/*
* Bitmap of bitmaps, where each layer is number-of-bits-per-word smaller than
* the previous. Hence an 'axmap', since we axe each previous layer into a
* much smaller piece. I swear, that is why it's named like that. It has
* nothing to do with anything remotely narcissistic.
*
* A set bit at layer N indicates a full word at layer N-1, and so forth. As
* the bitmap becomes progressively more full, checking for existence
* becomes cheaper (since fewer layers are walked, making it a lot more
* cache friendly) and locating the next free space likewise.
*
* Axmaps get pretty close to optimal (1 bit per block) space usage, since
* layers quickly diminish in size. Doing the size math is straight forward,
* since we have log64(blocks) layers of maps. For 20000 blocks, overhead
* is roughly 1.9%, or 1.019 bits per block. The number quickly converges
* towards 1.0158, or 1.58% of overhead.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "../arch/arch.h"
#include "axmap.h"
#include "../minmax.h"
#if BITS_PER_LONG == 64
#define UNIT_SHIFT 6
#elif BITS_PER_LONG == 32
#define UNIT_SHIFT 5
#else
#error "Number of arch bits unknown"
#endif
#define BLOCKS_PER_UNIT (1U << UNIT_SHIFT)
#define BLOCKS_PER_UNIT_MASK (BLOCKS_PER_UNIT - 1)
#define firstfree_valid(b) ((b)->first_free != (uint64_t) -1)
struct axmap_level {
int level;
unsigned long map_size;
unsigned long *map;
};
struct axmap {
unsigned int nr_levels;
struct axmap_level *levels;
uint64_t first_free;
uint64_t nr_bits;
};
static unsigned long ulog64(unsigned long val, unsigned int log)
{
while (log-- && val)
val >>= UNIT_SHIFT;
return val;
}
void axmap_reset(struct axmap *axmap)
{
int i;
for (i = 0; i < axmap->nr_levels; i++) {
struct axmap_level *al = &axmap->levels[i];
memset(al->map, 0, al->map_size * sizeof(unsigned long));
}
axmap->first_free = 0;
}
void axmap_free(struct axmap *axmap)
{
unsigned int i;
if (!axmap)
return;
for (i = 0; i < axmap->nr_levels; i++)
free(axmap->levels[i].map);
free(axmap->levels);
free(axmap);
}
struct axmap *axmap_new(unsigned long nr_bits)
{
struct axmap *axmap;
unsigned int i, levels;
axmap = malloc(sizeof(*axmap));
if (!axmap)
return NULL;
levels = 1;
i = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
while (i > 1) {
i = (i + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
levels++;
}
axmap->nr_levels = levels;
axmap->levels = malloc(axmap->nr_levels * sizeof(struct axmap_level));
axmap->nr_bits = nr_bits;
for (i = 0; i < axmap->nr_levels; i++) {
struct axmap_level *al = &axmap->levels[i];
al->level = i;
al->map_size = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
al->map = malloc(al->map_size * sizeof(unsigned long));
if (!al->map)
goto err;
nr_bits = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
}
axmap_reset(axmap);
return axmap;
err:
for (i = 0; i < axmap->nr_levels; i++)
if (axmap->levels[i].map)
free(axmap->levels[i].map);
free(axmap->levels);
free(axmap);
return NULL;
}
static int axmap_handler(struct axmap *axmap, uint64_t bit_nr,
int (*func)(struct axmap_level *, unsigned long, unsigned int,
void *), void *data)
{
struct axmap_level *al;
int i;
for (i = 0; i < axmap->nr_levels; i++) {
unsigned long index = ulog64(bit_nr, i);
unsigned long offset = index >> UNIT_SHIFT;
unsigned int bit = index & BLOCKS_PER_UNIT_MASK;
al = &axmap->levels[i];
if (func(al, offset, bit, data))
return 1;
}
return 0;
