src/vm-limit.c

   1 /* Functions for memory limit warnings.
   2    Copyright (C) 1990, 1992, 2001-2013 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 #include "mem-limits.h"
  23
  24 /*
  25   Level number of warnings already issued.
  26   0 -- no warnings issued.
  27   1 -- 75% warning already issued.
  28   2 -- 85% warning already issued.
  29   3 -- 95% warning issued; keep warning frequently.
  30 */
  31 enum warnlevel { not_warned, warned_75, warned_85, warned_95 };
  32 static enum warnlevel warnlevel;
  33
  34 /* Function to call to issue a warning;
  35    0 means don't issue them.  */
  36 static void (*warn_function) (const char *);
  37
  38 /* Start of data space; can be changed by calling malloc_init.  */
  39 static void *data_space_start;
  40
  41 /* Number of bytes of writable memory we can expect to be able to get.  */
  42 static size_t lim_data;
  43 \f
  44
  45 #ifdef HAVE_GETRLIMIT
  46
  47 # ifndef RLIMIT_AS
  48 #  define RLIMIT_AS RLIMIT_DATA
  49 # endif
  50
  51 static void
  52 get_lim_data (void)
  53 {
  54   /* Set LIM_DATA to the minimum of the maximum object size and the
  55      maximum address space.  Don't bother to check for values like
  56      RLIM_INFINITY since in practice they are not much less than SIZE_MAX.  */
  57   struct rlimit rlimit;
  58   lim_data
  59     = (getrlimit (RLIMIT_AS, &rlimit) == 0 && rlimit.rlim_cur <= SIZE_MAX
  60        ? rlimit.rlim_cur
  61        : SIZE_MAX);
  62 }
  63
  64 #elif defined WINDOWSNT
  65
  66 #include "w32heap.h"
  67
  68 static void
  69 get_lim_data (void)
  70 {
  71   extern size_t reserved_heap_size;
  72   lim_data = reserved_heap_size;
  73 }
  74
  75 #elif defined MSDOS
  76
  77 void
  78 get_lim_data (void)
  79 {
  80   _go32_dpmi_meminfo info;
  81   unsigned long lim1, lim2;
  82
  83   _go32_dpmi_get_free_memory_information (&info);
  84   /* DPMI server of Windows NT and its descendants reports in
  85      info.available_memory a much lower amount that is really
  86      available, which causes bogus "past 95% of memory limit"
  87      warnings.  Try to overcome that via circumstantial evidence.  */
  88   lim1 = info.available_memory;
  89   lim2 = info.available_physical_pages;
  90   /* DPMI Spec: "Fields that are unavailable will hold -1."  */
  91   if ((long)lim1 == -1L)
  92     lim1 = 0;
  93   if ((long)lim2 == -1L)
  94     lim2 = 0;
  95   else
  96     lim2 *= 4096;
  97   /* Surely, the available memory is at least what we have physically
  98      available, right?  */
  99   if (lim1 >= lim2)
 100     lim_data = lim1;
 101   else
 102     lim_data = lim2;
 103   /* Don't believe they will give us more that 0.5 GB.   */
 104   if (lim_data > 512U * 1024U * 1024U)
 105     lim_data = 512U * 1024U * 1024U;
 106 }
 107
 108 unsigned long
 109 ret_lim_data (void)
 110 {
 111   get_lim_data ();
 112   return lim_data;
 113 }
 114 #else
 115 # error "get_lim_data not implemented on this machine"
 116 #endif
 117 \f
 118 /* Verify amount of memory available, complaining if we're near the end. */
 119
 120 static void
 121 check_memory_limits (void)
 122 {
 123 #ifdef REL_ALLOC
 124   extern void *(*real_morecore) (ptrdiff_t);
 125 #endif
 126   extern void *(*__morecore) (ptrdiff_t);
 127
 128   void *cp;
 129   size_t five_percent;
 130   size_t data_size;
 131   enum warnlevel new_warnlevel;
 132
 133   if (lim_data == 0)
 134     get_lim_data ();
 135   five_percent = lim_data / 20;
 136
 137   /* Find current end of memory and issue warning if getting near max */
 138 #ifdef REL_ALLOC
 139   if (real_morecore)
 140     cp = (char *) (*real_morecore) (0);
 141   else
 142 #endif
 143   cp = (char *) (*__morecore) (0);
 144   data_size = (char *) cp - (char *) data_space_start;
 145
 146   if (!warn_function)
 147     return;
 148
