Jens Axboe | 7ebd796 | 2012-11-28 21:24:46 +0100 | [diff] [blame] | 1 | /* |
| 2 | * Bitmap of bitmaps, where each layer is number-of-bits-per-word smaller than |
| 3 | * the previous. Hence an 'axmap', since we axe each previous layer into a |
| 4 | * much smaller piece. I swear, that is why it's named like that. It has |
| 5 | * nothing to do with anything remotely narcissistic. |
| 6 | * |
| 7 | * A set bit at layer N indicates a full word at layer N-1, and so forth. As |
| 8 | * the bitmap becomes progressively more full, checking for existance |
| 9 | * becomes cheaper (since fewer layers are walked, making it a lot more |
| 10 | * cache friendly) and locating the next free space likewise. |
| 11 | * |
| 12 | * Axmaps get pretty close to optimal (1 bit per block) space usage, since |
| 13 | * layers quickly diminish in size. Doing the size math is straight forward, |
| 14 | * since we have log64(blocks) layers of maps. For 20000 blocks, overhead |
| 15 | * is roughly 1.9%, or 1.019 bits per block. The number quickly converges |
| 16 | * towards 1.0158, or 1.58% of overhead. |
| 17 | */ |
| 18 | #include <stdio.h> |
| 19 | #include <stdlib.h> |
| 20 | #include <string.h> |
| 21 | #include <assert.h> |
| 22 | |
| 23 | #include "../arch/arch.h" |
| 24 | #include "axmap.h" |
| 25 | #include "../smalloc.h" |
| 26 | #include "../minmax.h" |
| 27 | |
| 28 | #if BITS_PER_LONG == 64 |
| 29 | #define UNIT_SHIFT 6 |
| 30 | #elif BITS_PER_LONG == 32 |
| 31 | #define UNIT_SHIFT 5 |
| 32 | #else |
| 33 | #error "Number of arch bits unknown" |
| 34 | #endif |
| 35 | |
| 36 | #define BLOCKS_PER_UNIT (1UL << UNIT_SHIFT) |
| 37 | #define BLOCKS_PER_UNIT_MASK (BLOCKS_PER_UNIT - 1) |
| 38 | |
| 39 | #define firstfree_valid(b) ((b)->first_free != (uint64_t) -1) |
| 40 | |
| 41 | struct axmap_level { |
| 42 | int level; |
| 43 | unsigned long map_size; |
| 44 | unsigned long *map; |
| 45 | }; |
| 46 | |
| 47 | struct axmap { |
| 48 | unsigned int nr_levels; |
| 49 | struct axmap_level *levels; |
| 50 | uint64_t first_free; |
| 51 | }; |
| 52 | |
| 53 | static unsigned long ulog64(unsigned long val, unsigned int log) |
| 54 | { |
| 55 | while (log-- && val) |
| 56 | val >>= UNIT_SHIFT; |
| 57 | |
| 58 | return val; |
| 59 | } |
| 60 | |
| 61 | void axmap_reset(struct axmap *axmap) |
| 62 | { |
| 63 | int i; |
| 64 | |
| 65 | for (i = 0; i < axmap->nr_levels; i++) { |
| 66 | struct axmap_level *al = &axmap->levels[i]; |
| 67 | |
| 68 | memset(al->map, 0, al->map_size * sizeof(unsigned long)); |
| 69 | } |
Jens Axboe | 17f0fd3 | 2013-01-21 09:43:30 -0700 | [diff] [blame] | 70 | |
| 71 | axmap->first_free = 0; |
Jens Axboe | 7ebd796 | 2012-11-28 21:24:46 +0100 | [diff] [blame] | 72 | } |
| 73 | |
| 74 | void axmap_free(struct axmap *axmap) |
| 75 | { |
| 76 | unsigned int i; |
| 77 | |
| 78 | if (!axmap) |
| 79 | return; |
| 80 | |
| 81 | for (i = 0; i < axmap->nr_levels; i++) |
| 82 | sfree(axmap->levels[i].map); |
| 83 | |
| 84 | sfree(axmap->levels); |
| 85 | sfree(axmap); |
| 86 | } |
| 87 | |
| 88 | struct axmap *axmap_new(unsigned long nr_bits) |
| 89 | { |
| 90 | struct axmap *axmap; |
| 91 | unsigned int i, levels; |
| 92 | |
| 93 | axmap = smalloc(sizeof(*axmap)); |
| 94 | if (!axmap) |
| 95 | return NULL; |
| 96 | |
| 97 | levels = 1; |
| 98 | i = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT; |
| 99 | while (i > 1) { |
| 100 | i = (i + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT; |
