boehm-gc/allchblk.c

   1 /*
   2  * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
   3  * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
   4  * Copyright (c) 1998-1999 by Silicon Graphics.  All rights reserved.
   5  * Copyright (c) 1999 by Hewlett-Packard Company. All rights reserved.
   6  *
   7  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   8  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   9  *
  10  * Permission is hereby granted to use or copy this program
  11  * for any purpose,  provided the above notices are retained on all copies.
  12  * Permission to modify the code and to distribute modified code is granted,
  13  * provided the above notices are retained, and a notice that the code was
  14  * modified is included with the above copyright notice.
  15  */
  16
  17 /* #define DEBUG */
  18 #include <stdio.h>
  19 #include "private/gc_priv.h"
  20
  21 GC_bool GC_use_entire_heap = 0;
  22
  23 /*
  24  * Free heap blocks are kept on one of several free lists,
  25  * depending on the size of the block.  Each free list is doubly linked.
  26  * Adjacent free blocks are coalesced.
  27  */
  28
  29
  30 # define MAX_BLACK_LIST_ALLOC (2*HBLKSIZE)
  31                 /* largest block we will allocate starting on a black   */
  32                 /* listed block.  Must be >= HBLKSIZE.                  */
  33
  34
  35 # define UNIQUE_THRESHOLD 32
  36         /* Sizes up to this many HBLKs each have their own free list    */
  37 # define HUGE_THRESHOLD 256
  38         /* Sizes of at least this many heap blocks are mapped to a      */
  39         /* single free list.                                            */
  40 # define FL_COMPRESSION 8
  41         /* In between sizes map this many distinct sizes to a single    */
  42         /* bin.                                                         */
  43
  44 # define N_HBLK_FLS (HUGE_THRESHOLD - UNIQUE_THRESHOLD)/FL_COMPRESSION \
  45                                  + UNIQUE_THRESHOLD
  46
  47 struct hblk * GC_hblkfreelist[N_HBLK_FLS+1] = { 0 };
  48
  49 #ifndef USE_MUNMAP
  50   word GC_free_bytes[N_HBLK_FLS+1] = { 0 };
  51         /* Number of free bytes on each list.   */
  52
  53   /* Is bytes + the number of free bytes on lists n .. N_HBLK_FLS       */
  54   /* > GC_max_large_allocd_bytes?                                       */
  55   GC_bool GC_enough_large_bytes_left(bytes,n)
  56   word bytes;
  57   int n;
  58   {
  59     int i;
  60     for (i = N_HBLK_FLS; i >= n; --i) {
  61         bytes += GC_free_bytes[i];
  62         if (bytes > GC_max_large_allocd_bytes) return TRUE;
  63     }
  64     return FALSE;
  65   }
  66
  67 # define INCR_FREE_BYTES(n, b) GC_free_bytes[n] += (b);
  68
  69 # define FREE_ASSERT(e) GC_ASSERT(e)
  70
  71 #else /* USE_MUNMAP */
  72
  73 # define INCR_FREE_BYTES(n, b)
  74 # define FREE_ASSERT(e)
  75
  76 #endif /* USE_MUNMAP */
  77
  78 /* Map a number of blocks to the appropriate large block free list index. */
  79 int GC_hblk_fl_from_blocks(blocks_needed)
  80 word blocks_needed;
  81 {
  82     if (blocks_needed <= UNIQUE_THRESHOLD) return blocks_needed;
  83     if (blocks_needed >= HUGE_THRESHOLD) return N_HBLK_FLS;
  84     return (blocks_needed - UNIQUE_THRESHOLD)/FL_COMPRESSION
  85                                         + UNIQUE_THRESHOLD;
  86
  87 }
  88
  89 # define HBLK_IS_FREE(hdr) ((hdr) -> hb_map == GC_invalid_map)
  90 # define PHDR(hhdr) HDR(hhdr -> hb_prev)
  91 # define NHDR(hhdr) HDR(hhdr -> hb_next)
  92
  93 # ifdef USE_MUNMAP
  94 #   define IS_MAPPED(hhdr) (((hhdr) -> hb_flags & WAS_UNMAPPED) == 0)
  95 # else  /* !USE_MMAP */