 149   /* What level of warning does current memory usage demand?  */
 150   new_warnlevel
 151     = (data_size > five_percent * 19) ? warned_95
 152     : (data_size > five_percent * 17) ? warned_85
 153     : (data_size > five_percent * 15) ? warned_75
 154     : not_warned;
 155
 156   /* If we have gone up a level, give the appropriate warning.  */
 157   if (new_warnlevel > warnlevel || new_warnlevel == warned_95)
 158     {
 159       warnlevel = new_warnlevel;
 160       switch (warnlevel)
 161         {
 162         case warned_75:
 163           (*warn_function) ("Warning: past 75% of memory limit");
 164           break;
 165
 166         case warned_85:
 167           (*warn_function) ("Warning: past 85% of memory limit");
 168           break;
 169
 170         case warned_95:
 171           (*warn_function) ("Warning: past 95% of memory limit");
 172         }
 173     }
 174   /* Handle going down in usage levels, with some hysteresis.  */
 175   else
 176     {
 177       /* If we go down below 70% full, issue another 75% warning
 178          when we go up again.  */
 179       if (data_size < five_percent * 14)
 180         warnlevel = not_warned;
 181       /* If we go down below 80% full, issue another 85% warning
 182          when we go up again.  */
 183       else if (warnlevel > warned_75 && data_size < five_percent * 16)
 184         warnlevel = warned_75;
 185       /* If we go down below 90% full, issue another 95% warning
 186          when we go up again.  */
 187       else if (warnlevel > warned_85 && data_size < five_percent * 18)
 188         warnlevel = warned_85;
 189     }
 190
 191   if (EXCEEDS_LISP_PTR (cp))
 192     (*warn_function) ("Warning: memory in use exceeds lisp pointer size");
 193 }
 194 \f
 195 #if !defined (CANNOT_DUMP) || !defined (SYSTEM_MALLOC)
 196 /* Some systems that cannot dump also cannot implement these.  */
 197
 198 /*
 199  *      Return the address of the start of the data segment prior to
 200  *      doing an unexec.  After unexec the return value is undefined.
 201  *      See crt0.c for further information and definition of data_start.
 202  *
 203  *      Apparently, on BSD systems this is etext at startup.  On
 204  *      USG systems (swapping) this is highly mmu dependent and
 205  *      is also dependent on whether or not the program is running
 206  *      with shared text.  Generally there is a (possibly large)
 207  *      gap between end of text and start of data with shared text.
 208  *
 209  */
 210
 211 char *
 212 start_of_data (void)
 213 {
 214 #ifdef BSD_SYSTEM
 215   extern char etext;
 216   return (void *) &etext;
 217 #elif defined DATA_START
 218   return (void *) DATA_START;
 219 #elif defined ORDINARY_LINK
 220   /*
 221    * This is a hack.  Since we're not linking crt0.c or pre_crt0.c,
 222    * data_start isn't defined.  We take the address of environ, which
 223    * is known to live at or near the start of the system crt0.c, and
 224    * we don't sweat the handful of bytes that might lose.
 225    */
 226   return (void *) &environ;
 227 #else
 228   extern int data_start;
 229   return (void *) &data_start;
 230 #endif
 231 }
 232 #endif /* (not CANNOT_DUMP or not SYSTEM_MALLOC) */
 233 \f
 234 /* Enable memory usage warnings.
 235    START says where the end of pure storage is.
 236    WARNFUN specifies the function to call to issue a warning.  */
 237
 238 void
 239 memory_warnings (void *start, void (*warnfun) (const char *))
 240 {
 241   extern void (* __after_morecore_hook) (void);     /* From gmalloc.c */
 242
 243   if (start)
 244     data_space_start = start;
 245   else
 246     data_space_start = start_of_data ();
 247
 248   warn_function = warnfun;
 249   __after_morecore_hook = check_memory_limits;
 250
 251   /* Force data limit to be recalculated on each run.  */
 252   lim_data = 0;
 253 }