| 101 | levels++; |
| 102 | } |
| 103 | |
| 104 | axmap->nr_levels = levels; |
| 105 | axmap->levels = smalloc(axmap->nr_levels * sizeof(struct axmap_level)); |
Jens Axboe | 7ebd796 | 2012-11-28 21:24:46 +0100 | [diff] [blame] | 106 | |
| 107 | for (i = 0; i < axmap->nr_levels; i++) { |
| 108 | struct axmap_level *al = &axmap->levels[i]; |
| 109 | |
| 110 | al->level = i; |
| 111 | al->map_size = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT; |
| 112 | al->map = smalloc(al->map_size * sizeof(unsigned long)); |
| 113 | if (!al->map) |
| 114 | goto err; |
| 115 | |
| 116 | nr_bits = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT; |
| 117 | } |
| 118 | |
| 119 | axmap_reset(axmap); |
| 120 | return axmap; |
| 121 | err: |
| 122 | for (i = 0; i < axmap->nr_levels; i++) |
| 123 | if (axmap->levels[i].map) |
| 124 | sfree(axmap->levels[i].map); |
| 125 | |
| 126 | sfree(axmap->levels); |
| 127 | return NULL; |
| 128 | } |
| 129 | |
| 130 | static int axmap_handler(struct axmap *axmap, uint64_t bit_nr, |
| 131 | int (*func)(struct axmap_level *, unsigned long, unsigned int, |
| 132 | void *), void *data) |
| 133 | { |
| 134 | struct axmap_level *al; |
| 135 | int i; |
| 136 | |
| 137 | for (i = 0; i < axmap->nr_levels; i++) { |
| 138 | unsigned long index = ulog64(bit_nr, i); |
| 139 | unsigned long offset = index >> UNIT_SHIFT; |
| 140 | unsigned int bit = index & BLOCKS_PER_UNIT_MASK; |
| 141 | |
| 142 | al = &axmap->levels[i]; |
| 143 | |
| 144 | if (func(al, offset, bit, data)) |
| 145 | return 1; |
| 146 | } |
| 147 | |
| 148 | return 0; |
| 149 | } |
| 150 | |
| 151 | static int axmap_handler_topdown(struct axmap *axmap, uint64_t bit_nr, |
| 152 | int (*func)(struct axmap_level *, unsigned long, unsigned int, void *), |
| 153 | void *data) |
| 154 | { |
| 155 | struct axmap_level *al; |
| 156 | int i, level = axmap->nr_levels; |
| 157 | |
| 158 | for (i = axmap->nr_levels - 1; i >= 0; i--) { |
| 159 | unsigned long index = ulog64(bit_nr, --level); |
| 160 | unsigned long offset = index >> UNIT_SHIFT; |
| 161 | unsigned int bit = index & BLOCKS_PER_UNIT_MASK; |
| 162 | |
| 163 | al = &axmap->levels[i]; |
| 164 | |
| 165 | if (func(al, offset, bit, data)) |
| 166 | return 1; |
| 167 | } |
| 168 | |
| 169 | return 0; |
| 170 | } |
| 171 | |
| 172 | static int axmap_clear_fn(struct axmap_level *al, unsigned long offset, |
| 173 | unsigned int bit, void *unused) |
| 174 | { |
| 175 | if (!(al->map[offset] & (1UL << bit))) |
| 176 | return 1; |
| 177 | |
| 178 | al->map[offset] &= ~(1UL << bit); |
| 179 | return 0; |
| 180 | } |
| 181 | |
| 182 | void axmap_clear(struct axmap *axmap, uint64_t bit_nr) |
| 183 | { |
| 184 | axmap_handler(axmap, bit_nr, axmap_clear_fn, NULL); |
| 185 | } |
| 186 | |
| 187 | struct axmap_set_data { |
| 188 | unsigned int nr_bits; |
| 189 | unsigned int set_bits; |
| 190 | unsigned int fail_ok; |
| 191 | }; |
| 192 | |
| 193 | static unsigned long bit_masks[] = { |
| 194 | 0x0000000000000000, 0x0000000000000001, 0x0000000000000003, 0x0000000000000007, |
| 195 | 0x000000000000000f, 0x000000000000001f, 0x000000000000003f, 0x000000000000007f, |
| 196 | 0x00000000000000ff, 0x00000000000001ff, 0x00000000000003ff, 0x00000000000007ff, |
| 197 | 0x0000000000000fff, 0x0000000000001fff, 0x0000000000003fff, 0x0000000000007fff, |
| 198 | 0x000000000000ffff, 0x000000000001ffff, 0x000000000003ffff, 0x000000000007ffff, |
| 199 | 0x00000000000fffff, 0x00000000001fffff, 0x00000000003fffff, 0x00000000007fffff, |