  96 #   define IS_MAPPED(hhdr) 1
  97 # endif /* USE_MUNMAP */
  98
  99 # if !defined(NO_DEBUGGING)
 100 void GC_print_hblkfreelist()
 101 {
 102     struct hblk * h;
 103     word total_free = 0;
 104     hdr * hhdr;
 105     word sz;
 106     int i;
 107
 108     for (i = 0; i <= N_HBLK_FLS; ++i) {
 109       h = GC_hblkfreelist[i];
 110 #     ifdef USE_MUNMAP
 111         if (0 != h) GC_printf1("Free list %ld (Total size %ld):\n",
 112                                (unsigned long)i);
 113 #     else
 114         if (0 != h) GC_printf2("Free list %ld (Total size %ld):\n",
 115                                (unsigned long)i,
 116                                (unsigned long)GC_free_bytes[i]);
 117 #     endif
 118       while (h != 0) {
 119         hhdr = HDR(h);
 120         sz = hhdr -> hb_sz;
 121         GC_printf2("\t0x%lx size %lu ", (unsigned long)h, (unsigned long)sz);
 122         total_free += sz;
 123         if (GC_is_black_listed(h, HBLKSIZE) != 0) {
 124              GC_printf0("start black listed\n");
 125         } else if (GC_is_black_listed(h, hhdr -> hb_sz) != 0) {
 126              GC_printf0("partially black listed\n");
 127         } else {
 128              GC_printf0("not black listed\n");
 129         }
 130         h = hhdr -> hb_next;
 131       }
 132     }
 133     if (total_free != GC_large_free_bytes) {
 134         GC_printf1("GC_large_free_bytes = %lu (INCONSISTENT!!)\n",
 135                    (unsigned long) GC_large_free_bytes);
 136     }
 137     GC_printf1("Total of %lu bytes on free list\n", (unsigned long)total_free);
 138 }
 139
 140 /* Return the free list index on which the block described by the header */
 141 /* appears, or -1 if it appears nowhere.                                 */
 142 int free_list_index_of(wanted)
 143 hdr * wanted;
 144 {
 145     struct hblk * h;
 146     hdr * hhdr;
 147     int i;
 148
 149     for (i = 0; i <= N_HBLK_FLS; ++i) {
 150       h = GC_hblkfreelist[i];
 151       while (h != 0) {
 152         hhdr = HDR(h);
 153         if (hhdr == wanted) return i;
 154         h = hhdr -> hb_next;
 155       }
 156     }
 157     return -1;
 158 }
 159
 160 void GC_dump_regions()
 161 {
 162     unsigned i;
 163     ptr_t start, end;
 164     ptr_t p;
 165     size_t bytes;
 166     hdr *hhdr;
 167     for (i = 0; i < GC_n_heap_sects; ++i) {
 168         start = GC_heap_sects[i].hs_start;
 169         bytes = GC_heap_sects[i].hs_bytes;
 170         end = start + bytes;
 171         /* Merge in contiguous sections.        */
 172           while (i+1 < GC_n_heap_sects && GC_heap_sects[i+1].hs_start == end) {
 173             ++i;
 174             end = GC_heap_sects[i].hs_start + GC_heap_sects[i].hs_bytes;
 175           }
 176         GC_printf2("***Section from 0x%lx to 0x%lx\n", start, end);
 177         for (p = start; p < end;) {
 178             hhdr = HDR(p);
 179             GC_printf1("\t0x%lx ", (unsigned long)p);
 180             if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
 181                 GC_printf1("Missing header!!\n", hhdr);
 182                 p += HBLKSIZE;
 183                 continue;
 184             }
 185             if (HBLK_IS_FREE(hhdr)) {
 186                 int correct_index = GC_hblk_fl_from_blocks(
 187                                         divHBLKSZ(hhdr -> hb_sz));
 188                 int actual_index;
 189
 190                 GC_printf1("\tfree block of size 0x%lx bytes",
 191                            (unsigned long)(hhdr -> hb_sz));
 192                 if (IS_MAPPED(hhdr)) {
 193                     GC_printf0("\n");
 194                 } else {
