git.ozlabs.org Git - ccan/blob - ccan/alloc/alloc.c

   1 #include <unistd.h>
   2 #include <stdint.h>
   3 #include <string.h>
   4 #include <limits.h>
   5 #include <assert.h>
   6 #include <stdlib.h>
   7 #include "alloc.h"
   8 #include "bitops.h"
   9 #include "tiny.h"
  10 #include <ccan/build_assert/build_assert.h>
  11 #include <ccan/likely/likely.h>
  12 #include <ccan/alignof/alignof.h>
  13 #include <ccan/short_types/short_types.h>
  14 #include "config.h"
  15
  16 /*
  17    Inspired by (and parts taken from) Andrew Tridgell's alloc_mmap:
  18    http://samba.org/~tridge/junkcode/alloc_mmap/
  19
  20    Copyright (C) Andrew Tridgell 2007
  21
  22    This library is free software; you can redistribute it and/or
  23    modify it under the terms of the GNU Lesser General Public
  24    License as published by the Free Software Foundation; either
  25    version 2 of the License, or (at your option) any later version.
  26
  27    This library is distributed in the hope that it will be useful,
  28    but WITHOUT ANY WARRANTY; without even the implied warranty of
  29    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  30    Lesser General Public License for more details.
  31
  32    You should have received a copy of the GNU Lesser General Public
  33    License along with this library; if not, write to the Free Software
  34    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  35  */
  36
  37 /* We divide the pool into this many large pages (nearest power of 2) */
  38 #define MAX_LARGE_PAGES (256UL)
  39
  40 /* 32 small pages == 1 large page. */
  41 #define BITS_FROM_SMALL_TO_LARGE_PAGE 5
  42
  43 #define MAX_SMALL_PAGES (MAX_LARGE_PAGES << BITS_FROM_SMALL_TO_LARGE_PAGE)
  44
  45 /* Smallest pool size for this scheme: 128-byte small pages.  That's
  46  * 9/13% overhead for 32/64 bit. */
  47 #define MIN_USEFUL_SIZE (MAX_SMALL_PAGES * 128)
  48
  49 /* Every 4 buckets, we jump up a power of 2. ...8 10 12 14 16 20 24 28 32... */
  50 #define INTER_BUCKET_SPACE 4
  51
  52 #define SMALL_PAGES_PER_LARGE_PAGE (1 << BITS_FROM_SMALL_TO_LARGE_PAGE)
  53
  54 /* FIXME: Figure this out properly. */
  55 #define MAX_SIZE (1 << 30)
  56
  57 /* How few object to fit in a page before using a larger one? (8) */
  58 #define MAX_PAGE_OBJECT_ORDER   3
  59
  60 #define BITS_PER_LONG (sizeof(long) * CHAR_BIT)
  61
  62 struct bucket_state {
  63         u32 elements_per_page;
  64         u16 page_list;
  65         u16 full_list;
  66 };
  67
  68 struct header {
  69         /* Bitmap of which pages are large. */
  70         unsigned long pagesize[MAX_LARGE_PAGES / BITS_PER_LONG];
  71
  72         /* List of unused small/large pages. */
  73         u16 small_free_list;
  74         u16 large_free_list;
  75
  76         /* List of huge allocs. */
  77         unsigned long huge;
  78
  79         /* This is less defined: we have two buckets for each power of 2 */
  80         struct bucket_state bs[1];
  81 };
  82
  83 struct huge_alloc {
  84         unsigned long next, prev;
  85         unsigned long off, len;
  86 };
  87
  88 struct page_header {
  89         u16 next, prev;
  90         /* FIXME: We can just count all-0 and all-1 used[] elements. */
  91         unsigned elements_used : 25;
  92         unsigned bucket : 7;
  93         unsigned long used[1]; /* One bit per element. */
  94 };
  95
  96 /*
  97  * Every 4 buckets, the size doubles.
  98  * Between buckets, sizes increase linearly.
  99  *
 100  * eg. bucket 40 = 2^10                 = 1024
 101  *     bucket 41 = 2^10 + 2^10*4        = 1024 + 256
 102  *     bucket 42 = 2^10 + 2^10*4        = 1024 + 512
 103  *     bucket 43 = 2^10 + 2^10*4        = 1024 + 768
 104  *     bucket 45 = 2^11                 = 2048
 105  *
 106  * Care is taken to handle low numbered buckets, at cost of overflow.
 107  */
 108 static unsigned long bucket_to_size(unsigned int bucket)
 109 {
 110         unsigned long base = 1 << (bucket / INTER_BUCKET_SPACE);
 111         return base + ((bucket % INTER_BUCKET_SPACE)
 112                        << (bucket / INTER_BUCKET_SPACE))
 113                 / INTER_BUCKET_SPACE;
 114 }
 115
 116 /*
 117  * Say size is 10.
 118  *   fls(size/2) == 3.  1 << 3 == 8, so we're 2 too large, out of a possible
 119  * 8 too large.  That's 1/4 of the way to the next power of 2 == 1 bucket.
 120  *
 121  * We make sure we round up.  Note that this fails on 32 bit at size
 122  * 1879048193 (around bucket 120).
 123  */
 124 static unsigned int size_to_bucket(unsigned long size)
 125 {
 126         unsigned int base = fls(size/2);
 127         unsigned long overshoot;
 128
 129         overshoot = size - (1 << base);
 130         return base * INTER_BUCKET_SPACE
 131                 + ((overshoot * INTER_BUCKET_SPACE + (1 << base)-1) >> base);
 132 }
 133
 134 static unsigned int small_page_bits(unsigned long poolsize)
 135 {
 136         return fls(poolsize / MAX_SMALL_PAGES / 2);
 137 }
 138
 139 static struct page_header *from_pgnum(struct header *head,
 140                                       unsigned long pgnum,
 141                                       unsigned sp_bits)
 142 {
 143         return (struct page_header *)((char *)head + (pgnum << sp_bits));
 144 }
 145
 146 static u16 to_pgnum(struct header *head, void *p, unsigned sp_bits)
 147 {
 148         return ((char *)p - (char *)head) >> sp_bits;
 149 }
 150
 151 static size_t used_size(unsigned int num_elements)
 152 {
 153         return align_up(num_elements, BITS_PER_LONG) / CHAR_BIT;
 154 }
 155
 156 /*
 157  * We always align the first entry to the lower power of 2.
