libgc/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 /*
  17  * This implements:
  18  * 1. allocation of heap block headers
  19  * 2. A map from addresses to heap block addresses to heap block headers
  20  *
  21  * Access speed is crucial.  We implement an index structure based on a 2
  22  * level tree.
  23  */
  24
  25 # include "private/gc_priv.h"
  26
  27 bottom_index * GC_all_bottom_indices = 0;
  28                                 /* Pointer to first (lowest addr) */
  29                                 /* bottom_index.                  */
  30
  31 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 hdr * GC_find_header(h)
  37 ptr_t h;
  38 {
  39 #   ifdef HASH_TL
  40         register hdr * result;
  41         GET_HDR(h, result);
  42         return(result);
  43 #   else
  44         return(HDR_INNER(h));
  45 #   endif
  46 }
  47
  48 /* Routines to dynamically allocate collector data structures that will */
  49 /* never be freed.                                                       */
  50
  51 static ptr_t scratch_free_ptr = 0;
  52
  53 /* GC_scratch_last_end_ptr is end point of last obtained scratch area.  */
  54 /* GC_scratch_end_ptr is end point of current scratch area.             */
  55
  56 ptr_t GC_scratch_alloc(bytes)
  57 register word bytes;
  58 {
  59     register ptr_t result = scratch_free_ptr;
  60
  61 #   ifdef ALIGN_DOUBLE
  62 #       define GRANULARITY (2 * sizeof(word))
  63 #   else
  64 #       define GRANULARITY sizeof(word)
  65 #   endif
  66     bytes += GRANULARITY-1;
  67     bytes &= ~(GRANULARITY-1);
  68     scratch_free_ptr += bytes;
  69     if (scratch_free_ptr <= GC_scratch_end_ptr) {
  70         return(result);
  71     }
  72     {
  73         word bytes_to_get = MINHINCR * HBLKSIZE;
  74
  75         if (bytes_to_get <= bytes) {
  76           /* Undo the damage, and get memory directly */
  77             bytes_to_get = bytes;
  78 #           ifdef USE_MMAP
  79                 bytes_to_get += GC_page_size - 1;
  80                 bytes_to_get &= ~(GC_page_size - 1);
  81 #           endif
  82             result = (ptr_t)GET_MEM(bytes_to_get);
  83             scratch_free_ptr -= bytes;
  84             GC_scratch_last_end_ptr = result + bytes;
  85             return(result);
  86         }
  87         result = (ptr_t)GET_MEM(bytes_to_get);
  88         if (result == 0) {
  89 #           ifdef PRINTSTATS
  90                 GC_printf0("Out of memory - trying to allocate less\n");
  91 #           endif
  92             scratch_free_ptr -= bytes;
  93             bytes_to_get = bytes;
  94 #           ifdef USE_MMAP
  95                 bytes_to_get += GC_page_size - 1;
  96                 bytes_to_get &= ~(GC_page_size - 1);
  97 #           endif
  98             return((ptr_t)GET_MEM(bytes_to_get));
  99         }
 100         scratch_free_ptr = result;
 101         GC_scratch_end_ptr = scratch_free_ptr + bytes_to_get;
 102         GC_scratch_last_end_ptr = GC_scratch_end_ptr;
 103         return(GC_scratch_alloc(bytes));
 104     }
 105 }
 106
 107 static hdr * hdr_free_list = 0;
 108
 109 /* Return an uninitialized header */
 110 static hdr * alloc_hdr()
 111 {
 112     register hdr * result;
 113
 114     if (hdr_free_list == 0) {
 115         result = (hdr *) GC_scratch_alloc((word)(sizeof(hdr)));
 116     } else {
 117         result = hdr_free_list;
 118         hdr_free_list = (hdr *) (result -> hb_next);
 119     }
 120     return(result);
 121 }
 122
 123 static void free_hdr(hhdr)
 124 hdr * hhdr;
 125 {
 126     hhdr -> hb_next = (struct hblk *) hdr_free_list;
 127     hdr_free_list = hhdr;
 128 }
 129
 130 hdr * GC_invalid_header;
 131
 132 #ifdef USE_HDR_CACHE
 133   word GC_hdr_cache_hits = 0;
 134   word GC_hdr_cache_misses = 0;
