src/ralloc.c

   1 /* Block-relocating memory allocator.
   2    Copyright (C) 1990 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Emacs.
   5
   6 GNU Emacs is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 1, or (at your option)
   9 any later version.
  10
  11 GNU Emacs is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Emacs; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  19
  20 /* NOTES:
  21
  22    Only relocate the blocs neccessary for SIZE in r_alloc_sbrk,
  23    rather than all of them.  This means allowing for a possible
  24    hole between the first bloc and the end of malloc storage. */
  25
  26 #include "config.h"
  27 #include "lisp.h"               /* Needed for xterm.h */
  28 #undef NULL
  29 #include "mem_limits.h"
  30 #include "xterm.h"              /* Needed for BLOCK_INPUT */
  31
  32 #define NIL ((POINTER) 0)
  33
  34 \f
  35 /* System call to set the break value. */
  36 extern POINTER sbrk ();
  37
  38 /* The break value, as seen by malloc (). */
  39 static POINTER virtual_break_value;
  40
  41 /* The break value, viewed by the relocatable blocs. */
  42 static POINTER break_value;
  43
  44 /* The REAL (i.e., page aligned) break value of the process. */
  45 static POINTER page_break_value;
  46
  47 /* Macros for rounding.  Note that rounding to any value is possible
  48    by changing the definition of PAGE. */
  49 #define PAGE (getpagesize ())
  50 #define ALIGNED(addr) (((unsigned int) (addr) & (PAGE - 1)) == 0)
  51 #define ROUNDUP(size) (((unsigned int) (size) + PAGE) & ~(PAGE - 1))
  52 #define ROUND_TO_PAGE(addr) (addr & (~(PAGE - 1)))
  53 #define EXCEEDS_ELISP_PTR(ptr) ((unsigned int) (ptr) >> VALBITS)
  54 \f
  55 /* Level of warnings issued. */
  56 static int warnlevel;
  57
  58 /* Function to call to issue a warning;
  59    0 means don't issue them.  */
  60 static void (*warnfunction) ();
  61
  62 static void
  63 check_memory_limits (address)
  64      POINTER address;
  65 {
  66   SIZE data_size = address - data_space_start;
  67
  68   switch (warnlevel)
  69     {
  70     case 0:
  71       if (data_size > (lim_data / 4) * 3)
  72         {
  73           warnlevel++;
  74           (*warnfunction) ("Warning: past 75% of memory limit");
  75         }
  76       break;
  77
  78     case 1:
  79       if (data_size > (lim_data / 20) * 17)
  80         {
  81           warnlevel++;
  82           (*warnfunction) ("Warning: past 85% of memory limit");
  83         }
  84       break;
  85
  86     case 2:
  87       if (data_size > (lim_data / 20) * 19)
  88         {
  89           warnlevel++;
  90           (*warnfunction) ("Warning: past 95% of memory limit");
  91         }
  92       break;
  93
  94     default:
  95       (*warnfunction) ("Warning: past acceptable memory limits");
  96       break;
  97     }
  98
  99     if (EXCEEDS_ELISP_PTR (address))
 100       memory_full ();
 101 }
 102 \f
 103 /* Obtain SIZE bytes of space.  If enough space is not presently available
 104    in our process reserve, (i.e., (page_break_value - break_value)),
 105    this means getting more page-aligned space from the system. */
 106
 107 static void
 108 obtain (size)
 109      SIZE size;
 110 {
 111   SIZE already_available = page_break_value - break_value;
 112
 113   if (already_available < size)
 114     {
 115       SIZE get = ROUNDUP (size);
 116
 117       if (warnfunction)
 118         check_memory_limits (page_break_value);
 119
 120       if (((int) sbrk (get)) < 0)
 121         abort ();
 122
 123       page_break_value += get;
 124     }
 125
 126   break_value += size;
 127 }
 128
 129 /* Obtain SIZE bytes of space and return a pointer to the new area. */
 130
 131 static POINTER
 132 get_more_space (size)
 133      SIZE size;
 134 {
 135   POINTER ptr = break_value;
 136   obtain (size);
 137   return ptr;
 138 }
 139
 140 /* Note that SIZE bytes of space have been relinquished by the process.