 195                     GC_printf0("(unmapped)\n");
 196                 }
 197                 actual_index = free_list_index_of(hhdr);
 198                 if (-1 == actual_index) {
 199                     GC_printf1("\t\tBlock not on free list %ld!!\n",
 200                                 correct_index);
 201                 } else if (correct_index != actual_index) {
 202                     GC_printf2("\t\tBlock on list %ld, should be on %ld!!\n",
 203                                actual_index, correct_index);
 204                 }
 205                 p += hhdr -> hb_sz;
 206             } else {
 207                 GC_printf1("\tused for blocks of size 0x%lx bytes\n",
 208                            (unsigned long)WORDS_TO_BYTES(hhdr -> hb_sz));
 209                 p += HBLKSIZE * OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz);
 210             }
 211         }
 212     }
 213 }
 214
 215 # endif /* NO_DEBUGGING */
 216
 217 /* Initialize hdr for a block containing the indicated size and         */
 218 /* kind of objects.                                                     */
 219 /* Return FALSE on failure.                                             */
 220 static GC_bool setup_header(hhdr, sz, kind, flags)
 221 register hdr * hhdr;
 222 word sz;        /* object size in words */
 223 int kind;
 224 unsigned char flags;
 225 {
 226     register word descr;
 227
 228     /* Add description of valid object pointers */
 229       if (!GC_add_map_entry(sz)) return(FALSE);
 230       hhdr -> hb_map = GC_obj_map[sz > MAXOBJSZ? 0 : sz];
 231
 232     /* Set size, kind and mark proc fields */
 233       hhdr -> hb_sz = sz;
 234       hhdr -> hb_obj_kind = kind;
 235       hhdr -> hb_flags = flags;
 236       descr = GC_obj_kinds[kind].ok_descriptor;
 237       if (GC_obj_kinds[kind].ok_relocate_descr) descr += WORDS_TO_BYTES(sz);
 238       hhdr -> hb_descr = descr;
 239
 240     /* Clear mark bits */
 241       GC_clear_hdr_marks(hhdr);
 242
 243     hhdr -> hb_last_reclaimed = (unsigned short)GC_gc_no;
 244     return(TRUE);
 245 }
 246
 247 #define FL_UNKNOWN -1
 248 /*
 249  * Remove hhdr from the appropriate free list.
 250  * We assume it is on the nth free list, or on the size
 251  * appropriate free list if n is FL_UNKNOWN.
 252  */
 253 void GC_remove_from_fl(hhdr, n)
 254 hdr * hhdr;
 255 int n;
 256 {
 257     int index;
 258
 259     GC_ASSERT(((hhdr -> hb_sz) & (HBLKSIZE-1)) == 0);
 260 #   ifndef USE_MUNMAP
 261       /* We always need index to mainatin free counts.  */
 262       if (FL_UNKNOWN == n) {
 263           index = GC_hblk_fl_from_blocks(divHBLKSZ(hhdr -> hb_sz));
 264       } else {
 265           index = n;
 266       }
 267 #   endif
 268     if (hhdr -> hb_prev == 0) {
 269 #       ifdef USE_MUNMAP
 270           if (FL_UNKNOWN == n) {
 271             index = GC_hblk_fl_from_blocks(divHBLKSZ(hhdr -> hb_sz));
 272           } else {
 273             index = n;
 274           }
 275 #       endif
 276         GC_ASSERT(HDR(GC_hblkfreelist[index]) == hhdr);
 277         GC_hblkfreelist[index] = hhdr -> hb_next;
 278     } else {
 279         hdr *phdr;
 280         GET_HDR(hhdr -> hb_prev, phdr);
 281         phdr -> hb_next = hhdr -> hb_next;
 282     }
 283     INCR_FREE_BYTES(index, - (signed_word)(hhdr -> hb_sz));
 284     FREE_ASSERT(GC_free_bytes[index] >= 0);
 285     if (0 != hhdr -> hb_next) {
 286         hdr * nhdr;
 287         GC_ASSERT(!IS_FORWARDING_ADDR_OR_NIL(NHDR(hhdr)));
 288         GET_HDR(hhdr -> hb_next, nhdr);
 289         nhdr -> hb_prev = hhdr -> hb_prev;
 290     }
 291 }
 292
 293 /*
 294  * Return a pointer to the free block ending just before h, if any.
