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                 /* Initialize this: huge_alloc reads it. */
 493                 ph->elements_used = 0;
 494                 add_small_page_to_freelist(head, ph, sp_bits);
 495         }
 496
 497         return lpage;
 498 }
 499
 500 static u16 get_small_page(struct header *head, unsigned long poolsize,
 501                           unsigned int sp_bits)
 502 {
 503         u16 ret;
 504
 505         ret = pop_from_list(head, &head->small_free_list, sp_bits);
 506         if (likely(ret))
 507                 return ret;
 508         ret = get_large_page(head, poolsize, sp_bits);
 509         if (likely(ret))
 510                 ret = break_up_large_page(head, sp_bits, ret);
 511         return ret;
 512 }
 513
 514 static bool huge_allocated(struct header *head, unsigned long offset)
 515 {
 516         unsigned long i;
 517         struct huge_alloc *ha;
 518
 519         for (i = head->huge; i; i = ha->next) {
 520                 ha = (void *)((char *)head + i);
 521                 if (ha->off <= offset && ha->off + ha->len > offset)
 522                         return true;
 523         }
 524         return false;
 525 }
 526
 527 /* They want something really big.  Aim for contiguous pages (slow). */
 528 static void *unlikely_func huge_alloc(void *pool, unsigned long poolsize,
 529                                       unsigned long size, unsigned long align)
 530 {
 531         struct header *head = pool;
 532         struct huge_alloc *ha;
 533         unsigned long i, sp_bits, lp_bits, num, header_size;
 534
 535         sp_bits = small_page_bits(poolsize);
 536         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 537
 538         /* Allocate tracking structure optimistically. */
 539         ha = alloc_get(pool, poolsize, sizeof(*ha), ALIGNOF(*ha));
 540         if (!ha)
 541                 return NULL;
 542
 543         /* First search for contiguous small pages... */
 544         header_size = sizeof(*head) + sizeof(head->bs) * (max_bucket(lp_bits)-1);
 545
 546         num = 0;
 547         for (i = (header_size + (1 << sp_bits) - 1) >> sp_bits;
 548              i << sp_bits < poolsize;
 549              i++) {
 550                 struct page_header *pg;
 551                 unsigned long off = (i << sp_bits);
 552
 553                 /* Skip over large pages. */
 554                 if (test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE)) {
 555                         i += (1 << BITS_FROM_SMALL_TO_LARGE_PAGE)-1;
 556                         continue;
 557                 }
 558
 559                 /* Does this page meet alignment requirements? */
 560                 if (!num && off % align != 0)
 561                         continue;
 562
 563                 /* FIXME: This makes us O(n^2). */
 564                 if (huge_allocated(head, off)) {
 565                         num = 0;
 566                         continue;
 567                 }
 568
 569                 pg = (struct page_header *)((char *)head + off);
 570                 if (pg->elements_used) {
 571                         num = 0;
 572                         continue;
 573                 }
 574
 575                 num++;
 576                 if (num << sp_bits >= size) {
 577                         unsigned long pgnum;
 578
 579                         /* Remove from free list. */
 580                         for (pgnum = i; pgnum > i - num; pgnum--) {
 581                                 pg = from_pgnum(head, pgnum, sp_bits);
 582                                 del_from_list(head,
 583                                               &head->small_free_list,
 584                                               pg, sp_bits);
 585                         }
 586                         ha->off = (i - num + 1) << sp_bits;
 587                         ha->len = num << sp_bits;
 588                         goto done;
 589                 }
 590         }
 591
 592         /* Now search for large pages... */
 593         recombine_small_pages(head, poolsize, sp_bits);
 594
 595         num = 0;
 596         for (i = (header_size + (1 << lp_bits) - 1) >> lp_bits;
 597              (i << lp_bits) < poolsize; i++) {
 598                 struct page_header *pg;
 599                 unsigned long off = (i << lp_bits);
 600
 601                 /* Ignore small pages. */
 602                 if (!test_bit(head->pagesize, i))
