hi >= nitems(fib))
hi = nitems(fib);
while (lo + 1 != hi) {
mid = (lo + hi) >> 1;
if (fib[mid] <= size)
lo = mid;
else
hi = mid;
}
stats->histo[lo]++;
if (lo > stats->max_bucket)
stats->max_bucket = lo;
stats->err += size - stats->avg;
stats->num++;
stats->avg += stats->err / stats->num;
stats->err %= stats->num;
}
/*
* dump_gap_stats() - print stats on gap sizes
*/
static inline void
dump_gap_stats(const struct gap_stats *stats, struct sbuf *s)
{
int i;
sbuf_printf(s, "number of maximal free ranges: %jd\n",
(intmax_t)stats->num);
sbuf_printf(s, "largest free range: %jd\n", (intmax_t)stats->max);
sbuf_printf(s, "average maximal free range size: %jd\n",
(intmax_t)stats->avg);
sbuf_printf(s, "number of maximal free ranges of different sizes:\n");
sbuf_printf(s, " count | size range\n");
sbuf_printf(s, " ----- | ----------\n");
for (i = 0; i < stats->max_bucket; i++) {
if (stats->histo[i] != 0) {
sbuf_printf(s, "%20jd | ",
(intmax_t)stats->histo[i]);
if (fib[i] != fib[i + 1] - 1)
sbuf_printf(s, "%jd to %jd\n", (intmax_t)fib[i],
(intmax_t)fib[i + 1] - 1);
else
sbuf_printf(s, "%jd\n", (intmax_t)fib[i]);
}
}
sbuf_printf(s, "%20jd | ", (intmax_t)stats->histo[i]);
if (stats->histo[i] > 1)
sbuf_printf(s, "%jd to %jd\n", (intmax_t)fib[i],
(intmax_t)stats->max);
else
sbuf_printf(s, "%jd\n", (intmax_t)stats->max);
}
/*
* blist_stats() - dump radix tree stats
*/
void
blist_stats(blist_t bl, struct sbuf *s)
{
struct gap_stats gstats;
struct gap_stats *stats = &gstats;
daddr_t i, nodes, radix;
u_daddr_t diff, mask;
int digit;
init_gap_stats(stats);
nodes = 0;
i = bl->bl_radix;
while (i < bl->bl_radix + bl->bl_blocks) {
/*
* Find max size subtree starting at i.
*/
radix = BLIST_BMAP_RADIX;
while (((i / radix) & BLIST_META_MASK) == 0)
radix *= BLIST_META_RADIX;
/*
* Check for skippable subtrees starting at i.
*/
while (radix > BLIST_BMAP_RADIX) {
if (bl->bl_root[nodes].bm_bitmap == 0) {
if (gap_stats_counting(stats))
update_gap_stats(stats, i);
break;
}
/*
* Skip subtree root.
*/
nodes++;
radix /= BLIST_META_RADIX;
}
if (radix == BLIST_BMAP_RADIX) {
/*
* Scan leaf.
*/
mask = bl->bl_root[nodes].bm_bitmap;
diff = mask ^ (mask << 1);
if (gap_stats_counting(stats))
diff ^= 1;
while (diff != 0) {
digit = bitpos(diff);
update_gap_stats(stats, i + digit);
diff ^= bitrange(digit, 1);
}
}
nodes += radix_to_skip(radix);
i += radix;
}
update_gap_stats(stats, i);
dump_gap_stats(stats, s);
}
/************************************************************************
* ALLOCATION SUPPORT FUNCTIONS *
************************************************************************
*
* These support functions do all the actual work. They may seem
* rather longish, but that's because I've commented them up. The
* actual code is straight forward.
*
*/
/*
* BLST_NEXT_LEAF_ALLOC() - allocate the blocks starting with the next leaf.
*
* 'scan' is a leaf node, and its first block is at address 'start'. The
* next leaf node could be adjacent, or several nodes away if the least
* common ancestor of 'scan' and its neighbor is several levels up. Use
* addresses to determine how many meta-nodes lie between the leaves. If
* sequence of leaves starting with the next one has enough initial bits
* set, clear them and clear the bits in the meta nodes on the path up to
* the least common ancestor to mark any subtrees made completely empty.