 295  */
 296 struct hblk * GC_free_block_ending_at(h)
 297 struct hblk *h;
 298 {
 299     struct hblk * p = h - 1;
 300     hdr * phdr;
 301
 302     GET_HDR(p, phdr);
 303     while (0 != phdr && IS_FORWARDING_ADDR_OR_NIL(phdr)) {
 304         p = FORWARDED_ADDR(p,phdr);
 305         phdr = HDR(p);
 306     }
 307     if (0 != phdr) {
 308         if(HBLK_IS_FREE(phdr)) {
 309             return p;
 310         } else {
 311             return 0;
 312         }
 313     }
 314     p = GC_prev_block(h - 1);
 315     if (0 != p) {
 316       phdr = HDR(p);
 317       if (HBLK_IS_FREE(phdr) && (ptr_t)p + phdr -> hb_sz == (ptr_t)h) {
 318         return p;
 319       }
 320     }
 321     return 0;
 322 }
 323
 324 /*
 325  * Add hhdr to the appropriate free list.
 326  * We maintain individual free lists sorted by address.
 327  */
 328 void GC_add_to_fl(h, hhdr)
 329 struct hblk *h;
 330 hdr * hhdr;
 331 {
 332     int index = GC_hblk_fl_from_blocks(divHBLKSZ(hhdr -> hb_sz));
 333     struct hblk *second = GC_hblkfreelist[index];
 334     hdr * second_hdr;
 335 #   ifdef GC_ASSERTIONS
 336       struct hblk *next = (struct hblk *)((word)h + hhdr -> hb_sz);
 337       hdr * nexthdr = HDR(next);
 338       struct hblk *prev = GC_free_block_ending_at(h);
 339       hdr * prevhdr = HDR(prev);
 340       GC_ASSERT(nexthdr == 0 || !HBLK_IS_FREE(nexthdr) || !IS_MAPPED(nexthdr));
 341       GC_ASSERT(prev == 0 || !HBLK_IS_FREE(prevhdr) || !IS_MAPPED(prevhdr));
 342 #   endif
 343     GC_ASSERT(((hhdr -> hb_sz) & (HBLKSIZE-1)) == 0);
 344     GC_hblkfreelist[index] = h;
 345     INCR_FREE_BYTES(index, hhdr -> hb_sz);
 346     FREE_ASSERT(GC_free_bytes[index] <= GC_large_free_bytes)
 347     hhdr -> hb_next = second;
 348     hhdr -> hb_prev = 0;
 349     if (0 != second) {
 350       GET_HDR(second, second_hdr);
 351       second_hdr -> hb_prev = h;
 352     }
 353     GC_invalidate_map(hhdr);
 354 }
 355
 356 #ifdef USE_MUNMAP
 357
 358 /* Unmap blocks that haven't been recently touched.  This is the only way */
 359 /* way blocks are ever unmapped.                                          */
 360 void GC_unmap_old(void)
 361 {
 362     struct hblk * h;
 363     hdr * hhdr;
 364     word sz;
 365     unsigned short last_rec, threshold;
 366     int i;
 367 #   define UNMAP_THRESHOLD 6
 368
 369     for (i = 0; i <= N_HBLK_FLS; ++i) {
 370       for (h = GC_hblkfreelist[i]; 0 != h; h = hhdr -> hb_next) {
 371         hhdr = HDR(h);
 372         if (!IS_MAPPED(hhdr)) continue;
 373         threshold = (unsigned short)(GC_gc_no - UNMAP_THRESHOLD);
 374         last_rec = hhdr -> hb_last_reclaimed;
 375         if (last_rec > GC_gc_no
 376             || last_rec < threshold && threshold < GC_gc_no
 377                                        /* not recently wrapped */) {
 378           sz = hhdr -> hb_sz;
 379           GC_unmap((ptr_t)h, sz);
 380           hhdr -> hb_flags |= WAS_UNMAPPED;
 381         }
 382       }
 383     }
 384 }
 385
 386 /* Merge all unmapped blocks that are adjacent to other free            */
 387 /* blocks.  This may involve remapping, since all blocks are either     */
 388 /* fully mapped or fully unmapped.                                      */
 389 void GC_merge_unmapped(void)
 390 {
 391     struct hblk * h, *next;
 392     hdr * hhdr, *nexthdr;
 393     word size, nextsize;
 394     int i;
 395
 396     for (i = 0; i <= N_HBLK_FLS; ++i) {
 397       h = GC_hblkfreelist[i];
 398       while (h != 0) {
 399         GET_HDR(h, hhdr);
 400         size = hhdr->hb_sz;
 401         next = (struct hblk *)((word)h + size);
