7 #include "build_assert/build_assert.h"
11 #define ALIGNOF(t) __alignof__(t)
13 /* Alignment by measuring structure padding. */
14 #define ALIGNOF(t) (sizeof(struct { char c; t _h; }) - 1 - sizeof(t))
17 /* FIXME: Doesn't handle non-page-aligned poolsize. */
20 #define MIN_SIZE (getpagesize() * 2)
22 /* What's the granularity of sub-page allocs? */
23 #define BITMAP_GRANULARITY 4
27 * file := pagestates pad metadata
28 * pagestates := pages * 2-bits-per-page
29 * pad := pad to next ALIGNOF(metadata)
31 * metadata := metalen next-ptr metabits
32 * metabits := freeblock | bitblock
34 * bitblock := 2-bits-per-bit-in-page 1
38 /* Length (after this header). (FIXME: implied by page bits!). */
39 unsigned long metalen;
40 /* Next meta header, or 0 */
42 /* Bits start here. */
45 /* Assumes a is a power of two. */
46 static unsigned long align_up(unsigned long x, unsigned long a)
48 return (x + a - 1) & ~(a - 1);
51 static unsigned long div_up(unsigned long x, unsigned long a)
53 return (x + a - 1) / a;
56 /* It turns out that we spend a lot of time dealing with bit pairs.
57 * These routines manipulate them.
59 static uint8_t get_bit_pair(const uint8_t *bits, unsigned long index)
61 return bits[index * 2 / CHAR_BIT] >> (index * 2 % CHAR_BIT) & 3;
64 static void set_bit_pair(uint8_t *bits, unsigned long index, uint8_t val)
66 bits[index * 2 / CHAR_BIT] &= ~(3 << (index * 2 % CHAR_BIT));
67 bits[index * 2 / CHAR_BIT] |= (val << (index * 2 % CHAR_BIT));
70 /* This is used for page states and subpage allocations */
76 SPECIAL, /* Sub-page allocation for page states. */
79 /* The types for subpage metadata. */
80 enum sub_metadata_type
82 /* FREE is same as alloc state */
86 /* Page states are represented by bitpairs, at the start of the pool. */
87 #define BITS_PER_PAGE 2
89 static enum alloc_state get_page_state(const void *pool, unsigned long page)
91 return get_bit_pair(pool, page);
94 static void set_page_state(void *pool, unsigned long page, enum alloc_state s)
96 set_bit_pair(pool, page, s);
99 /* The offset of metadata for a subpage allocation is found at the end
101 #define SUBPAGE_METAOFF (getpagesize() - sizeof(unsigned long))
103 /* This is the length of metadata in bits. It consists of two bits
104 * for every BITMAP_GRANULARITY of usable bytes in the page, then two
105 * bits for the tailer.. */
106 #define BITMAP_METABITLEN \
107 ((div_up(SUBPAGE_METAOFF, BITMAP_GRANULARITY) + 1) * BITS_PER_PAGE)
109 /* This is the length in bytes. */
110 #define BITMAP_METALEN (div_up(BITMAP_METABITLEN, CHAR_BIT))
112 static struct metaheader *first_mheader(void *pool, unsigned long poolsize)
114 unsigned int pagestatelen;
116 pagestatelen = align_up(div_up(poolsize/getpagesize() * BITS_PER_PAGE,
118 ALIGNOF(struct metaheader));
119 return (struct metaheader *)((char *)pool + pagestatelen);
122 static struct metaheader *next_mheader(void *pool, struct metaheader *mh)
127 return (struct metaheader *)((char *)pool + mh->next);
130 static unsigned long pool_offset(void *pool, void *p)
132 return (char *)p - (char *)pool;
135 void alloc_init(void *pool, unsigned long poolsize)
137 /* FIXME: Alignment assumptions about pool. */
138 unsigned long len, i;
139 struct metaheader *mh;
141 if (poolsize < MIN_SIZE)
144 mh = first_mheader(pool, poolsize);
146 /* len covers all page states, plus the metaheader. */