 135 #endif
 136
 137 void GC_init_headers()
 138 {
 139     register unsigned i;
 140
 141     GC_all_nils = (bottom_index *)GC_scratch_alloc((word)sizeof(bottom_index));
 142     BZERO(GC_all_nils, sizeof(bottom_index));
 143     for (i = 0; i < TOP_SZ; i++) {
 144         GC_top_index[i] = GC_all_nils;
 145     }
 146     GC_invalid_header = alloc_hdr();
 147     GC_invalidate_map(GC_invalid_header);
 148 }
 149
 150 /* Make sure that there is a bottom level index block for address addr  */
 151 /* Return FALSE on failure.                                             */
 152 static GC_bool get_index(addr)
 153 word addr;
 154 {
 155     word hi = (word)(addr) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE);
 156     bottom_index * r;
 157     bottom_index * p;
 158     bottom_index ** prev;
 159     bottom_index *pi;
 160
 161 #   ifdef HASH_TL
 162       unsigned i = TL_HASH(hi);
 163       bottom_index * old;
 164
 165       old = p = GC_top_index[i];
 166       while(p != GC_all_nils) {
 167           if (p -> key == hi) return(TRUE);
 168           p = p -> hash_link;
 169       }
 170       r = (bottom_index*)GC_scratch_alloc((word)(sizeof (bottom_index)));
 171       if (r == 0) return(FALSE);
 172       BZERO(r, sizeof (bottom_index));
 173       r -> hash_link = old;
 174       GC_top_index[i] = r;
 175 #   else
 176       if (GC_top_index[hi] != GC_all_nils) return(TRUE);
 177       r = (bottom_index*)GC_scratch_alloc((word)(sizeof (bottom_index)));
 178       if (r == 0) return(FALSE);
 179       GC_top_index[hi] = r;
 180       BZERO(r, sizeof (bottom_index));
 181 #   endif
 182     r -> key = hi;
 183     /* Add it to the list of bottom indices */
 184       prev = &GC_all_bottom_indices;    /* pointer to p */
 185       pi = 0;                           /* bottom_index preceding p */
 186       while ((p = *prev) != 0 && p -> key < hi) {
 187         pi = p;
 188         prev = &(p -> asc_link);
 189       }
 190       r -> desc_link = pi;
 191       if (0 == p) {
 192         GC_all_bottom_indices_end = r;
 193       } else {
 194         p -> desc_link = r;
 195       }
 196       r -> asc_link = p;
 197       *prev = r;
 198     return(TRUE);
 199 }
 200
 201 /* Install a header for block h.        */
 202 /* The header is uninitialized.         */
 203 /* Returns the header or 0 on failure.  */
 204 struct hblkhdr * GC_install_header(h)
 205 register struct hblk * h;
 206 {
 207     hdr * result;
 208
 209     if (!get_index((word) h)) return(0);
 210     result = alloc_hdr();
 211     SET_HDR(h, result);
 212 #   ifdef USE_MUNMAP
 213         result -> hb_last_reclaimed = GC_gc_no;
 214 #   endif
 215     return(result);
 216 }
 217
 218 /* Set up forwarding counts for block h of size sz */
 219 GC_bool GC_install_counts(h, sz)
 220 register struct hblk * h;
 221 register word sz; /* bytes */
 222 {
 223     register struct hblk * hbp;
 224     register int i;
 225
 226     for (hbp = h; (char *)hbp < (char *)h + sz; hbp += BOTTOM_SZ) {
 227         if (!get_index((word) hbp)) return(FALSE);
 228     }
 229     if (!get_index((word)h + sz - 1)) return(FALSE);
 230     for (hbp = h + 1; (char *)hbp < (char *)h + sz; hbp += 1) {
 231         i = HBLK_PTR_DIFF(hbp, h);
 232         SET_HDR(hbp, (hdr *)(i > MAX_JUMP? MAX_JUMP : i));
 233     }
 234     return(TRUE);
 235 }
 236
 237 /* Remove the header for block h */
 238 void GC_remove_header(h)
 239 register struct hblk * h;
 240 {
 241     hdr ** ha;
 242
 243     GET_HDR_ADDR(h, ha);
 244     free_hdr(*ha);
 245     *ha = 0;
 246 }
 247
 248 /* Remove forwarding counts for h */
 249 void GC_remove_counts(h, sz)
 250 register struct hblk * h;
 251 register word sz; /* bytes */
 252 {
 253     register struct hblk * hbp;
 254
