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 <ccan/compiler/compiler.h>
  15 #include "config.h"
  16
  17 /*
  18    Inspired by (and parts taken from) Andrew Tridgell's alloc_mmap:
  19    http://samba.org/~tridge/junkcode/alloc_mmap/
  20
  21    Copyright (C) Andrew Tridgell 2007
  22
  23    This library is free software; you can redistribute it and/or
  24    modify it under the terms of the GNU Lesser General Public
  25    License as published by the Free Software Foundation; either
  26    version 2 of the License, or (at your option) any later version.
  27
  28    This library is distributed in the hope that it will be useful,
  29    but WITHOUT ANY WARRANTY; without even the implied warranty of
  30    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  31    Lesser General Public License for more details.
  32
  33    You should have received a copy of the GNU Lesser General Public
  34    License along with this library; if not, write to the Free Software
  35    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  36  */
  37
  38 /* We divide the pool into this many large pages (nearest power of 2) */
  39 #define MAX_LARGE_PAGES (256UL)
  40
  41 /* 32 small pages == 1 large page. */
  42 #define BITS_FROM_SMALL_TO_LARGE_PAGE 5
  43
  44 #define MAX_SMALL_PAGES (MAX_LARGE_PAGES << BITS_FROM_SMALL_TO_LARGE_PAGE)
  45
  46 /* Smallest pool size for this scheme: 128-byte small pages.  That's
  47  * 9/13% overhead for 32/64 bit. */
  48 #define MIN_USEFUL_SIZE (MAX_SMALL_PAGES * 128)
  49
  50 /* Every 4 buckets, we jump up a power of 2. ...8 10 12 14 16 20 24 28 32... */
  51 #define INTER_BUCKET_SPACE 4
  52
  53 #define SMALL_PAGES_PER_LARGE_PAGE (1 << BITS_FROM_SMALL_TO_LARGE_PAGE)
  54
  55 /* FIXME: Figure this out properly. */
  56 #define MAX_SIZE (1 << 30)
  57
  58 /* How few object to fit in a page before using a larger one? (8) */
  59 #define MAX_PAGE_OBJECT_ORDER   3
  60
  61 #define BITS_PER_LONG (sizeof(long) * CHAR_BIT)
  62
  63 struct bucket_state {
  64         u32 elements_per_page;
  65         u16 page_list;
  66         u16 full_list;
  67 };
  68
  69 struct header {
  70         /* Bitmap of which pages are large. */
  71         unsigned long pagesize[MAX_LARGE_PAGES / BITS_PER_LONG];
  72
  73         /* List of unused small/large pages. */
  74         u16 small_free_list;
  75         u16 large_free_list;
  76
  77         /* List of huge allocs. */
  78         unsigned long huge;
  79
  80         /* This is less defined: we have two buckets for each power of 2 */
  81         struct bucket_state bs[1];
  82 };
  83
  84 struct huge_alloc {
  85         unsigned long next, prev;
  86         unsigned long off, len;
  87 };
  88
  89 struct page_header {
  90         u16 next, prev;
  91         /* FIXME: We can just count all-0 and all-1 used[] elements. */
  92         unsigned elements_used : 25;
  93         unsigned bucket : 7;
  94         unsigned long used[1]; /* One bit per element. */
  95 };
  96
  97 /*
  98  * Every 4 buckets, the size doubles.
  99  * Between buckets, sizes increase linearly.
 100  *
 101  * eg. bucket 40 = 2^10                 = 1024
 102  *     bucket 41 = 2^10 + 2^10*4        = 1024 + 256
 103  *     bucket 42 = 2^10 + 2^10*4        = 1024 + 512
 104  *     bucket 43 = 2^10 + 2^10*4        = 1024 + 768
 105  *     bucket 45 = 2^11                 = 2048
 106  *
 107  * Care is taken to handle low numbered buckets, at cost of overflow.
 108  */
 109 static unsigned long bucket_to_size(unsigned int bucket)
 110 {
 111         unsigned long base = 1UL << (bucket / INTER_BUCKET_SPACE);
 112         return base + ((bucket % INTER_BUCKET_SPACE)
 113                        << (bucket / INTER_BUCKET_SPACE))
 114                 / INTER_BUCKET_SPACE;
 115 }
 116
 117 /*
 118  * Say size is 10.
 119  *   fls(size/2) == 3.  1 << 3 == 8, so we're 2 too large, out of a possible
 120  * 8 too large.  That's 1/4 of the way to the next power of 2 == 1 bucket.
 121  *
 122  * We make sure we round up.  Note that this fails on 32 bit at size
 123  * 1879048193 (around bucket 120).
 124  */
 125 static unsigned int size_to_bucket(unsigned long size)
 126 {
 127         unsigned int base = afls(size/2);
 128         unsigned long overshoot;
 129
 130         overshoot = size - (1UL << base);
 131         return base * INTER_BUCKET_SPACE
 132                 + ((overshoot * INTER_BUCKET_SPACE + (1UL << base)-1) >> base);
 133 }
 134
 135 static unsigned int small_page_bits(unsigned long poolsize)
 136 {
 137         return afls(poolsize / MAX_SMALL_PAGES - 1);
 138 }
 139
 140 static struct page_header *from_pgnum(struct header *head,
 141                                       unsigned long pgnum,
 142                                       unsigned sp_bits)
 143 {
 144         return (struct page_header *)((char *)head + (pgnum << sp_bits));
 145 }
 146
 147 static u16 to_pgnum(struct header *head, void *p, unsigned sp_bits)
 148 {
 149         return ((char *)p - (char *)head) >> sp_bits;
 150 }
 151
 152 static size_t used_size(unsigned int num_elements)
 153 {
 154         return align_up(num_elements, BITS_PER_LONG) / CHAR_BIT;
 155 }
 156
 157 /*
 158  * We always align the first entry to the lower power of 2.