 158  * eg. the 12-byte bucket gets 8-byte aligned.  The 4096-byte bucket
 159  * gets 4096-byte aligned.
 160  */
 161 static unsigned long page_header_size(unsigned int align_bits,
 162                                       unsigned long num_elements)
 163 {
 164         unsigned long size;
 165
 166         size = sizeof(struct page_header)
 167                 - sizeof(((struct page_header *)0)->used)
 168                 + used_size(num_elements);
 169         return align_up(size, 1 << align_bits);
 170 }
 171
 172 static void add_to_list(struct header *head,
 173                         u16 *list, struct page_header *ph, unsigned sp_bits)
 174 {
 175         unsigned long h = *list, offset = to_pgnum(head, ph, sp_bits);
 176
 177         ph->next = h;
 178         if (h) {
 179                 struct page_header *prev = from_pgnum(head, h, sp_bits);
 180                 assert(prev->prev == 0);
 181                 prev->prev = offset;
 182         }
 183         *list = offset;
 184         ph->prev = 0;
 185 }
 186
 187 static void del_from_list(struct header *head,
 188                           u16 *list, struct page_header *ph, unsigned sp_bits)
 189 {
 190         /* Front of list? */
 191         if (ph->prev == 0) {
 192                 *list = ph->next;
 193         } else {
 194                 struct page_header *prev = from_pgnum(head, ph->prev, sp_bits);
 195                 prev->next = ph->next;
 196         }
 197         if (ph->next != 0) {
 198                 struct page_header *next = from_pgnum(head, ph->next, sp_bits);
 199                 next->prev = ph->prev;
 200         }
 201 }
 202
 203 static u16 pop_from_list(struct header *head,
 204                                    u16 *list,
 205                                    unsigned int sp_bits)
 206 {
 207         u16 h = *list;
 208         struct page_header *ph = from_pgnum(head, h, sp_bits);
 209
 210         if (likely(h)) {
 211                 *list = ph->next;
 212                 if (*list)
 213                         from_pgnum(head, *list, sp_bits)->prev = 0;
 214         }
 215         return h;
 216 }
 217
 218 static void add_to_huge_list(struct header *head, struct huge_alloc *ha)
 219 {
 220         unsigned long h = head->huge;
 221         unsigned long offset = (char *)ha - (char *)head;
 222
 223         ha->next = h;
 224         if (h) {
 225                 struct huge_alloc *prev = (void *)((char *)head + h);
 226                 assert(prev->prev == 0);
 227                 prev->prev = offset;
 228         }
 229         head->huge = offset;
 230         ha->prev = 0;
 231 }
 232
 233 static void del_from_huge(struct header *head, struct huge_alloc *ha)
 234 {
 235         /* Front of list? */
 236         if (ha->prev == 0) {
 237                 head->huge = ha->next;
 238         } else {
 239                 struct huge_alloc *prev = (void *)((char *)head + ha->prev);
 240                 prev->next = ha->next;
 241         }
 242         if (ha->next != 0) {
 243                 struct huge_alloc *next = (void *)((char *)head + ha->next);
 244                 next->prev = ha->prev;
 245         }
 246 }
 247
 248 static void add_small_page_to_freelist(struct header *head,
 249                                        struct page_header *ph,
 250                                        unsigned int sp_bits)
 251 {
 252         add_to_list(head, &head->small_free_list, ph, sp_bits);
 253 }
 254
 255 static void add_large_page_to_freelist(struct header *head,
 256                                        struct page_header *ph,
 257                                        unsigned int sp_bits)
 258 {
 259         add_to_list(head, &head->large_free_list, ph, sp_bits);
 260 }
 261
 262 static void add_to_bucket_list(struct header *head,
 263                                struct bucket_state *bs,
 264                                struct page_header *ph,
 265                                unsigned int sp_bits)
 266 {
 267         add_to_list(head, &bs->page_list, ph, sp_bits);
 268 }
 269
 270 static void del_from_bucket_list(struct header *head,
 271                                  struct bucket_state *bs,
 272                                  struct page_header *ph,
 273                                  unsigned int sp_bits)
 274 {
 275         del_from_list(head, &bs->page_list, ph, sp_bits);
 276 }
 277
 278 static void del_from_bucket_full_list(struct header *head,
 279                                       struct bucket_state *bs,
 280                                       struct page_header *ph,
 281                                       unsigned int sp_bits)
 282 {
 283         del_from_list(head, &bs->full_list, ph, sp_bits);
 284 }
 285
 286 static void add_to_bucket_full_list(struct header *head,
 287                                     struct bucket_state *bs,
 288                                     struct page_header *ph,
 289                                     unsigned int sp_bits)
 290 {
 291         add_to_list(head, &bs->full_list, ph, sp_bits);
 292 }
 293
 294 static void clear_bit(unsigned long bitmap[], unsigned int off)
 295 {
 296         bitmap[off / BITS_PER_LONG] &= ~(1 << (off % BITS_PER_LONG));
 297 }
 298
 299 static bool test_bit(const unsigned long bitmap[], unsigned int off)
 300 {
 301         return bitmap[off / BITS_PER_LONG] & (1 << (off % BITS_PER_LONG));
 302 }
 303
 304 static void set_bit(unsigned long bitmap[], unsigned int off)
 305 {
 306         bitmap[off / BITS_PER_LONG] |= (1 << (off % BITS_PER_LONG));
 307 }
 308
 309 /* There must be a bit to be found. */
 310 static unsigned int find_free_bit(const unsigned long bitmap[])
 311 {
 312         unsigned int i;
 313
 314         for (i = 0; bitmap[i] == -1UL; i++);
 315         return (i*BITS_PER_LONG) + ffsl(~bitmap[i]) - 1;
 316 }
 317
 318 /* How many elements can we fit in a page? */
 319 static unsigned long elements_per_page(unsigned long align_bits,
 320                                        unsigned long esize,
 321                                        unsigned long psize)
 322 {
 323         unsigned long num, overhead;
 324
 325         /* First approximation: no extra room for bitmap. */
