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 /* Return true if PTR cannot be represented as an Emacs Lisp object.  */
  75 static bool
  76 exceeds_lisp_ptr (void *ptr)
  77 {
  78   return (! USE_LSB_TAG
  79           && VAL_MAX < UINTPTR_MAX
  80           && ((uintptr_t) ptr & ~DATA_SEG_BITS) >> VALBITS != 0);
  81 }
  82
  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   _go32_dpmi_meminfo info;
 119   unsigned long lim1, lim2;
 120
 121   _go32_dpmi_get_free_memory_information (&info);
 122   /* DPMI server of Windows NT and its descendants reports in
 123      info.available_memory a much lower amount that is really
 124      available, which causes bogus "past 95% of memory limit"
 125      warnings.  Try to overcome that via circumstantial evidence.  */
 126   lim1 = info.available_memory;
 127   lim2 = info.available_physical_pages;
 128   /* DPMI Spec: "Fields that are unavailable will hold -1."  */
 129   if ((long)lim1 == -1L)
 130     lim1 = 0;
 131   if ((long)lim2 == -1L)
 132     lim2 = 0;
 133   else
 134     lim2 *= 4096;
 135   /* Surely, the available memory is at least what we have physically
 136      available, right?  */
 137   if (lim1 >= lim2)
 138     lim_data = lim1;
 139   else
 140     lim_data = lim2;
 141   /* Don't believe they will give us more that 0.5 GB.   */
 142   if (lim_data > 512U * 1024U * 1024U)
 143     lim_data = 512U * 1024U * 1024U;
 144 }
 145
 146 unsigned long
 147 ret_lim_data (void)
 148 {
 149   get_lim_data ();
 150   return lim_data;
 151 }
 152 #else
 153 # error "get_lim_data not implemented on this machine"
 154 #endif
 155 \f
 156 /* Verify amount of memory available, complaining if we're near the end. */
 157
 158 static void
 159 check_memory_limits (void)
 160 {
 161 #ifdef REL_ALLOC
 162   extern void *(*real_morecore) (ptrdiff_t);
 163 #else
 164   void *(*real_morecore) (ptrdiff_t) = 0;
 165 #endif
 166   extern void *(*__morecore) (ptrdiff_t);
 167
 168   char *cp;
 169   size_t five_percent;
 170   size_t data_size;
 171   enum warnlevel new_warnlevel;
 172
 173   if (lim_data == 0)
 174     get_lim_data ();
 175   five_percent = lim_data / 20;
 176
 177   /* Find current end of memory and issue warning if getting near max */
 178   cp = (real_morecore ? real_morecore : __morecore) (0);
 179   data_size = cp - data_space_start;
 180
 181   if (!warn_function)
 182     return;
 183
 184   /* What level of warning does current memory usage demand?  */
 185   new_warnlevel
 186     = (data_size > five_percent * 19) ? warned_95
 187     : (data_size > five_percent * 17) ? warned_85
 188     : (data_size > five_percent * 15) ? warned_75
 189     : not_warned;
 190
 191   /* If we have gone up a level, give the appropriate warning.  */
 192   if (new_warnlevel > warnlevel || new_warnlevel == warned_95)
 193     {
 194       warnlevel = new_warnlevel;
 195       switch (warnlevel)
 196         {
 197         case warned_75:
 198           (*warn_function) ("Warning: past 75% of memory limit");
 199           break;
 200
 201         case warned_85:
 202           (*warn_function) ("Warning: past 85% of memory limit");
 203           break;
 204
 205         case warned_95:
 206           (*warn_function) ("Warning: past 95% of memory limit");
 207         }
 208     }
 209   /* Handle going down in usage levels, with some hysteresis.  */
 210   else
 211     {
 212       /* If we go down below 70% full, issue another 75% warning
 213          when we go up again.  */
 214       if (data_size < five_percent * 14)
 215         warnlevel = not_warned;
 216       /* If we go down below 80% full, issue another 85% warning
 217          when we go up again.  */
 218       else if (warnlevel > warned_75 && data_size < five_percent * 16)
 219         warnlevel = warned_75;
 220       /* If we go down below 90% full, issue another 95% warning
 221          when we go up again.  */
 222       else if (warnlevel > warned_85 && data_size < five_percent * 18)
 223         warnlevel = warned_85;
 224     }
 225
 226   if (exceeds_lisp_ptr (cp))
 227     (*warn_function) ("Warning: memory in use exceeds lisp pointer size");
 228 }
 229 \f
 230 /* Enable memory usage warnings.
 231    START says where the end of pure storage is.
 232    WARNFUN specifies the function to call to issue a warning.  */
 233
 234 void
 235 memory_warnings (void *start, void (*warnfun) (const char *))
 236 {
 237   extern void (* __after_morecore_hook) (void);     /* From gmalloc.c */
 238
 239   data_space_start = start ? start : data_start;
 240
 241   warn_function = warnfun;
 242   __after_morecore_hook = check_memory_limits;
 243
 244   /* Force data limit to be recalculated on each run.  */
 245   lim_data = 0;
 246 }