 255     for (hbp = h+1; (char *)hbp < (char *)h + sz; hbp += 1) {
 256         SET_HDR(hbp, 0);
 257     }
 258 }
 259
 260 /* Apply fn to all allocated blocks */
 261 /*VARARGS1*/
 262 void GC_apply_to_all_blocks(fn, client_data)
 263 void (*fn) GC_PROTO((struct hblk *h, word client_data));
 264 word client_data;
 265 {
 266     register int j;
 267     register bottom_index * index_p;
 268
 269     for (index_p = GC_all_bottom_indices; index_p != 0;
 270          index_p = index_p -> asc_link) {
 271         for (j = BOTTOM_SZ-1; j >= 0;) {
 272             if (!IS_FORWARDING_ADDR_OR_NIL(index_p->index[j])) {
 273                 if (index_p->index[j]->hb_map != GC_invalid_map) {
 274                     (*fn)(((struct hblk *)
 275                               (((index_p->key << LOG_BOTTOM_SZ) + (word)j)
 276                                << LOG_HBLKSIZE)),
 277                           client_data);
 278                 }
 279                 j--;
 280              } else if (index_p->index[j] == 0) {
 281                 j--;
 282              } else {
 283                 j -= (word)(index_p->index[j]);
 284              }
 285          }
 286      }
 287 }
 288
 289 /* Get the next valid block whose address is at least h */
 290 /* Return 0 if there is none.                           */
 291 struct hblk * GC_next_used_block(h)
 292 struct hblk * h;
 293 {
 294     register bottom_index * bi;
 295     register word j = ((word)h >> LOG_HBLKSIZE) & (BOTTOM_SZ-1);
 296
 297     GET_BI(h, bi);
 298     if (bi == GC_all_nils) {
 299         register word hi = (word)h >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE);
 300         bi = GC_all_bottom_indices;
 301         while (bi != 0 && bi -> key < hi) bi = bi -> asc_link;
 302         j = 0;
 303     }
 304     while(bi != 0) {
 305         while (j < BOTTOM_SZ) {
 306             hdr * hhdr = bi -> index[j];
 307             if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
 308                 j++;
 309             } else {
 310                 if (hhdr->hb_map != GC_invalid_map) {
 311                     return((struct hblk *)
 312                               (((bi -> key << LOG_BOTTOM_SZ) + j)
 313                                << LOG_HBLKSIZE));
 314                 } else {
 315                     j += divHBLKSZ(hhdr -> hb_sz);
 316                 }
 317             }
 318         }
 319         j = 0;
 320         bi = bi -> asc_link;
 321     }
 322     return(0);
 323 }
 324
 325 /* Get the last (highest address) block whose address is        */
 326 /* at most h.  Return 0 if there is none.                       */
 327 /* Unlike the above, this may return a free block.              */
 328 struct hblk * GC_prev_block(h)
 329 struct hblk * h;
 330 {
 331     register bottom_index * bi;
 332     register signed_word j = ((word)h >> LOG_HBLKSIZE) & (BOTTOM_SZ-1);
 333
 334     GET_BI(h, bi);
 335     if (bi == GC_all_nils) {
 336         register word hi = (word)h >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE);
 337         bi = GC_all_bottom_indices_end;
 338         while (bi != 0 && bi -> key > hi) bi = bi -> desc_link;
 339         j = BOTTOM_SZ - 1;
 340     }
 341     while(bi != 0) {
 342         while (j >= 0) {
 343             hdr * hhdr = bi -> index[j];
 344             if (0 == hhdr) {
 345                 --j;
 346             } else if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
 347                 j -= (signed_word)hhdr;
 348             } else {
 349                 return((struct hblk *)
 350                           (((bi -> key << LOG_BOTTOM_SZ) + j)
 351                                << LOG_HBLKSIZE));
 352             }
 353         }
 354         j = BOTTOM_SZ - 1;
 355         bi = bi -> desc_link;
 356     }
 357     return(0);
 358 }