 326         overhead = align_up(sizeof(struct page_header), 1 << align_bits);
 327         num = (psize - overhead) / esize;
 328
 329         while (page_header_size(align_bits, num) + esize * num > psize)
 330                 num--;
 331         return num;
 332 }
 333
 334 static bool large_page_bucket(unsigned int bucket, unsigned int sp_bits)
 335 {
 336         unsigned long max_smallsize;
 337
 338         /* Note: this doesn't take into account page header. */
 339         max_smallsize = (1UL << sp_bits) >> MAX_PAGE_OBJECT_ORDER;
 340
 341         return bucket_to_size(bucket) > max_smallsize;
 342 }
 343
 344 static unsigned int max_bucket(unsigned int lp_bits)
 345 {
 346         return (lp_bits - MAX_PAGE_OBJECT_ORDER) * INTER_BUCKET_SPACE;
 347 }
 348
 349 void alloc_init(void *pool, unsigned long poolsize)
 350 {
 351         struct header *head = pool;
 352         struct page_header *ph;
 353         unsigned int lp_bits, sp_bits, num_buckets;
 354         unsigned long header_size, i;
 355
 356         if (poolsize < MIN_USEFUL_SIZE) {
 357                 tiny_alloc_init(pool, poolsize);
 358                 return;
 359         }
 360
 361         /* We rely on page numbers fitting in 16 bit. */
 362         BUILD_ASSERT(MAX_SMALL_PAGES < 65536);
 363
 364         sp_bits = small_page_bits(poolsize);
 365         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 366
 367         num_buckets = max_bucket(lp_bits);
 368
 369         head = pool;
 370         header_size = sizeof(*head) + sizeof(head->bs) * (num_buckets-1);
 371
 372         memset(head, 0, header_size);
 373         for (i = 0; i < num_buckets; i++) {
 374                 unsigned long pagesize;
 375
 376                 if (large_page_bucket(i, sp_bits))
 377                         pagesize = 1UL << lp_bits;
 378                 else
 379                         pagesize = 1UL << sp_bits;
 380
 381                 head->bs[i].elements_per_page
 382                         = elements_per_page(i / INTER_BUCKET_SPACE,
 383                                             bucket_to_size(i),
 384                                             pagesize);
 385         }
 386
 387         /* They start as all large pages. */
 388         memset(head->pagesize, 0xFF, sizeof(head->pagesize));
 389         /* FIXME: small pages for last bit? */
 390
 391         /* Split first page into small pages. */
 392         assert(header_size < (1UL << lp_bits));
 393         clear_bit(head->pagesize, 0);
 394
 395         /* Skip over page(s) used by header, add rest to free list */
 396         for (i = align_up(header_size, (1 << sp_bits)) >> sp_bits;
 397              i < SMALL_PAGES_PER_LARGE_PAGE;
 398              i++) {
 399                 ph = from_pgnum(head, i, sp_bits);
 400                 ph->elements_used = 0;
 401                 add_small_page_to_freelist(head, ph, sp_bits);
 402         }
 403
 404         /* Add the rest of the pages as large pages. */
 405         i = SMALL_PAGES_PER_LARGE_PAGE;
 406         while ((i << sp_bits) + (1 << lp_bits) <= poolsize) {
 407                 ph = from_pgnum(head, i, sp_bits);
 408                 ph->elements_used = 0;
 409                 add_large_page_to_freelist(head, ph, sp_bits);
 410                 i += SMALL_PAGES_PER_LARGE_PAGE;
 411         }
 412 }
 413
 414 /* A large page worth of small pages are free: delete them from free list. */
 415 static void del_large_from_small_free_list(struct header *head,
 416                                            struct page_header *ph,
 417                                            unsigned int sp_bits)
 418 {
 419         unsigned long i;
 420
 421         for (i = 0; i < SMALL_PAGES_PER_LARGE_PAGE; i++) {
 422                 del_from_list(head, &head->small_free_list,
 423                               (void *)ph + (i << sp_bits),
 424                               sp_bits);
 425         }
 426 }
 427
 428 static bool all_empty(struct header *head,
 429                       unsigned long pgnum,
 430                       unsigned sp_bits)
 431 {
 432         unsigned long i;
 433
 434         for (i = 0; i < SMALL_PAGES_PER_LARGE_PAGE; i++) {
 435                 struct page_header *ph = from_pgnum(head, pgnum + i, sp_bits);
 436                 if (ph->elements_used)
 437                         return false;
 438         }
 439         return true;
 440 }
 441
 442 static void recombine_small_pages(struct header *head, unsigned long poolsize,
 443                                   unsigned int sp_bits)
 444 {
 445         unsigned long i;
 446         unsigned int lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 447
 448         /* Look for small pages to coalesce, after first large page. */
 449         for (i = SMALL_PAGES_PER_LARGE_PAGE;
 450              i < (poolsize >> lp_bits) << BITS_FROM_SMALL_TO_LARGE_PAGE;
 451              i += SMALL_PAGES_PER_LARGE_PAGE) {
 452                 /* Already a large page? */
 453                 if (test_bit(head->pagesize, i / SMALL_PAGES_PER_LARGE_PAGE))
 454                         continue;
 455                 if (all_empty(head, i, sp_bits)) {
 456                         struct page_header *ph = from_pgnum(head, i, sp_bits);
 457                         set_bit(head->pagesize,
 458                                 i / SMALL_PAGES_PER_LARGE_PAGE);
 459                         del_large_from_small_free_list(head, ph, sp_bits);
 460                         add_large_page_to_freelist(head, ph, sp_bits);
 461                 }
 462         }
 463 }
 464
 465 static u16 get_large_page(struct header *head, unsigned long poolsize,
 466                           unsigned int sp_bits)
 467 {
 468         unsigned int lp_bits, page;
 469
 470         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 471
 472         page = pop_from_list(head, &head->large_free_list, sp_bits);
 473         if (likely(page))
 474                 return page;
 475
 476         recombine_small_pages(head, poolsize, sp_bits);
 477
 478         return pop_from_list(head, &head->large_free_list, sp_bits);
 479 }
 480
 481 /* Returns small page. */
 482 static unsigned long break_up_large_page(struct header *head,
 483                                          unsigned int sp_bits,