 603                         continue;
 604
 605                 /* Does this page meet alignment requirements? */
 606                 if (!num && off % align != 0)
 607                         continue;
 608
 609                 /* FIXME: This makes us O(n^2). */
 610                 if (huge_allocated(head, off)) {
 611                         num = 0;
 612                         continue;
 613                 }
 614
 615                 pg = (struct page_header *)((char *)head + off);
 616                 if (pg->elements_used) {
 617                         num = 0;
 618                         continue;
 619                 }
 620
 621                 num++;
 622                 if (num << lp_bits >= size) {
 623                         unsigned long pgnum;
 624
 625                         /* Remove from free list. */
 626                         for (pgnum = i; pgnum > i - num; pgnum--) {
 627                                 pg = from_pgnum(head, pgnum, lp_bits);
 628                                 del_from_list(head,
 629                                               &head->large_free_list,
 630                                               pg, sp_bits);
 631                         }
 632                         ha->off = (i - num + 1) << lp_bits;
 633                         ha->len = num << lp_bits;
 634                         goto done;
 635                 }
 636         }
 637
 638         /* Unable to satisfy: free huge alloc structure. */
 639         alloc_free(pool, poolsize, ha);
 640         return NULL;
 641
 642 done:
 643         add_to_huge_list(pool, ha);
 644         return (char *)pool + ha->off;
 645 }
 646
 647 static void unlikely_func huge_free(struct header *head,
 648                                     unsigned long poolsize, void *free)
 649 {
 650         unsigned long i, off, pgnum, free_off = (char *)free - (char *)head;
 651         unsigned int sp_bits, lp_bits;
 652         struct huge_alloc *ha;
 653
 654         for (i = head->huge; i; i = ha->next) {
 655                 ha = (void *)((char *)head + i);
 656                 if (free_off == ha->off)
 657                         break;
 658         }
 659         assert(i);
 660
 661         /* Free up all the pages, delete and free ha */
 662         sp_bits = small_page_bits(poolsize);
 663         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 664         pgnum = free_off >> sp_bits;
 665
 666         if (test_bit(head->pagesize, pgnum >> BITS_FROM_SMALL_TO_LARGE_PAGE)) {
 667                 for (off = ha->off; off < ha->off + ha->len; off += 1 << lp_bits) {
 668                         add_large_page_to_freelist(head,
 669                                                    (void *)((char *)head + off),
 670                                                    sp_bits);
 671                 }
 672         } else {
 673                 for (off = ha->off; off < ha->off + ha->len; off += 1 << sp_bits) {
 674                         add_small_page_to_freelist(head,
 675                                                    (void *)((char *)head + off),
 676                                                    sp_bits);
 677                 }
 678         }
 679         del_from_huge(head, ha);
 680         alloc_free(head, poolsize, ha);
 681 }
 682
 683 static unsigned long unlikely_func huge_size(struct header *head, void *p)
 684 {
 685         unsigned long i, off = (char *)p - (char *)head;
 686         struct huge_alloc *ha;
 687
 688         for (i = head->huge; i; i = ha->next) {
 689                 ha = (void *)((char *)head + i);
 690                 if (off == ha->off) {
 691                         return ha->len;
 692                 }
 693         }
 694         abort();
 695 }
 696
 697 void *alloc_get(void *pool, unsigned long poolsize,
 698                 unsigned long size, unsigned long align)
 699 {
 700         struct header *head = pool;
 701         unsigned int bucket;
 702         unsigned long i;
 703         struct bucket_state *bs;
 704         struct page_header *ph;
 705         unsigned int sp_bits;
 706
 707         if (poolsize < MIN_USEFUL_SIZE) {
 708                 return tiny_alloc_get(pool, poolsize, size, align);
 709         }
 710
 711         size = align_up(size, align);
 712         if (unlikely(!size))
 713                 size = 1;
 714         bucket = size_to_bucket(size);
 715
