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 existance
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 "../smalloc.h"
26 #include "../minmax.h"
28 #if BITS_PER_LONG == 64
30 #elif BITS_PER_LONG == 32
33 #error "Number of arch bits unknown"
36 #define BLOCKS_PER_UNIT (1UL << UNIT_SHIFT)
37 #define BLOCKS_PER_UNIT_MASK (BLOCKS_PER_UNIT - 1)
39 #define firstfree_valid(b) ((b)->first_free != (uint64_t) -1)
43 unsigned long map_size;
48 unsigned int nr_levels;
49 struct axmap_level *levels;
54 static unsigned long ulog64(unsigned long val, unsigned int log)
62 void axmap_reset(struct axmap *axmap)
66 for (i = 0; i < axmap->nr_levels; i++) {
67 struct axmap_level *al = &axmap->levels[i];
69 memset(al->map, 0, al->map_size * sizeof(unsigned long));
72 axmap->first_free = 0;
75 void axmap_free(struct axmap *axmap)
82 for (i = 0; i < axmap->nr_levels; i++)
83 sfree(axmap->levels[i].map);
89 struct axmap *axmap_new(unsigned long nr_bits)
92 unsigned int i, levels;
94 axmap = smalloc(sizeof(*axmap));
99 i = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
101 i = (i + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
105 axmap->nr_levels = levels;
106 axmap->levels = smalloc(axmap->nr_levels * sizeof(struct axmap_level));
107 axmap->nr_bits = nr_bits;
109 for (i = 0; i < axmap->nr_levels; i++) {
110 struct axmap_level *al = &axmap->levels[i];
113 al->map_size = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
114 al->map = smalloc(al->map_size * sizeof(unsigned long));
118 nr_bits = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
124 for (i = 0; i < axmap->nr_levels; i++)
125 if (axmap->levels[i].map)
126 sfree(axmap->levels[i].map);
128 sfree(axmap->levels);
132 static int axmap_handler(struct axmap *axmap, uint64_t bit_nr,
133 int (*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 int axmap_handler_topdown(struct axmap *axmap, uint64_t bit_nr,
154 int (*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 int 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);
189 struct axmap_set_data {
190 unsigned int nr_bits;
191 unsigned int set_bits;
192 unsigned int fail_ok;
195 static unsigned long bit_masks[] = {
196 0x0000000000000000, 0x0000000000000001, 0x0000000000000003, 0x0000000000000007,
197 0x000000000000000f, 0x000000000000001f, 0x000000000000003f, 0x000000000000007f,
198 0x00000000000000ff, 0x00000000000001ff, 0x00000000000003ff, 0x00000000000007ff,
199 0x0000000000000fff, 0x0000000000001fff, 0x0000000000003fff, 0x0000000000007fff,
200 0x000000000000ffff, 0x000000000001ffff, 0x000000000003ffff, 0x000000000007ffff,
201 0x00000000000fffff, 0x00000000001fffff, 0x00000000003fffff, 0x00000000007fffff,
202 0x0000000000ffffff, 0x0000000001ffffff, 0x0000000003ffffff, 0x0000000007ffffff,
203 0x000000000fffffff, 0x000000001fffffff, 0x000000003fffffff, 0x000000007fffffff,
205 #if BITS_PER_LONG == 64
206 0x00000001ffffffff, 0x00000003ffffffff, 0x00000007ffffffff, 0x0000000fffffffff,
207 0x0000001fffffffff, 0x0000003fffffffff, 0x0000007fffffffff, 0x000000ffffffffff,
208 0x000001ffffffffff, 0x000003ffffffffff, 0x000007ffffffffff, 0x00000fffffffffff,
209 0x00001fffffffffff, 0x00003fffffffffff, 0x00007fffffffffff, 0x0000ffffffffffff,
210 0x0001ffffffffffff, 0x0003ffffffffffff, 0x0007ffffffffffff, 0x000fffffffffffff,
211 0x001fffffffffffff, 0x003fffffffffffff, 0x007fffffffffffff, 0x00ffffffffffffff,