 402         GET_HDR(next, nexthdr);
 403         /* Coalesce with successor, if possible */
 404           if (0 != nexthdr && HBLK_IS_FREE(nexthdr)) {
 405             nextsize = nexthdr -> hb_sz;
 406             if (IS_MAPPED(hhdr)) {
 407               GC_ASSERT(!IS_MAPPED(nexthdr));
 408               /* make both consistent, so that we can merge */
 409                 if (size > nextsize) {
 410                   GC_remap((ptr_t)next, nextsize);
 411                 } else {
 412                   GC_unmap((ptr_t)h, size);
 413                   hhdr -> hb_flags |= WAS_UNMAPPED;
 414                 }
 415             } else if (IS_MAPPED(nexthdr)) {
 416               GC_ASSERT(!IS_MAPPED(hhdr));
 417               if (size > nextsize) {
 418                 GC_unmap((ptr_t)next, nextsize);
 419               } else {
 420                 GC_remap((ptr_t)h, size);
 421                 hhdr -> hb_flags &= ~WAS_UNMAPPED;
 422               }
 423             } else {
 424               /* Unmap any gap in the middle */
 425                 GC_unmap_gap((ptr_t)h, size, (ptr_t)next, nexthdr -> hb_sz);
 426             }
 427             /* If they are both unmapped, we merge, but leave unmapped. */
 428             GC_remove_from_fl(hhdr, i);
 429             GC_remove_from_fl(nexthdr, FL_UNKNOWN);
 430             hhdr -> hb_sz += nexthdr -> hb_sz;
 431             GC_remove_header(next);
 432             GC_add_to_fl(h, hhdr);
 433             /* Start over at beginning of list */
 434             h = GC_hblkfreelist[i];
 435           } else /* not mergable with successor */ {
 436             h = hhdr -> hb_next;
 437           }
 438       } /* while (h != 0) ... */
 439     } /* for ... */
 440 }
 441
 442 #endif /* USE_MUNMAP */
 443
 444 /*
 445  * Return a pointer to a block starting at h of length bytes.
 446  * Memory for the block is mapped.
 447  * Remove the block from its free list, and return the remainder (if any)
 448  * to its appropriate free list.
 449  * May fail by returning 0.
 450  * The header for the returned block must be set up by the caller.
 451  * If the return value is not 0, then hhdr is the header for it.
 452  */
 453 struct hblk * GC_get_first_part(h, hhdr, bytes, index)
 454 struct hblk *h;
 455 hdr * hhdr;
 456 word bytes;
 457 int index;
 458 {
 459     word total_size = hhdr -> hb_sz;
 460     struct hblk * rest;
 461     hdr * rest_hdr;
 462
 463     GC_ASSERT((total_size & (HBLKSIZE-1)) == 0);
 464     GC_remove_from_fl(hhdr, index);
 465     if (total_size == bytes) return h;
 466     rest = (struct hblk *)((word)h + bytes);
 467     rest_hdr = GC_install_header(rest);
 468     if (0 == rest_hdr) return(0);
 469     rest_hdr -> hb_sz = total_size - bytes;
 470     rest_hdr -> hb_flags = 0;
 471 #   ifdef GC_ASSERTIONS
 472       /* Mark h not free, to avoid assertion about adjacent free blocks. */
 473         hhdr -> hb_map = 0;
 474 #   endif
 475     GC_add_to_fl(rest, rest_hdr);
 476     return h;
 477 }
 478
 479 /*
 480  * H is a free block.  N points at an address inside it.
 481  * A new header for n has already been set up.  Fix up h's header
 482  * to reflect the fact that it is being split, move it to the
 483  * appropriate free list.
 484  * N replaces h in the original free list.
 485  *
 486  * Nhdr is not completely filled in, since it is about to allocated.
 487  * It may in fact end up on the wrong free list for its size.
 488  * (Hence adding it to a free list is silly.  But this path is hopefully
 489  * rare enough that it doesn't matter.  The code is cleaner this way.)