 716         sp_bits = small_page_bits(poolsize);
 717
 718         if (bucket >= max_bucket(sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE)) {
 719                 return huge_alloc(pool, poolsize, size, align);
 720         }
 721
 722         bs = &head->bs[bucket];
 723
 724         if (!bs->page_list) {
 725                 struct page_header *ph;
 726
 727                 if (large_page_bucket(bucket, sp_bits))
 728                         bs->page_list = get_large_page(head, poolsize,
 729                                                        sp_bits);
 730                 else
 731                         bs->page_list = get_small_page(head, poolsize,
 732                                                        sp_bits);
 733                 /* FIXME: Try large-aligned alloc?  Header stuffing? */
 734                 if (unlikely(!bs->page_list))
 735                         return NULL;
 736                 ph = from_pgnum(head, bs->page_list, sp_bits);
 737                 ph->bucket = bucket;
 738                 ph->elements_used = 0;
 739                 ph->next = 0;
 740                 memset(ph->used, 0, used_size(bs->elements_per_page));
 741         }
 742
 743         ph = from_pgnum(head, bs->page_list, sp_bits);
 744
 745         i = find_free_bit(ph->used);
 746         set_bit(ph->used, i);
 747         ph->elements_used++;
 748
 749         /* check if this page is now full */
 750         if (unlikely(ph->elements_used == bs->elements_per_page)) {
 751                 del_from_bucket_list(head, bs, ph, sp_bits);
 752                 add_to_bucket_full_list(head, bs, ph, sp_bits);
 753         }
 754
 755         return (char *)ph + page_header_size(ph->bucket / INTER_BUCKET_SPACE,
 756                                              bs->elements_per_page)
 757                + i * bucket_to_size(bucket);
 758 }
 759
 760 void alloc_free(void *pool, unsigned long poolsize, void *free)
 761 {
 762         struct header *head = pool;
 763         struct bucket_state *bs;
 764         unsigned int sp_bits;
 765         unsigned long i, pgnum, pgoffset, offset = (char *)free - (char *)pool;
 766         bool smallpage;
 767         struct page_header *ph;
 768
 769         if (poolsize < MIN_USEFUL_SIZE) {
 770                 return tiny_alloc_free(pool, poolsize, free);
 771         }
 772
 773         /* Get page header. */
 774         sp_bits = small_page_bits(poolsize);
 775         pgnum = offset >> sp_bits;
 776
 777         /* Big page? Round down further. */
 778         if (test_bit(head->pagesize, pgnum >> BITS_FROM_SMALL_TO_LARGE_PAGE)) {
 779                 smallpage = false;
 780                 pgnum &= ~(SMALL_PAGES_PER_LARGE_PAGE - 1);
 781         } else
 782                 smallpage = true;
 783
 784         /* Step back to page header. */
 785         ph = from_pgnum(head, pgnum, sp_bits);
 786         if ((void *)ph == free) {
 787                 huge_free(head, poolsize, free);
 788                 return;
 789         }
 790
 791         bs = &head->bs[ph->bucket];
 792         pgoffset = offset - (pgnum << sp_bits)
 793                 - page_header_size(ph->bucket / INTER_BUCKET_SPACE,
 794                                    bs->elements_per_page);
 795
 796         if (unlikely(ph->elements_used == bs->elements_per_page)) {
 797                 del_from_bucket_full_list(head, bs, ph, sp_bits);
 798                 add_to_bucket_list(head, bs, ph, sp_bits);
 799         }
 800
 801         /* Which element are we? */
 802         i = pgoffset / bucket_to_size(ph->bucket);
 803         clear_bit(ph->used, i);
 804         ph->elements_used--;
 805
 806         if (unlikely(ph->elements_used == 0)) {
 807                 bs = &head->bs[ph->bucket];
 808                 del_from_bucket_list(head, bs, ph, sp_bits);
 809                 if (smallpage)
 810                         add_small_page_to_freelist(head, ph, sp_bits);
 811                 else
 812                         add_large_page_to_freelist(head, ph, sp_bits);
 813         }
 814 }
 815
 816 unsigned long alloc_size(void *pool, unsigned long poolsize, void *p)
 817 {
 818         struct header *head = pool;
 819         unsigned int pgnum, sp_bits;
 820         unsigned long offset = (char *)p - (char *)pool;
 821         struct page_header *ph;
 822
 823         if (poolsize < MIN_USEFUL_SIZE)
 824                 return tiny_alloc_size(pool, poolsize, p);
