boehm-gc/headers.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) 1996 by Silicon Graphics.  All rights reserved.
   5  *
   6  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   7  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   8  *
   9  * Permission is hereby granted to use or copy this program
  10  * for any purpose,  provided the above notices are retained on all copies.
  11  * Permission to modify the code and to distribute modified code is granted,
  12  * provided the above notices are retained, and a notice that the code was
  13  * modified is included with the above copyright notice.
  14  */
  15
  16 #include "private/gc_priv.h"
  17
  18 /*
  19  * This implements:
  20  * 1. allocation of heap block headers
  21  * 2. A map from addresses to heap block addresses to heap block headers
  22  *
  23  * Access speed is crucial.  We implement an index structure based on a 2
  24  * level tree.
  25  */
  26
  27 STATIC bottom_index * GC_all_bottom_indices = 0;
  28                                 /* Pointer to first (lowest addr) */
  29                                 /* bottom_index.                  */
  30
  31 STATIC bottom_index * GC_all_bottom_indices_end = 0;
  32                                 /* Pointer to last (highest addr) */
  33                                 /* bottom_index.                  */
  34
  35 /* Non-macro version of header location routine */
  36 GC_INNER hdr * GC_find_header(ptr_t h)
  37 {
  38 #   ifdef HASH_TL
  39         hdr * result;
  40         GET_HDR(h, result);
  41         return(result);
  42 #   else
  43         return(HDR_INNER(h));
  44 #   endif
  45 }
  46
  47 /* Handle a header cache miss.  Returns a pointer to the        */
  48 /* header corresponding to p, if p can possibly be a valid      */
  49 /* object pointer, and 0 otherwise.                             */
  50 /* GUARANTEED to return 0 for a pointer past the first page     */
  51 /* of an object unless both GC_all_interior_pointers is set     */
  52 /* and p is in fact a valid object pointer.                     */
  53 /* Never returns a pointer to a free hblk.                      */
  54 GC_INNER hdr *
  55 #ifdef PRINT_BLACK_LIST
  56   GC_header_cache_miss(ptr_t p, hdr_cache_entry *hce, ptr_t source)
  57 #else
  58   GC_header_cache_miss(ptr_t p, hdr_cache_entry *hce)
  59 #endif
  60 {
  61   hdr *hhdr;
  62   HC_MISS();
  63   GET_HDR(p, hhdr);
  64   if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
  65     if (GC_all_interior_pointers) {
  66       if (hhdr != 0) {
  67         ptr_t current = p;
  68
  69         current = (ptr_t)HBLKPTR(current);
  70         do {
  71             current = current - HBLKSIZE*(word)hhdr;
  72             hhdr = HDR(current);
  73         } while(IS_FORWARDING_ADDR_OR_NIL(hhdr));
  74         /* current points to near the start of the large object */
  75         if (hhdr -> hb_flags & IGNORE_OFF_PAGE)
  76             return 0;
  77         if (HBLK_IS_FREE(hhdr)
  78             || p - current >= (ptrdiff_t)(hhdr->hb_sz)) {
  79             GC_ADD_TO_BLACK_LIST_NORMAL(p, source);
  80             /* Pointer past the end of the block */
  81             return 0;
  82         }
  83       } else {
  84         GC_ADD_TO_BLACK_LIST_NORMAL(p, source);
  85         /* And return zero: */
  86       }
  87       GC_ASSERT(hhdr == 0 || !HBLK_IS_FREE(hhdr));
  88       return hhdr;
  89       /* Pointers past the first page are probably too rare     */
  90       /* to add them to the cache.  We don't.                   */
  91       /* And correctness relies on the fact that we don't.      */
