src/vm-limit.c

   1 /* Functions for memory limit warnings.
   2    Copyright (C) 1990, 1992, 2001-2017 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 3 of the License, or (at
   9 your option) 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.  If not, see <https://www.gnu.org/licenses/>.  */
  18
  19 #include <config.h>
  20 #include <unistd.h> /* for 'environ', on AIX */
  21 #include "lisp.h"
  22
  23 #ifdef MSDOS
  24 #include "dosfns.h"
  25 extern int etext;
  26 #endif
  27
  28 /* Some systems need this before <sys/resource.h>.  */
  29 #include <sys/types.h>
  30
  31 #ifdef HAVE_SYS_RESOURCE_H
  32 # include <sys/time.h>
  33 # include <sys/resource.h>
  34 #else
  35 # if HAVE_SYS_VLIMIT_H
  36 #  include <sys/vlimit.h>       /* Obsolete, says glibc */
  37 # endif
  38 #endif
  39
  40 /* Start of data.  It is OK if this is approximate; it's used only as
  41    a heuristic.  */
  42 #ifdef DATA_START
  43 # define data_start ((char *) DATA_START)
  44 #else
  45 extern char data_start[];
  46 # ifndef HAVE_DATA_START
  47 /* Initialize to nonzero, so that it's put into data and not bss.
  48    Link this file's object code first, so that this symbol is near the
  49    start of data.  */
  50 char data_start[1] = { 1 };
  51 # endif
  52 #endif
  53
  54 #ifdef HAVE_MALLOC_H
  55 # include <malloc.h>
  56 #endif
  57 #ifndef DOUG_LEA_MALLOC
  58 # ifndef __MALLOC_HOOK_VOLATILE
  59 #  define __MALLOC_HOOK_VOLATILE volatile
  60 # endif
  61 extern void *(*__morecore) (ptrdiff_t);
  62 extern void (*__MALLOC_HOOK_VOLATILE __after_morecore_hook) (void);
  63 #endif
  64
  65 /* From ralloc.c.  */
  66 #ifdef REL_ALLOC
  67 extern void *(*real_morecore) (ptrdiff_t);
  68 #endif
  69
  70 /*
  71   Level number of warnings already issued.
  72   0 -- no warnings issued.
  73   1 -- 75% warning already issued.
  74   2 -- 85% warning already issued.
  75   3 -- 95% warning issued; keep warning frequently.
  76 */
  77 enum warnlevel { not_warned, warned_75, warned_85, warned_95 };
  78 static enum warnlevel warnlevel;
  79
  80 /* Function to call to issue a warning;
  81    0 means don't issue them.  */
  82 static void (*warn_function) (const char *);
  83
  84 /* Start of data space; can be changed by calling memory_warnings.  */
  85 static char *data_space_start;
  86
  87 /* Number of bytes of writable memory we can expect to be able to get.  */
  88 static size_t lim_data;
  89 \f
  90 #ifdef HAVE_GETRLIMIT
  91
  92 # ifndef RLIMIT_AS
  93 #  define RLIMIT_AS RLIMIT_DATA
  94 # endif
  95
  96 static void
  97 get_lim_data (void)
  98 {
  99   /* Set LIM_DATA to the minimum of the maximum object size and the
 100      maximum address space.  Don't bother to check for values like
 101      RLIM_INFINITY since in practice they are not much less than SIZE_MAX.  */
 102   struct rlimit rlimit;
 103   lim_data
 104     = (getrlimit (RLIMIT_AS, &rlimit) == 0 && rlimit.rlim_cur <= SIZE_MAX
 105        ? rlimit.rlim_cur
 106        : SIZE_MAX);
 107 }
 108
 109 #elif defined WINDOWSNT
 110
 111 #include "w32heap.h"
 112
 113 static void
 114 get_lim_data (void)
 115 {
 116   extern size_t reserved_heap_size;
 117   lim_data = reserved_heap_size;
 118 }
 119
 120 #elif defined MSDOS
 121
 122 void
 123 get_lim_data (void)
 124 {
 125   unsigned long totalram, freeram, totalswap, freeswap;
 126
 127   dos_memory_info (&totalram, &freeram, &totalswap, &freeswap);
 128   lim_data = freeram;
 129   /* Don't believe they will give us more that 0.5 GB.   */
 130   if (lim_data > 512U * 1024U * 1024U)
 131     lim_data = 512U * 1024U * 1024U;
 132 }
 133
 134 unsigned long
 135 ret_lim_data (void)
 136 {
 137   get_lim_data ();
 138   return lim_data;
 139 }
 140 #else
 141 # error "get_lim_data not implemented on this machine"
 142 #endif
 143 \f
 144 /* Verify amount of memory available, complaining if we're near the end. */
 145
 146 static void
 147 check_memory_limits (void)
 148 {
 149 #ifndef REL_ALLOC
 150   void *(*real_morecore) (ptrdiff_t) = 0;
 151 #endif
 152
 153   char *cp;
 154   size_t five_percent;
 155   size_t data_size;
 156   enum warnlevel new_warnlevel;
 157
 158   if (lim_data == 0)
 159     get_lim_data ();
 160   five_percent = lim_data / 20;
 161
 162   /* Find current end of memory and issue warning if getting near max */
 163   cp = (real_morecore ? real_morecore : __morecore) (0);
 164   data_size = cp - data_space_start;
 165
 166   if (!warn_function)
 167     return;
 168
 169   /* What level of warning does current memory usage demand?  */
 170   new_warnlevel
 171     = (data_size > five_percent * 19) ? warned_95
 172     : (data_size > five_percent * 17) ? warned_85
 173     : (data_size > five_percent * 15) ? warned_75
 174     : not_warned;
 175
 176   /* If we have gone up a level, give the appropriate warning.  */
 177   if (new_warnlevel > warnlevel || new_warnlevel == warned_95)
 178     {
 179       warnlevel = new_warnlevel;
 180       static char const *const warn_diagnostic[] =
 181         {
 182           "Warning: past 75% of memory limit",
 183           "Warning: past 85% of memory limit",
 184           "Warning: past 95% of memory limit"
 185         };
 186       warn_function (warn_diagnostic[warnlevel - 1]);
 187     }
 188   /* Handle going down in usage levels, with some hysteresis.  */
 189   else
 190     {
 191       /* If we go down below 70% full, issue another 75% warning
 192          when we go up again.  */
 193       if (data_size < five_percent * 14)
 194         warnlevel = not_warned;
 195       /* If we go down below 80% full, issue another 85% warning
 196          when we go up again.  */
 197       else if (warnlevel > warned_75 && data_size < five_percent * 16)
 198         warnlevel = warned_75;
 199       /* If we go down below 90% full, issue another 95% warning
 200          when we go up again.  */
 201       else if (warnlevel > warned_85 && data_size < five_percent * 18)
 202         warnlevel = warned_85;
 203     }
 204 }
 205 \f
 206 /* Enable memory usage warnings.
 207    START says where the end of pure storage is.
 208    WARNFUN specifies the function to call to issue a warning.  */
 209
 210 void
 211 memory_warnings (void *start, void (*warnfun) (const char *))
 212 {
 213   data_space_start = start ? start : data_start;
 214
 215   warn_function = warnfun;
 216   __after_morecore_hook = check_memory_limits;
 217
 218   /* Force data limit to be recalculated on each run.  */
 219   lim_data = 0;
 220 }