147 len = (char *)(mh + 1) - (char *)pool;
148 /* Mark all page states FREE */
149 BUILD_ASSERT(FREE == 0);
150 memset(pool, 0, len);
152 /* metaheader len takes us up to next page boundary. */
153 mh->metalen = align_up(len, getpagesize()) - len;
155 /* Mark the pagestate and metadata page(s) allocated. */
156 set_page_state(pool, 0, TAKEN_START);
157 for (i = 1; i < div_up(len, getpagesize()); i++)
158 set_page_state(pool, i, TAKEN);
161 /* Two bits per element, representing page states. Returns -1 on fail. */
162 static long alloc_from_bitmap(uint8_t *bits, unsigned long elems,
163 unsigned long want, unsigned long align)
169 /* We allocate from far end, to increase ability to expand metadata. */
170 for (i = elems - 1; i >= 0; i--) {
171 switch (get_bit_pair(bits, i)) {
173 if (++free >= want) {
176 /* They might ask for large alignment. */
177 if (align && i % align)
180 for (j = i+1; j < i + want; j++)
181 set_bit_pair(bits, j, TAKEN);
182 set_bit_pair(bits, i, TAKEN_START);
197 static unsigned long alloc_get_pages(void *pool, unsigned long poolsize,
198 unsigned long pages, unsigned long align)
204 /* We allocate from far end, to increase ability to expand metadata. */
205 for (i = poolsize / getpagesize() - 1; i >= 0; i--) {
206 switch (get_page_state(pool, i)) {
208 if (++free >= pages) {
209 unsigned long j, addr;
211 addr = (unsigned long)pool + i * getpagesize();
213 /* They might ask for multi-page alignment. */
217 for (j = i+1; j < i + pages; j++)
218 set_page_state(pool, j, TAKEN);
219 set_page_state(pool, i, TAKEN_START);
234 /* Offset to metadata is at end of page. */
235 static unsigned long *metadata_off(void *pool, unsigned long page)
237 return (unsigned long *)
238 ((char *)pool + (page+1)*getpagesize() - sizeof(unsigned long));
241 static uint8_t *get_page_metadata(void *pool, unsigned long page)
243 return (uint8_t *)pool + *metadata_off(pool, page);
246 static void set_page_metadata(void *pool, unsigned long page, uint8_t *meta)
248 *metadata_off(pool, page) = meta - (uint8_t *)pool;
251 static unsigned long sub_page_alloc(void *pool, unsigned long page,
252 unsigned long size, unsigned long align)
254 uint8_t *bits = get_page_metadata(pool, page);
257 /* TAKEN at end means a bitwise alloc. */
258 assert(get_bit_pair(bits, getpagesize()/BITMAP_GRANULARITY-1) == TAKEN);
260 /* Our bits are the same as the page bits. */
261 i = alloc_from_bitmap(bits, SUBPAGE_METAOFF/BITMAP_GRANULARITY,
262 div_up(size, BITMAP_GRANULARITY),
263 align / BITMAP_GRANULARITY);
265 /* Can't allocate? */
269 return page*getpagesize() + i*BITMAP_GRANULARITY;
272 static uint8_t *alloc_metaspace(struct metaheader *mh, unsigned long bytes)
274 uint8_t *meta = (uint8_t *)(mh + 1);
275 unsigned long free = 0, len;
278 /* TAKEN tags end a subpage alloc. */
279 for (i = mh->metalen * CHAR_BIT / BITS_PER_PAGE - 1; i >= 0; i -= len) {
280 switch (get_bit_pair(meta, i)) {
284 if (free == bytes * CHAR_BIT / BITS_PER_PAGE) {
285 /* TAKEN marks end of metablock. */
286 set_page_state(meta, i + free - 1, TAKEN);
287 return meta + i / (CHAR_BIT / BITS_PER_PAGE);
291 /* Skip over this allocated part. */
292 len = BITMAP_METALEN * CHAR_BIT / BITS_PER_PAGE;
303 /* We need this many bytes of metadata. */
304 static uint8_t *new_metadata(void *pool, unsigned long poolsize,