 490  */
 491 void GC_split_block(h, hhdr, n, nhdr, index)
 492 struct hblk *h;
 493 hdr * hhdr;
 494 struct hblk *n;
 495 hdr * nhdr;
 496 int index;      /* Index of free list */
 497 {
 498     word total_size = hhdr -> hb_sz;
 499     word h_size = (word)n - (word)h;
 500     struct hblk *prev = hhdr -> hb_prev;
 501     struct hblk *next = hhdr -> hb_next;
 502
 503     /* Replace h with n on its freelist */
 504       nhdr -> hb_prev = prev;
 505       nhdr -> hb_next = next;
 506       nhdr -> hb_sz = total_size - h_size;
 507       nhdr -> hb_flags = 0;
 508       if (0 != prev) {
 509         HDR(prev) -> hb_next = n;
 510       } else {
 511         GC_hblkfreelist[index] = n;
 512       }
 513       if (0 != next) {
 514         HDR(next) -> hb_prev = n;
 515       }
 516       INCR_FREE_BYTES(index, -(signed_word)h_size);
 517       FREE_ASSERT(GC_free_bytes[index] > 0);
 518 #     ifdef GC_ASSERTIONS
 519         nhdr -> hb_map = 0;     /* Don't fail test for consecutive      */
 520                                 /* free blocks in GC_add_to_fl.         */
 521 #     endif
 522 #   ifdef USE_MUNMAP
 523       hhdr -> hb_last_reclaimed = GC_gc_no;
 524 #   endif
 525     hhdr -> hb_sz = h_size;
 526     GC_add_to_fl(h, hhdr);
 527     GC_invalidate_map(nhdr);
 528 }
 529
 530 struct hblk * GC_allochblk_nth();
 531
 532 /*
 533  * Allocate (and return pointer to) a heap block
 534  *   for objects of size sz words, searching the nth free list.
 535  *
 536  * NOTE: We set obj_map field in header correctly.
 537  *       Caller is responsible for building an object freelist in block.
 538  *
 539  * Unlike older versions of the collectors, the client is responsible
 540  * for clearing the block, if necessary.
 541  */
 542 struct hblk *
 543 GC_allochblk(sz, kind, flags)
 544 word sz;
 545 int kind;
 546 unsigned flags;  /* IGNORE_OFF_PAGE or 0 */
 547 {
 548     word blocks = OBJ_SZ_TO_BLOCKS(sz);
 549     int start_list = GC_hblk_fl_from_blocks(blocks);
 550     int i;
 551     for (i = start_list; i <= N_HBLK_FLS; ++i) {
 552         struct hblk * result = GC_allochblk_nth(sz, kind, flags, i);
 553         if (0 != result) {
 554             return result;
 555         }
 556     }
 557     return 0;
 558 }
 559 /*
 560  * The same, but with search restricted to nth free list.
 561  */
 562 struct hblk *
 563 GC_allochblk_nth(sz, kind, flags, n)
 564 word sz;
 565 int kind;
 566 unsigned char flags;  /* IGNORE_OFF_PAGE or 0 */
 567 int n;
 568 {
 569     register struct hblk *hbp;
 570     register hdr * hhdr;                /* Header corr. to hbp */
 571     register struct hblk *thishbp;
 572     register hdr * thishdr;             /* Header corr. to hbp */
 573     signed_word size_needed;    /* number of bytes in requested objects */
 574     signed_word size_avail;     /* bytes available in this block        */
 575
 576     size_needed = HBLKSIZE * OBJ_SZ_TO_BLOCKS(sz);
 577
 578     /* search for a big enough block in free list */
 579         hbp = GC_hblkfreelist[n];
 580         for(; 0 != hbp; hbp = hhdr -> hb_next) {
 581             GET_HDR(hbp, hhdr);
 582             size_avail = hhdr->hb_sz;
 583             if (size_avail < size_needed) continue;
 584             if (!GC_use_entire_heap
 585                 && size_avail != size_needed
 586                 && USED_HEAP_SIZE >= GC_requested_heapsize
 587                 && !GC_incremental && GC_should_collect()) {
 588 #               ifdef USE_MUNMAP
 589                     continue;
 590 #               else
 591                     /* If we enough large blocks left to cover any      */
 592                     /* previous request for large blocks, we go ahead   */
 593                     /* and split.  Assuming a steady state, that should */
 594                     /* be safe.  It means that we can use the full      */
 595                     /* heap if we allocate only small objects.          */
 596                     if (!GC_enough_large_bytes_left(GC_large_allocd_bytes, n)) {
 597                       continue;
 598                     }
 599 #               endif /* !USE_MUNMAP */
 600             }
 601             /* If the next heap block is obviously better, go on.       */
 602             /* This prevents us from disassembling a single large block */
 603             /* to get tiny blocks.                                      */
 604             {
 605               signed_word next_size;
 606
 607               thishbp = hhdr -> hb_next;
 608               if (thishbp != 0) {
 609                 GET_HDR(thishbp, thishdr);
 610                 next_size = (signed_word)(thishdr -> hb_sz);
 611                 if (next_size < size_avail
 612                   && next_size >= size_needed
 613                   && !GC_is_black_listed(thishbp, (word)size_needed)) {
 614                   continue;
 615                 }
 616               }
 617             }
 618             if ( !IS_UNCOLLECTABLE(kind) &&
 619                  (kind != PTRFREE || size_needed > MAX_BLACK_LIST_ALLOC)) {
 620               struct hblk * lasthbp = hbp;
 621               ptr_t search_end = (ptr_t)hbp + size_avail - size_needed;
 622               signed_word orig_avail = size_avail;
 623               signed_word eff_size_needed = ((flags & IGNORE_OFF_PAGE)?