 825
 826         /* Get page header. */
 827         sp_bits = small_page_bits(poolsize);
 828         pgnum = offset >> sp_bits;
 829
 830         /* Big page? Round down further. */
 831         if (test_bit(head->pagesize, pgnum >> BITS_FROM_SMALL_TO_LARGE_PAGE))
 832                 pgnum &= ~(SMALL_PAGES_PER_LARGE_PAGE - 1);
 833
 834         /* Step back to page header. */
 835         ph = from_pgnum(head, pgnum, sp_bits);
 836         if ((void *)ph == p)
 837                 return huge_size(head, p);
 838
 839         return bucket_to_size(ph->bucket);
 840 }
 841
 842 /* Useful for gdb breakpoints. */
 843 static bool check_fail(void)
 844 {
 845         return false;
 846 }
 847
 848 static unsigned long count_bits(const unsigned long bitmap[],
 849                                 unsigned long limit)
 850 {
 851         unsigned long i, count = 0;
 852
 853         while (limit >= BITS_PER_LONG) {
 854                 count += popcount(bitmap[0]);
 855                 bitmap++;
 856                 limit -= BITS_PER_LONG;
 857         }
 858
 859         for (i = 0; i < limit; i++)
 860                 if (test_bit(bitmap, i))
 861                         count++;
 862         return count;
 863 }
 864
 865 static bool out_of_bounds(unsigned long pgnum,
 866                           unsigned int sp_bits,
 867                           unsigned long pagesize,
 868                           unsigned long poolsize)
 869 {
 870         if (((pgnum << sp_bits) >> sp_bits) != pgnum)
 871                 return true;
 872
 873         if ((pgnum << sp_bits) > poolsize)
 874                 return true;
 875
 876         return ((pgnum << sp_bits) + pagesize > poolsize);
 877 }
 878
 879 static bool check_bucket(struct header *head,
 880                          unsigned long poolsize,
 881                          unsigned long pages[],
 882                          struct bucket_state *bs,
 883                          unsigned int bindex)
 884 {
 885         bool lp_bucket;
 886         struct page_header *ph;
 887         unsigned long taken, i, prev, pagesize, sp_bits, lp_bits;
 888
 889         sp_bits = small_page_bits(poolsize);
 890         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 891
 892         lp_bucket = large_page_bucket(bindex, sp_bits);
 893
 894         pagesize = 1UL << (lp_bucket ? lp_bits : sp_bits);
 895
 896         /* This many elements fit? */
 897         taken = page_header_size(bindex / INTER_BUCKET_SPACE,
 898                                  bs->elements_per_page);
 899         taken += bucket_to_size(bindex) * bs->elements_per_page;
 900         if (taken > pagesize)
 901                 return check_fail();
 902
 903         /* One more wouldn't fit? */
 904         taken = page_header_size(bindex / INTER_BUCKET_SPACE,
 905                                  bs->elements_per_page + 1);
 906         taken += bucket_to_size(bindex) * (bs->elements_per_page + 1);
 907         if (taken <= pagesize)
 908                 return check_fail();
 909
 910         /* Walk used list. */
 911         prev = 0;
 912         for (i = bs->page_list; i; i = ph->next) {
 913                 /* Bad pointer? */
 914                 if (out_of_bounds(i, sp_bits, pagesize, poolsize))
 915                         return check_fail();
 916                 /* Wrong size page? */
 917                 if (!!test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE)
 918                     != lp_bucket)
 919                         return check_fail();
 920                 /* Large page not on boundary? */
 921                 if (lp_bucket && (i % SMALL_PAGES_PER_LARGE_PAGE) != 0)
 922                         return check_fail();
 923                 ph = from_pgnum(head, i, sp_bits);
 924                 /* Linked list corrupt? */
 925                 if (ph->prev != prev)
 926                         return check_fail();
 927                 /* Already seen this page? */
 928                 if (test_bit(pages, i))
 929                         return check_fail();
 930                 set_bit(pages, i);
 931                 /* Empty or full? */
 932                 if (ph->elements_used == 0)
 933                         return check_fail();
 934                 if (ph->elements_used >= bs->elements_per_page)
 935                         return check_fail();
 936                 /* Used bits don't agree? */