307 struct metaheader *mh, *newmh;
310 for (mh = first_mheader(pool,poolsize); mh; mh = next_mheader(pool,mh)){
311 uint8_t *meta = alloc_metaspace(mh, bytes);
317 /* No room for metadata? Can we expand an existing one? */
318 for (mh = first_mheader(pool,poolsize); mh; mh = next_mheader(pool,mh)){
319 /* It should end on a page boundary. */
320 unsigned long nextpage;
322 nextpage = pool_offset(pool, (char *)(mh + 1) + mh->metalen);
323 assert(nextpage % getpagesize() == 0);
325 /* Now, can we grab that page? */
326 if (get_page_state(pool, nextpage / getpagesize()) != FREE)
329 /* OK, expand metadata, do it again. */
330 set_page_state(pool, nextpage / getpagesize(), TAKEN);
331 BUILD_ASSERT(FREE == 0);
332 memset((char *)pool + nextpage, 0, getpagesize());
333 mh->metalen += getpagesize();
334 return alloc_metaspace(mh, bytes);
337 /* No metadata left at all? */
338 page = alloc_get_pages(pool, poolsize, div_up(bytes, getpagesize()), 1);
342 newmh = (struct metaheader *)((char *)pool + page * getpagesize());
343 newmh->metalen = getpagesize() - sizeof(*mh);
344 BUILD_ASSERT(FREE == 0);
345 memset(newmh + 1, 0, newmh->metalen);
347 /* Sew it into linked list */
348 mh = first_mheader(pool,poolsize);
349 newmh->next = mh->next;
350 mh->next = pool_offset(pool, newmh);
352 return alloc_metaspace(newmh, bytes);
355 static void alloc_free_pages(void *pool, unsigned long pagenum)
357 assert(get_page_state(pool, pagenum) == TAKEN_START);
358 set_page_state(pool, pagenum, FREE);
359 while (get_page_state(pool, ++pagenum) == TAKEN)
360 set_page_state(pool, pagenum, FREE);
363 static unsigned long alloc_sub_page(void *pool, unsigned long poolsize,
364 unsigned long size, unsigned long align)
369 /* Look for partial page. */
370 for (i = 0; i < poolsize / getpagesize(); i++) {
372 if (get_page_state(pool, i) != SPECIAL)
375 ret = sub_page_alloc(pool, i, size, align);
380 /* Create new SUBPAGE page. */
381 i = alloc_get_pages(pool, poolsize, 1, 1);
385 /* Get metadata for page. */
386 metadata = new_metadata(pool, poolsize, BITMAP_METALEN);
388 alloc_free_pages(pool, i);
392 /* Actually, this is a subpage page now. */
393 set_page_state(pool, i, SPECIAL);
395 /* Set metadata pointer for page. */
396 set_page_metadata(pool, i, metadata);
398 /* Do allocation like normal */
399 return sub_page_alloc(pool, i, size, align);
402 /* Returns true if we cleaned any pages. */
403 static bool clean_empty_subpages(void *pool, unsigned long poolsize)
406 bool progress = false;
408 for (i = 0; i < poolsize/getpagesize(); i++) {
411 if (get_page_state(pool, i) != SPECIAL)
414 meta = get_page_metadata(pool, i);
415 for (j = 0; j < SUBPAGE_METAOFF/BITMAP_GRANULARITY; j++)
416 if (get_page_state(meta, j) != FREE)
419 /* So, is this page totally empty? */
420 if (j == SUBPAGE_METAOFF/BITMAP_GRANULARITY) {
421 set_page_state(pool, i, FREE);
428 /* Returns true if we cleaned any pages. */
429 static bool clean_metadata(void *pool, unsigned long poolsize)
431 struct metaheader *mh, *prev_mh = NULL;
432 bool progress = false;
434 for (mh = first_mheader(pool,poolsize); mh; mh = next_mheader(pool,mh)){
438 meta = (uint8_t *)(mh + 1);
439 BUILD_ASSERT(FREE == 0);
440 for (i = mh->metalen - 1; i > 0; i--)
444 /* Completely empty? */
445 if (prev_mh && i == mh->metalen) {
446 alloc_free_pages(pool,