*/
static int
blst_next_leaf_alloc(blmeta_t *scan, daddr_t start, int count, int maxcount)
{
u_daddr_t radix;
daddr_t blk;
int avail, digit;
start += BLIST_BMAP_RADIX;
for (blk = start; blk - start < maxcount; blk += BLIST_BMAP_RADIX) {
/* Skip meta-nodes, as long as they promise more free blocks. */
radix = BLIST_BMAP_RADIX;
while (((++scan)->bm_bitmap & 1) == 1 &&
((blk / radix) & BLIST_META_MASK) == 0)
radix *= BLIST_META_RADIX;
if (~scan->bm_bitmap != 0) {
/*
* Either there is no next leaf with any free blocks,
* or we've reached the next leaf and found that some
* of its blocks are not free. In the first case,
* bitpos() returns zero here.
*/
avail = blk - start + bitpos(~scan->bm_bitmap);
if (avail < count || avail == 0) {
/*
* There isn't a next leaf with enough free
* blocks at its beginning to bother
* allocating.
*/
return (avail);
}
maxcount = imin(avail, maxcount);
if (maxcount % BLIST_BMAP_RADIX == 0) {
/*
* There was no next leaf. Back scan up to
* last leaf.
*/
--scan;
while (radix != BLIST_BMAP_RADIX) {
radix /= BLIST_META_RADIX;
--scan;
}
blk -= BLIST_BMAP_RADIX;
}
}
}
/*
* 'scan' is the last leaf that provides blocks. Clear from 1 to
* BLIST_BMAP_RADIX bits to represent the allocation of those last
* blocks.
*/
if (maxcount % BLIST_BMAP_RADIX != 0)
scan->bm_bitmap &= ~bitrange(0, maxcount % BLIST_BMAP_RADIX);
else
scan->bm_bitmap = 0;
for (;;) {
/* Back up over meta-nodes, clearing bits if necessary. */
blk -= BLIST_BMAP_RADIX;
radix = BLIST_BMAP_RADIX;
while ((digit = ((blk / radix) & BLIST_META_MASK)) == 0) {
if ((scan--)->bm_bitmap == 0)
scan->bm_bitmap ^= 1;
radix *= BLIST_META_RADIX;
}
if ((scan--)->bm_bitmap == 0)
scan[-digit * radix_to_skip(radix)].bm_bitmap ^=
(u_daddr_t)1 << digit;
if (blk == start)
break;
/* Clear all the bits of this leaf. */
scan->bm_bitmap = 0;
}
return (maxcount);
}
/*
* BLST_LEAF_ALLOC() - allocate at a leaf in the radix tree (a bitmap).
*
* This function is the core of the allocator. Its execution time is
* proportional to log(count), plus height of the tree if the allocation
* crosses a leaf boundary.
*/
static daddr_t
blst_leaf_alloc(blmeta_t *scan, daddr_t blk, int *count, int maxcount)
{
u_daddr_t mask;
int bighint, count1, hi, lo, num_shifts;
count1 = *count - 1;
num_shifts = fls(count1);
mask = ~scan->bm_bitmap;
while ((mask & (mask + 1)) != 0 && num_shifts > 0) {
/*
* If bit i is 0 in mask, then bits in [i, i + (count1 >>
* num_shifts)] are 1 in scan->bm_bitmap. Reduce num_shifts to
* 0, while preserving this invariant. The updates to mask
* leave fewer bits 0, but each bit that remains 0 represents a
* longer string of consecutive 1-bits in scan->bm_bitmap. If
* more updates to mask cannot set more bits, because mask is
* partitioned with all 1 bits following all 0 bits, the loop
* terminates immediately.
*/
num_shifts--;
mask |= mask >> ((count1 >> num_shifts) + 1) / 2;
}
bighint = count1 >> num_shifts;
if (~mask == 0) {
/*
* Update bighint. There is no allocation bigger than
* count1 >> num_shifts starting in this leaf.
*/
scan->bm_bighint = bighint;
return (SWAPBLK_NONE);
}
/* Discard any candidates that appear before blk. */
if ((blk & BLIST_BMAP_MASK) != 0) {
if ((~mask & bitrange(0, blk & BLIST_BMAP_MASK)) != 0) {
/* Grow bighint in case all discarded bits are set. */
bighint += blk & BLIST_BMAP_MASK;
mask |= bitrange(0, blk & BLIST_BMAP_MASK);
if (~mask == 0) {
scan->bm_bighint = bighint;
return (SWAPBLK_NONE);
}
}
blk -= blk & BLIST_BMAP_MASK;
}
/*
* The least significant set bit in mask marks the start of the first
* available range of sufficient size. Find its position.
