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 <http://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 /* From gmalloc.c.  */
  55 extern void (* __after_morecore_hook) (void);
  56 extern void *(*__morecore) (ptrdiff_t);
  57
  58 /* From ralloc.c.  */
  59 #ifdef REL_ALLOC
  60 extern void *(*real_morecore) (ptrdiff_t);
  61 #endif
  62
  63 /*
  64   Level number of warnings already issued.
  65   0 -- no warnings issued.
  66   1 -- 75% warning already issued.
  67   2 -- 85% warning already issued.
  68   3 -- 95% warning issued; keep warning frequently.
  69 */
  70 enum warnlevel { not_warned, warned_75, warned_85, warned_95 };
  71 static enum warnlevel warnlevel;
  72
  73 /* Function to call to issue a warning;
  74    0 means don't issue them.  */
  75 static void (*warn_function) (const char *);
  76
  77 /* Start of data space; can be changed by calling memory_warnings.  */
  78 static char *data_space_start;
  79
  80 /* Number of bytes of writable memory we can expect to be able to get.  */
  81 static size_t lim_data;
  82 \f
  83 #ifdef HAVE_GETRLIMIT
  84
  85 # ifndef RLIMIT_AS
  86 #  define RLIMIT_AS RLIMIT_DATA
  87 # endif
  88
  89 static void
  90 get_lim_data (void)
  91 {
  92   /* Set LIM_DATA to the minimum of the maximum object size and the
  93      maximum address space.  Don't bother to check for values like
  94      RLIM_INFINITY since in practice they are not much less than SIZE_MAX.  */
  95   struct rlimit rlimit;
  96   lim_data
  97     = (getrlimit (RLIMIT_AS, &rlimit) == 0 && rlimit.rlim_cur <= SIZE_MAX
  98        ? rlimit.rlim_cur
  99        : SIZE_MAX);
 100 }
 101
 102 #elif defined WINDOWSNT
 103
 104 #include "w32heap.h"
 105
 106 static void
 107 get_lim_data (void)
 108 {
 109   extern size_t reserved_heap_size;
 110   lim_data = reserved_heap_size;
 111 }
 112
 113 #elif defined MSDOS
 114
 115 void
 116 get_lim_data (void)
 117 {
 118   unsigned long totalram, freeram, totalswap, freeswap;
 119
 120   dos_memory_info (&totalram, &freeram, &totalswap, &freeswap);
 121   lim_data = freeram;
 122   /* Don't believe they will give us more that 0.5 GB.   */
 123   if (lim_data > 512U * 1024U * 1024U)
 124     lim_data = 512U * 1024U * 1024U;
 125 }
 126
 127 unsigned long
 128 ret_lim_data (void)
 129 {
 130   get_lim_data ();
 131   return lim_data;
 132 }
 133 #else
 134 # error "get_lim_data not implemented on this machine"
 135 #endif
 136 \f
 137 /* Verify amount of memory available, complaining if we're near the end. */
 138
 139 static void
 140 check_memory_limits (void)
 141 {
 142 #ifndef REL_ALLOC
 143   void *(*real_morecore) (ptrdiff_t) = 0;
 144 #endif
 145
 146   char *cp;
 147   size_t five_percent;
 148   size_t data_size;
 149   enum warnlevel new_warnlevel;
 150
 151   if (lim_data == 0)
 152     get_lim_data ();
 153   five_percent = lim_data / 20;
 154
 155   /* Find current end of memory and issue warning if getting near max */
 156   cp = (real_morecore ? real_morecore : __morecore) (0);
 157   data_size = cp - data_space_start;
 158
 159   if (!warn_function)
 160     return;
 161
 162   /* What level of warning does current memory usage demand?  */
 163   new_warnlevel
 164     = (data_size > five_percent * 19) ? warned_95
 165     : (data_size > five_percent * 17) ? warned_85
 166     : (data_size > five_percent * 15) ? warned_75
 167     : not_warned;
 168
 169   /* If we have gone up a level, give the appropriate warning.  */
 170   if (new_warnlevel > warnlevel || new_warnlevel == warned_95)
 171     {
 172       warnlevel = new_warnlevel;
 173       static char const *const warn_diagnostic[] =
 174         {
 175           "Warning: past 75% of memory limit",
 176           "Warning: past 85% of memory limit",
 177           "Warning: past 95% of memory limit"
 178         };
 179       warn_function (warn_diagnostic[warnlevel - 1]);
 180     }
 181   /* Handle going down in usage levels, with some hysteresis.  */
 182   else
 183     {
 184       /* If we go down below 70% full, issue another 75% warning
 185          when we go up again.  */
 186       if (data_size < five_percent * 14)
 187         warnlevel = not_warned;
 188       /* If we go down below 80% full, issue another 85% warning
 189          when we go up again.  */
 190       else if (warnlevel > warned_75 && data_size < five_percent * 16)
 191         warnlevel = warned_75;
 192       /* If we go down below 90% full, issue another 95% warning
 193          when we go up again.  */
 194       else if (warnlevel > warned_85 && data_size < five_percent * 18)
 195         warnlevel = warned_85;
 196     }
 197 }
 198 \f
 199 /* Enable memory usage warnings.
 200    START says where the end of pure storage is.
 201    WARNFUN specifies the function to call to issue a warning.  */
 202
 203 void
 204 memory_warnings (void *start, void (*warnfun) (const char *))
 205 {
 206   data_space_start = start ? start : data_start;
 207
 208   warn_function = warnfun;
 209   __after_morecore_hook = check_memory_limits;
 210
 211   /* Force data limit to be recalculated on each run.  */
 212   lim_data = 0;
 213 }