 484                                          u16 lpage)
 485 {
 486         unsigned int i;
 487
 488         clear_bit(head->pagesize, lpage >> BITS_FROM_SMALL_TO_LARGE_PAGE);
 489
 490         for (i = 1; i < SMALL_PAGES_PER_LARGE_PAGE; i++) {
 491                 struct page_header *ph = from_pgnum(head, lpage + i, sp_bits);
 492                 add_small_page_to_freelist(head, ph, sp_bits);
 493         }
 494
 495         return lpage;
 496 }
 497
 498 static u16 get_small_page(struct header *head, unsigned long poolsize,
 499                           unsigned int sp_bits)
 500 {
 501         u16 ret;
 502
 503         ret = pop_from_list(head, &head->small_free_list, sp_bits);
 504         if (likely(ret))
 505                 return ret;
 506         ret = get_large_page(head, poolsize, sp_bits);
 507         if (likely(ret))
 508                 ret = break_up_large_page(head, sp_bits, ret);
 509         return ret;
 510 }
 511
 512 static bool huge_allocated(struct header *head, unsigned long offset)
 513 {
 514         unsigned long i;
 515         struct huge_alloc *ha;
 516
 517         for (i = head->huge; i; i = ha->next) {
 518                 ha = (void *)((char *)head + i);
 519                 if (ha->off <= offset && ha->off + ha->len > offset)
 520                         return true;
 521         }
 522         return false;
 523 }
 524
 525 /* They want something really big.  Aim for contiguous pages (slow). */
 526 static void *unlikely_func huge_alloc(void *pool, unsigned long poolsize,
 527                                       unsigned long size, unsigned long align)
 528 {
 529         struct header *head = pool;
 530         struct huge_alloc *ha;
 531         unsigned long i, sp_bits, lp_bits, num, header_size;
 532
 533         sp_bits = small_page_bits(poolsize);
 534         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 535
 536         /* Allocate tracking structure optimistically. */
 537         ha = alloc_get(pool, poolsize, sizeof(*ha), ALIGNOF(*ha));
 538         if (!ha)
 539                 return NULL;
 540
 541         /* First search for contiguous small pages... */
 542         header_size = sizeof(*head) + sizeof(head->bs) * (max_bucket(lp_bits)-1);
 543
 544         num = 0;
 545         for (i = (header_size + (1 << sp_bits) - 1) >> sp_bits;
 546              i << sp_bits < poolsize;
 547              i++) {
 548                 struct page_header *pg;
 549                 unsigned long off = (i << sp_bits);
 550
 551                 /* Skip over large pages. */
 552                 if (test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE)) {
 553                         i += (1 << BITS_FROM_SMALL_TO_LARGE_PAGE)-1;
 554                         continue;
 555                 }
 556
 557                 /* Does this page meet alignment requirements? */
 558                 if (!num && off % align != 0)
 559                         continue;
 560
 561                 /* FIXME: This makes us O(n^2). */
 562                 if (huge_allocated(head, off)) {
 563                         num = 0;
 564                         continue;
 565                 }
 566
 567                 pg = (struct page_header *)((char *)head + off);
 568                 if (pg->elements_used) {
 569                         num = 0;
 570                         continue;
 571                 }
 572
 573                 num++;
 574                 if (num << sp_bits >= size) {
 575                         unsigned long pgnum;
 576
 577                         /* Remove from free list. */
 578                         for (pgnum = i; pgnum > i - num; pgnum--) {
 579                                 pg = from_pgnum(head, pgnum, sp_bits);
 580                                 del_from_list(head,
 581                                               &head->small_free_list,
 582                                               pg, sp_bits);
 583                         }
 584                         ha->off = (i - num + 1) << sp_bits;
 585                         ha->len = num << sp_bits;
 586                         goto done;
 587                 }
 588         }
 589
 590         /* Now search for large pages... */
 591         recombine_small_pages(head, poolsize, sp_bits);
 592
 593         num = 0;
 594         for (i = (header_size + (1 << lp_bits) - 1) >> lp_bits;
 595              (i << lp_bits) < poolsize; i++) {
 596                 struct page_header *pg;
 597                 unsigned long off = (i << lp_bits);
 598
 599                 /* Ignore small pages. */
 600                 if (!test_bit(head->pagesize, i))
 601                         continue;
 602
 603                 /* Does this page meet alignment requirements? */
 604                 if (!num && off % align != 0)
 605                         continue;
 606
 607                 /* FIXME: This makes us O(n^2). */
 608                 if (huge_allocated(head, off)) {
 609                         num = 0;
 610                         continue;
 611                 }
 612
 613                 pg = (struct page_header *)((char *)head + off);
 614                 if (pg->elements_used) {
 615                         num = 0;
 616                         continue;
 617                 }
 618
 619                 num++;
 620                 if (num << lp_bits >= size) {
 621                         unsigned long pgnum;
 622
 623                         /* Remove from free list. */
 624                         for (pgnum = i; pgnum > i - num; pgnum--) {
 625                                 pg = from_pgnum(head, pgnum, lp_bits);
 626                                 del_from_list(head,
 627                                               &head->large_free_list,
 628                                               pg, sp_bits);
 629                         }
 630                         ha->off = (i - num + 1) << lp_bits;
 631                         ha->len = num << lp_bits;
 632                         goto done;
 633                 }
 634         }
 635
 636         /* Unable to satisfy: free huge alloc structure. */
 637         alloc_free(pool, poolsize, ha);
 638         return NULL;
 639
 640 done:
 641         add_to_huge_list(pool, ha);
 642         return (char *)pool + ha->off;
 643 }
 644
 645 static void unlikely_func huge_free(struct header *head,
 646                                     unsigned long poolsize, void *free)
 647 {
 648         unsigned long i, off, pgnum, free_off = (char *)free - (char *)head;
 649         unsigned int sp_bits, lp_bits;
 650         struct huge_alloc *ha;
 651
 652         for (i = head->huge; i; i = ha->next) {
 653                 ha = (void *)((char *)head + i);
 654                 if (free_off == ha->off)
 655                         break;
 656         }
 657         assert(i);
 658
 659         /* Free up all the pages, delete and free ha */
 660         sp_bits = small_page_bits(poolsize);
 661         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 662         pgnum = free_off >> sp_bits;
 663
 664         if (test_bit(head->pagesize, pgnum >> BITS_FROM_SMALL_TO_LARGE_PAGE)) {
 665                 for (off = ha->off; off < ha->off + ha->len; off += 1 << lp_bits) {
 666                         add_large_page_to_freelist(head,
 667                                                    (void *)((char *)head + off),
 668                                                    sp_bits);
 669                 }
 670         } else {
 671                 for (off = ha->off; off < ha->off + ha->len; off += 1 << sp_bits) {
 672                         add_small_page_to_freelist(head,
 673                                                    (void *)((char *)head + off),
 674                                                    sp_bits);
 675                 }
 676         }
 677         del_from_huge(head, ha);
 678         alloc_free(head, poolsize, ha);
 679 }
 680
 681 static unsigned long unlikely_func huge_size(struct header *head, void *p)
 682 {
 683         unsigned long i, off = (char *)p - (char *)head;
 684         struct huge_alloc *ha;
 685
 686         for (i = head->huge; i; i = ha->next) {
 687                 ha = (void *)((char *)head + i);
 688                 if (off == ha->off) {
 689                         return ha->len;
 690                 }
 691         }
 692         abort();
 693 }
 694
 695 void *alloc_get(void *pool, unsigned long poolsize,
 696                 unsigned long size, unsigned long align)
 697 {
 698         struct header *head = pool;
 699         unsigned int bucket;
 700         unsigned long i;
 701         struct bucket_state *bs;
 702         struct page_header *ph;
 703         unsigned int sp_bits;
 704
 705         if (poolsize < MIN_USEFUL_SIZE) {
 706                 return tiny_alloc_get(pool, poolsize, size, align);
 707         }
 708
 709         size = align_up(size, align);
 710         if (unlikely(!size))
 711                 size = 1;
 712         bucket = size_to_bucket(size);
 713
 714         sp_bits = small_page_bits(poolsize);
 715
 716         if (bucket >= max_bucket(sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE)) {
 717                 return huge_alloc(pool, poolsize, size, align);
 718         }
 719
 720         bs = &head->bs[bucket];
 721
 722         if (!bs->page_list) {
 723                 struct page_header *ph;
 724
 725                 if (large_page_bucket(bucket, sp_bits))
 726                         bs->page_list = get_large_page(head, poolsize,
 727                                                        sp_bits);
 728                 else
 729                         bs->page_list = get_small_page(head, poolsize,
 730                                                        sp_bits);
 731                 /* FIXME: Try large-aligned alloc?  Header stuffing? */
 732                 if (unlikely(!bs->page_list))
 733                         return NULL;
 734                 ph = from_pgnum(head, bs->page_list, sp_bits);
 735                 ph->bucket = bucket;
 736                 ph->elements_used = 0;
 737                 ph->next = 0;
 738                 memset(ph->used, 0, used_size(bs->elements_per_page));
 739         }
 740
 741         ph = from_pgnum(head, bs->page_list, sp_bits);
 742
 743         i = find_free_bit(ph->used);
 744         set_bit(ph->used, i);
 745         ph->elements_used++;
 746
 747         /* check if this page is now full */
 748         if (unlikely(ph->elements_used == bs->elements_per_page)) {
 749                 del_from_bucket_list(head, bs, ph, sp_bits);
 750                 add_to_bucket_full_list(head, bs, ph, sp_bits);
 751         }
 752
 753         return (char *)ph + page_header_size(ph->bucket / INTER_BUCKET_SPACE,
 754                                              bs->elements_per_page)
 755                + i * bucket_to_size(bucket);
 756 }
 757
 758 void alloc_free(void *pool, unsigned long poolsize, void *free)
 759 {
 760         struct header *head = pool;
 761         struct bucket_state *bs;
 762         unsigned int sp_bits;
 763         unsigned long i, pgnum, pgoffset, offset = (char *)free - (char *)pool;
 764         bool smallpage;
 765         struct page_header *ph;
 766
 767         if (poolsize < MIN_USEFUL_SIZE) {
 768                 return tiny_alloc_free(pool, poolsize, free);
 769         }
 770
 771         /* Get page header. */
 772         sp_bits = small_page_bits(poolsize);
 773         pgnum = offset >> sp_bits;
 774
 775         /* Big page? Round down further. */
 776         if (test_bit(head->pagesize, pgnum >> BITS_FROM_SMALL_TO_LARGE_PAGE)) {
 777                 smallpage = false;
 778                 pgnum &= ~(SMALL_PAGES_PER_LARGE_PAGE - 1);
 779         } else
 780                 smallpage = true;
 781
 782         /* Step back to page header. */
 783         ph = from_pgnum(head, pgnum, sp_bits);
 784         if ((void *)ph == free) {
 785                 huge_free(head, poolsize, free);
 786                 return;
 787         }
 788
 789         bs = &head->bs[ph->bucket];
 790         pgoffset = offset - (pgnum << sp_bits)
 791                 - page_header_size(ph->bucket / INTER_BUCKET_SPACE,
 792                                    bs->elements_per_page);
 793
 794         if (unlikely(ph->elements_used == bs->elements_per_page)) {
 795                 del_from_bucket_full_list(head, bs, ph, sp_bits);