 159  * eg. the 12-byte bucket gets 8-byte aligned.  The 4096-byte bucket
 160  * gets 4096-byte aligned.
 161  */
 162 static unsigned long page_header_size(unsigned int align_bits,
 163                                       unsigned long num_elements)
 164 {
 165         unsigned long size;
 166
 167         size = sizeof(struct page_header)
 168                 - sizeof(((struct page_header *)0)->used)
 169                 + used_size(num_elements);
 170         return align_up(size, 1UL << align_bits);
 171 }
 172
 173 static void add_to_list(struct header *head,
 174                         u16 *list, struct page_header *ph, unsigned sp_bits)
 175 {
 176         unsigned long h = *list, offset = to_pgnum(head, ph, sp_bits);
 177
 178         ph->next = h;
 179         if (h) {
 180                 struct page_header *prev = from_pgnum(head, h, sp_bits);
 181                 assert(prev->prev == 0);
 182                 prev->prev = offset;
 183         }
 184         *list = offset;
 185         ph->prev = 0;
 186 }
 187
 188 static void del_from_list(struct header *head,
 189                           u16 *list, struct page_header *ph, unsigned sp_bits)
 190 {
 191         /* Front of list? */
 192         if (ph->prev == 0) {
 193                 *list = ph->next;
 194         } else {
 195                 struct page_header *prev = from_pgnum(head, ph->prev, sp_bits);
 196                 prev->next = ph->next;
 197         }
 198         if (ph->next != 0) {
 199                 struct page_header *next = from_pgnum(head, ph->next, sp_bits);
 200                 next->prev = ph->prev;
 201         }
 202 }
 203
 204 static u16 pop_from_list(struct header *head,
 205                                    u16 *list,
 206                                    unsigned int sp_bits)
 207 {
 208         u16 h = *list;
 209         struct page_header *ph = from_pgnum(head, h, sp_bits);
 210
 211         if (likely(h)) {
 212                 *list = ph->next;
 213                 if (*list)
 214                         from_pgnum(head, *list, sp_bits)->prev = 0;
 215         }
 216         return h;
 217 }
 218
 219 static void add_to_huge_list(struct header *head, struct huge_alloc *ha)
 220 {
 221         unsigned long h = head->huge;
 222         unsigned long offset = (char *)ha - (char *)head;
 223
 224         ha->next = h;
 225         if (h) {
 226                 struct huge_alloc *prev = (void *)((char *)head + h);
 227                 assert(prev->prev == 0);
 228                 prev->prev = offset;
 229         }
 230         head->huge = offset;
 231         ha->prev = 0;
 232 }
 233
 234 static void del_from_huge(struct header *head, struct huge_alloc *ha)
 235 {
 236         /* Front of list? */
 237         if (ha->prev == 0) {
 238                 head->huge = ha->next;
 239         } else {
 240                 struct huge_alloc *prev = (void *)((char *)head + ha->prev);
 241                 prev->next = ha->next;
 242         }
 243         if (ha->next != 0) {
 244                 struct huge_alloc *next = (void *)((char *)head + ha->next);
 245                 next->prev = ha->prev;
 246         }
 247 }
 248
 249 static void add_small_page_to_freelist(struct header *head,
 250                                        struct page_header *ph,
 251                                        unsigned int sp_bits)
 252 {
 253         add_to_list(head, &head->small_free_list, ph, sp_bits);
 254 }
 255
 256 static void add_large_page_to_freelist(struct header *head,
 257                                        struct page_header *ph,
 258                                        unsigned int sp_bits)
 259 {
 260         add_to_list(head, &head->large_free_list, ph, sp_bits);
 261 }
 262
 263 static void add_to_bucket_list(struct header *head,
 264                                struct bucket_state *bs,
 265                                struct page_header *ph,
 266                                unsigned int sp_bits)
 267 {
 268         add_to_list(head, &bs->page_list, ph, sp_bits);
 269 }
 270
 271 static void del_from_bucket_list(struct header *head,
 272                                  struct bucket_state *bs,
 273                                  struct page_header *ph,
 274                                  unsigned int sp_bits)
 275 {
 276         del_from_list(head, &bs->page_list, ph, sp_bits);
 277 }
 278
 279 static void del_from_bucket_full_list(struct header *head,
 280                                       struct bucket_state *bs,
 281                                       struct page_header *ph,
 282                                       unsigned int sp_bits)
 283 {
 284         del_from_list(head, &bs->full_list, ph, sp_bits);
 285 }
 286
 287 static void add_to_bucket_full_list(struct header *head,
 288                                     struct bucket_state *bs,
 289                                     struct page_header *ph,
 290                                     unsigned int sp_bits)
 291 {
 292         add_to_list(head, &bs->full_list, ph, sp_bits);
 293 }
 294
 295 static void clear_bit(unsigned long bitmap[], unsigned int off)
 296 {
 297         bitmap[off / BITS_PER_LONG] &= ~(1UL << (off % BITS_PER_LONG));
 298 }
 299
 300 static bool test_bit(const unsigned long bitmap[], unsigned int off)
 301 {
 302         return bitmap[off / BITS_PER_LONG] & (1UL << (off % BITS_PER_LONG));
 303 }
 304
 305 static void set_bit(unsigned long bitmap[], unsigned int off)
 306 {
 307         bitmap[off / BITS_PER_LONG] |= (1UL << (off % BITS_PER_LONG));
 308 }
 309
 310 /* There must be a bit to be found. */
 311 static unsigned int find_free_bit(const unsigned long bitmap[])
 312 {
 313         unsigned int i;
 314
 315         for (i = 0; bitmap[i] == -1UL; i++);
 316         return (i*BITS_PER_LONG) + affsl(~bitmap[i]) - 1;
 317 }
 318
 319 /* How many elements can we fit in a page? */
 320 static unsigned long elements_per_page(unsigned long align_bits,
 321                                        unsigned long esize,
 322                                        unsigned long psize)
 323 {
 324         unsigned long num, overhead;
 325
 326         /* First approximation: no extra room for bitmap. */
 327         overhead = align_up(sizeof(struct page_header), 1UL << align_bits);
