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.
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 existence
9 * becomes cheaper (since fewer layers are walked, making it a lot more
10 * cache friendly) and locating the next free space likewise.
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.
23 #include "../arch/arch.h"
25 #include "../minmax.h"
27 #if BITS_PER_LONG == 64
29 #elif BITS_PER_LONG == 32
32 #error "Number of arch bits unknown"
35 #define BLOCKS_PER_UNIT (1U << UNIT_SHIFT)
36 #define BLOCKS_PER_UNIT_MASK (BLOCKS_PER_UNIT - 1)
38 #define firstfree_valid(b) ((b)->first_free != (uint64_t) -1)
42 unsigned long map_size;
47 unsigned int nr_levels;
48 struct axmap_level *levels;
53 static unsigned long ulog64(unsigned long val, unsigned int log)
61 void axmap_reset(struct axmap *axmap)
65 for (i = 0; i < axmap->nr_levels; i++) {
66 struct axmap_level *al = &axmap->levels[i];
68 memset(al->map, 0, al->map_size * sizeof(unsigned long));
71 axmap->first_free = 0;
74 void axmap_free(struct axmap *axmap)
81 for (i = 0; i < axmap->nr_levels; i++)
82 free(axmap->levels[i].map);
88 struct axmap *axmap_new(unsigned long nr_bits)
91 unsigned int i, levels;
93 axmap = malloc(sizeof(*axmap));
98 i = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
100 i = (i + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
104 axmap->nr_levels = levels;
105 axmap->levels = calloc(axmap->nr_levels, sizeof(struct axmap_level));
106 axmap->nr_bits = nr_bits;
108 for (i = 0; i < axmap->nr_levels; i++) {
109 struct axmap_level *al = &axmap->levels[i];
112 al->map_size = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
113 al->map = malloc(al->map_size * sizeof(unsigned long));
117 nr_bits = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
123 for (i = 0; i < axmap->nr_levels; i++)
124 if (axmap->levels[i].map)
125 free(axmap->levels[i].map);
132 static bool axmap_handler(struct axmap *axmap, uint64_t bit_nr,
133 bool (*func)(struct axmap_level *, unsigned long, unsigned int,
136 struct axmap_level *al;
139 for (i = 0; i < axmap->nr_levels; i++) {
140 unsigned long index = ulog64(bit_nr, i);
141 unsigned long offset = index >> UNIT_SHIFT;
142 unsigned int bit = index & BLOCKS_PER_UNIT_MASK;
144 al = &axmap->levels[i];
146 if (func(al, offset, bit, data))
153 static bool axmap_handler_topdown(struct axmap *axmap, uint64_t bit_nr,
154 bool (*func)(struct axmap_level *, unsigned long, unsigned int, void *),
157 struct axmap_level *al;
158 int i, level = axmap->nr_levels;
160 for (i = axmap->nr_levels - 1; i >= 0; i--) {
161 unsigned long index = ulog64(bit_nr, --level);
162 unsigned long offset = index >> UNIT_SHIFT;
163 unsigned int bit = index & BLOCKS_PER_UNIT_MASK;
165 al = &axmap->levels[i];
167 if (func(al, offset, bit, data))
174 static bool axmap_clear_fn(struct axmap_level *al, unsigned long offset,
175 unsigned int bit, void *unused)
177 if (!(al->map[offset] & (1UL << bit)))
180 al->map[offset] &= ~(1UL << bit);
184 void axmap_clear(struct axmap *axmap, uint64_t bit_nr)
186 axmap_handler(axmap, bit_nr, axmap_clear_fn, NULL);
188 if (bit_nr < axmap->first_free)
189 axmap->first_free = bit_nr;
192 struct axmap_set_data {
193 unsigned int nr_bits;
194 unsigned int set_bits;
197 static const unsigned long bit_masks[] = {
198 0x0000000000000000, 0x0000000000000001, 0x0000000000000003, 0x0000000000000007,
199 0x000000000000000f, 0x000000000000001f, 0x000000000000003f, 0x000000000000007f,
200 0x00000000000000ff, 0x00000000000001ff, 0x00000000000003ff, 0x00000000000007ff,
201 0x0000000000000fff, 0x0000000000001fff, 0x0000000000003fff, 0x0000000000007fff,
202 0x000000000000ffff, 0x000000000001ffff, 0x000000000003ffff, 0x000000000007ffff,
203 0x00000000000fffff, 0x00000000001fffff, 0x00000000003fffff, 0x00000000007fffff,
204 0x0000000000ffffff, 0x0000000001ffffff, 0x0000000003ffffff, 0x0000000007ffffff,
205 0x000000000fffffff, 0x000000001fffffff, 0x000000003fffffff, 0x000000007fffffff,
207 #if BITS_PER_LONG == 64
208 0x00000001ffffffff, 0x00000003ffffffff, 0x00000007ffffffff, 0x0000000fffffffff,
209 0x0000001fffffffff, 0x0000003fffffffff, 0x0000007fffffffff, 0x000000ffffffffff,
210 0x000001ffffffffff, 0x000003ffffffffff, 0x000007ffffffffff, 0x00000fffffffffff,
211 0x00001fffffffffff, 0x00003fffffffffff, 0x00007fffffffffff, 0x0000ffffffffffff,
212 0x0001ffffffffffff, 0x0003ffffffffffff, 0x0007ffffffffffff, 0x000fffffffffffff,
213 0x001fffffffffffff, 0x003fffffffffffff, 0x007fffffffffffff, 0x00ffffffffffffff,