 796                 add_to_bucket_list(head, bs, ph, sp_bits);
 797         }
 798
 799         /* Which element are we? */
 800         i = pgoffset / bucket_to_size(ph->bucket);
 801         clear_bit(ph->used, i);
 802         ph->elements_used--;
 803
 804         if (unlikely(ph->elements_used == 0)) {
 805                 bs = &head->bs[ph->bucket];
 806                 del_from_bucket_list(head, bs, ph, sp_bits);
 807                 if (smallpage)
 808                         add_small_page_to_freelist(head, ph, sp_bits);
 809                 else
 810                         add_large_page_to_freelist(head, ph, sp_bits);
 811         }
 812 }
 813
 814 unsigned long alloc_size(void *pool, unsigned long poolsize, void *p)
 815 {
 816         struct header *head = pool;
 817         unsigned int pgnum, sp_bits;
 818         unsigned long offset = (char *)p - (char *)pool;
 819         struct page_header *ph;
 820
 821         if (poolsize < MIN_USEFUL_SIZE)
 822                 return tiny_alloc_size(pool, poolsize, p);
 823
 824         /* Get page header. */
 825         sp_bits = small_page_bits(poolsize);
 826         pgnum = offset >> sp_bits;
 827
 828         /* Big page? Round down further. */
 829         if (test_bit(head->pagesize, pgnum >> BITS_FROM_SMALL_TO_LARGE_PAGE))
 830                 pgnum &= ~(SMALL_PAGES_PER_LARGE_PAGE - 1);
 831
 832         /* Step back to page header. */
 833         ph = from_pgnum(head, pgnum, sp_bits);
 834         if ((void *)ph == p)
 835                 return huge_size(head, p);
 836
 837         return bucket_to_size(ph->bucket);
 838 }
 839
 840 /* Useful for gdb breakpoints. */
 841 static bool check_fail(void)
 842 {
 843         return false;
 844 }
 845
 846 static unsigned long count_bits(const unsigned long bitmap[],
 847                                 unsigned long limit)
 848 {
 849         unsigned long i, count = 0;
 850
 851         while (limit >= BITS_PER_LONG) {
 852                 count += popcount(bitmap[0]);
 853                 bitmap++;
 854                 limit -= BITS_PER_LONG;
 855         }
 856
 857         for (i = 0; i < limit; i++)
 858                 if (test_bit(bitmap, i))
 859                         count++;
 860         return count;
 861 }
 862
 863 static bool out_of_bounds(unsigned long pgnum,
 864                           unsigned int sp_bits,
 865                           unsigned long pagesize,
 866                           unsigned long poolsize)
 867 {
 868         if (((pgnum << sp_bits) >> sp_bits) != pgnum)
 869                 return true;
 870
 871         if ((pgnum << sp_bits) > poolsize)
 872                 return true;
 873
 874         return ((pgnum << sp_bits) + pagesize > poolsize);
 875 }
 876
 877 static bool check_bucket(struct header *head,
 878                          unsigned long poolsize,
 879                          unsigned long pages[],
 880                          struct bucket_state *bs,
 881                          unsigned int bindex)
 882 {
 883         bool lp_bucket;
 884         struct page_header *ph;
 885         unsigned long taken, i, prev, pagesize, sp_bits, lp_bits;
 886
 887         sp_bits = small_page_bits(poolsize);
 888         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 889
 890         lp_bucket = large_page_bucket(bindex, sp_bits);
 891
 892         pagesize = 1UL << (lp_bucket ? lp_bits : sp_bits);
 893
 894         /* This many elements fit? */
 895         taken = page_header_size(bindex / INTER_BUCKET_SPACE,
 896                                  bs->elements_per_page);
 897         taken += bucket_to_size(bindex) * bs->elements_per_page;
 898         if (taken > pagesize)
 899                 return check_fail();
 900
 901         /* One more wouldn't fit? */
 902         taken = page_header_size(bindex / INTER_BUCKET_SPACE,
 903                                  bs->elements_per_page + 1);
 904         taken += bucket_to_size(bindex) * (bs->elements_per_page + 1);
 905         if (taken <= pagesize)
 906                 return check_fail();
 907
 908         /* Walk used list. */
 909         prev = 0;
 910         for (i = bs->page_list; i; i = ph->next) {
 911                 /* Bad pointer? */
 912                 if (out_of_bounds(i, sp_bits, pagesize, poolsize))
 913                         return check_fail();
 914                 /* Wrong size page? */
 915                 if (!!test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE)
 916                     != lp_bucket)
 917                         return check_fail();
 918                 /* Large page not on boundary? */
 919                 if (lp_bucket && (i % SMALL_PAGES_PER_LARGE_PAGE) != 0)
 920                         return check_fail();
 921                 ph = from_pgnum(head, i, sp_bits);
 922                 /* Linked list corrupt? */
 923                 if (ph->prev != prev)
 924                         return check_fail();
 925                 /* Already seen this page? */
 926                 if (test_bit(pages, i))
 927                         return check_fail();
 928                 set_bit(pages, i);
 929                 /* Empty or full? */
 930                 if (ph->elements_used == 0)
 931                         return check_fail();
 932                 if (ph->elements_used >= bs->elements_per_page)
 933                         return check_fail();
 934                 /* Used bits don't agree? */
 935                 if (ph->elements_used != count_bits(ph->used,
 936                                                     bs->elements_per_page))
 937                         return check_fail();
 938                 /* Wrong bucket? */
 939                 if (ph->bucket != bindex)
 940                         return check_fail();
 941                 prev = i;
 942         }
 943
 944         /* Walk full list. */
 945         prev = 0;
 946         for (i = bs->full_list; i; i = ph->next) {
 947                 /* Bad pointer? */
 948                 if (out_of_bounds(i, sp_bits, pagesize, poolsize))
 949                         return check_fail();
 950                 /* Wrong size page? */
 951                 if (!!test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE)