 328         num = (psize - overhead) / esize;
 329
 330         while (page_header_size(align_bits, num) + esize * num > psize)
 331                 num--;
 332         return num;
 333 }
 334
 335 static bool large_page_bucket(unsigned int bucket, unsigned int sp_bits)
 336 {
 337         unsigned long max_smallsize;
 338
 339         /* Note: this doesn't take into account page header. */
 340         max_smallsize = (1UL << sp_bits) >> MAX_PAGE_OBJECT_ORDER;
 341
 342         return bucket_to_size(bucket) > max_smallsize;
 343 }
 344
 345 static unsigned int max_bucket(unsigned int lp_bits)
 346 {
 347         return (lp_bits - MAX_PAGE_OBJECT_ORDER) * INTER_BUCKET_SPACE;
 348 }
 349
 350 void alloc_init(void *pool, unsigned long poolsize)
 351 {
 352         struct header *head = pool;
 353         struct page_header *ph;
 354         unsigned int lp_bits, sp_bits, num_buckets;
 355         unsigned long header_size, i;
 356
 357         if (poolsize < MIN_USEFUL_SIZE) {
 358                 tiny_alloc_init(pool, poolsize);
 359                 return;
 360         }
 361
 362         /* We rely on page numbers fitting in 16 bit. */
 363         BUILD_ASSERT(MAX_SMALL_PAGES < 65536);
 364
 365         sp_bits = small_page_bits(poolsize);
 366         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 367
 368         num_buckets = max_bucket(lp_bits);
 369
 370         head = pool;
 371         header_size = sizeof(*head) + sizeof(head->bs) * (num_buckets-1);
 372
 373         memset(head, 0, header_size);
 374         for (i = 0; i < num_buckets; i++) {
 375                 unsigned long pagesize;
 376
 377                 if (large_page_bucket(i, sp_bits))
 378                         pagesize = 1UL << lp_bits;
 379                 else
 380                         pagesize = 1UL << sp_bits;
 381
 382                 head->bs[i].elements_per_page
 383                         = elements_per_page(i / INTER_BUCKET_SPACE,
 384                                             bucket_to_size(i),
 385                                             pagesize);
 386         }
 387
 388         /* They start as all large pages. */
 389         memset(head->pagesize, 0xFF, sizeof(head->pagesize));
 390         /* FIXME: small pages for last bit? */
 391
 392         /* Split first page into small pages. */
 393         assert(header_size < (1UL << lp_bits));
 394         clear_bit(head->pagesize, 0);
 395
 396         /* Skip over page(s) used by header, add rest to free list */
 397         for (i = align_up(header_size, (1UL << sp_bits)) >> sp_bits;
 398              i < SMALL_PAGES_PER_LARGE_PAGE;
 399              i++) {
 400                 ph = from_pgnum(head, i, sp_bits);
 401                 ph->elements_used = 0;
 402                 add_small_page_to_freelist(head, ph, sp_bits);
 403         }
 404
 405         /* Add the rest of the pages as large pages. */
 406         i = SMALL_PAGES_PER_LARGE_PAGE;
 407         while ((i << sp_bits) + (1UL << lp_bits) <= poolsize) {
 408                 assert(i < MAX_SMALL_PAGES);
 409                 ph = from_pgnum(head, i, sp_bits);
 410                 ph->elements_used = 0;
 411                 add_large_page_to_freelist(head, ph, sp_bits);
 412                 i += SMALL_PAGES_PER_LARGE_PAGE;
 413         }
 414 }
 415
 416 /* A large page worth of small pages are free: delete them from free list. */
 417 static void del_large_from_small_free_list(struct header *head,
 418                                            struct page_header *ph,
 419                                            unsigned int sp_bits)
 420 {
 421         unsigned long i;
 422
 423         for (i = 0; i < SMALL_PAGES_PER_LARGE_PAGE; i++) {
 424                 del_from_list(head, &head->small_free_list,
 425                               (struct page_header *)((char *)ph
 426                                                      + (i << sp_bits)),
 427                               sp_bits);
 428         }
 429 }
 430
 431 static bool all_empty(struct header *head,
 432                       unsigned long pgnum,
 433                       unsigned sp_bits)
 434 {
 435         unsigned long i;
 436
 437         for (i = 0; i < SMALL_PAGES_PER_LARGE_PAGE; i++) {
 438                 struct page_header *ph = from_pgnum(head, pgnum + i, sp_bits);
 439                 if (ph->elements_used)
 440                         return false;
 441         }
 442         return true;
 443 }
 444
 445 static void recombine_small_pages(struct header *head, unsigned long poolsize,
 446                                   unsigned int sp_bits)
 447 {
 448         unsigned long i;
 449         unsigned int lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 450
 451         /* Look for small pages to coalesce, after first large page. */
 452         for (i = SMALL_PAGES_PER_LARGE_PAGE;
 453              i < (poolsize >> lp_bits) << BITS_FROM_SMALL_TO_LARGE_PAGE;
 454              i += SMALL_PAGES_PER_LARGE_PAGE) {
 455                 /* Already a large page? */
 456                 if (test_bit(head->pagesize, i / SMALL_PAGES_PER_LARGE_PAGE))
 457                         continue;
 458                 if (all_empty(head, i, sp_bits)) {
 459                         struct page_header *ph = from_pgnum(head, i, sp_bits);
 460                         set_bit(head->pagesize,
 461                                 i / SMALL_PAGES_PER_LARGE_PAGE);
 462                         del_large_from_small_free_list(head, ph, sp_bits);
 463                         add_large_page_to_freelist(head, ph, sp_bits);
 464                 }
 465         }
 466 }
 467
 468 static u16 get_large_page(struct header *head, unsigned long poolsize,
 469                           unsigned int sp_bits)
 470 {
 471         unsigned int page;
 472
 473         page = pop_from_list(head, &head->large_free_list, sp_bits);
 474         if (likely(page))
 475                 return page;
 476
 477         recombine_small_pages(head, poolsize, sp_bits);
 478
 479         return pop_from_list(head, &head->large_free_list, sp_bits);
 480 }
 481
 482 /* Returns small page. */
 483 static unsigned long break_up_large_page(struct header *head,
 484                                          unsigned int sp_bits,