  92     } else {
  93       if (hhdr == 0) {
  94         GC_ADD_TO_BLACK_LIST_NORMAL(p, source);
  95       }
  96       return 0;
  97     }
  98   } else {
  99     if (HBLK_IS_FREE(hhdr)) {
 100       GC_ADD_TO_BLACK_LIST_NORMAL(p, source);
 101       return 0;
 102     } else {
 103       hce -> block_addr = (word)(p) >> LOG_HBLKSIZE;
 104       hce -> hce_hdr = hhdr;
 105       return hhdr;
 106     }
 107   }
 108 }
 109
 110 /* Routines to dynamically allocate collector data structures that will */
 111 /* never be freed.                                                       */
 112
 113 static ptr_t scratch_free_ptr = 0;
 114
 115 /* GC_scratch_last_end_ptr is end point of last obtained scratch area.  */
 116 /* GC_scratch_end_ptr is end point of current scratch area.             */
 117
 118 GC_INNER ptr_t GC_scratch_alloc(size_t bytes)
 119 {
 120     register ptr_t result = scratch_free_ptr;
 121
 122     bytes += GRANULE_BYTES-1;
 123     bytes &= ~(GRANULE_BYTES-1);
 124     scratch_free_ptr += bytes;
 125     if ((word)scratch_free_ptr <= (word)GC_scratch_end_ptr) {
 126         return(result);
 127     }
 128     {
 129         word bytes_to_get = MINHINCR * HBLKSIZE;
 130
 131         if (bytes_to_get <= bytes) {
 132           /* Undo the damage, and get memory directly */
 133             bytes_to_get = bytes;
 134 #           ifdef USE_MMAP
 135                 bytes_to_get += GC_page_size - 1;
 136                 bytes_to_get &= ~(GC_page_size - 1);
 137 #           endif
 138             result = (ptr_t)GET_MEM(bytes_to_get);
 139             GC_add_to_our_memory(result, bytes_to_get);
 140             scratch_free_ptr -= bytes;
 141             GC_scratch_last_end_ptr = result + bytes;
 142             return(result);
 143         }
 144         result = (ptr_t)GET_MEM(bytes_to_get);
 145         GC_add_to_our_memory(result, bytes_to_get);
 146         if (result == 0) {
 147             GC_COND_LOG_PRINTF("Out of memory - trying to allocate less\n");
 148             scratch_free_ptr -= bytes;
 149             bytes_to_get = bytes;
 150 #           ifdef USE_MMAP
 151                 bytes_to_get += GC_page_size - 1;
 152                 bytes_to_get &= ~(GC_page_size - 1);
 153 #           endif
 154             result = (ptr_t)GET_MEM(bytes_to_get);
 155             GC_add_to_our_memory(result, bytes_to_get);
 156             return result;
 157         }
 158         scratch_free_ptr = result;
 159         GC_scratch_end_ptr = scratch_free_ptr + bytes_to_get;
 160         GC_scratch_last_end_ptr = GC_scratch_end_ptr;
 161         return(GC_scratch_alloc(bytes));
 162     }
 163 }
 164
 165 static hdr * hdr_free_list = 0;
 166
 167 /* Return an uninitialized header */
 168 static hdr * alloc_hdr(void)
 169 {
 170     register hdr * result;
 171
 172     if (hdr_free_list == 0) {
 173         result = (hdr *) GC_scratch_alloc((word)(sizeof(hdr)));
 174     } else {
 175         result = hdr_free_list;
 176         hdr_free_list = (hdr *) (result -> hb_next);
 177     }
 178     return(result);
 179 }
 180
 181 GC_INLINE void free_hdr(hdr * hhdr)
 182 {
 183     hhdr -> hb_next = (struct hblk *) hdr_free_list;
 184     hdr_free_list = hhdr;
 185 }
 186
 187 #ifdef COUNT_HDR_CACHE_HITS
 188   /* Used for debugging/profiling (the symbols are externally visible). */
 189   word GC_hdr_cache_hits = 0;
 190   word GC_hdr_cache_misses = 0;
 191 #endif
 192
 193 GC_INNER void GC_init_headers(void)
 194 {
 195     register unsigned i;
 196
 197     GC_all_nils = (bottom_index *)GC_scratch_alloc((word)sizeof(bottom_index));
 198     if (GC_all_nils == NULL) {
