freebsd-dev/sys/kern/subr_blist.c
Mark Johnston ce9eea6425 Correct the condition under which we allocate a terminator node.
We will have last_block < blocks if the block count is divisible
by BLIST_BMAP_RADIX, but a terminator node is still needed if the
tree isn't balanced.  In this case we were overruning the blist
array by 16 bytes during initialization.

While here, add a check for the invalid blocks == 0 case.

PR:		231116
Reviewed by:	alc, kib (previous version), Doug Moore <dougm@rice.edu>
Approved by:	re (gjb)
MFC after:	1 week
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D17020
2018-09-05 19:05:30 +00:00

1300 lines
34 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 radix tree also implements two collapsed states for meta nodes:
* the ALL-ALLOCATED state and the ALL-FREE state. If a meta node is
* in either of these two states, all information contained underneath
* the node is considered stale. These states are used to optimize
* allocation and freeing operations.
*
* 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 features of the blist code are used in the 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. In order to support large radixes,
* portions of the tree may reside outside our memory allocation. We
* handle this with an early-termination optimization (when bighint is
* set to -1) on the scan. The memory allocation is only large enough
* to cover the number of blocks requested at creation time even if it
* must be encompassed in larger root-node radix.
*
* 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/types.h>
#include <sys/malloc.h>
#include <sys/sbuf.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)
static __inline int imax(int a, int b) { return (a > b ? a : b); }
#include <sys/blist.h>
void panic(const char *ctl, ...);
#endif
/*
* static support functions
*/
static daddr_t blst_leaf_alloc(blmeta_t *scan, daddr_t blk, int count);
static daddr_t blst_meta_alloc(blmeta_t *scan, daddr_t cursor, daddr_t count,
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));
}
/*
* Use binary search, or a faster method, to find the 1 bit in a u_daddr_t.
* Assumes that the argument has only one bit set.
*/
static inline int
bitpos(u_daddr_t mask)
{
int hi, lo, mid;
switch (sizeof(mask)) {
#ifdef HAVE_INLINE_FFSLL
case sizeof(long long):
return (ffsll(mask) - 1);
#endif
default:
lo = 0;
hi = BLIST_BMAP_RADIX;
while (lo + 1 < hi) {
mid = (lo + hi) >> 1;
if ((mask >> mid) != 0)
lo = mid;
else
hi = mid;
}
return (lo);
}
}
/*
* 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;
daddr_t i, last_block;
u_daddr_t nodes, radix, skip;
int digit;
if (blocks == 0)
panic("invalid block count");
/*
* Calculate the radix and node count used for scanning.
*/
last_block = blocks - 1;
radix = BLIST_BMAP_RADIX;
while (radix < blocks) {
if (((last_block / radix + 1) & BLIST_META_MASK) != 0)
/*
* We must widen the blist to avoid partially
* filled nodes.
*/
last_block |= radix - 1;
radix *= BLIST_META_RADIX;
}
/*
* Count the meta-nodes in the expanded tree, including the final
* terminator, from the bottom level up to the root.
*/
nodes = 1;
if (radix - blocks >= BLIST_BMAP_RADIX)
nodes++;
last_block /= BLIST_BMAP_RADIX;
while (last_block > 0) {
nodes += last_block + 1;
last_block /= 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;
bl->bl_cursor = 0;
/*
* Initialize the empty tree by filling in root values, then initialize
* just the terminators in the rest of the tree.
*/
bl->bl_root[0].bm_bighint = 0;
if (radix == BLIST_BMAP_RADIX)
bl->bl_root[0].u.bmu_bitmap = 0;
else
bl->bl_root[0].u.bmu_avail = 0;
last_block = blocks - 1;
i = 0;
while (radix > BLIST_BMAP_RADIX) {
radix /= BLIST_META_RADIX;
skip = radix_to_skip(radix);
digit = last_block / radix;
i += 1 + digit * skip;
if (digit != BLIST_META_MASK) {
/*
* Add a terminator.
*/
bl->bl_root[i + skip].bm_bighint = (daddr_t)-1;
bl->bl_root[i + skip].u.bmu_bitmap = 0;
}
last_block %= 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, daddr_t count)
{
daddr_t blk;
/*
* 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
* reduce the hint, stopping further iterations.