 485                                          u16 lpage)
 486 {
 487         unsigned int i;
 488
 489         clear_bit(head->pagesize, lpage >> BITS_FROM_SMALL_TO_LARGE_PAGE);
 490
 491         for (i = 1; i < SMALL_PAGES_PER_LARGE_PAGE; i++) {
 492                 struct page_header *ph = from_pgnum(head, lpage + i, sp_bits);
 493                 /* Initialize this: huge_alloc reads it. */
 494                 ph->elements_used = 0;
 495                 add_small_page_to_freelist(head, ph, sp_bits);
 496         }
 497
 498         return lpage;
 499 }
 500
 501 static u16 get_small_page(struct header *head, unsigned long poolsize,
 502                           unsigned int sp_bits)
 503 {
 504         u16 ret;
 505
 506         ret = pop_from_list(head, &head->small_free_list, sp_bits);
 507         if (likely(ret))
 508                 return ret;
 509         ret = get_large_page(head, poolsize, sp_bits);
 510         if (likely(ret))
 511                 ret = break_up_large_page(head, sp_bits, ret);
 512         return ret;
 513 }
 514
 515 static bool huge_allocated(struct header *head, unsigned long offset)
 516 {
 517         unsigned long i;
 518         struct huge_alloc *ha;
 519
 520         for (i = head->huge; i; i = ha->next) {
 521                 ha = (void *)((char *)head + i);
 522                 if (ha->off <= offset && ha->off + ha->len > offset)
 523                         return true;
 524         }
 525         return false;
 526 }
 527
 528 /* They want something really big.  Aim for contiguous pages (slow). */
 529 static COLD void *huge_alloc(void *pool, unsigned long poolsize,
 530                              unsigned long size, unsigned long align)
 531 {
 532         struct header *head = pool;
 533         struct huge_alloc *ha;
 534         unsigned long i, sp_bits, lp_bits, num, header_size;
 535
 536         sp_bits = small_page_bits(poolsize);
 537         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 538
 539         /* Allocate tracking structure optimistically. */
 540         ha = alloc_get(pool, poolsize, sizeof(*ha), ALIGNOF(*ha));
 541         if (!ha)
 542                 return NULL;
 543
 544         /* First search for contiguous small pages... */
 545         header_size = sizeof(*head) + sizeof(head->bs) * (max_bucket(lp_bits)-1);
 546
 547         num = 0;
 548         for (i = (header_size + (1UL << sp_bits) - 1) >> sp_bits;
 549              i << sp_bits < poolsize;
 550              i++) {
 551                 struct page_header *pg;
 552                 unsigned long off = (i << sp_bits);
 553
 554                 /* Skip over large pages. */
 555                 if (test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE)) {
 556                         i += (1UL << BITS_FROM_SMALL_TO_LARGE_PAGE)-1;
 557                         continue;
 558                 }
 559
 560                 /* Does this page meet alignment requirements? */
 561                 if (!num && off % align != 0)
 562                         continue;
 563
 564                 /* FIXME: This makes us O(n^2). */
 565                 if (huge_allocated(head, off)) {
 566                         num = 0;
 567                         continue;
 568                 }
 569
 570                 pg = (struct page_header *)((char *)head + off);
 571                 if (pg->elements_used) {
 572                         num = 0;
 573                         continue;
 574                 }
 575
 576                 num++;
 577                 if (num << sp_bits >= size) {
 578                         unsigned long pgnum;
 579
 580                         /* Remove from free list. */
 581                         for (pgnum = i; pgnum > i - num; pgnum--) {
 582                                 pg = from_pgnum(head, pgnum, sp_bits);
 583                                 del_from_list(head,
 584                                               &head->small_free_list,
 585                                               pg, sp_bits);
 586                         }
 587                         ha->off = (i - num + 1) << sp_bits;
 588                         ha->len = num << sp_bits;
 589                         goto done;
 590                 }
 591         }
 592
 593         /* Now search for large pages... */
 594         recombine_small_pages(head, poolsize, sp_bits);
 595
 596         num = 0;
 597         for (i = (header_size + (1UL << lp_bits) - 1) >> lp_bits;
 598              (i << lp_bits) < poolsize; i++) {
 599                 struct page_header *pg;
 600                 unsigned long off = (i << lp_bits);
 601
 602                 /* Ignore small pages. */
 603                 if (!test_bit(head->pagesize, i))
 604                         continue;
 605
 606                 /* Does this page meet alignment requirements? */
 607                 if (!num && off % align != 0)
 608                         continue;
 609
 610                 /* FIXME: This makes us O(n^2). */
 611                 if (huge_allocated(head, off)) {
 612                         num = 0;
 613                         continue;
 614                 }
 615
 616                 pg = (struct page_header *)((char *)head + off);
 617                 if (pg->elements_used) {
 618                         num = 0;
 619                         continue;
 620                 }
 621
 622                 num++;
 623                 if (num << lp_bits >= size) {
 624                         unsigned long pgnum;
 625
 626                         /* Remove from free list. */
 627                         for (pgnum = i; pgnum > i - num; pgnum--) {
 628                                 pg = from_pgnum(head, pgnum, lp_bits);
 629                                 del_from_list(head,
 630                                               &head->large_free_list,
 631                                               pg, sp_bits);
 632                         }
 633                         ha->off = (i - num + 1) << lp_bits;
 634                         ha->len = num << lp_bits;
 635                         goto done;
 636                 }
 637         }
 638
 639         /* Unable to satisfy: free huge alloc structure. */
 640         alloc_free(pool, poolsize, ha);