447 pool_offset(pool, mh)/getpagesize());
448 prev_mh->next = mh->next;
454 /* Some pages at end are free? */
455 for (p = (uint8_t *)(mh+1)+mh->metalen - getpagesize();
457 p -= getpagesize()) {
470 void *alloc_get(void *pool, unsigned long poolsize,
471 unsigned long size, unsigned long align)
473 bool subpage_clean = false, metadata_clean = false;
476 if (poolsize < MIN_SIZE)
480 /* Sub-page allocations have an overhead of ~12%. */
481 if (size + size/8 >= getpagesize() || align >= getpagesize()) {
482 unsigned long pages = div_up(size, getpagesize());
484 ret = alloc_get_pages(pool, poolsize, pages, align)
487 ret = alloc_sub_page(pool, poolsize, size, align);
490 return (char *)pool + ret;
492 /* Allocation failed: garbage collection. */
493 if (!subpage_clean) {
494 subpage_clean = true;
495 if (clean_empty_subpages(pool, poolsize))
499 if (!metadata_clean) {
500 metadata_clean = true;
501 if (clean_metadata(pool, poolsize))
505 /* FIXME: Compact metadata? */
509 static void subpage_free(void *pool, unsigned long pagenum, void *free)
511 unsigned long off = (unsigned long)free % getpagesize();
514 assert(off < SUBPAGE_METAOFF);
515 assert(off % BITMAP_GRANULARITY == 0);
517 metadata = get_page_metadata(pool, pagenum);
519 off /= BITMAP_GRANULARITY;
521 set_page_state(metadata, off++, FREE);
522 while (off < SUBPAGE_METAOFF / BITMAP_GRANULARITY
523 && get_page_state(metadata, off) == TAKEN)
524 set_page_state(metadata, off++, FREE);
527 void alloc_free(void *pool, unsigned long poolsize, void *free)
529 unsigned long pagenum;
530 struct metaheader *mh;
535 assert(poolsize >= MIN_SIZE);
537 mh = first_mheader(pool, poolsize);
538 assert((char *)free >= (char *)(mh + 1) + mh->metalen);
539 assert((char *)pool + poolsize > (char *)free);
541 pagenum = pool_offset(pool, free) / getpagesize();
543 if (get_page_state(pool, pagenum) == SPECIAL)
544 subpage_free(pool, pagenum, free);
546 assert((unsigned long)free % getpagesize() == 0);
547 alloc_free_pages(pool, pagenum);
551 static bool is_metadata_page(void *pool, unsigned long poolsize,
554 struct metaheader *mh;
556 for (mh = first_mheader(pool,poolsize); mh; mh = next_mheader(pool,mh)){
557 unsigned long start, end;
559 start = pool_offset(pool, mh);
560 end = pool_offset(pool, (char *)(mh+1) + mh->metalen);
561 if (page >= start/getpagesize() && page < end/getpagesize())
567 static bool check_subpage(void *pool, unsigned long poolsize,
570 unsigned long *mhoff = metadata_off(pool, page);
572 enum alloc_state last_state = FREE;
574 if (*mhoff + sizeof(struct metaheader) > poolsize)
577 if (*mhoff % ALIGNOF(struct metaheader) != 0)
580 /* It must point to a metadata page. */
581 if (!is_metadata_page(pool, poolsize, *mhoff / getpagesize()))
584 /* Marker at end of subpage allocation is "taken" */
585 if (get_bit_pair((uint8_t *)pool + *mhoff,
586 getpagesize()/BITMAP_GRANULARITY - 1) != TAKEN)
589 for (i = 0; i < SUBPAGE_METAOFF / BITMAP_GRANULARITY; i++) {
590 enum alloc_state state;
592 state = get_bit_pair((uint8_t *)pool + *mhoff, i);
597 if (last_state == FREE)
608 bool alloc_check(void *pool, unsigned long poolsize)
611 struct metaheader *mh;
612 enum alloc_state last_state = FREE;
613 bool was_metadata = false;
615 if (poolsize < MIN_SIZE)
618 if (get_page_state(pool, 0) != TAKEN_START)