*/
while (count <= bl->bl_root->bm_bighint) {
blk = blst_meta_alloc(bl->bl_root, bl->bl_cursor, count,
bl->bl_radix);
if (blk != SWAPBLK_NONE) {
bl->bl_cursor = blk + count;
if (bl->bl_cursor == bl->bl_blocks)
bl->bl_cursor = 0;
return (blk);
} else if (bl->bl_cursor != 0)
bl->bl_cursor = 0;
}
return (SWAPBLK_NONE);
}
/*
* blist_avail() - return the number of free blocks.
*/
daddr_t
blist_avail(blist_t bl)
{
if (bl->bl_radix == BLIST_BMAP_RADIX)
return (bitcount64(bl->bl_root->u.bmu_bitmap));
else
return (bl->bl_root->u.bmu_avail);
}
/*
* blist_free() - free up space in the block bitmap. Return the base
* of a contiguous region. Panic if an inconsistancy is
* found.
*/
void
blist_free(blist_t bl, daddr_t blkno, daddr_t count)
{
blst_meta_free(bl->bl_root, blkno, count, bl->bl_radix);
}
/*
* 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)
{
return (blst_meta_fill(bl->bl_root, blkno, count, bl->bl_radix));
}
/*
* 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 cursor = %08jx {\n", (uintmax_t)bl->bl_cursor);
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 bit, diff, mask;
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].u.bmu_avail == 0) {
if (gap_stats_counting(stats))
update_gap_stats(stats, i);
break;
}
if (bl->bl_root[nodes].u.bmu_avail == radix) {
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].u.bmu_bitmap;
diff = mask ^ (mask << 1);
if (gap_stats_counting(stats))
diff ^= 1;
while (diff != 0) {
bit = diff & -diff;
update_gap_stats(stats, i + bitpos(bit));
diff ^= bit;
}
}
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.
*
*/
/*
* blist_leaf_alloc() - allocate at a leaf in the radix tree (a bitmap).
*
* This is the core of the allocator and is optimized for the
* BLIST_BMAP_RADIX block allocation case. Otherwise, execution
* time is proportional to log2(count) + bitpos time.
*/
static daddr_t
blst_leaf_alloc(blmeta_t *scan, daddr_t blk, int count)
{
u_daddr_t mask;
int count1, hi, lo, num_shifts, range1, range_ext;
range1 = 0;
count1 = count - 1;
num_shifts = fls(count1);
mask = scan->u.bmu_bitmap;
while ((-mask & ~mask) != 0 && num_shifts > 0) {
/*
* If bit i is set in mask, then bits in [i, i+range1] are set
* in scan->u.bmu_bitmap. The value of range1 is equal to
* count1 >> num_shifts. Grow range and reduce num_shifts to 0,
* while preserving these invariants. The updates to mask leave
* fewer bits set, but each bit that remains set represents a
* longer string of consecutive bits set in scan->u.bmu_bitmap.
* If more updates to mask cannot clear more bits, because mask
* is partitioned with all 0 bits preceding all 1 bits, the loop
* terminates immediately.
*/
num_shifts--;
range_ext = range1 + ((count1 >> num_shifts) & 1);
/*
* mask is a signed quantity for the shift because when it is
* shifted right, the sign bit should copied; when the last
* block of the leaf is free, pretend, for a while, that all the
* blocks that follow it are also free.
*/
mask &= (daddr_t)mask >> range_ext;
range1 += range_ext;
}
if (mask == 0) {
/*
* Update bighint. There is no allocation bigger than range1
* starting in this leaf.
*/
scan->bm_bighint = range1;
return (SWAPBLK_NONE);
}
/* Discard any candidates that appear before blk. */
mask &= (u_daddr_t)-1 << (blk & BLIST_BMAP_MASK);
if (mask == 0)
return (SWAPBLK_NONE);
/*
* The least significant set bit in mask marks the start of the first
* available range of sufficient size. Clear all the bits but that one,
* and then find its position.
*/
mask &= -mask;
lo = bitpos(mask);
hi = lo + count;
if (hi > BLIST_BMAP_RADIX) {
/*
* An allocation within this leaf is impossible, so a successful
* allocation depends on the next leaf providing some of the blocks.