 641         return NULL;
 642
 643 done:
 644         add_to_huge_list(pool, ha);
 645         return (char *)pool + ha->off;
 646 }
 647
 648 static COLD void
 649 huge_free(struct header *head, unsigned long poolsize, void *free)
 650 {
 651         unsigned long i, off, pgnum, free_off = (char *)free - (char *)head;
 652         unsigned int sp_bits, lp_bits;
 653         struct huge_alloc *ha;
 654
 655         for (i = head->huge; i; i = ha->next) {
 656                 ha = (void *)((char *)head + i);
 657                 if (free_off == ha->off)
 658                         break;
 659         }
 660         assert(i);
 661
 662         /* Free up all the pages, delete and free ha */
 663         sp_bits = small_page_bits(poolsize);
 664         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 665         pgnum = free_off >> sp_bits;
 666
 667         if (test_bit(head->pagesize, pgnum >> BITS_FROM_SMALL_TO_LARGE_PAGE)) {
 668                 for (off = ha->off;
 669                      off < ha->off + ha->len;
 670                      off += 1UL << lp_bits) {
 671                         add_large_page_to_freelist(head,
 672                                                    (void *)((char *)head + off),
 673                                                    sp_bits);
 674                 }
 675         } else {
 676                 for (off = ha->off;
 677                      off < ha->off + ha->len;
 678                      off += 1UL << sp_bits) {
 679                         add_small_page_to_freelist(head,
 680                                                    (void *)((char *)head + off),
 681                                                    sp_bits);
 682                 }
 683         }
 684         del_from_huge(head, ha);
 685         alloc_free(head, poolsize, ha);
 686 }
 687
 688 static COLD unsigned long huge_size(struct header *head, void *p)
 689 {
 690         unsigned long i, off = (char *)p - (char *)head;
 691         struct huge_alloc *ha;
 692
 693         for (i = head->huge; i; i = ha->next) {
 694                 ha = (void *)((char *)head + i);
 695                 if (off == ha->off) {
 696                         return ha->len;
 697                 }
 698         }
 699         abort();
 700 }
 701
 702 void *alloc_get(void *pool, unsigned long poolsize,
 703                 unsigned long size, unsigned long align)
 704 {
 705         struct header *head = pool;
 706         unsigned int bucket;
 707         unsigned long i;
 708         struct bucket_state *bs;
 709         struct page_header *ph;
 710         unsigned int sp_bits;
 711
 712         if (poolsize < MIN_USEFUL_SIZE) {
 713                 return tiny_alloc_get(pool, poolsize, size, align);
 714         }
 715
 716         size = align_up(size, align);
 717         if (unlikely(!size))
 718                 size = 1;
 719         bucket = size_to_bucket(size);
 720
 721         sp_bits = small_page_bits(poolsize);
 722
 723         if (bucket >= max_bucket(sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE)) {
 724                 return huge_alloc(pool, poolsize, size, align);
 725         }
 726
 727         bs = &head->bs[bucket];
 728
 729         if (!bs->page_list) {
 730                 struct page_header *ph;
 731
 732                 if (large_page_bucket(bucket, sp_bits))
 733                         bs->page_list = get_large_page(head, poolsize,
 734                                                        sp_bits);
 735                 else
 736                         bs->page_list = get_small_page(head, poolsize,
 737                                                        sp_bits);
 738                 /* FIXME: Try large-aligned alloc?  Header stuffing? */
 739                 if (unlikely(!bs->page_list))
 740                         return NULL;
 741                 ph = from_pgnum(head, bs->page_list, sp_bits);
 742                 ph->bucket = bucket;
 743                 ph->elements_used = 0;
 744                 ph->next = 0;
 745                 memset(ph->used, 0, used_size(bs->elements_per_page));
 746         }
 747
 748         ph = from_pgnum(head, bs->page_list, sp_bits);
 749
 750         i = find_free_bit(ph->used);
 751         set_bit(ph->used, i);
 752         ph->elements_used++;
 753
 754         /* check if this page is now full */
 755         if (unlikely(ph->elements_used == bs->elements_per_page)) {
 756                 del_from_bucket_list(head, bs, ph, sp_bits);
 757                 add_to_bucket_full_list(head, bs, ph, sp_bits);
 758         }
 759
 760         return (char *)ph + page_header_size(ph->bucket / INTER_BUCKET_SPACE,
 761                                              bs->elements_per_page)
 762                + i * bucket_to_size(bucket);
 763 }
 764
 765 void alloc_free(void *pool, unsigned long poolsize, void *free)
 766 {
 767         struct header *head = pool;
 768         struct bucket_state *bs;
 769         unsigned int sp_bits;
 770         unsigned long i, pgnum, pgoffset, offset = (char *)free - (char *)pool;
 771         bool smallpage;
 772         struct page_header *ph;
 773
 774         if (poolsize < MIN_USEFUL_SIZE) {
 775                 return tiny_alloc_free(pool, poolsize, free);
 776         }
 777
 778         /* Get page header. */
 779         sp_bits = small_page_bits(poolsize);
 780         pgnum = offset >> sp_bits;
 781
 782         /* Big page? Round down further. */
 783         if (test_bit(head->pagesize, pgnum >> BITS_FROM_SMALL_TO_LARGE_PAGE)) {
 784                 smallpage = false;
 785                 pgnum &= ~(SMALL_PAGES_PER_LARGE_PAGE - 1);
 786         } else
 787                 smallpage = true;
 788
 789         /* Step back to page header. */
 790         ph = from_pgnum(head, pgnum, sp_bits);
 791         if ((void *)ph == free) {
 792                 huge_free(head, poolsize, free);
 793                 return;
 794         }
 795
 796         bs = &head->bs[ph->bucket];
 797         pgoffset = offset - (pgnum << sp_bits)
 798                 - page_header_size(ph->bucket / INTER_BUCKET_SPACE,
 799                                    bs->elements_per_page);
 800
 801         if (unlikely(ph->elements_used == bs->elements_per_page)) {