 199       GC_err_printf("Insufficient memory for GC_all_nils\n");
 200       EXIT();
 201     }
 202     BZERO(GC_all_nils, sizeof(bottom_index));
 203     for (i = 0; i < TOP_SZ; i++) {
 204         GC_top_index[i] = GC_all_nils;
 205     }
 206 }
 207
 208 /* Make sure that there is a bottom level index block for address addr  */
 209 /* Return FALSE on failure.                                             */
 210 static GC_bool get_index(word addr)
 211 {
 212     word hi = (word)(addr) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE);
 213     bottom_index * r;
 214     bottom_index * p;
 215     bottom_index ** prev;
 216     bottom_index *pi;
 217
 218 #   ifdef HASH_TL
 219       word i = TL_HASH(hi);
 220       bottom_index * old;
 221
 222       old = p = GC_top_index[i];
 223       while(p != GC_all_nils) {
 224           if (p -> key == hi) return(TRUE);
 225           p = p -> hash_link;
 226       }
 227       r = (bottom_index*)GC_scratch_alloc((word)(sizeof (bottom_index)));
 228       if (r == 0) return(FALSE);
 229       BZERO(r, sizeof (bottom_index));
 230       r -> hash_link = old;
 231       GC_top_index[i] = r;
 232 #   else
 233       if (GC_top_index[hi] != GC_all_nils) return(TRUE);
 234       r = (bottom_index*)GC_scratch_alloc((word)(sizeof (bottom_index)));
 235       if (r == 0) return(FALSE);
 236       GC_top_index[hi] = r;
 237       BZERO(r, sizeof (bottom_index));
 238 #   endif
 239     r -> key = hi;
 240     /* Add it to the list of bottom indices */
 241       prev = &GC_all_bottom_indices;    /* pointer to p */
 242       pi = 0;                           /* bottom_index preceding p */
 243       while ((p = *prev) != 0 && p -> key < hi) {
 244         pi = p;
 245         prev = &(p -> asc_link);
 246       }
 247       r -> desc_link = pi;
 248       if (0 == p) {
 249         GC_all_bottom_indices_end = r;
 250       } else {
 251         p -> desc_link = r;
 252       }
 253       r -> asc_link = p;
 254       *prev = r;
 255     return(TRUE);
 256 }
 257
 258 /* Install a header for block h.        */
 259 /* The header is uninitialized.         */
 260 /* Returns the header or 0 on failure.  */
 261 GC_INNER struct hblkhdr * GC_install_header(struct hblk *h)
 262 {
 263     hdr * result;
 264
 265     if (!get_index((word) h)) return(0);
 266     result = alloc_hdr();
 267     if (result) {
 268       SET_HDR(h, result);
 269 #     ifdef USE_MUNMAP
 270         result -> hb_last_reclaimed = (unsigned short)GC_gc_no;
 271 #     endif
 272     }
 273     return(result);
 274 }
 275
 276 /* Set up forwarding counts for block h of size sz */
 277 GC_INNER GC_bool GC_install_counts(struct hblk *h, size_t sz/* bytes */)
 278 {
 279     struct hblk * hbp;
 280     word i;
 281
 282     for (hbp = h; (word)hbp < (word)h + sz; hbp += BOTTOM_SZ) {
 283         if (!get_index((word) hbp)) return(FALSE);
 284     }
 285     if (!get_index((word)h + sz - 1)) return(FALSE);
 286     for (hbp = h + 1; (word)hbp < (word)h + sz; hbp += 1) {
 287         i = HBLK_PTR_DIFF(hbp, h);
 288         SET_HDR(hbp, (hdr *)(i > MAX_JUMP? MAX_JUMP : i));
 289     }
 290     return(TRUE);
 291 }
 292
 293 /* Remove the header for block h */
 294 GC_INNER void GC_remove_header(struct hblk *h)
 295 {
 296     hdr **ha;
 297     GET_HDR_ADDR(h, ha);
 298     free_hdr(*ha);
 299     *ha = 0;
 300 }
 301
 302 /* Remove forwarding counts for h */
 303 GC_INNER void GC_remove_counts(struct hblk *h, size_t sz/* bytes */)
 304 {
 305     register struct hblk * hbp;
 306     for (hbp = h+1; (word)hbp < (word)h + sz; hbp += 1) {
 307         SET_HDR(hbp, 0);
 308     }
 309 }
 310
 311 /* Apply fn to all allocated blocks */