*/
if (((blk / BLIST_BMAP_RADIX + 1) & BLIST_META_MASK) == 0) {
/*
* The next leaf has a different meta-node parent, so it
* is not necessarily initialized. Update bighint,
* comparing the range found at the end of mask to the
* largest earlier range that could have been made to
* vanish in the initial processing of mask.
*/
scan->bm_bighint = imax(BLIST_BMAP_RADIX - lo, range1);
return (SWAPBLK_NONE);
}
hi -= BLIST_BMAP_RADIX;
if (((scan[1].u.bmu_bitmap + 1) & ~((u_daddr_t)-1 << hi)) != 0) {
/*
* The next leaf doesn't have enough free blocks at the
* beginning to complete the spanning 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);
}
/* Clear the first 'hi' bits in the next leaf, allocating them. */
scan[1].u.bmu_bitmap &= (u_daddr_t)-1 << hi;
hi = BLIST_BMAP_RADIX;
}
/* Set the bits of mask at position 'lo' and higher. */
mask = -mask;
if (hi == BLIST_BMAP_RADIX) {
/*
* Update bighint. There is no allocation bigger than range1
* available in this leaf after this allocation completes.
*/
scan->bm_bighint = range1;
} else {
/* Clear the bits of mask at position 'hi' and higher. */
mask &= (u_daddr_t)-1 >> (BLIST_BMAP_RADIX - hi);
/* If this allocation uses all the bits, clear the hint. */
if (mask == scan->u.bmu_bitmap)
scan->bm_bighint = 0;
}
/* Clear the allocated bits from this leaf. */
scan->u.bmu_bitmap &= ~mask;
return ((blk & ~BLIST_BMAP_MASK) + 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, daddr_t count, u_daddr_t radix)
{
daddr_t blk, i, next_skip, r, skip;
int child;
bool scan_from_start;
if (radix == BLIST_BMAP_RADIX)
return (blst_leaf_alloc(scan, cursor, count));
if (scan->u.bmu_avail < count) {
/*
* The meta node's hint must be too large if the allocation
* exceeds the number of free blocks. Reduce the hint, and
* return failure.
*/
scan->bm_bighint = scan->u.bmu_avail;
return (SWAPBLK_NONE);
}
blk = cursor & -radix;
skip = radix_to_skip(radix);
next_skip = skip / BLIST_META_RADIX;
/*
* An ALL-FREE meta node requires special handling before allocating
* any of its blocks.
*/
if (scan->u.bmu_avail == radix) {
radix /= BLIST_META_RADIX;
/*
* Reinitialize each of the meta node's children. An ALL-FREE
* meta node cannot have a terminator in any subtree.
*/
for (i = 1; i < skip; i += next_skip) {
if (next_skip == 1)
scan[i].u.bmu_bitmap = (u_daddr_t)-1;
else
scan[i].u.bmu_avail = radix;
scan[i].bm_bighint = radix;
}
} else {
radix /= BLIST_META_RADIX;
}
if (count > radix) {
/*
* The allocation exceeds the number of blocks that are
* managed by a subtree of this meta node.
*/
panic("allocation too large");
}
scan_from_start = cursor == blk;
child = (cursor - blk) / radix;
blk += child * radix;
for (i = 1 + child * next_skip; i < skip; i += next_skip) {
if (count <= scan[i].bm_bighint) {
/*
* The allocation might fit beginning in the i'th subtree.
*/
r = blst_meta_alloc(&scan[i],
cursor > blk ? cursor : blk, count, radix);
if (r != SWAPBLK_NONE) {
scan->u.bmu_avail -= count;
return (r);
}
} else if (scan[i].bm_bighint == (daddr_t)-1) {
/*
* Terminator
*/
break;
}
blk += radix;
}
/*
* We couldn't allocate count in this subtree, update bighint.
*/
if (scan_from_start && scan->bm_bighint >= count)
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;
int n;
/*
* free some data in this bitmap
* mask=0000111111111110000
* \_________/\__/
* count n
*/
n = blk & BLIST_BMAP_MASK;
mask = ((u_daddr_t)-1 << n) &
((u_daddr_t)-1 >> (BLIST_BMAP_RADIX - count - n));
if (scan->u.bmu_bitmap & mask)
panic("freeing free block");
scan->u.bmu_bitmap |= mask;
/*
* We could probably do a better job here. We are required to make
* bighint at least as large as the biggest contiguous block of
* data. If we just shoehorn it, a little extra overhead will
* be incured on the next allocation (but only that one typically).