 802                 del_from_bucket_full_list(head, bs, ph, sp_bits);
 803                 add_to_bucket_list(head, bs, ph, sp_bits);
 804         }
 805
 806         /* Which element are we? */
 807         i = pgoffset / bucket_to_size(ph->bucket);
 808         clear_bit(ph->used, i);
 809         ph->elements_used--;
 810
 811         if (unlikely(ph->elements_used == 0)) {
 812                 bs = &head->bs[ph->bucket];
 813                 del_from_bucket_list(head, bs, ph, sp_bits);
 814                 if (smallpage)
 815                         add_small_page_to_freelist(head, ph, sp_bits);
 816                 else
 817                         add_large_page_to_freelist(head, ph, sp_bits);
 818         }
 819 }
 820
 821 unsigned long alloc_size(void *pool, unsigned long poolsize, void *p)
 822 {
 823         struct header *head = pool;
 824         unsigned int pgnum, sp_bits;
 825         unsigned long offset = (char *)p - (char *)pool;
 826         struct page_header *ph;
 827
 828         if (poolsize < MIN_USEFUL_SIZE)
 829                 return tiny_alloc_size(pool, poolsize, p);
 830
 831         /* Get page header. */
 832         sp_bits = small_page_bits(poolsize);
 833         pgnum = offset >> sp_bits;
 834
 835         /* Big page? Round down further. */
 836         if (test_bit(head->pagesize, pgnum >> BITS_FROM_SMALL_TO_LARGE_PAGE))
 837                 pgnum &= ~(SMALL_PAGES_PER_LARGE_PAGE - 1);
 838
 839         /* Step back to page header. */
 840         ph = from_pgnum(head, pgnum, sp_bits);
 841         if ((void *)ph == p)
 842                 return huge_size(head, p);
 843
 844         return bucket_to_size(ph->bucket);
 845 }
 846
 847 /* Useful for gdb breakpoints. */
 848 static bool check_fail(void)
 849 {
 850         return false;
 851 }
 852
 853 static unsigned long count_bits(const unsigned long bitmap[],
 854                                 unsigned long limit)
 855 {
 856         unsigned long i, count = 0;
 857
 858         while (limit >= BITS_PER_LONG) {
 859                 count += popcount(bitmap[0]);
 860                 bitmap++;
 861                 limit -= BITS_PER_LONG;
 862         }
 863
 864         for (i = 0; i < limit; i++)
 865                 if (test_bit(bitmap, i))
 866                         count++;
 867         return count;
 868 }
 869
 870 static bool out_of_bounds(unsigned long pgnum,
 871                           unsigned int sp_bits,
 872                           unsigned long pagesize,
 873                           unsigned long poolsize)
 874 {
 875         if (((pgnum << sp_bits) >> sp_bits) != pgnum)
 876                 return true;
 877
 878         if ((pgnum << sp_bits) > poolsize)
 879                 return true;
 880
 881         return ((pgnum << sp_bits) + pagesize > poolsize);
 882 }
 883
 884 static bool check_bucket(struct header *head,
 885                          unsigned long poolsize,
 886                          unsigned long pages[],
 887                          struct bucket_state *bs,
 888                          unsigned int bindex)
 889 {
 890         bool lp_bucket;
 891         struct page_header *ph;
 892         unsigned long taken, i, prev, pagesize, sp_bits, lp_bits;
 893
 894         sp_bits = small_page_bits(poolsize);
 895         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 896
 897         lp_bucket = large_page_bucket(bindex, sp_bits);
 898
 899         pagesize = 1UL << (lp_bucket ? lp_bits : sp_bits);
 900
 901         /* This many elements fit? */
 902         taken = page_header_size(bindex / INTER_BUCKET_SPACE,
 903                                  bs->elements_per_page);
 904         taken += bucket_to_size(bindex) * bs->elements_per_page;
 905         if (taken > pagesize)
 906                 return check_fail();
 907
 908         /* One more wouldn't fit? */
 909         taken = page_header_size(bindex / INTER_BUCKET_SPACE,
 910                                  bs->elements_per_page + 1);
 911         taken += bucket_to_size(bindex) * (bs->elements_per_page + 1);
 912         if (taken <= pagesize)
 913                 return check_fail();
 914
 915         /* Walk used list. */
 916         prev = 0;
 917         for (i = bs->page_list; i; i = ph->next) {
 918                 /* Bad pointer? */
 919                 if (out_of_bounds(i, sp_bits, pagesize, poolsize))
 920                         return check_fail();
 921                 /* Wrong size page? */
 922                 if (!!test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE)
 923                     != lp_bucket)
 924                         return check_fail();
 925                 /* Large page not on boundary? */
 926                 if (lp_bucket && (i % SMALL_PAGES_PER_LARGE_PAGE) != 0)
 927                         return check_fail();
 928                 ph = from_pgnum(head, i, sp_bits);
 929                 /* Linked list corrupt? */
 930                 if (ph->prev != prev)
 931                         return check_fail();
 932                 /* Already seen this page? */
 933                 if (test_bit(pages, i))
 934                         return check_fail();
 935                 set_bit(pages, i);
 936                 /* Empty or full? */
 937                 if (ph->elements_used == 0)
 938                         return check_fail();
 939                 if (ph->elements_used >= bs->elements_per_page)
 940                         return check_fail();
 941                 /* Used bits don't agree? */
 942                 if (ph->elements_used != count_bits(ph->used,
 943                                                     bs->elements_per_page))
 944                         return check_fail();
 945                 /* Wrong bucket? */
 946                 if (ph->bucket != bindex)
 947                         return check_fail();
 948                 prev = i;
 949         }
 950
 951         /* Walk full list. */
 952         prev = 0;
 953         for (i = bs->full_list; i; i = ph->next) {
 954                 /* Bad pointer? */
 955                 if (out_of_bounds(i, sp_bits, pagesize, poolsize))
 956                         return check_fail();
 957                 /* Wrong size page? */
 958                 if (!!test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE)