 624                                                 HBLKSIZE
 625                                                 : size_needed);
 626
 627
 628               while ((ptr_t)lasthbp <= search_end
 629                      && (thishbp = GC_is_black_listed(lasthbp,
 630                                                       (word)eff_size_needed))
 631                         != 0) {
 632                 lasthbp = thishbp;
 633               }
 634               size_avail -= (ptr_t)lasthbp - (ptr_t)hbp;
 635               thishbp = lasthbp;
 636               if (size_avail >= size_needed) {
 637                 if (thishbp != hbp &&
 638                     0 != (thishdr = GC_install_header(thishbp))) {
 639                   /* Make sure it's mapped before we mangle it. */
 640 #                   ifdef USE_MUNMAP
 641                       if (!IS_MAPPED(hhdr)) {
 642                         GC_remap((ptr_t)hbp, hhdr -> hb_sz);
 643                         hhdr -> hb_flags &= ~WAS_UNMAPPED;
 644                       }
 645 #                   endif
 646                   /* Split the block at thishbp */
 647                       GC_split_block(hbp, hhdr, thishbp, thishdr, n);
 648                   /* Advance to thishbp */
 649                       hbp = thishbp;
 650                       hhdr = thishdr;
 651                       /* We must now allocate thishbp, since it may     */
 652                       /* be on the wrong free list.                     */
 653                 }
 654               } else if (size_needed > (signed_word)BL_LIMIT
 655                          && orig_avail - size_needed
 656                             > (signed_word)BL_LIMIT) {
 657                 /* Punt, since anything else risks unreasonable heap growth. */
 658                 if (0 == GETENV("GC_NO_BLACKLIST_WARNING")) {
 659                   WARN("Needed to allocate blacklisted block at 0x%lx\n",
 660                        (word)hbp);
 661                 }
 662                 size_avail = orig_avail;
 663               } else if (size_avail == 0 && size_needed == HBLKSIZE
 664                          && IS_MAPPED(hhdr)) {
 665                 if (!GC_find_leak) {
 666                   static unsigned count = 0;
 667
 668                   /* The block is completely blacklisted.  We need      */
 669                   /* to drop some such blocks, since otherwise we spend */
 670                   /* all our time traversing them if pointerfree        */
 671                   /* blocks are unpopular.                              */
 672                   /* A dropped block will be reconsidered at next GC.   */
 673                   if ((++count & 3) == 0) {
 674                     /* Allocate and drop the block in small chunks, to  */
 675                     /* maximize the chance that we will recover some    */
 676                     /* later.                                           */
 677                       word total_size = hhdr -> hb_sz;
 678                       struct hblk * limit = hbp + divHBLKSZ(total_size);
 679                       struct hblk * h;
 680                       struct hblk * prev = hhdr -> hb_prev;
 681
 682                       GC_words_wasted += total_size;
 683                       GC_large_free_bytes -= total_size;
 684                       GC_remove_from_fl(hhdr, n);
 685                       for (h = hbp; h < limit; h++) {
 686                         if (h == hbp || 0 != (hhdr = GC_install_header(h))) {
 687                           (void) setup_header(
 688                                   hhdr,
 689                                   BYTES_TO_WORDS(HBLKSIZE),
 690                                   PTRFREE, 0); /* Cant fail */
 691                           if (GC_debugging_started) {
 692                             BZERO(h, HBLKSIZE);