214 0x01ffffffffffffff, 0x03ffffffffffffff, 0x07ffffffffffffff, 0x0fffffffffffffff,
215 0x1fffffffffffffff, 0x3fffffffffffffff, 0x7fffffffffffffff, 0xffffffffffffffff
219 static bool axmap_set_fn(struct axmap_level *al, unsigned long offset,
220 unsigned int bit, void *__data)
222 struct axmap_set_data *data = __data;
223 unsigned long mask, overlap;
224 unsigned int nr_bits;
226 nr_bits = min(data->nr_bits, BLOCKS_PER_UNIT - bit);
228 mask = bit_masks[nr_bits] << bit;
231 * Mask off any potential overlap, only sets contig regions
233 overlap = al->map[offset] & mask;
238 const int __bit = ffz(~overlap);
243 nr_bits = __bit - bit;
244 mask = bit_masks[nr_bits] << bit;
248 assert(!(al->map[offset] & mask));
249 al->map[offset] |= mask;
252 data->set_bits = nr_bits;
255 return al->map[offset] != -1UL;
258 static void __axmap_set(struct axmap *axmap, uint64_t bit_nr,
259 struct axmap_set_data *data)
261 unsigned int set_bits, nr_bits = data->nr_bits;
263 if (axmap->first_free >= bit_nr &&
264 axmap->first_free < bit_nr + data->nr_bits)
265 axmap->first_free = -1ULL;
267 if (bit_nr > axmap->nr_bits)
269 else if (bit_nr + nr_bits > axmap->nr_bits)
270 nr_bits = axmap->nr_bits - bit_nr;
274 axmap_handler(axmap, bit_nr, axmap_set_fn, data);
275 set_bits += data->set_bits;
277 if (!data->set_bits ||
278 data->set_bits != (BLOCKS_PER_UNIT - nr_bits))
281 nr_bits -= data->set_bits;
282 bit_nr += data->set_bits;
284 data->nr_bits = nr_bits;
287 data->set_bits = set_bits;
290 void axmap_set(struct axmap *axmap, uint64_t bit_nr)
292 struct axmap_set_data data = { .nr_bits = 1, };
294 __axmap_set(axmap, bit_nr, &data);
297 unsigned int axmap_set_nr(struct axmap *axmap, uint64_t bit_nr,
298 unsigned int nr_bits)
300 unsigned int set_bits = 0;
303 struct axmap_set_data data = { .nr_bits = nr_bits, };
304 unsigned int max_bits, this_set;
306 max_bits = BLOCKS_PER_UNIT - (bit_nr & BLOCKS_PER_UNIT_MASK);
307 if (max_bits < nr_bits)
308 data.nr_bits = max_bits;
310 this_set = data.nr_bits;
311 __axmap_set(axmap, bit_nr, &data);
312 set_bits += data.set_bits;
313 if (data.set_bits != this_set)
316 nr_bits -= data.set_bits;
317 bit_nr += data.set_bits;
323 static bool axmap_isset_fn(struct axmap_level *al, unsigned long offset,
324 unsigned int bit, void *unused)
326 return (al->map[offset] & (1UL << bit)) != 0;
329 bool axmap_isset(struct axmap *axmap, uint64_t bit_nr)
331 if (bit_nr <= axmap->nr_bits)
332 return axmap_handler_topdown(axmap, bit_nr, axmap_isset_fn, NULL);
337 static uint64_t axmap_find_first_free(struct axmap *axmap, unsigned int level,
340 uint64_t ret = -1ULL;
345 * Start at the bottom, then converge towards first free bit at the top
347 for (i = level; i >= 0; i--) {
348 struct axmap_level *al = &axmap->levels[i];
351 * Clear 'ret', this is a bug condition.
353 if (index >= al->map_size) {
358 for (j = index; j < al->map_size; j++) {
359 if (al->map[j] == -1UL)
363 * First free bit here is our index into the first
364 * free bit at the next higher level
366 ret = index = (j << UNIT_SHIFT) + ffz(al->map[j]);
371 if (ret < axmap->nr_bits)
374 return (uint64_t) -1ULL;
377 static uint64_t axmap_first_free(struct axmap *axmap)
379 if (!firstfree_valid(axmap))
380 axmap->first_free = axmap_find_first_free(axmap, axmap->nr_levels - 1, 0);
382 return axmap->first_free;
385 struct axmap_next_free_data {
387 unsigned long offset;
391 static bool axmap_next_free_fn(struct axmap_level *al, unsigned long offset,
392 unsigned int bit, void *__data)
394 struct axmap_next_free_data *data = __data;
395 uint64_t mask = ~bit_masks[(data->bit + 1) & BLOCKS_PER_UNIT_MASK];
397 if (!(mask & ~al->map[offset]))
400 if (al->map[offset] != -1UL) {
401 data->level = al->level;
402 data->offset = offset;
406 data->bit = (data->bit + BLOCKS_PER_UNIT - 1) / BLOCKS_PER_UNIT;
411 * 'bit_nr' is already set. Find the next free bit after this one.
413 uint64_t axmap_next_free(struct axmap *axmap, uint64_t bit_nr)
415 struct axmap_next_free_data data = { .level = -1U, .bit = bit_nr, };
418 if (firstfree_valid(axmap) && bit_nr < axmap->first_free)
419 return axmap->first_free;
421 if (!axmap_handler(axmap, bit_nr, axmap_next_free_fn, &data))
422 return axmap_first_free(axmap);
424 assert(data.level != -1U);
427 * In the rare case that the map is unaligned, we might end up
428 * finding an offset that's beyond the valid end. For that case,
429 * find the first free one, the map is practically full.
431 ret = axmap_find_first_free(axmap, data.level, data.offset);
435 return axmap_first_free(axmap);