 959                     != lp_bucket)
 960                 /* Large page not on boundary? */
 961                 if (lp_bucket && (i % SMALL_PAGES_PER_LARGE_PAGE) != 0)
 962                         return check_fail();
 963                 ph = from_pgnum(head, i, sp_bits);
 964                 /* Linked list corrupt? */
 965                 if (ph->prev != prev)
 966                         return check_fail();
 967                 /* Already seen this page? */
 968                 if (test_bit(pages, i))
 969                         return check_fail();
 970                 set_bit(pages, i);
 971                 /* Not full? */
 972                 if (ph->elements_used != bs->elements_per_page)
 973                         return check_fail();
 974                 /* Used bits don't agree? */
 975                 if (ph->elements_used != count_bits(ph->used,
 976                                                     bs->elements_per_page))
 977                         return check_fail();
 978                 /* Wrong bucket? */
 979                 if (ph->bucket != bindex)
 980                         return check_fail();
 981                 prev = i;
 982         }
 983         return true;
 984 }
 985
 986 bool alloc_check(void *pool, unsigned long poolsize)
 987 {
 988         struct header *head = pool;
 989         unsigned long prev, i, lp_bits, sp_bits, header_size, num_buckets;
 990         struct page_header *ph;
 991         struct huge_alloc *ha;
 992         unsigned long pages[MAX_SMALL_PAGES / BITS_PER_LONG] = { 0 };
 993
 994         if (poolsize < MIN_USEFUL_SIZE)
 995                 return tiny_alloc_check(pool, poolsize);
 996
 997         sp_bits = small_page_bits(poolsize);
 998         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 999
1000         num_buckets = max_bucket(lp_bits);
1001
1002         header_size = sizeof(*head) + sizeof(head->bs) * (num_buckets-1);
1003
1004         /* First, set all bits taken by header. */
1005         for (i = 0; i < header_size; i += (1UL << sp_bits))
1006                 set_bit(pages, i >> sp_bits);
1007
1008         /* Check small page free list. */
1009         prev = 0;
1010         for (i = head->small_free_list; i; i = ph->next) {
1011                 /* Bad pointer? */
1012                 if (out_of_bounds(i, sp_bits, 1UL << sp_bits, poolsize))
1013                         return check_fail();
1014                 /* Large page? */
1015                 if (test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE))
1016                         return check_fail();
1017                 ph = from_pgnum(head, i, sp_bits);
1018                 /* Linked list corrupt? */
1019                 if (ph->prev != prev)
1020                         return check_fail();
1021                 /* Already seen this page? */
1022                 if (test_bit(pages, i))
1023                         return check_fail();
1024                 set_bit(pages, i);
1025                 prev = i;
1026         }
1027
1028         /* Check large page free list. */
1029         prev = 0;
1030         for (i = head->large_free_list; i; i = ph->next) {
1031                 /* Bad pointer? */
1032                 if (out_of_bounds(i, sp_bits, 1UL << lp_bits, poolsize))
1033                         return check_fail();
1034                 /* Not large page? */
1035                 if (!test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE))
1036                         return check_fail();
1037                 /* Not page boundary? */
1038                 if ((i % SMALL_PAGES_PER_LARGE_PAGE) != 0)
1039                         return check_fail();
1040                 ph = from_pgnum(head, i, sp_bits);
1041                 /* Linked list corrupt? */
1042                 if (ph->prev != prev)
1043                         return check_fail();
1044                 /* Already seen this page? */
1045                 if (test_bit(pages, i))
1046                         return check_fail();
1047                 set_bit(pages, i);
1048                 prev = i;
1049         }
1050
1051         /* Check the buckets. */
1052         for (i = 0; i < max_bucket(lp_bits); i++) {
1053                 struct bucket_state *bs = &head->bs[i];
1054
1055                 if (!check_bucket(head, poolsize, pages, bs, i))
1056                         return false;
1057         }
1058
1059         /* Check the huge alloc list. */
1060         prev = 0;
1061         for (i = head->huge; i; i = ha->next) {
1062                 unsigned long pgbits, j;
1063
1064                 /* Bad pointer? */
1065                 if (i >= poolsize || i + sizeof(*ha) > poolsize)
1066                         return check_fail();
1067                 ha = (void *)((char *)head + i);
1068
1069                 /* Check contents of ha. */
1070                 if (ha->off > poolsize || ha->off + ha->len > poolsize)
1071                         return check_fail();
1072
1073                 /* Large or small page? */
1074                 pgbits = test_bit(head->pagesize, ha->off >> lp_bits)
1075                         ? lp_bits : sp_bits;
1076
1077                 /* Not page boundary? */
1078                 if ((ha->off % (1UL << pgbits)) != 0)
1079                         return check_fail();
1080
1081                 /* Not page length? */
1082                 if ((ha->len % (1UL << pgbits)) != 0)
1083                         return check_fail();
1084
1085                 /* Linked list corrupt? */
1086                 if (ha->prev != prev)
1087                         return check_fail();
1088
1089                 for (j = ha->off; j < ha->off + ha->len; j += (1UL<<sp_bits)) {
1090                         /* Already seen this page? */
1091                         if (test_bit(pages, j >> sp_bits))
1092                                 return check_fail();
1093                         set_bit(pages, j >> sp_bits);
1094                 }
1095
1096                 prev = i;
1097         }
1098
1099         /* Make sure every page accounted for. */
1100         for (i = 0; i < poolsize >> sp_bits; i++) {
1101                 if (!test_bit(pages, i))
1102                         return check_fail();