}
static int axmap_handler_topdown(struct axmap *axmap, uint64_t bit_nr,
int (*func)(struct axmap_level *, unsigned long, unsigned int, void *),
void *data)
{
struct axmap_level *al;
int i, level = axmap->nr_levels;
for (i = axmap->nr_levels - 1; i >= 0; i--) {
unsigned long index = ulog64(bit_nr, --level);
unsigned long offset = index >> UNIT_SHIFT;
unsigned int bit = index & BLOCKS_PER_UNIT_MASK;
al = &axmap->levels[i];
if (func(al, offset, bit, data))
return 1;
}
return 0;
}
static int axmap_clear_fn(struct axmap_level *al, unsigned long offset,
unsigned int bit, void *unused)
{
if (!(al->map[offset] & (1UL << bit)))
return 1;
al->map[offset] &= ~(1UL << bit);
return 0;
}
void axmap_clear(struct axmap *axmap, uint64_t bit_nr)
{
axmap_handler(axmap, bit_nr, axmap_clear_fn, NULL);
}
struct axmap_set_data {
unsigned int nr_bits;
unsigned int set_bits;
};
static unsigned long bit_masks[] = {
0x0000000000000000, 0x0000000000000001, 0x0000000000000003, 0x0000000000000007,
0x000000000000000f, 0x000000000000001f, 0x000000000000003f, 0x000000000000007f,
0x00000000000000ff, 0x00000000000001ff, 0x00000000000003ff, 0x00000000000007ff,
0x0000000000000fff, 0x0000000000001fff, 0x0000000000003fff, 0x0000000000007fff,
0x000000000000ffff, 0x000000000001ffff, 0x000000000003ffff, 0x000000000007ffff,
0x00000000000fffff, 0x00000000001fffff, 0x00000000003fffff, 0x00000000007fffff,
0x0000000000ffffff, 0x0000000001ffffff, 0x0000000003ffffff, 0x0000000007ffffff,
0x000000000fffffff, 0x000000001fffffff, 0x000000003fffffff, 0x000000007fffffff,
0x00000000ffffffff,
#if BITS_PER_LONG == 64
0x00000001ffffffff, 0x00000003ffffffff, 0x00000007ffffffff, 0x0000000fffffffff,
0x0000001fffffffff, 0x0000003fffffffff, 0x0000007fffffffff, 0x000000ffffffffff,
0x000001ffffffffff, 0x000003ffffffffff, 0x000007ffffffffff, 0x00000fffffffffff,
0x00001fffffffffff, 0x00003fffffffffff, 0x00007fffffffffff, 0x0000ffffffffffff,
0x0001ffffffffffff, 0x0003ffffffffffff, 0x0007ffffffffffff, 0x000fffffffffffff,
0x001fffffffffffff, 0x003fffffffffffff, 0x007fffffffffffff, 0x00ffffffffffffff,
0x01ffffffffffffff, 0x03ffffffffffffff, 0x07ffffffffffffff, 0x0fffffffffffffff,
0x1fffffffffffffff, 0x3fffffffffffffff, 0x7fffffffffffffff, 0xffffffffffffffff
#endif
};
static int axmap_set_fn(struct axmap_level *al, unsigned long offset,
unsigned int bit, void *__data)
{
struct axmap_set_data *data = __data;
unsigned long mask, overlap;
unsigned int nr_bits;
nr_bits = min(data->nr_bits, BLOCKS_PER_UNIT - bit);
mask = bit_masks[nr_bits] << bit;
/*
* Mask off any potential overlap, only sets contig regions
*/
overlap = al->map[offset] & mask;
if (overlap == mask)
return 1;
while (overlap) {
unsigned long clear_mask = ~(1UL << ffz(~overlap));
mask &= clear_mask;
overlap &= clear_mask;
nr_bits--;
}
assert(mask);
assert(!(al->map[offset] & mask));
al->map[offset] |= mask;
if (!al->level)
data->set_bits = nr_bits;
data->nr_bits = 1;
return al->map[offset] != -1UL;
}
static void __axmap_set(struct axmap *axmap, uint64_t bit_nr,
struct axmap_set_data *data)
{
unsigned int set_bits, nr_bits = data->nr_bits;
if (axmap->first_free >= bit_nr &&
axmap->first_free < bit_nr + data->nr_bits)
axmap->first_free = -1ULL;
if (bit_nr > axmap->nr_bits)
return;
else if (bit_nr + nr_bits > axmap->nr_bits)
nr_bits = axmap->nr_bits - bit_nr;
set_bits = 0;
while (nr_bits) {
axmap_handler(axmap, bit_nr, axmap_set_fn, data);