*/
scan->bm_bighint = BLIST_BMAP_RADIX;
}
/*
* 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, i, next_skip, skip, v;
int child;
if (scan->bm_bighint == (daddr_t)-1)
panic("freeing invalid range");
if (radix == BLIST_BMAP_RADIX)
return (blst_leaf_free(scan, freeBlk, count));
skip = radix_to_skip(radix);
next_skip = skip / BLIST_META_RADIX;
if (scan->u.bmu_avail == 0) {
/*
* ALL-ALLOCATED special case, with possible
* shortcut to ALL-FREE special case.
*/
scan->u.bmu_avail = count;
scan->bm_bighint = count;
if (count != radix) {
for (i = 1; i < skip; i += next_skip) {
if (scan[i].bm_bighint == (daddr_t)-1)
break;
scan[i].bm_bighint = 0;
if (next_skip == 1) {
scan[i].u.bmu_bitmap = 0;
} else {
scan[i].u.bmu_avail = 0;
}
}
/* fall through */
}
} else {
scan->u.bmu_avail += count;
/* scan->bm_bighint = radix; */
}
/*
* ALL-FREE special case.
*/
if (scan->u.bmu_avail == radix)
return;
if (scan->u.bmu_avail > radix)
panic("blst_meta_free: freeing already free blocks (%lld) %lld/%lld",
(long long)count, (long long)scan->u.bmu_avail,
(long long)radix);
/*
* Break the free down into its components
*/
blk = freeBlk & -radix;
radix /= BLIST_META_RADIX;
child = (freeBlk - blk) / radix;
blk += child * radix;
i = 1 + child * next_skip;
while (i < skip && blk < freeBlk + count) {
v = blk + radix - freeBlk;
if (v > count)
v = count;
blst_meta_free(&scan[i], freeBlk, v, radix);
if (scan->bm_bighint < scan[i].bm_bighint)
scan->bm_bighint = scan[i].bm_bighint;
count -= v;
freeBlk += v;
blk += radix;
i += next_skip;
}
}
/*
* BLIST_RADIX_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 i, next_skip, skip;
/*
* Leaf node
*/
if (radix == BLIST_BMAP_RADIX) {
u_daddr_t v = scan->u.bmu_bitmap;
if (v == (u_daddr_t)-1) {
blist_free(dest, blk, count);
} else if (v != 0) {
int i;
for (i = 0; i < BLIST_BMAP_RADIX && i < count; ++i) {
if (v & ((u_daddr_t)1 << i))
blist_free(dest, blk + i, 1);
}
}
return;
}
/*
* Meta node
*/
if (scan->u.bmu_avail == 0) {
/*
* Source all allocated, leave dest allocated
*/
return;
}
if (scan->u.bmu_avail == radix) {
/*
* Source all free, free entire dest
*/
if (count < radix)
blist_free(dest, blk, count);
else
blist_free(dest, blk, radix);
return;
}
skip = radix_to_skip(radix);
next_skip = skip / BLIST_META_RADIX;
radix /= BLIST_META_RADIX;
for (i = 1; count && i < skip; i += next_skip) {
if (scan[i].bm_bighint == (daddr_t)-1)
break;
if (count >= radix) {
blst_copy(&scan[i], blk, radix, dest, radix);
count -= radix;
} else {
if (count) {
blst_copy(&scan[i], blk, radix, dest, count);
}
count = 0;
}
blk += radix;
}
}
/*
* 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;
int n;
n = blk & BLIST_BMAP_MASK;
mask = ((u_daddr_t)-1 << n) &
((u_daddr_t)-1 >> (BLIST_BMAP_RADIX - count - n));
/* Count the number of blocks that we are allocating. */
nblks = bitcount64(scan->u.bmu_bitmap & mask);
scan->u.bmu_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, i, nblks, next_skip, skip, v;
int child;
if (scan->bm_bighint == (daddr_t)-1)
panic("filling invalid range");
if (count > radix) {
/*
* The allocation exceeds the number of blocks that are
* managed by this node.