1103                 if (test_bit(head->pagesize,
1104                              i >> BITS_FROM_SMALL_TO_LARGE_PAGE)) {
1105                         /* Large page, skip rest. */
1106                         i += SMALL_PAGES_PER_LARGE_PAGE - 1;
1107                 }
1108         }
1109
1110         return true;
1111 }
1112
1113 static unsigned long print_overhead(FILE *out, const char *desc,
1114                                     unsigned long bytes,
1115                                     unsigned long poolsize)
1116 {
1117         fprintf(out, "Overhead (%s): %lu bytes (%.3g%%)\n",
1118                 desc, bytes, 100.0 * bytes / poolsize);
1119         return bytes;
1120 }
1121
1122 static unsigned long count_list(struct header *head,
1123                                 u16 pgnum,
1124                                 unsigned int sp_bits,
1125                                 unsigned long *total_elems)
1126 {
1127         struct page_header *p;
1128         unsigned long ret = 0;
1129
1130         while (pgnum) {
1131                 p = from_pgnum(head, pgnum, sp_bits);
1132                 if (total_elems)
1133                         (*total_elems) += p->elements_used;
1134                 ret++;
1135                 pgnum = p->next;
1136         }
1137         return ret;
1138 }
1139
1140 static unsigned long visualize_bucket(FILE *out, struct header *head,
1141                                       unsigned int bucket,
1142                                       unsigned long poolsize,
1143                                       unsigned int sp_bits)
1144 {
1145         unsigned long num_full, num_partial, num_pages, page_size,
1146                 elems, hdr_min, hdr_size, elems_per_page, overhead = 0;
1147
1148         elems_per_page = head->bs[bucket].elements_per_page;
1149
1150         /* If we used byte-based bitmaps, we could get pg hdr to: */
1151         hdr_min = sizeof(struct page_header)
1152                 - sizeof(((struct page_header *)0)->used)
1153                 + align_up(elems_per_page, CHAR_BIT) / CHAR_BIT;
1154         hdr_size = page_header_size(bucket / INTER_BUCKET_SPACE,
1155                                     elems_per_page);
1156
1157         elems = 0;
1158         num_full = count_list(head, head->bs[bucket].full_list, sp_bits,
1159                               &elems);
1160         num_partial = count_list(head, head->bs[bucket].page_list, sp_bits,
1161                                  &elems);
1162         num_pages = num_full + num_partial;
1163         if (!num_pages)
1164                 return 0;
1165
1166         fprintf(out, "Bucket %u (%lu bytes):"
1167                 " %lu full, %lu partial = %lu elements\n",
1168                 bucket, bucket_to_size(bucket), num_full, num_partial, elems);
1169         /* Strict requirement of page header size. */
1170         overhead += print_overhead(out, "page headers",
1171                                    hdr_min * num_pages, poolsize);
1172         /* Gap between minimal page header and actual start. */
1173         overhead += print_overhead(out, "page post-header alignments",
1174                                    (hdr_size - hdr_min) * num_pages, poolsize);
1175         /* Between last element and end of page. */
1176         page_size = (1UL << sp_bits);
1177         if (large_page_bucket(bucket, sp_bits))
1178                 page_size <<= BITS_FROM_SMALL_TO_LARGE_PAGE;
1179
1180         overhead += print_overhead(out, "page tails",
1181                                    (page_size - (hdr_size
1182                                                  + (elems_per_page
1183                                                     * bucket_to_size(bucket))))
1184                                    * num_pages, poolsize);
1185         return overhead;
1186 }
1187
1188 void alloc_visualize(FILE *out, void *pool, unsigned long poolsize)
1189 {
1190         struct header *head = pool;
1191         unsigned long i, lp_bits, sp_bits, header_size, num_buckets, count,
1192                 overhead = 0;
1193
1194         fprintf(out, "Pool %p size %lu: (%s allocator)\n", pool, poolsize,
1195                 poolsize < MIN_USEFUL_SIZE ? "tiny" : "standard");
1196
1197         if (poolsize < MIN_USEFUL_SIZE) {
1198                 tiny_alloc_visualize(out, pool, poolsize);
1199                 return;
1200         }
1201
1202         sp_bits = small_page_bits(poolsize);
1203         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
1204
1205         num_buckets = max_bucket(lp_bits);
1206         header_size = sizeof(*head) + sizeof(head->bs) * (num_buckets-1);
1207
1208         fprintf(out, "Large page size %lu, small page size %lu.\n",
1209                 1UL << lp_bits, 1UL << sp_bits);
1210         overhead += print_overhead(out, "unused pool tail",
1211                                    poolsize % (1UL << lp_bits), poolsize);
1212         fprintf(out, "Main header %lu bytes (%lu small pages).\n",
1213                 header_size, align_up(header_size, 1UL << sp_bits) >> sp_bits);
1214         overhead += print_overhead(out, "partial header page",
1215                                    align_up(header_size, 1UL << sp_bits)
1216                                    - header_size, poolsize);
1217         /* Total large pages. */
1218         i = count_bits(head->pagesize, poolsize >> lp_bits);
1219         /* Used pages. */
1220         count = i - count_list(head, head->large_free_list, sp_bits, NULL);
1221         fprintf(out, "%lu/%lu large pages used (%.3g%%)\n",
1222                 count, i, count ? 100.0 * count / i : 0.0);
1223
1224         /* Total small pages. */
1225         i = ((poolsize >> lp_bits) - i) << BITS_FROM_SMALL_TO_LARGE_PAGE;
1226         /* Used pages */
1227         count = i - count_list(head, head->small_free_list, sp_bits, NULL);
1228         fprintf(out, "%lu/%lu small pages used (%.3g%%)\n",
1229                 count, i, count ? 100.0 * count / i : 0.0);
1230
1231         /* Summary of each bucket. */
1232         fprintf(out, "%lu buckets:\n", num_buckets);
1233         for (i = 0; i < num_buckets; i++)
1234                 overhead += visualize_bucket(out, head, i, poolsize, sp_bits);
1235
1236         print_overhead(out, "total", overhead, poolsize);
1237 }