 937                 if (ph->elements_used != count_bits(ph->used,
 938                                                     bs->elements_per_page))
 939                         return check_fail();
 940                 /* Wrong bucket? */
 941                 if (ph->bucket != bindex)
 942                         return check_fail();
 943                 prev = i;
 944         }
 945
 946         /* Walk full list. */
 947         prev = 0;
 948         for (i = bs->full_list; i; i = ph->next) {
 949                 /* Bad pointer? */
 950                 if (out_of_bounds(i, sp_bits, pagesize, poolsize))
 951                         return check_fail();
 952                 /* Wrong size page? */
 953                 if (!!test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE)
 954                     != lp_bucket)
 955                 /* Large page not on boundary? */
 956                 if (lp_bucket && (i % SMALL_PAGES_PER_LARGE_PAGE) != 0)
 957                         return check_fail();
 958                 ph = from_pgnum(head, i, sp_bits);
 959                 /* Linked list corrupt? */
 960                 if (ph->prev != prev)
 961                         return check_fail();
 962                 /* Already seen this page? */
 963                 if (test_bit(pages, i))
 964                         return check_fail();
 965                 set_bit(pages, i);
 966                 /* Not full? */
 967                 if (ph->elements_used != bs->elements_per_page)
 968                         return check_fail();
 969                 /* Used bits don't agree? */
 970                 if (ph->elements_used != count_bits(ph->used,
 971                                                     bs->elements_per_page))
 972                         return check_fail();
 973                 /* Wrong bucket? */
 974                 if (ph->bucket != bindex)
 975                         return check_fail();
 976                 prev = i;
 977         }
 978         return true;
 979 }
 980
 981 bool alloc_check(void *pool, unsigned long poolsize)
 982 {
 983         struct header *head = pool;
 984         unsigned long prev, i, lp_bits, sp_bits, header_size, num_buckets;
 985         struct page_header *ph;
 986         struct huge_alloc *ha;
 987         unsigned long pages[MAX_SMALL_PAGES / BITS_PER_LONG] = { 0 };
 988
 989         if (poolsize < MIN_USEFUL_SIZE)
 990                 return tiny_alloc_check(pool, poolsize);
 991
 992         sp_bits = small_page_bits(poolsize);
 993         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
 994
 995         num_buckets = max_bucket(lp_bits);
 996
 997         header_size = sizeof(*head) + sizeof(head->bs) * (num_buckets-1);
 998
 999         /* First, set all bits taken by header. */
1000         for (i = 0; i < header_size; i += (1UL << sp_bits))
1001                 set_bit(pages, i >> sp_bits);
1002
1003         /* Check small page free list. */
1004         prev = 0;
1005         for (i = head->small_free_list; i; i = ph->next) {
1006                 /* Bad pointer? */
1007                 if (out_of_bounds(i, sp_bits, 1 << sp_bits, poolsize))
1008                         return check_fail();
1009                 /* Large page? */
1010                 if (test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE))
1011                         return check_fail();
1012                 ph = from_pgnum(head, i, sp_bits);
1013                 /* Linked list corrupt? */
1014                 if (ph->prev != prev)
1015                         return check_fail();
1016                 /* Already seen this page? */
1017                 if (test_bit(pages, i))
1018                         return check_fail();
1019                 set_bit(pages, i);
1020                 prev = i;
1021         }
1022
1023         /* Check large page free list. */
1024         prev = 0;
1025         for (i = head->large_free_list; i; i = ph->next) {
1026                 /* Bad pointer? */
1027                 if (out_of_bounds(i, sp_bits, 1 << lp_bits, poolsize))
1028                         return check_fail();
1029                 /* Not large page? */
1030                 if (!test_bit(head->pagesize, i >> BITS_FROM_SMALL_TO_LARGE_PAGE))
1031                         return check_fail();
1032                 /* Not page boundary? */
1033                 if ((i % SMALL_PAGES_PER_LARGE_PAGE) != 0)
1034                         return check_fail();
