src/vm-limit.c

   1 /* Functions for memory limit warnings.
   2    Copyright (C) 1990, 1992, 2001-2014 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
   9 (at 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 <dpmi.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 /*
  55   Level number of warnings already issued.
  56   0 -- no warnings issued.
  57   1 -- 75% warning already issued.
  58   2 -- 85% warning already issued.
  59   3 -- 95% warning issued; keep warning frequently.
  60 */
  61 enum warnlevel { not_warned, warned_75, warned_85, warned_95 };
  62 static enum warnlevel warnlevel;
  63
  64 /* Function to call to issue a warning;
  65    0 means don't issue them.  */
  66 static void (*warn_function) (const char *);
  67
  68 /* Start of data space; can be changed by calling memory_warnings.  */
  69 static char *data_space_start;
  70
  71 /* Number of bytes of writable memory we can expect to be able to get.  */
  72 static size_t lim_data;
  73 \f
  74 #ifdef HAVE_GETRLIMIT
  75
  76 # ifndef RLIMIT_AS
  77 #  define RLIMIT_AS RLIMIT_DATA
  78 # endif
  79
  80 static void
  81 get_lim_data (void)
  82 {
  83   /* Set LIM_DATA to the minimum of the maximum object size and the
  84      maximum address space.  Don't bother to check for values like
  85      RLIM_INFINITY since in practice they are not much less than SIZE_MAX.  */
  86   struct rlimit rlimit;
  87   lim_data
  88     = (getrlimit (RLIMIT_AS, &rlimit) == 0 && rlimit.rlim_cur <= SIZE_MAX
  89        ? rlimit.rlim_cur
  90        : SIZE_MAX);
  91 }
  92
  93 #elif defined WINDOWSNT
  94
  95 #include "w32heap.h"
  96
  97 static void
  98 get_lim_data (void)
  99 {
 100   extern size_t reserved_heap_size;
 101   lim_data = reserved_heap_size;
 102 }
 103
 104 #elif defined MSDOS
 105
 106 void
 107 get_lim_data (void)
 108 {
 109   _go32_dpmi_meminfo info;
 110   unsigned long lim1, lim2;
 111
 112   _go32_dpmi_get_free_memory_information (&info);
 113   /* DPMI server of Windows NT and its descendants reports in
 114      info.available_memory a much lower amount that is really
 115      available, which causes bogus "past 95% of memory limit"
 116      warnings.  Try to overcome that via circumstantial evidence.  */
 117   lim1 = info.available_memory;
 118   lim2 = info.available_physical_pages;
 119   /* DPMI Spec: "Fields that are unavailable will hold -1."  */
 120   if ((long)lim1 == -1L)
 121     lim1 = 0;
 122   if ((long)lim2 == -1L)
 123     lim2 = 0;
 124   else
 125     lim2 *= 4096;
 126   /* Surely, the available memory is at least what we have physically
 127      available, right?  */
 128   if (lim1 >= lim2)
 129     lim_data = lim1;
 130   else
 131     lim_data = lim2;
 132   /* Don't believe they will give us more that 0.5 GB.   */
 133   if (lim_data > 512U * 1024U * 1024U)
 134     lim_data = 512U * 1024U * 1024U;
 135 }
 136
 137 unsigned long
 138 ret_lim_data (void)
 139 {
 140   get_lim_data ();
 141   return lim_data;
 142 }
 143 #else
 144 # error "get_lim_data not implemented on this machine"
 145 #endif
 146 \f
 147 /* Verify amount of memory available, complaining if we're near the end. */
 148
 149 static void
 150 check_memory_limits (void)
 151 {
 152 #ifdef REL_ALLOC
 153   extern void *(*real_morecore) (ptrdiff_t);
 154 #else
 155   void *(*real_morecore) (ptrdiff_t) = 0;
 156 #endif
 157   extern void *(*__morecore) (ptrdiff_t);
 158
 159   char *cp;
 160   size_t five_percent;
 161   size_t data_size;
 162   enum warnlevel new_warnlevel;
 163
 164   if (lim_data == 0)
 165     get_lim_data ();
 166   five_percent = lim_data / 20;
 167
 168   /* Find current end of memory and issue warning if getting near max */
 169   cp = (real_morecore ? real_morecore : __morecore) (0);
 170   data_size = cp - data_space_start;
 171
 172   if (!warn_function)
 173     return;
 174
 175   /* What level of warning does current memory usage demand?  */
 176   new_warnlevel
 177     = (data_size > five_percent * 19) ? warned_95
 178     : (data_size > five_percent * 17) ? warned_85
 179     : (data_size > five_percent * 15) ? warned_75
 180     : not_warned;
 181
 182   /* If we have gone up a level, give the appropriate warning.  */
 183   if (new_warnlevel > warnlevel || new_warnlevel == warned_95)
 184     {
 185       warnlevel = new_warnlevel;
 186       switch (warnlevel)
 187         {
 188         case warned_75:
 189           (*warn_function) ("Warning: past 75% of memory limit");
 190           break;
 191
 192         case warned_85:
 193           (*warn_function) ("Warning: past 85% of memory limit");
 194           break;
 195
 196         case warned_95:
 197           (*warn_function) ("Warning: past 95% of memory limit");
 198         }
 199     }
 200   /* Handle going down in usage levels, with some hysteresis.  */
 201   else
 202     {
 203       /* If we go down below 70% full, issue another 75% warning
 204          when we go up again.  */
 205       if (data_size < five_percent * 14)
 206         warnlevel = not_warned;
 207       /* If we go down below 80% full, issue another 85% warning
 208          when we go up again.  */
 209       else if (warnlevel > warned_75 && data_size < five_percent * 16)
 210         warnlevel = warned_75;
 211       /* If we go down below 90% full, issue another 95% warning
 212          when we go up again.  */
 213       else if (warnlevel > warned_85 && data_size < five_percent * 18)
 214         warnlevel = warned_85;
 215     }
 216 }
 217 \f
 218 /* Enable memory usage warnings.
 219    START says where the end of pure storage is.
 220    WARNFUN specifies the function to call to issue a warning.  */
 221
 222 void
 223 memory_warnings (void *start, void (*warnfun) (const char *))
 224 {
 225   extern void (* __after_morecore_hook) (void);     /* From gmalloc.c */
 226
 227   data_space_start = start ? start : data_start;
 228
 229   warn_function = warnfun;
 230   __after_morecore_hook = check_memory_limits;
 231
 232   /* Force data limit to be recalculated on each run.  */
 233   lim_data = 0;
 234 }