*/
panic("fill too large");
}
if (radix == BLIST_BMAP_RADIX)
return (blst_leaf_fill(scan, allocBlk, count));
if (count == radix || scan->u.bmu_avail == 0) {
/*
* ALL-ALLOCATED special case
*/
nblks = scan->u.bmu_avail;
scan->u.bmu_avail = 0;
scan->bm_bighint = 0;
return (nblks);
}
skip = radix_to_skip(radix);
next_skip = skip / BLIST_META_RADIX;
blk = allocBlk & -radix;
/*
* An ALL-FREE meta node requires special handling before allocating
* any of its blocks.
*/
if (scan->u.bmu_avail == radix) {
radix /= BLIST_META_RADIX;
/*
* Reinitialize each of the meta node's children. An ALL-FREE
* meta node cannot have a terminator in any subtree.
*/
for (i = 1; i < skip; i += next_skip) {
if (next_skip == 1)
scan[i].u.bmu_bitmap = (u_daddr_t)-1;
else
scan[i].u.bmu_avail = radix;
scan[i].bm_bighint = radix;
}
} else {
radix /= BLIST_META_RADIX;
}
nblks = 0;
child = (allocBlk - blk) / radix;
blk += child * radix;
i = 1 + child * next_skip;
while (i < skip && blk < allocBlk + count) {
v = blk + radix - allocBlk;
if (v > count)
v = count;
nblks += blst_meta_fill(&scan[i], allocBlk, v, radix);
count -= v;
allocBlk += v;
blk += radix;
i += next_skip;
}
scan->u.bmu_avail -= nblks;
return (nblks);
}
#ifdef BLIST_DEBUG
static void
blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t radix, int tab)
{
daddr_t i, next_skip, skip;
if (radix == BLIST_BMAP_RADIX) {
printf(
"%*.*s(%08llx,%lld): bitmap %016llx big=%lld\n",
tab, tab, "",
(long long)blk, (long long)radix,
(long long)scan->u.bmu_bitmap,
(long long)scan->bm_bighint
);
return;
}
if (scan->u.bmu_avail == 0) {
printf(
"%*.*s(%08llx,%lld) ALL ALLOCATED\n",
tab, tab, "",
(long long)blk,
(long long)radix
);
return;
}
if (scan->u.bmu_avail == radix) {
printf(
"%*.*s(%08llx,%lld) ALL FREE\n",
tab, tab, "",
(long long)blk,
(long long)radix
);
return;
}
printf(
"%*.*s(%08llx,%lld): subtree (%lld/%lld) big=%lld {\n",
tab, tab, "",
(long long)blk, (long long)radix,
(long long)scan->u.bmu_avail,
(long long)radix,
(long long)scan->bm_bighint
);
skip = radix_to_skip(radix);
next_skip = skip / BLIST_META_RADIX;
radix /= BLIST_META_RADIX;
tab += 4;
for (i = 1; i < skip; i += next_skip) {
if (scan[i].bm_bighint == (daddr_t)-1) {
printf(
"%*.*s(%08llx,%lld): Terminator\n",
tab, tab, "",
(long long)blk, (long long)radix
);
break;
}
blst_radix_print(&scan[i], blk, radix, tab);
blk += radix;
}
tab -= 4;
printf(
"%*.*s}\n",
tab, tab, ""
);
}
#endif
#ifdef BLIST_DEBUG
int
main(int ac, char **av)
{
int size = 1024;
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;
long long count = 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, "%lld", &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, "%lld", &count) == 1) {
daddr_t blk = blist_alloc(bl, count);
printf(" R=%08llx\n", (long long)blk);
} else {
printf("?\n");
}
break;
case 'f':
if (sscanf(buf + 1, "%llx %lld", &da, &count) == 2) {
blist_free(bl, da, count);
} else {
printf("?\n");
}
break;
case 'l':
if (sscanf(buf + 1, "%llx %lld", &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 -allocate\n"
"f %x %d -free\n"
"l %x %d -fill\n"
"r %d -resize\n"
"h/? -help"
);
break;
default:
printf("?\n");
break;
}
}
return(0);
}
void
panic(const char *ctl, ...)
{
va_list va;
va_start(va, ctl);
vfprintf(stderr, ctl, va);
fprintf(stderr, "\n");
va_end(va);
exit(1);
}
#endif