1035                 ph = from_pgnum(head, i, sp_bits);
1036                 /* Linked list corrupt? */
1037                 if (ph->prev != prev)
1038                         return check_fail();
1039                 /* Already seen this page? */
1040                 if (test_bit(pages, i))
1041                         return check_fail();
1042                 set_bit(pages, i);
1043                 prev = i;
1044         }
1045
1046         /* Check the buckets. */
1047         for (i = 0; i < max_bucket(lp_bits); i++) {
1048                 struct bucket_state *bs = &head->bs[i];
1049
1050                 if (!check_bucket(head, poolsize, pages, bs, i))
1051                         return false;
1052         }
1053
1054         /* Check the huge alloc list. */
1055         prev = 0;
1056         for (i = head->huge; i; i = ha->next) {
1057                 unsigned long pgbits, j;
1058
1059                 /* Bad pointer? */
1060                 if (i >= poolsize || i + sizeof(*ha) > poolsize)
1061                         return check_fail();
1062                 ha = (void *)((char *)head + i);
1063
1064                 /* Check contents of ha. */
1065                 if (ha->off > poolsize || ha->off + ha->len > poolsize)
1066                         return check_fail();
1067
1068                 /* Large or small page? */
1069                 pgbits = test_bit(head->pagesize, ha->off >> lp_bits)
1070                         ? lp_bits : sp_bits;
1071
1072                 /* Not page boundary? */
1073                 if ((ha->off % (1UL << pgbits)) != 0)
1074                         return check_fail();
1075
1076                 /* Not page length? */
1077                 if ((ha->len % (1UL << pgbits)) != 0)
1078                         return check_fail();
1079
1080                 /* Linked list corrupt? */
1081                 if (ha->prev != prev)
1082                         return check_fail();
1083
1084                 for (j = ha->off; j < ha->off + ha->len; j += (1 << sp_bits)) {
1085                         /* Already seen this page? */
1086                         if (test_bit(pages, j >> sp_bits))
1087                                 return check_fail();
1088                         set_bit(pages, j >> sp_bits);
1089                 }
1090
1091                 prev = i;
1092         }
1093
1094         /* Make sure every page accounted for. */
1095         for (i = 0; i < poolsize >> sp_bits; i++) {
1096                 if (!test_bit(pages, i))
1097                         return check_fail();
1098                 if (test_bit(head->pagesize,
1099                              i >> BITS_FROM_SMALL_TO_LARGE_PAGE)) {
1100                         /* Large page, skip rest. */
1101                         i += SMALL_PAGES_PER_LARGE_PAGE - 1;
1102                 }
1103         }
1104
1105         return true;
1106 }
1107
1108 static unsigned long print_overhead(FILE *out, const char *desc,
1109                                     unsigned long bytes,
1110                                     unsigned long poolsize)
1111 {
1112         fprintf(out, "Overhead (%s): %lu bytes (%.3g%%)\n",
1113                 desc, bytes, 100.0 * bytes / poolsize);
1114         return bytes;
1115 }
1116
1117 static unsigned long count_list(struct header *head,
1118                                 u16 pgnum,
1119                                 unsigned int sp_bits,
1120                                 unsigned long *total_elems)
1121 {
1122         struct page_header *p;
1123         unsigned long ret = 0;
1124
1125         while (pgnum) {
1126                 p = from_pgnum(head, pgnum, sp_bits);
1127                 if (total_elems)
1128                         (*total_elems) += p->elements_used;
1129                 ret++;
1130                 pgnum = p->next;
1131         }
1132         return ret;
1133 }
1134
1135 static unsigned long visualize_bucket(FILE *out, struct header *head,
1136                                       unsigned int bucket,
1137                                       unsigned long poolsize,
1138                                       unsigned int sp_bits)
1139 {
1140         unsigned long num_full, num_partial, num_pages, page_size,
1141                 elems, hdr_min, hdr_size, elems_per_page, overhead = 0;
1142
1143         elems_per_page = head->bs[bucket].elements_per_page;
1144