 312 /*VARARGS1*/
 313 void GC_apply_to_all_blocks(void (*fn)(struct hblk *h, word client_data),
 314                             word client_data)
 315 {
 316     signed_word j;
 317     bottom_index * index_p;
 318
 319     for (index_p = GC_all_bottom_indices; index_p != 0;
 320          index_p = index_p -> asc_link) {
 321         for (j = BOTTOM_SZ-1; j >= 0;) {
 322             if (!IS_FORWARDING_ADDR_OR_NIL(index_p->index[j])) {
 323                 if (!HBLK_IS_FREE(index_p->index[j])) {
 324                     (*fn)(((struct hblk *)
 325                               (((index_p->key << LOG_BOTTOM_SZ) + (word)j)
 326                                << LOG_HBLKSIZE)),
 327                           client_data);
 328                 }
 329                 j--;
 330              } else if (index_p->index[j] == 0) {
 331                 j--;
 332              } else {
 333                 j -= (signed_word)(index_p->index[j]);
 334              }
 335          }
 336      }
 337 }
 338
 339 /* Get the next valid block whose address is at least h */
 340 /* Return 0 if there is none.                           */
 341 GC_INNER struct hblk * GC_next_used_block(struct hblk *h)
 342 {
 343     register bottom_index * bi;
 344     register word j = ((word)h >> LOG_HBLKSIZE) & (BOTTOM_SZ-1);
 345
 346     GET_BI(h, bi);
 347     if (bi == GC_all_nils) {
 348         register word hi = (word)h >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE);
 349         bi = GC_all_bottom_indices;
 350         while (bi != 0 && bi -> key < hi) bi = bi -> asc_link;
 351         j = 0;
 352     }
 353     while(bi != 0) {
 354         while (j < BOTTOM_SZ) {
 355             hdr * hhdr = bi -> index[j];
 356             if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
 357                 j++;
 358             } else {
 359                 if (!HBLK_IS_FREE(hhdr)) {
 360                     return((struct hblk *)
 361                               (((bi -> key << LOG_BOTTOM_SZ) + j)
 362                                << LOG_HBLKSIZE));
 363                 } else {
 364                     j += divHBLKSZ(hhdr -> hb_sz);
 365                 }
 366             }
 367         }
 368         j = 0;
 369         bi = bi -> asc_link;
 370     }
 371     return(0);
 372 }
 373
 374 /* Get the last (highest address) block whose address is        */
 375 /* at most h.  Return 0 if there is none.                       */
 376 /* Unlike the above, this may return a free block.              */
 377 GC_INNER struct hblk * GC_prev_block(struct hblk *h)
 378 {
 379     register bottom_index * bi;
 380     register signed_word j = ((word)h >> LOG_HBLKSIZE) & (BOTTOM_SZ-1);
 381
 382     GET_BI(h, bi);
 383     if (bi == GC_all_nils) {
 384         register word hi = (word)h >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE);
 385         bi = GC_all_bottom_indices_end;
 386         while (bi != 0 && bi -> key > hi) bi = bi -> desc_link;
 387         j = BOTTOM_SZ - 1;
 388     }
 389     while(bi != 0) {
 390         while (j >= 0) {
 391             hdr * hhdr = bi -> index[j];
 392             if (0 == hhdr) {
 393                 --j;
 394             } else if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
 395                 j -= (signed_word)hhdr;
 396             } else {
 397                 return((struct hblk *)
 398                           (((bi -> key << LOG_BOTTOM_SZ) + j)
 399                                << LOG_HBLKSIZE));
 400             }
 401         }
 402         j = BOTTOM_SZ - 1;
 403         bi = bi -> desc_link;
 404     }
 405     return(0);
 406 }