 693                           }
 694                         }
 695                       }
 696                     /* Restore hbp to point at free block */
 697                       hbp = prev;
 698                       if (0 == hbp) {
 699                         return GC_allochblk_nth(sz, kind, flags, n);
 700                       }
 701                       hhdr = HDR(hbp);
 702                   }
 703                 }
 704               }
 705             }
 706             if( size_avail >= size_needed ) {
 707 #               ifdef USE_MUNMAP
 708                   if (!IS_MAPPED(hhdr)) {
 709                     GC_remap((ptr_t)hbp, hhdr -> hb_sz);
 710                     hhdr -> hb_flags &= ~WAS_UNMAPPED;
 711                   }
 712 #               endif
 713                 /* hbp may be on the wrong freelist; the parameter n    */
 714                 /* is important.                                        */
 715                 hbp = GC_get_first_part(hbp, hhdr, size_needed, n);
 716                 break;
 717             }
 718         }
 719
 720     if (0 == hbp) return 0;
 721
 722     /* Notify virtual dirty bit implementation that we are about to write. */
 723         GC_write_hint(hbp);
 724
 725     /* Add it to map of valid blocks */
 726         if (!GC_install_counts(hbp, (word)size_needed)) return(0);
 727         /* This leaks memory under very rare conditions. */
 728
 729     /* Set up header */
 730         if (!setup_header(hhdr, sz, kind, flags)) {
 731             GC_remove_counts(hbp, (word)size_needed);
 732             return(0); /* ditto */
 733         }
 734
 735     /* We just successfully allocated a block.  Restart count of        */
 736     /* consecutive failures.                                            */
 737     {
 738         extern unsigned GC_fail_count;
 739
 740         GC_fail_count = 0;
 741     }
 742
 743     GC_large_free_bytes -= size_needed;
 744
 745     GC_ASSERT(IS_MAPPED(hhdr));
 746     return( hbp );
 747 }
 748
 749 struct hblk * GC_freehblk_ptr = 0;  /* Search position hint for GC_freehblk */
 750
 751 /*
 752  * Free a heap block.
 753  *
 754  * Coalesce the block with its neighbors if possible.
 755  *
 756  * All mark words are assumed to be cleared.
 757  */
 758 void
 759 GC_freehblk(hbp)
 760 struct hblk *hbp;
 761 {
 762 struct hblk *next, *prev;
 763 hdr *hhdr, *prevhdr, *nexthdr;
 764 signed_word size;
 765
 766
 767     GET_HDR(hbp, hhdr);
 768     size = hhdr->hb_sz;
 769     size = HBLKSIZE * OBJ_SZ_TO_BLOCKS(size);
 770     GC_remove_counts(hbp, (word)size);
 771     hhdr->hb_sz = size;
 772
 773     /* Check for duplicate deallocation in the easy case */
 774       if (HBLK_IS_FREE(hhdr)) {
 775         GC_printf1("Duplicate large block deallocation of 0x%lx\n",
 776                    (unsigned long) hbp);
 777         ABORT("Duplicate large block deallocation");
 778       }
 779
 780     GC_ASSERT(IS_MAPPED(hhdr));
 781     GC_invalidate_map(hhdr);
 782     next = (struct hblk *)((word)hbp + size);
 783     GET_HDR(next, nexthdr);
 784     prev = GC_free_block_ending_at(hbp);
 785     /* Coalesce with successor, if possible */
 786       if(0 != nexthdr && HBLK_IS_FREE(nexthdr) && IS_MAPPED(nexthdr)) {
 787         GC_remove_from_fl(nexthdr, FL_UNKNOWN);
 788         hhdr -> hb_sz += nexthdr -> hb_sz;
 789         GC_remove_header(next);
 790       }
 791     /* Coalesce with predecessor, if possible. */
 792       if (0 != prev) {
 793         prevhdr = HDR(prev);
 794         if (IS_MAPPED(prevhdr)) {
 795           GC_remove_from_fl(prevhdr, FL_UNKNOWN);
 796           prevhdr -> hb_sz += hhdr -> hb_sz;
 797           GC_remove_header(hbp);
 798           hbp = prev;
 799           hhdr = prevhdr;
 800         }
 801       }
 802
 803     GC_large_free_bytes += size;
 804     GC_add_to_fl(hbp, hhdr);
 805 }
 806