1145         /* If we used byte-based bitmaps, we could get pg hdr to: */
1146         hdr_min = sizeof(struct page_header)
1147                 - sizeof(((struct page_header *)0)->used)
1148                 + align_up(elems_per_page, CHAR_BIT) / CHAR_BIT;
1149         hdr_size = page_header_size(bucket / INTER_BUCKET_SPACE,
1150                                     elems_per_page);
1151
1152         elems = 0;
1153         num_full = count_list(head, head->bs[bucket].full_list, sp_bits,
1154                               &elems);
1155         num_partial = count_list(head, head->bs[bucket].page_list, sp_bits,
1156                                  &elems);
1157         num_pages = num_full + num_partial;
1158         if (!num_pages)
1159                 return 0;
1160
1161         fprintf(out, "Bucket %u (%lu bytes):"
1162                 " %lu full, %lu partial = %lu elements\n",
1163                 bucket, bucket_to_size(bucket), num_full, num_partial, elems);
1164         /* Strict requirement of page header size. */
1165         overhead += print_overhead(out, "page headers",
1166                                    hdr_min * num_pages, poolsize);
1167         /* Gap between minimal page header and actual start. */
1168         overhead += print_overhead(out, "page post-header alignments",
1169                                    (hdr_size - hdr_min) * num_pages, poolsize);
1170         /* Between last element and end of page. */
1171         page_size = (1 << sp_bits);
1172         if (large_page_bucket(bucket, sp_bits))
1173                 page_size <<= BITS_FROM_SMALL_TO_LARGE_PAGE;
1174
1175         overhead += print_overhead(out, "page tails",
1176                                    (page_size - (hdr_size
1177                                                  + (elems_per_page
1178                                                     * bucket_to_size(bucket))))
1179                                    * num_pages, poolsize);
1180         return overhead;
1181 }
1182
1183 void alloc_visualize(FILE *out, void *pool, unsigned long poolsize)
1184 {
1185         struct header *head = pool;
1186         unsigned long i, lp_bits, sp_bits, header_size, num_buckets, count,
1187                 overhead = 0;
1188
1189         fprintf(out, "Pool %p size %lu: (%s allocator)\n", pool, poolsize,
1190                 poolsize < MIN_USEFUL_SIZE ? "tiny" : "standard");
1191
1192         if (poolsize < MIN_USEFUL_SIZE) {
1193                 tiny_alloc_visualize(out, pool, poolsize);
1194                 return;
1195         }
1196
1197         sp_bits = small_page_bits(poolsize);
1198         lp_bits = sp_bits + BITS_FROM_SMALL_TO_LARGE_PAGE;
1199
1200         num_buckets = max_bucket(lp_bits);
1201         header_size = sizeof(*head) + sizeof(head->bs) * (num_buckets-1);
1202
1203         fprintf(out, "Large page size %lu, small page size %lu.\n",
1204                 1UL << lp_bits, 1UL << sp_bits);
1205         overhead += print_overhead(out, "unused pool tail",
1206                                    poolsize % (1 << lp_bits), poolsize);
1207         fprintf(out, "Main header %lu bytes (%lu small pages).\n",
1208                 header_size, align_up(header_size, 1 << sp_bits) >> sp_bits);
1209         overhead += print_overhead(out, "partial header page",
1210                                    align_up(header_size, 1 << sp_bits)
1211                                    - header_size, poolsize);
1212         /* Total large pages. */
1213         i = count_bits(head->pagesize, poolsize >> lp_bits);
1214         /* Used pages. */
1215         count = i - count_list(head, head->large_free_list, sp_bits, NULL);
1216         fprintf(out, "%lu/%lu large pages used (%.3g%%)\n",
1217                 count, i, count ? 100.0 * count / i : 0.0);
1218
1219         /* Total small pages. */
1220         i = ((poolsize >> lp_bits) - i) << BITS_FROM_SMALL_TO_LARGE_PAGE;
1221         /* Used pages */
1222         count = i - count_list(head, head->small_free_list, sp_bits, NULL);
1223         fprintf(out, "%lu/%lu small pages used (%.3g%%)\n",
1224                 count, i, count ? 100.0 * count / i : 0.0);
1225
1226         /* Summary of each bucket. */
1227         fprintf(out, "%lu buckets:\n", num_buckets);
1228         for (i = 0; i < num_buckets; i++)
1229                 overhead += visualize_bucket(out, head, i, poolsize, sp_bits);
1230
1231         print_overhead(out, "total", overhead, poolsize);
1232 }