| 200 | 0x0000000000ffffff, 0x0000000001ffffff, 0x0000000003ffffff, 0x0000000007ffffff, |
| 201 | 0x000000000fffffff, 0x000000001fffffff, 0x000000003fffffff, 0x000000007fffffff, |
| 202 | 0x00000000ffffffff, |
| 203 | #if BITS_PER_LONG == 64 |
| 204 | 0x00000001ffffffff, 0x00000003ffffffff, 0x00000007ffffffff, 0x0000000fffffffff, |
| 205 | 0x0000001fffffffff, 0x0000003fffffffff, 0x0000007fffffffff, 0x000000ffffffffff, |
| 206 | 0x000001ffffffffff, 0x000003ffffffffff, 0x000007ffffffffff, 0x00000fffffffffff, |
| 207 | 0x00001fffffffffff, 0x00003fffffffffff, 0x00007fffffffffff, 0x0000ffffffffffff, |
| 208 | 0x0001ffffffffffff, 0x0003ffffffffffff, 0x0007ffffffffffff, 0x000fffffffffffff, |
| 209 | 0x001fffffffffffff, 0x003fffffffffffff, 0x007fffffffffffff, 0x00ffffffffffffff, |
| 210 | 0x01ffffffffffffff, 0x03ffffffffffffff, 0x07ffffffffffffff, 0x0fffffffffffffff, |
| 211 | 0x1fffffffffffffff, 0x3fffffffffffffff, 0x7fffffffffffffff, 0xffffffffffffffff |
| 212 | #endif |
| 213 | }; |
| 214 | |
| 215 | static int axmap_set_fn(struct axmap_level *al, unsigned long offset, |
| 216 | unsigned int bit, void *__data) |
| 217 | { |
| 218 | struct axmap_set_data *data = __data; |
| 219 | unsigned long mask, overlap; |
| 220 | unsigned int nr_bits; |
| 221 | |
| 222 | nr_bits = min(data->nr_bits, BLOCKS_PER_UNIT - bit); |
| 223 | |
| 224 | mask = bit_masks[nr_bits] << bit; |
| 225 | |
| 226 | /* |
| 227 | * Mask off any potential overlap, only sets contig regions |
| 228 | */ |
| 229 | overlap = al->map[offset] & mask; |
| 230 | if (overlap == mask) { |
| 231 | assert(data->fail_ok); |
| 232 | return 1; |
| 233 | } |
| 234 | |
| 235 | while (overlap) { |
| 236 | unsigned long clear_mask = ~(1UL << ffz(~overlap)); |
| 237 | |
| 238 | mask &= clear_mask; |
| 239 | overlap &= clear_mask; |
| 240 | nr_bits--; |
| 241 | } |
| 242 | |
| 243 | assert(mask); |
| 244 | assert(!(al->map[offset] & mask)); |
| 245 | |
| 246 | al->map[offset] |= mask; |
| 247 | |
| 248 | if (!al->level) |
| 249 | data->set_bits = nr_bits; |
| 250 | |
| 251 | data->nr_bits = 1; |
| 252 | return al->map[offset] != -1UL; |
| 253 | } |
| 254 | |
| 255 | static void __axmap_set(struct axmap *axmap, uint64_t bit_nr, |
| 256 | struct axmap_set_data *data) |
| 257 | { |
| 258 | unsigned int set_bits, nr_bits = data->nr_bits; |
| 259 | |
| 260 | if (axmap->first_free >= bit_nr && |
| 261 | axmap->first_free < bit_nr + data->nr_bits) |
| 262 | axmap->first_free = -1ULL; |
| 263 | |
| 264 | set_bits = 0; |
| 265 | while (nr_bits) { |
| 266 | axmap_handler(axmap, bit_nr, axmap_set_fn, data); |
| 267 | set_bits += data->set_bits; |
| 268 | |
| 269 | if (data->set_bits != (BLOCKS_PER_UNIT - nr_bits)) |
| 270 | break; |
| 271 | |
| 272 | nr_bits -= data->set_bits; |
| 273 | bit_nr += data->set_bits; |
| 274 | |
| 275 | data->nr_bits = nr_bits; |
| 276 | data->fail_ok = 1; |
| 277 | } |
| 278 | |
| 279 | data->set_bits = set_bits; |
| 280 | } |
| 281 | |
| 282 | void axmap_set(struct axmap *axmap, uint64_t bit_nr) |
| 283 | { |
| 284 | struct axmap_set_data data = { .nr_bits = 1, }; |
| 285 | |
| 286 | __axmap_set(axmap, bit_nr, &data); |
| 287 | } |
| 288 | |
| 289 | unsigned int axmap_set_nr(struct axmap *axmap, uint64_t bit_nr, unsigned int nr_bits) |
| 290 | { |
| 291 | struct axmap_set_data data = { .nr_bits = nr_bits, }; |
| 292 | |
| 293 | __axmap_set(axmap, bit_nr, &data); |
| 294 | return data.set_bits; |
| 295 | } |