 141    If SIZE is more than a page, return the space the system. */
 142
 143 static void
 144 relinquish (size)
 145      SIZE size;
 146 {
 147   SIZE page_part = ROUND_TO_PAGE (size);
 148
 149   if (page_part)
 150     {
 151       if (((int) (sbrk (- page_part))) < 0)
 152         abort ();
 153
 154       page_break_value -= page_part;
 155     }
 156
 157   break_value -= size;
 158   bzero (break_value, (size - page_part));
 159 }
 160 \f
 161 typedef struct bp
 162 {
 163   struct bp *next;
 164   struct bp *prev;
 165   POINTER *variable;
 166   POINTER data;
 167   SIZE size;
 168 } *bloc_ptr;
 169
 170 #define NIL_BLOC ((bloc_ptr) 0)
 171 #define BLOC_PTR_SIZE (sizeof (struct bp))
 172
 173 /* Head and tail of the list of relocatable blocs. */
 174 static bloc_ptr first_bloc, last_bloc;
 175
 176 /* Declared in dispnew.c, this version dosen't fuck up if regions overlap. */
 177 extern void safe_bcopy ();
 178
 179 /* Find the bloc reference by the address in PTR.  Returns a pointer
 180    to that block. */
 181
 182 static bloc_ptr
 183 find_bloc (ptr)
 184      POINTER *ptr;
 185 {
 186   register bloc_ptr p = first_bloc;
 187
 188   while (p != NIL_BLOC)
 189     {
 190       if (p->variable == ptr && p->data == *ptr)
 191         return p;
 192
 193       p = p->next;
 194     }
 195
 196   return p;
 197 }
 198
 199 /* Allocate a bloc of SIZE bytes and append it to the chain of blocs.
 200    Returns a pointer to the new bloc. */
 201
 202 static bloc_ptr
 203 get_bloc (size)
 204      SIZE size;
 205 {
 206   register bloc_ptr new_bloc = (bloc_ptr) malloc (BLOC_PTR_SIZE);
 207
 208   new_bloc->data = get_more_space (size);
 209   new_bloc->size = size;
 210   new_bloc->next = NIL_BLOC;
 211   new_bloc->variable = NIL;
 212
 213   if (first_bloc)
 214     {
 215       new_bloc->prev = last_bloc;
 216       last_bloc->next = new_bloc;
 217       last_bloc = new_bloc;
 218     }
 219   else
 220     {
 221       first_bloc = last_bloc = new_bloc;
 222       new_bloc->prev = NIL_BLOC;
 223     }
 224
 225   return new_bloc;
 226 }
 227
 228 /* Relocate all blocs from BLOC on upward in the list to the zone
 229    indicated by ADDRESS.  Direction of relocation is determined by
 230    the position of ADDRESS relative to BLOC->data.
 231
 232    Note that ordering of blocs is not affected by this function. */
 233
 234 static void
 235 relocate_some_blocs (bloc, address)
 236      bloc_ptr bloc;
 237      POINTER address;
 238 {
 239   register bloc_ptr b;
 240   POINTER data_zone = bloc->data;
 241   register SIZE data_zone_size = 0;
 242   register SIZE offset = bloc->data - address;
 243   POINTER new_data_zone = data_zone - offset;
 244
 245   for (b = bloc; b != NIL_BLOC; b = b->next)
 246     {
 247       data_zone_size += b->size;
 248       b->data -= offset;
 249       *b->variable = b->data;
 250     }
 251
 252   safe_bcopy (data_zone, new_data_zone, data_zone_size);
 253 }
 254
 255 /* Free BLOC from the chain of blocs, relocating any blocs above it
 256    and returning BLOC->size bytes to the free area. */
 257
 258 static void
 259 free_bloc (bloc)
 260      bloc_ptr bloc;
 261 {
 262   if (bloc == first_bloc && bloc == last_bloc)
 263     {
 264       first_bloc = last_bloc = NIL_BLOC;
 265     }
 266   else if (bloc == last_bloc)
 267     {
 268       last_bloc = bloc->prev;
 269       last_bloc->next = NIL_BLOC;
 270     }
 271   else if (bloc == first_bloc)
 272     {
 273       first_bloc = bloc->next;
 274       first_bloc->prev = NIL_BLOC;
 275       relocate_some_blocs (bloc->next, bloc->data);
 276     }
 277   else
 278     {
 279       bloc->next->prev = bloc->prev;
 280       bloc->prev->next = bloc->next;
 281       relocate_some_blocs (bloc->next, bloc->data);