*/
lo = bitpos(~mask);
/*
* Find how much space is available starting at that position.
*/
if ((mask & (mask + 1)) != 0) {
/* Count the 1 bits starting at position lo. */
hi = bitpos(mask & (mask + 1)) + count1;
if (maxcount < hi - lo)
hi = lo + maxcount;
*count = hi - lo;
mask = ~bitrange(lo, *count);
} else if (maxcount <= BLIST_BMAP_RADIX - lo) {
/* All the blocks we can use are available here. */
hi = lo + maxcount;
*count = maxcount;
mask = ~bitrange(lo, *count);
if (hi == BLIST_BMAP_RADIX)
scan->bm_bighint = bighint;
} else {
/* Check next leaf for some of the blocks we want or need. */
count1 = *count - (BLIST_BMAP_RADIX - lo);
maxcount -= BLIST_BMAP_RADIX - lo;
hi = blst_next_leaf_alloc(scan, blk, count1, maxcount);
if (hi < count1)
/*
* The next leaf cannot supply enough blocks to reach
* the minimum required allocation. The hint cannot be
* updated, because the same allocation request could
* be satisfied later, by this leaf, if the state of
* the next leaf changes, and without any changes to
* this leaf.
*/
return (SWAPBLK_NONE);
*count = BLIST_BMAP_RADIX - lo + hi;
scan->bm_bighint = bighint;
}
/* Clear the allocated bits from this leaf. */
scan->bm_bitmap &= mask;
return (blk + lo);
}
/*
* blist_meta_alloc() - allocate at a meta in the radix tree.
*
* Attempt to allocate at a meta node. If we can't, we update
* bighint and return a failure. Updating bighint optimize future
* calls that hit this node. We have to check for our collapse cases
* and we have a few optimizations strewn in as well.
*/
static daddr_t
blst_meta_alloc(blmeta_t *scan, daddr_t cursor, int *count,
int maxcount, u_daddr_t radix)
{
daddr_t blk, i, r, skip;
u_daddr_t mask;
bool scan_from_start;
int digit;
if (radix == BLIST_BMAP_RADIX)
return (blst_leaf_alloc(scan, cursor, count, maxcount));
blk = cursor & -radix;
scan_from_start = (cursor == blk);
radix /= BLIST_META_RADIX;
skip = radix_to_skip(radix);
mask = scan->bm_bitmap;
/* Discard any candidates that appear before cursor. */
digit = (cursor / radix) & BLIST_META_MASK;
mask &= (u_daddr_t)-1 << digit;
if (mask == 0)
return (SWAPBLK_NONE);
/*
* If the first try is for a block that includes the cursor, pre-undo
* the digit * radix offset in the first call; otherwise, ignore the
* cursor entirely.
*/
if (((mask >> digit) & 1) == 1)
cursor -= digit * radix;
else
cursor = blk;
/*
* Examine the nonempty subtree associated with each bit set in mask.
*/
do {
digit = bitpos(mask);
i = 1 + digit * skip;
if (*count <= scan[i].bm_bighint) {
/*
* The allocation might fit beginning in the i'th subtree.
*/
r = blst_meta_alloc(&scan[i], cursor + digit * radix,
count, maxcount, radix);
if (r != SWAPBLK_NONE) {
if (scan[i].bm_bitmap == 0)
scan->bm_bitmap ^= bitrange(digit, 1);
return (r);
}
}
cursor = blk;
} while ((mask ^= bitrange(digit, 1)) != 0);
/*
* We couldn't allocate count in this subtree. If the whole tree was
* scanned, and the last tree node is allocated, update bighint.
*/
if (scan_from_start && !(digit == BLIST_META_RADIX - 1 &&
scan[i].bm_bighint == BLIST_MAX_ALLOC))
scan->bm_bighint = *count - 1;
return (SWAPBLK_NONE);
}
/*
* BLST_LEAF_FREE() - free allocated block from leaf bitmap
*
*/
static void
blst_leaf_free(blmeta_t *scan, daddr_t blk, int count)
{
u_daddr_t mask;
/*
* free some data in this bitmap
* mask=0000111111111110000
* \_________/\__/
* count n
*/
mask = bitrange(blk & BLIST_BMAP_MASK, count);
KASSERT((scan->bm_bitmap & mask) == 0,
("freeing free block: %jx, size %d, mask %jx",
(uintmax_t)blk, count, (uintmax_t)scan->bm_bitmap & mask));
scan->bm_bitmap |= mask;
}
/*
* BLST_META_FREE() - free allocated blocks from radix tree meta info
*
* This support routine frees a range of blocks from the bitmap.