set_bits += data->set_bits;
if (!data->set_bits ||
data->set_bits != (BLOCKS_PER_UNIT - nr_bits))
break;
nr_bits -= data->set_bits;
bit_nr += data->set_bits;
data->nr_bits = nr_bits;
}
data->set_bits = set_bits;
}
void axmap_set(struct axmap *axmap, uint64_t bit_nr)
{
struct axmap_set_data data = { .nr_bits = 1, };
__axmap_set(axmap, bit_nr, &data);
}
unsigned int axmap_set_nr(struct axmap *axmap, uint64_t bit_nr, unsigned int nr_bits)
{
unsigned int set_bits = 0;
do {
struct axmap_set_data data = { .nr_bits = nr_bits, };
unsigned int max_bits, this_set;
max_bits = BLOCKS_PER_UNIT - (bit_nr & BLOCKS_PER_UNIT_MASK);
if (max_bits < nr_bits)
data.nr_bits = max_bits;
this_set = data.nr_bits;
__axmap_set(axmap, bit_nr, &data);
set_bits += data.set_bits;
if (data.set_bits != this_set)
break;
nr_bits -= data.set_bits;
bit_nr += data.set_bits;
} while (nr_bits);
return set_bits;
}
static int axmap_isset_fn(struct axmap_level *al, unsigned long offset,
unsigned int bit, void *unused)
{
return (al->map[offset] & (1UL << bit)) != 0;
}
int axmap_isset(struct axmap *axmap, uint64_t bit_nr)
{
if (bit_nr <= axmap->nr_bits)
return axmap_handler_topdown(axmap, bit_nr, axmap_isset_fn, NULL);
return 0;
}
static uint64_t axmap_find_first_free(struct axmap *axmap, unsigned int level,
uint64_t index)
{
uint64_t ret = -1ULL;
unsigned long j;
int i;
/*
* Start at the bottom, then converge towards first free bit at the top
*/
for (i = level; i >= 0; i--) {
struct axmap_level *al = &axmap->levels[i];
/*
* Clear 'ret', this is a bug condition.
*/
if (index >= al->map_size) {
ret = -1ULL;
break;
}
for (j = index; j < al->map_size; j++) {
if (al->map[j] == -1UL)
continue;
/*
* First free bit here is our index into the first
* free bit at the next higher level
*/
ret = index = (j << UNIT_SHIFT) + ffz(al->map[j]);
break;
}
}
if (ret < axmap->nr_bits)
return ret;
return (uint64_t) -1ULL;
}
static uint64_t axmap_first_free(struct axmap *axmap)
{
if (firstfree_valid(axmap))
return axmap->first_free;
axmap->first_free = axmap_find_first_free(axmap, axmap->nr_levels - 1, 0);
return axmap->first_free;
}
struct axmap_next_free_data {
unsigned int level;
unsigned long offset;
uint64_t bit;
};
static int axmap_next_free_fn(struct axmap_level *al, unsigned long offset,
unsigned int bit, void *__data)
{
struct axmap_next_free_data *data = __data;
uint64_t mask = ~bit_masks[(data->bit + 1) & BLOCKS_PER_UNIT_MASK];
if (!(mask & ~al->map[offset]))
return 0;
if (al->map[offset] != -1UL) {
data->level = al->level;
data->offset = offset;
return 1;
}
data->bit = (data->bit + BLOCKS_PER_UNIT - 1) / BLOCKS_PER_UNIT;
return 0;
}
/*
* 'bit_nr' is already set. Find the next free bit after this one.
*/
uint64_t axmap_next_free(struct axmap *axmap, uint64_t bit_nr)
{
struct axmap_next_free_data data = { .level = -1U, .bit = bit_nr, };
uint64_t ret;
if (firstfree_valid(axmap) && bit_nr < axmap->first_free)
return axmap->first_free;
if (!axmap_handler(axmap, bit_nr, axmap_next_free_fn, &data))
return axmap_first_free(axmap);
assert(data.level != -1U);
/*
* In the rare case that the map is unaligned, we might end up
* finding an offset that's beyond the valid end. For that case,
* find the first free one, the map is practically full.
*/
ret = axmap_find_first_free(axmap, data.level, data.offset);
if (ret != -1ULL)
return ret;
return axmap_first_free(axmap);
}