| 296 | |
| 297 | static int axmap_isset_fn(struct axmap_level *al, unsigned long offset, |
| 298 | unsigned int bit, void *unused) |
| 299 | { |
| 300 | return (al->map[offset] & (1UL << bit)) != 0; |
| 301 | } |
| 302 | |
| 303 | int axmap_isset(struct axmap *axmap, uint64_t bit_nr) |
| 304 | { |
| 305 | return axmap_handler_topdown(axmap, bit_nr, axmap_isset_fn, NULL); |
| 306 | } |
| 307 | |
| 308 | static uint64_t axmap_find_first_free(struct axmap *axmap, unsigned int level, |
| 309 | uint64_t index) |
| 310 | { |
| 311 | unsigned long j; |
Jens Axboe | 55348b4 | 2013-01-23 10:15:05 -0700 | [diff] [blame] | 312 | int i, found = 0; |
Jens Axboe | 7ebd796 | 2012-11-28 21:24:46 +0100 | [diff] [blame] | 313 | |
| 314 | /* |
| 315 | * Start at the bottom, then converge towards first free bit at the top |
| 316 | */ |
| 317 | for (i = level; i >= 0; i--) { |
| 318 | struct axmap_level *al = &axmap->levels[i]; |
| 319 | |
| 320 | if (index >= al->map_size) { |
| 321 | index = -1ULL; |
| 322 | break; |
| 323 | } |
| 324 | |
| 325 | for (j = index; j < al->map_size; j++) { |
| 326 | if (al->map[j] == -1UL) |
| 327 | continue; |
| 328 | |
| 329 | /* |
| 330 | * First free bit here is our index into the first |
| 331 | * free bit at the next higher level |
| 332 | */ |
| 333 | index = (j << UNIT_SHIFT) + ffz(al->map[j]); |
Jens Axboe | 55348b4 | 2013-01-23 10:15:05 -0700 | [diff] [blame] | 334 | found = 1; |
Jens Axboe | 7ebd796 | 2012-11-28 21:24:46 +0100 | [diff] [blame] | 335 | break; |
| 336 | } |
| 337 | } |
| 338 | |
Jens Axboe | 55348b4 | 2013-01-23 10:15:05 -0700 | [diff] [blame] | 339 | return found ? index : (uint64_t) -1ULL; |
Jens Axboe | 7ebd796 | 2012-11-28 21:24:46 +0100 | [diff] [blame] | 340 | } |
| 341 | |
| 342 | uint64_t axmap_first_free(struct axmap *axmap) |
| 343 | { |
| 344 | if (firstfree_valid(axmap)) |
| 345 | return axmap->first_free; |
| 346 | |
| 347 | axmap->first_free = axmap_find_first_free(axmap, axmap->nr_levels - 1, 0); |
| 348 | return axmap->first_free; |
| 349 | } |
| 350 | |
| 351 | struct axmap_next_free_data { |
| 352 | unsigned int level; |
| 353 | unsigned long offset; |
| 354 | uint64_t bit; |
| 355 | }; |
| 356 | |
| 357 | static int axmap_next_free_fn(struct axmap_level *al, unsigned long offset, |
| 358 | unsigned int bit, void *__data) |
| 359 | { |
| 360 | struct axmap_next_free_data *data = __data; |
| 361 | uint64_t mask = ~((1UL << ((data->bit & BLOCKS_PER_UNIT_MASK) + 1)) - 1); |
| 362 | |
| 363 | if (!(mask & al->map[offset])) |
| 364 | return 0; |
| 365 | |
| 366 | if (al->map[offset] != -1UL) { |
| 367 | data->level = al->level; |
| 368 | data->offset = offset; |
| 369 | return 1; |
| 370 | } |
| 371 | |
| 372 | data->bit = (data->bit + BLOCKS_PER_UNIT - 1) / BLOCKS_PER_UNIT; |
| 373 | return 0; |
| 374 | } |
| 375 | |
| 376 | /* |
| 377 | * 'bit_nr' is already set. Find the next free bit after this one. |
| 378 | */ |
| 379 | uint64_t axmap_next_free(struct axmap *axmap, uint64_t bit_nr) |
| 380 | { |
| 381 | struct axmap_next_free_data data = { .level = -1U, .bit = bit_nr, }; |
| 382 | |
| 383 | if (firstfree_valid(axmap) && bit_nr < axmap->first_free) |
| 384 | return axmap->first_free; |
| 385 | |
| 386 | if (!axmap_handler(axmap, bit_nr, axmap_next_free_fn, &data)) |
| 387 | return axmap_first_free(axmap); |
| 388 | |
| 389 | assert(data.level != -1U); |
| 390 | |
| 391 | return axmap_find_first_free(axmap, data.level, data.offset); |
| 392 | } |