 952                     != lp_bucket)
 953                 /* Large page not on boundary? */
 954                 if (lp_bucket && (i % SMALL_PAGES_PER_LARGE_PAGE) != 0)
 955                         return check_fail();
 956                 ph = from_pgnum(head, i, sp_bits);
 957                 /* Linked list corrupt? */
 958                 if (ph->prev != prev)
 959                         return check_fail();
 960                 /* Already seen this page? */
 961                 if (test_bit(pages, i))
 962                         return check_fail();
 963                 set_bit(pages, i);
 964                 /* Not full? */
 965                 if (ph->elements_used != bs->elements_per_page)
 966                         return check_fail();
 967                 /* Used bits don't agree? */
 968                 if (ph->elements_used != count_bits(ph->used,
 969                                                     bs->elements_per_page))
 970                         return check_fail();
 971                 /* Wrong bucket? */
 972                 if (ph->bucket != bindex)
 973                         return check_fail();
 974                 prev = i;
 975         }
 976         return true;
 977 }
 978
 979 bool alloc_check(void *pool, unsigned long poolsize)
 980 {
 981         struct header *head = pool;
 982         unsigned long prev, i, lp_bits, sp_bits, header_size, num_buckets;
 983         struct page_header *ph;
 984         struct huge_alloc *ha;
 985         unsigned long pages[MAX_SMALL_PAGES / BITS_PER_LONG] = { 0 };
 986
 987         if (poolsize < MIN_USEFUL_SIZE)
 988                 return tiny_alloc_check(pool, poolsize);
 989
 990         sp_bits = small_page_bits(poolsize);
 991         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 992
 993         num_buckets = max_bucket(lp_bits);
 994
 995         header_size = sizeof(*head) + sizeof(head->bs) * (num_buckets-1);
 996
 997         /* First, set all bits taken by header. */
 998         for (i = 0; i < header_size; i += (1UL << sp_bits))
 999                 set_bit(pages, i >> sp_bits);
1000
1001         /* Check small page free list. */
1002         prev = 0;
1003         for (i = head->small_free_list; i; i = ph->next) {
1004                 /* Bad pointer? */
1005                 if (out_of_bounds(i, sp_bits, 1 << sp_bits, poolsize))
1006                         return check_fail();
1007                 /* Large page? */
1008                 if (test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE))
1009                         return check_fail();
1010                 ph = from_pgnum(head, i, sp_bits);
1011                 /* Linked list corrupt? */
1012                 if (ph->prev != prev)
1013                         return check_fail();
1014                 /* Already seen this page? */
1015                 if (test_bit(pages, i))
1016                         return check_fail();
1017                 set_bit(pages, i);
1018                 prev = i;
1019         }
1020
1021         /* Check large page free list. */
1022         prev = 0;
1023         for (i = head->large_free_list; i; i = ph->next) {
1024                 /* Bad pointer? */
1025                 if (out_of_bounds(i, sp_bits, 1 << lp_bits, poolsize))
1026                         return check_fail();
1027                 /* Not large page? */
1028                 if (!test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE))
1029                         return check_fail();
1030                 /* Not page boundary? */
1031                 if ((i % SMALL_PAGES_PER_LARGE_PAGE) != 0)
1032                         return check_fail();
1033                 ph = from_pgnum(head, i, sp_bits);
1034                 /* Linked list corrupt? */
1035                 if (ph->prev != prev)
1036                         return check_fail();
1037                 /* Already seen this page? */
1038                 if (test_bit(pages, i))
1039                         return check_fail();
1040                 set_bit(pages, i);
1041                 prev = i;
1042         }
1043
1044         /* Check the buckets. */
1045         for (i = 0; i < max_bucket(lp_bits); i++) {
1046                 struct bucket_state *bs = &head->bs[i];
1047
1048                 if (!check_bucket(head, poolsize, pages, bs, i))
1049                         return false;
1050         }
1051
1052         /* Check the huge alloc list. */
1053         prev = 0;
1054         for (i = head->huge; i; i = ha->next) {
1055                 unsigned long pgbits, j;
1056
1057                 /* Bad pointer? */
1058                 if (i >= poolsize || i + sizeof(*ha) > poolsize)
1059                         return check_fail();
1060                 ha = (void *)((char *)head + i);
1061
1062                 /* Check contents of ha. */
1063                 if (ha->off > poolsize || ha->off + ha->len > poolsize)
1064                         return check_fail();
1065
1066                 /* Large or small page? */
1067                 pgbits = test_bit(head->pagesize, ha->off >> lp_bits)
1068                         ? lp_bits : sp_bits;
1069
1070                 /* Not page boundary? */
1071                 if ((ha->off % (1UL << pgbits)) != 0)
1072                         return check_fail();
1073
1074                 /* Not page length? */
1075                 if ((ha->len % (1UL << pgbits)) != 0)
1076                         return check_fail();
1077
1078                 /* Linked list corrupt? */
1079                 if (ha->prev != prev)
1080                         return check_fail();
1081
1082                 for (j = ha->off; j < ha->off + ha->len; j += (1 << sp_bits)) {
1083                         /* Already seen this page? */
1084                         if (test_bit(pages, j >> sp_bits))
1085                                 return check_fail();
1086                         set_bit(pages, j >> sp_bits);
1087                 }
1088
1089                 prev = i;
1090         }
1091
1092         /* Make sure every page accounted for. */
1093         for (i = 0; i < poolsize >> sp_bits; i++) {
1094                 if (!test_bit(pages, i))
1095                         return check_fail();
1096                 if (test_bit(head->pagesize,