212 0x01ffffffffffffff, 0x03ffffffffffffff, 0x07ffffffffffffff, 0x0fffffffffffffff,
213 0x1fffffffffffffff, 0x3fffffffffffffff, 0x7fffffffffffffff, 0xffffffffffffffff
217 static int axmap_set_fn(struct axmap_level *al, unsigned long offset,
218 unsigned int bit, void *__data)
220 struct axmap_set_data *data = __data;
221 unsigned long mask, overlap;
222 unsigned int nr_bits;
224 nr_bits = min(data->nr_bits, BLOCKS_PER_UNIT - bit);
226 mask = bit_masks[nr_bits] << bit;
229 * Mask off any potential overlap, only sets contig regions
231 overlap = al->map[offset] & mask;
232 if (overlap == mask) {
233 assert(data->fail_ok);
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 != (BLOCKS_PER_UNIT - nr_bits))
279 nr_bits -= data->set_bits;
280 bit_nr += data->set_bits;
282 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, unsigned int nr_bits)
298 struct axmap_set_data data = { .nr_bits = nr_bits, };
300 __axmap_set(axmap, bit_nr, &data);
301 return data.set_bits;
304 static int axmap_isset_fn(struct axmap_level *al, unsigned long offset,
305 unsigned int bit, void *unused)
307 return (al->map[offset] & (1UL << bit)) != 0;
310 int axmap_isset(struct axmap *axmap, uint64_t bit_nr)
312 if (bit_nr <= axmap->nr_bits)
313 return axmap_handler_topdown(axmap, bit_nr, axmap_isset_fn, NULL);
318 static uint64_t axmap_find_first_free(struct axmap *axmap, unsigned int level,
321 uint64_t ret = -1ULL;
326 * Start at the bottom, then converge towards first free bit at the top
328 for (i = level; i >= 0; i--) {
329 struct axmap_level *al = &axmap->levels[i];
332 * Clear 'ret', this is a bug condition.
334 if (index >= al->map_size) {
339 for (j = index; j < al->map_size; j++) {
340 if (al->map[j] == -1UL)
344 * First free bit here is our index into the first
345 * free bit at the next higher level
347 ret = index = (j << UNIT_SHIFT) + ffz(al->map[j]);
352 if (ret < axmap->nr_bits)
355 return (uint64_t) -1ULL;
358 uint64_t axmap_first_free(struct axmap *axmap)
360 if (firstfree_valid(axmap))
361 return axmap->first_free;
363 axmap->first_free = axmap_find_first_free(axmap, axmap->nr_levels - 1, 0);
364 return axmap->first_free;
367 struct axmap_next_free_data {
369 unsigned long offset;
373 static int axmap_next_free_fn(struct axmap_level *al, unsigned long offset,
374 unsigned int bit, void *__data)
376 struct axmap_next_free_data *data = __data;
377 uint64_t mask = ~bit_masks[(data->bit + 1) & BLOCKS_PER_UNIT_MASK];
379 if (!(mask & ~al->map[offset]))
382 if (al->map[offset] != -1UL) {
383 data->level = al->level;
384 data->offset = offset;
388 data->bit = (data->bit + BLOCKS_PER_UNIT - 1) / BLOCKS_PER_UNIT;
393 * 'bit_nr' is already set. Find the next free bit after this one.
395 uint64_t axmap_next_free(struct axmap *axmap, uint64_t bit_nr)
397 struct axmap_next_free_data data = { .level = -1U, .bit = bit_nr, };
400 if (firstfree_valid(axmap) && bit_nr < axmap->first_free)
401 return axmap->first_free;
403 if (!axmap_handler(axmap, bit_nr, axmap_next_free_fn, &data))
404 return axmap_first_free(axmap);
406 assert(data.level != -1U);
409 * In the rare case that the map is unaligned, we might end up
410 * finding an offset that's beyond the valid end. For that case,
411 * find the first free one, the map is practically full.
413 ret = axmap_find_first_free(axmap, data.level, data.offset);
417 return axmap_first_free(axmap);