 282     }
 283
 284   relinquish (bloc->size);
 285   free (bloc);
 286 }
 287 \f
 288 static int use_relocatable_buffers;
 289
 290 /* Obtain SIZE bytes of storage from the free pool, or the system,
 291    as neccessary.  If relocatable blocs are in use, this means
 292    relocating them. */
 293
 294 POINTER
 295 r_alloc_sbrk (size)
 296      long size;
 297 {
 298   POINTER ptr;
 299
 300   if (! use_relocatable_buffers)
 301     return sbrk (size);
 302
 303   if (size > 0)
 304     {
 305       obtain (size);
 306       if (first_bloc)
 307         {
 308           relocate_some_blocs (first_bloc, first_bloc->data + size);
 309           bzero (virtual_break_value, size);
 310         }
 311     }
 312   else if (size < 0)
 313     {
 314       if (first_bloc)
 315         relocate_some_blocs (first_bloc, first_bloc->data + size);
 316       relinquish (- size);
 317     }
 318
 319   ptr = virtual_break_value;
 320   virtual_break_value += size;
 321   return ptr;
 322 }
 323
 324 /* Allocate a relocatable bloc of storage of size SIZE.  A pointer to
 325    the data is returned in *PTR.  PTR is thus the address of some variable
 326    which will use the data area. */
 327
 328 POINTER
 329 r_alloc (ptr, size)
 330      POINTER *ptr;
 331      SIZE size;
 332 {
 333   register bloc_ptr new_bloc;
 334
 335   BLOCK_INPUT;
 336   new_bloc = get_bloc (size);
 337   new_bloc->variable = ptr;
 338   *ptr = new_bloc->data;
 339   UNBLOCK_INPUT;
 340
 341   return *ptr;
 342 }
 343
 344 /* Free a bloc of relocatable storage whose data is pointed to by PTR. */
 345
 346 void
 347 r_alloc_free (ptr)
 348      register POINTER *ptr;
 349 {
 350   register bloc_ptr dead_bloc;
 351
 352   BLOCK_INPUT;
 353   dead_bloc = find_bloc (ptr);
 354   if (dead_bloc == NIL_BLOC)
 355     abort ();
 356
 357   free_bloc (dead_bloc);
 358   UNBLOCK_INPUT;
 359 }
 360
 361 /* Given a pointer at address PTR to relocatable data, resize it
 362    to SIZE.  This is done by obtaining a new block and freeing the
 363    old, unless SIZE is less than or equal to the current bloc size,
 364    in which case nothing happens and the current value is returned.
 365
 366    The contents of PTR is changed to reflect the new bloc, and this
 367    value is returned. */
 368
 369 POINTER
 370 r_re_alloc (ptr, size)
 371      POINTER *ptr;
 372      SIZE size;
 373 {
 374   register bloc_ptr old_bloc, new_bloc;
 375
 376   BLOCK_INPUT;
 377   old_bloc = find_bloc (ptr);
 378   if (old_bloc == NIL_BLOC)
 379     abort ();
 380
 381   if (size <= old_bloc->size)
 382     return *ptr;
 383
 384   new_bloc = get_bloc (size);
 385   new_bloc->variable = ptr;
 386   safe_bcopy (old_bloc->data, new_bloc->data, old_bloc->size);
 387   *ptr = new_bloc->data;
 388
 389   free_bloc (old_bloc);
 390   UNBLOCK_INPUT;
 391
 392   return *ptr;
 393 }
 394 \f
 395 /* The hook `malloc' uses for the function which gets more space
 396    from the system.  */
 397 extern POINTER (*__morecore) ();
 398
 399 /* Intialize various things for memory allocation. */
 400
 401 void
 402 malloc_init (start, warn_func)
 403      POINTER start;
 404      void (*warn_func) ();
 405 {
 406   static int malloc_initialized = 0;
 407
 408   if (start)
 409     data_space_start = start;
 410
 411   if (malloc_initialized)
 412     return;
 413
 414   malloc_initialized = 1;
 415   __morecore = r_alloc_sbrk;
 416   virtual_break_value = break_value = sbrk (0);
 417   page_break_value = (POINTER) ROUNDUP (break_value);
 418   bzero (break_value, (page_break_value - break_value));
 419   use_relocatable_buffers = 1;
 420
 421   lim_data = 0;
 422   warnlevel = 0;
 423   warnfunction = warn_func;
 424
 425   get_lim_data ();
 426 }