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 = malloc(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 unsigned long clear_mask = ~(1UL << ffz(~overlap));
241 overlap &= clear_mask;
246 assert(!(al->map[offset] & mask));
248 al->map[offset] |= mask;
251 data->set_bits = nr_bits;
254 return al->map[offset] != -1UL;
257 static void __axmap_set(struct axmap *axmap, uint64_t bit_nr,
258 struct axmap_set_data *data)
260 unsigned int set_bits, nr_bits = data->nr_bits;
262 if (axmap->first_free >= bit_nr &&
263 axmap->first_free < bit_nr + data->nr_bits)
264 axmap->first_free = -1ULL;
266 if (bit_nr > axmap->nr_bits)
268 else if (bit_nr + nr_bits > axmap->nr_bits)
269 nr_bits = axmap->nr_bits - bit_nr;
273 axmap_handler(axmap, bit_nr, axmap_set_fn, data);
274 set_bits += data->set_bits;
276 if (!data->set_bits ||
277 data->set_bits != (BLOCKS_PER_UNIT - nr_bits))
280 nr_bits -= data->set_bits;
281 bit_nr += data->set_bits;
283 data->nr_bits = nr_bits;
286 data->set_bits = set_bits;
289 void axmap_set(struct axmap *axmap, uint64_t bit_nr)
291 struct axmap_set_data data = { .nr_bits = 1, };
293 __axmap_set(axmap, bit_nr, &data);
296 unsigned int axmap_set_nr(struct axmap *axmap, uint64_t bit_nr,
297 unsigned int nr_bits)
299 unsigned int set_bits = 0;
302 struct axmap_set_data data = { .nr_bits = nr_bits, };
303 unsigned int max_bits, this_set;
305 max_bits = BLOCKS_PER_UNIT - (bit_nr & BLOCKS_PER_UNIT_MASK);
306 if (max_bits < nr_bits)
307 data.nr_bits = max_bits;
309 this_set = data.nr_bits;
310 __axmap_set(axmap, bit_nr, &data);
311 set_bits += data.set_bits;
312 if (data.set_bits != this_set)
315 nr_bits -= data.set_bits;
316 bit_nr += data.set_bits;
322 static bool axmap_isset_fn(struct axmap_level *al, unsigned long offset,
323 unsigned int bit, void *unused)
325 return (al->map[offset] & (1UL << bit)) != 0;
328 bool axmap_isset(struct axmap *axmap, uint64_t bit_nr)
330 if (bit_nr <= axmap->nr_bits)
331 return axmap_handler_topdown(axmap, bit_nr, axmap_isset_fn, NULL);
336 static uint64_t axmap_find_first_free(struct axmap *axmap, unsigned int level,
339 uint64_t ret = -1ULL;
344 * Start at the bottom, then converge towards first free bit at the top
346 for (i = level; i >= 0; i--) {
347 struct axmap_level *al = &axmap->levels[i];
350 * Clear 'ret', this is a bug condition.
352 if (index >= al->map_size) {
357 for (j = index; j < al->map_size; j++) {
358 if (al->map[j] == -1UL)
362 * First free bit here is our index into the first
363 * free bit at the next higher level
365 ret = index = (j << UNIT_SHIFT) + ffz(al->map[j]);
370 if (ret < axmap->nr_bits)
373 return (uint64_t) -1ULL;
376 static uint64_t axmap_first_free(struct axmap *axmap)
378 if (!firstfree_valid(axmap))
379 axmap->first_free = axmap_find_first_free(axmap, axmap->nr_levels - 1, 0);
381 return axmap->first_free;
384 struct axmap_next_free_data {
386 unsigned long offset;
390 static bool axmap_next_free_fn(struct axmap_level *al, unsigned long offset,
391 unsigned int bit, void *__data)
393 struct axmap_next_free_data *data = __data;
394 uint64_t mask = ~bit_masks[(data->bit + 1) & BLOCKS_PER_UNIT_MASK];
396 if (!(mask & ~al->map[offset]))
399 if (al->map[offset] != -1UL) {
400 data->level = al->level;
401 data->offset = offset;
405 data->bit = (data->bit + BLOCKS_PER_UNIT - 1) / BLOCKS_PER_UNIT;
410 * 'bit_nr' is already set. Find the next free bit after this one.
412 uint64_t axmap_next_free(struct axmap *axmap, uint64_t bit_nr)
414 struct axmap_next_free_data data = { .level = -1U, .bit = bit_nr, };
417 if (firstfree_valid(axmap) && bit_nr < axmap->first_free)
418 return axmap->first_free;
420 if (!axmap_handler(axmap, bit_nr, axmap_next_free_fn, &data))
421 return axmap_first_free(axmap);
423 assert(data.level != -1U);
426 * In the rare case that the map is unaligned, we might end up
427 * finding an offset that's beyond the valid end. For that case,
428 * find the first free one, the map is practically full.
430 ret = axmap_find_first_free(axmap, data.level, data.offset);
434 return axmap_first_free(axmap);