* The range must be entirely enclosed by this radix node. If a
* meta node, we break the range down recursively to free blocks
* in subnodes (which means that this code can free an arbitrary
* range whereas the allocation code cannot allocate an arbitrary
* range).
*/
static void
blst_meta_free(blmeta_t *scan, daddr_t freeBlk, daddr_t count, u_daddr_t radix)
{
daddr_t blk, endBlk, i, skip;
int digit, endDigit;
/*
* We could probably do a better job here. We are required to make
* bighint at least as large as the biggest allocable block of data.
* If we just shoehorn it, a little extra overhead will be incurred
* on the next allocation (but only that one typically).
*/
scan->bm_bighint = BLIST_MAX_ALLOC;
if (radix == BLIST_BMAP_RADIX)
return (blst_leaf_free(scan, freeBlk, count));
endBlk = ummin(freeBlk + count, (freeBlk + radix) & -radix);
radix /= BLIST_META_RADIX;
skip = radix_to_skip(radix);
blk = freeBlk & -radix;
digit = (blk / radix) & BLIST_META_MASK;
endDigit = 1 + (((endBlk - 1) / radix) & BLIST_META_MASK);
scan->bm_bitmap |= bitrange(digit, endDigit - digit);
for (i = 1 + digit * skip; blk < endBlk; i += skip) {
blk += radix;
count = ummin(blk, endBlk) - freeBlk;
blst_meta_free(&scan[i], freeBlk, count, radix);
freeBlk = blk;
}
}
/*
* BLST_COPY() - copy one radix tree to another
*
* Locates free space in the source tree and frees it in the destination
* tree. The space may not already be free in the destination.
*/
static void
blst_copy(blmeta_t *scan, daddr_t blk, daddr_t radix, blist_t dest,
daddr_t count)
{
daddr_t endBlk, i, skip;
/*
* Leaf node
*/
if (radix == BLIST_BMAP_RADIX) {
u_daddr_t v = scan->bm_bitmap;
if (v == (u_daddr_t)-1) {
blist_free(dest, blk, count);
} else if (v != 0) {
int i;
for (i = 0; i < count; ++i) {
if (v & ((u_daddr_t)1 << i))
blist_free(dest, blk + i, 1);
}
}
return;
}
/*
* Meta node
*/
if (scan->bm_bitmap == 0) {
/*
* Source all allocated, leave dest allocated
*/
return;
}
endBlk = blk + count;
radix /= BLIST_META_RADIX;
skip = radix_to_skip(radix);
for (i = 1; blk < endBlk; i += skip) {
blk += radix;
count = radix;
if (blk >= endBlk)
count -= blk - endBlk;
blst_copy(&scan[i], blk - radix, radix, dest, count);
}
}
/*
* BLST_LEAF_FILL() - allocate specific blocks in leaf bitmap
*
* This routine allocates all blocks in the specified range
* regardless of any existing allocations in that range. Returns
* the number of blocks allocated by the call.
*/
static daddr_t
blst_leaf_fill(blmeta_t *scan, daddr_t blk, int count)
{
daddr_t nblks;
u_daddr_t mask;
mask = bitrange(blk & BLIST_BMAP_MASK, count);
/* Count the number of blocks that we are allocating. */
nblks = bitcount64(scan->bm_bitmap & mask);
scan->bm_bitmap &= ~mask;
return (nblks);
}
/*
* BLIST_META_FILL() - allocate specific blocks at a meta node
*
* This routine allocates the specified range of blocks,
* regardless of any existing allocations in the range. The
* range must be within the extent of this node. Returns the
* number of blocks allocated by the call.