621 /* First check metadata pages. */
622 /* Metadata pages will be marked TAKEN. */
623 for (mh = first_mheader(pool,poolsize); mh; mh = next_mheader(pool,mh)){
624 unsigned long start, end;
626 start = pool_offset(pool, mh);
627 if (start + sizeof(*mh) > poolsize)
630 end = pool_offset(pool, (char *)(mh+1) + mh->metalen);
634 /* Non-first pages should start on a page boundary. */
635 if (mh != first_mheader(pool, poolsize)
636 && start % getpagesize() != 0)
639 /* It should end on a page boundary. */
640 if (end % getpagesize() != 0)
644 for (i = 0; i < poolsize / getpagesize(); i++) {
645 enum alloc_state state = get_page_state(pool, i);
646 bool is_metadata = is_metadata_page(pool, poolsize,i);
650 /* metadata pages are never free. */
656 /* This should continue a previous block. */
657 if (last_state == FREE)
659 if (is_metadata != was_metadata)
663 /* Check metadata pointer etc. */
664 if (!check_subpage(pool, poolsize, i))
668 was_metadata = is_metadata;
673 void alloc_visualize(FILE *out, void *pool, unsigned long poolsize)
675 struct metaheader *mh;
676 unsigned long pagebitlen, metadata_pages, count[1<<BITS_PER_PAGE], tot;
679 if (poolsize < MIN_SIZE) {
680 fprintf(out, "Pool smaller than %u: no content\n", MIN_SIZE);
684 memset(count, 0, sizeof(count));
685 for (i = 0; i < poolsize / getpagesize(); i++)
686 count[get_page_state(pool, i)]++;
688 mh = first_mheader(pool, poolsize);
689 pagebitlen = (char *)mh - (char *)pool;
690 fprintf(out, "%lu bytes of page bits: FREE/TAKEN/TAKEN_START/SUBPAGE = %lu/%lu/%lu/%lu\n",
691 pagebitlen, count[0], count[1], count[2], count[3]);
693 /* One metadata page for every page of page bits. */
694 metadata_pages = div_up(pagebitlen, getpagesize());
696 /* Now do each metadata page. */
697 for (; mh; mh = next_mheader(pool,mh)) {
698 unsigned long free = 0, subpageblocks = 0, len = 0;
699 uint8_t *meta = (uint8_t *)(mh + 1);
701 metadata_pages += (sizeof(*mh) + mh->metalen) / getpagesize();
703 /* TAKEN tags end a subpage alloc. */
704 for (i = mh->metalen * CHAR_BIT/BITS_PER_PAGE - 1;
707 switch (get_page_state(meta, i)) {
713 /* Skip over this allocated part. */
714 len = BITMAP_METALEN * CHAR_BIT;
722 fprintf(out, "Metadata %lu-%lu: %lu free, %lu subpageblocks, %lu%% density\n",
723 pool_offset(pool, mh),
724 pool_offset(pool, (char *)(mh+1) + mh->metalen),
726 subpageblocks * BITMAP_METALEN * 100
727 / (free + subpageblocks * BITMAP_METALEN));
730 /* Account for total pages allocated. */
731 tot = (count[1] + count[2] - metadata_pages) * getpagesize();
733 fprintf(out, "Total metadata bytes = %lu\n",
734 metadata_pages * getpagesize());
736 /* Now do every subpage. */
737 for (i = 0; i < poolsize / getpagesize(); i++) {
740 if (get_page_state(pool, i) != SPECIAL)
743 memset(count, 0, sizeof(count));
744 meta = get_page_metadata(pool, i);
745 for (j = 0; j < SUBPAGE_METAOFF/BITMAP_GRANULARITY; j++)
746 count[get_page_state(meta, j)]++;
748 fprintf(out, "Subpage %lu: "
749 "FREE/TAKEN/TAKEN_START = %lu/%lu/%lu %lu%% density\n",
750 i, count[0], count[1], count[2],
751 ((count[1] + count[2]) * BITMAP_GRANULARITY) * 100
753 tot += (count[1] + count[2]) * BITMAP_GRANULARITY;
756 /* This is optimistic, since we overalloc in several cases. */
757 fprintf(out, "Best possible allocation density = %lu%%\n",
758 tot * 100 / poolsize);