1097                              i >> BITS_FROM_SMALL_TO_LARGE_PAGE)) {
1098                         /* Large page, skip rest. */
1099                         i += SMALL_PAGES_PER_LARGE_PAGE - 1;
1100                 }
1101         }
1102
1103         return true;
1104 }
1105
1106 static unsigned long print_overhead(FILE *out, const char *desc,
1107                                     unsigned long bytes,
1108                                     unsigned long poolsize)
1109 {
1110         fprintf(out, "Overhead (%s): %lu bytes (%.3g%%)\n",
1111                 desc, bytes, 100.0 * bytes / poolsize);
1112         return bytes;
1113 }
1114
1115 static unsigned long count_list(struct header *head,
1116                                 u16 pgnum,
1117                                 unsigned int sp_bits,
1118                                 unsigned long *total_elems)
1119 {
1120         struct page_header *p;
1121         unsigned long ret = 0;
1122
1123         while (pgnum) {
1124                 p = from_pgnum(head, pgnum, sp_bits);
1125                 if (total_elems)
1126                         (*total_elems) += p->elements_used;
1127                 ret++;
1128                 pgnum = p->next;
1129         }
1130         return ret;
1131 }
1132
1133 static unsigned long visualize_bucket(FILE *out, struct header *head,
1134                                       unsigned int bucket,
1135                                       unsigned long poolsize,
1136                                       unsigned int sp_bits)
1137 {
1138         unsigned long num_full, num_partial, num_pages, page_size,
1139                 elems, hdr_min, hdr_size, elems_per_page, overhead = 0;
1140
1141         elems_per_page = head->bs[bucket].elements_per_page;
1142
1143         /* If we used byte-based bitmaps, we could get pg hdr to: */
1144         hdr_min = sizeof(struct page_header)
1145                 - sizeof(((struct page_header *)0)->used)
1146                 + align_up(elems_per_page, CHAR_BIT) / CHAR_BIT;
1147         hdr_size = page_header_size(bucket / INTER_BUCKET_SPACE,
1148                                     elems_per_page);
1149
1150         elems = 0;
1151         num_full = count_list(head, head->bs[bucket].full_list, sp_bits,
1152                               &elems);
1153         num_partial = count_list(head, head->bs[bucket].page_list, sp_bits,
1154                                  &elems);
1155         num_pages = num_full + num_partial;
1156         if (!num_pages)
1157                 return 0;
1158
1159         fprintf(out, "Bucket %u (%lu bytes):"
1160                 " %lu full, %lu partial = %lu elements\n",
1161                 bucket, bucket_to_size(bucket), num_full, num_partial, elems);
1162         /* Strict requirement of page header size. */
1163         overhead += print_overhead(out, "page headers",
1164                                    hdr_min * num_pages, poolsize);
1165         /* Gap between minimal page header and actual start. */
1166         overhead += print_overhead(out, "page post-header alignments",
1167                                    (hdr_size - hdr_min) * num_pages, poolsize);
1168         /* Between last element and end of page. */
1169         page_size = (1 << sp_bits);
1170         if (large_page_bucket(bucket, sp_bits))
1171                 page_size <<= BITS_FROM_SMALL_TO_LARGE_PAGE;
1172
1173         overhead += print_overhead(out, "page tails",
1174                                    (page_size - (hdr_size
1175                                                  + (elems_per_page
1176                                                     * bucket_to_size(bucket))))
1177                                    * num_pages, poolsize);
1178         return overhead;
1179 }
1180
1181 void alloc_visualize(FILE *out, void *pool, unsigned long poolsize)
1182 {
1183         struct header *head = pool;
1184         unsigned long i, lp_bits, sp_bits, header_size, num_buckets, count,
1185                 overhead = 0;
1186
1187         fprintf(out, "Pool %p size %lu: (%s allocator)\n", pool, poolsize,
1188                 poolsize < MIN_USEFUL_SIZE ? "tiny" : "standard");
1189
1190         if (poolsize < MIN_USEFUL_SIZE) {
1191                 tiny_alloc_visualize(out, pool, poolsize);
1192                 return;
1193         }
1194
1195         sp_bits = small_page_bits(poolsize);
1196         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
1197
1198         num_buckets = max_bucket(lp_bits);
1199         header_size = sizeof(*head) + sizeof(head->bs) * (num_buckets-1);
1200
1201         fprintf(out, "Large page size %lu, small page size %lu.\n",
1202                 1UL << lp_bits, 1UL << sp_bits);
1203         overhead += print_overhead(out, "unused pool tail",
1204                                    poolsize % (1 << lp_bits), poolsize);
1205         fprintf(out, "Main header %lu bytes (%lu small pages).\n",
1206                 header_size, align_up(header_size, 1 << sp_bits) >> sp_bits);
1207         overhead += print_overhead(out, "partial header page",
1208                                    align_up(header_size, 1 << sp_bits)
1209                                    - header_size, poolsize);
1210         /* Total large pages. */
1211         i = count_bits(head->pagesize, poolsize >> lp_bits);
1212         /* Used pages. */
1213         count = i - count_list(head, head->large_free_list, sp_bits, NULL);
1214         fprintf(out, "%lu/%lu large pages used (%.3g%%)\n",
1215                 count, i, count ? 100.0 * count / i : 0.0);
1216
1217         /* Total small pages. */
1218         i = ((poolsize >> lp_bits) - i) << BITS_FROM_SMALL_TO_LARGE_PAGE;
1219         /* Used pages */
1220         count = i - count_list(head, head->small_free_list, sp_bits, NULL);
1221         fprintf(out, "%lu/%lu small pages used (%.3g%%)\n",
1222                 count, i, count ? 100.0 * count / i : 0.0);
1223
1224         /* Summary of each bucket. */
1225         fprintf(out, "%lu buckets:\n", num_buckets);
1226         for (i = 0; i < num_buckets; i++)
1227                 overhead += visualize_bucket(out, head, i, poolsize, sp_bits);
1228
1229         print_overhead(out, "total", overhead, poolsize);
1230 }