*/
static daddr_t
blst_meta_fill(blmeta_t *scan, daddr_t allocBlk, daddr_t count, u_daddr_t radix)
{
daddr_t blk, endBlk, i, nblks, skip;
int digit;
if (radix == BLIST_BMAP_RADIX)
return (blst_leaf_fill(scan, allocBlk, count));
endBlk = ummin(allocBlk + count, (allocBlk + radix) & -radix);
radix /= BLIST_META_RADIX;
skip = radix_to_skip(radix);
blk = allocBlk & -radix;
nblks = 0;
while (blk < endBlk) {
digit = (blk / radix) & BLIST_META_MASK;
i = 1 + digit * skip;
blk += radix;
count = ummin(blk, endBlk) - allocBlk;
nblks += blst_meta_fill(&scan[i], allocBlk, count, radix);
if (scan[i].bm_bitmap == 0)
scan->bm_bitmap &= ~((u_daddr_t)1 << digit);
allocBlk = blk;
}
return (nblks);
}
#ifdef BLIST_DEBUG
static void
blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t radix, int tab)
{
daddr_t skip;
u_daddr_t mask;
int digit;
if (radix == BLIST_BMAP_RADIX) {
printf(
"%*.*s(%08llx,%lld): bitmap %0*llx big=%lld\n",
tab, tab, "",
(long long)blk, (long long)radix,
1 + (BLIST_BMAP_RADIX - 1) / 4,
(long long)scan->bm_bitmap,
(long long)scan->bm_bighint
);
return;
}
printf(
"%*.*s(%08llx): subtree (%lld/%lld) bitmap %0*llx big=%lld {\n",
tab, tab, "",
(long long)blk, (long long)radix,
(long long)radix,
1 + (BLIST_META_RADIX - 1) / 4,
(long long)scan->bm_bitmap,
(long long)scan->bm_bighint
);
radix /= BLIST_META_RADIX;
skip = radix_to_skip(radix);
tab += 4;
mask = scan->bm_bitmap;
/* Examine the nonempty subtree associated with each bit set in mask */
do {
digit = bitpos(mask);
blst_radix_print(&scan[1 + digit * skip], blk + digit * radix,
radix, tab);
} while ((mask ^= bitrange(digit, 1)) != 0);
tab -= 4;
printf(
"%*.*s}\n",
tab, tab, ""
);
}
#endif
#ifdef BLIST_DEBUG
int
main(int ac, char **av)
{
int size = BLIST_META_RADIX * BLIST_BMAP_RADIX;
int i;
blist_t bl;
struct sbuf *s;
for (i = 1; i < ac; ++i) {
const char *ptr = av[i];
if (*ptr != '-') {
size = strtol(ptr, NULL, 0);
continue;
}
ptr += 2;
fprintf(stderr, "Bad option: %s\n", ptr - 2);
exit(1);
}
bl = blist_create(size, M_WAITOK);
blist_free(bl, 0, size);
for (;;) {
char buf[1024];
long long da = 0;
int count = 0, maxcount = 0;
printf("%lld/%lld/%lld> ", (long long)blist_avail(bl),
(long long)size, (long long)bl->bl_radix);
fflush(stdout);
if (fgets(buf, sizeof(buf), stdin) == NULL)
break;
switch(buf[0]) {
case 'r':
if (sscanf(buf + 1, "%d", &count) == 1) {
blist_resize(&bl, count, 1, M_WAITOK);
} else {
printf("?\n");
}
case 'p':
blist_print(bl);
break;
case 's':
s = sbuf_new_auto();
blist_stats(bl, s);
sbuf_finish(s);
printf("%s", sbuf_data(s));
sbuf_delete(s);
break;
case 'a':
if (sscanf(buf + 1, "%d%d", &count, &maxcount) == 2) {
daddr_t blk = blist_alloc(bl, &count, maxcount);
printf(" R=%08llx, c=%08d\n",
(long long)blk, count);
} else {
printf("?\n");
}
break;
case 'f':
if (sscanf(buf + 1, "%llx %d", &da, &count) == 2) {
blist_free(bl, da, count);
} else {
printf("?\n");
}
break;
case 'l':
if (sscanf(buf + 1, "%llx %d", &da, &count) == 2) {
printf(" n=%jd\n",
(intmax_t)blist_fill(bl, da, count));
} else {
printf("?\n");
}
break;
case '?':
case 'h':
puts(
"p -print\n"
"s -stats\n"
"a %d %d -allocate\n"
"f %x %d -free\n"
"l %x %d -fill\n"
"r %d -resize\n"
"h/? -help\n"
"q -quit"
);
break;
case 'q':
break;
default:
printf("?\n");
break;
}
if (buf[0] == 'q')
break;
}
return (0);
}
#endif