ggc-common.c (ggc_rlimit_bound): Don't check RSS limit.

	* ggc-common.c (ggc_rlimit_bound): Don't check RSS limit.
	Check DATA limit only if there's no AS limit.  Ignore insanely
	low DATA limits.
	(ggc_min_heapsize_heuristic): Don't divide AS or RSS limits by 8,
	but take care that the AS limit isn't overrun.
	* doc/invoke.texi: Update documentation of min-heapsize parameter.

From-SVN: r85722

gcc/ChangeLog

+2004-08-09  Geoffrey Keating  <geoffk@apple.com>
+
+	* ggc-common.c (ggc_rlimit_bound): Don't check RSS limit.
+	Check DATA limit only if there's no AS limit.  Ignore insanely
+	low DATA limits.
+	(ggc_min_heapsize_heuristic): Don't divide AS or RSS limits by 8,
+	but take care that the AS limit isn't overrun.
+	* doc/invoke.texi: Update documentation of min-heapsize parameter.
+
 2004-08-09  Jeff Law  <law@redhat.com>
 
 	* Makefile.in (OBJC-common): Add tree-ssa-threadupdate.c

gcc/doc/invoke.texi

@@ -5310,7 +5310,7 @@ generation.
 
 The default is 30% + 70% * (RAM/1GB) with an upper bound of 100% when
 RAM >= 1GB.  If @code{getrlimit} is available, the notion of "RAM" is
-the smallest of actual RAM, RLIMIT_RSS, RLIMIT_DATA and RLIMIT_AS.  If
+the smallest of actual RAM and RLIMIT_DATA or RLIMIT_AS.  If
 GCC is not able to calculate RAM on a particular platform, the lower
 bound of 30% is used.  Setting this parameter and
 @option{ggc-min-heapsize} to zero causes a full collection to occur at
@@ -5325,14 +5325,14 @@ by @option{ggc-min-expand}% beyond @option{ggc-min-heapsize}.  Again,
 tuning this may improve compilation speed, and has no effect on code
 generation.
 
-The default is RAM/8, with a lower bound of 4096 (four megabytes) and an
-upper bound of 131072 (128 megabytes).  If @code{getrlimit} is
-available, the notion of "RAM" is the smallest of actual RAM,
-RLIMIT_RSS, RLIMIT_DATA and RLIMIT_AS.  If GCC is not able to calculate
-RAM on a particular platform, the lower bound is used.  Setting this
-parameter very large effectively disables garbage collection.  Setting
-this parameter and @option{ggc-min-expand} to zero causes a full
-collection to occur at every opportunity.
+The default is the smaller of RAM/8, RLIMIT_RSS, or a limit which
+tries to ensure that RLIMIT_DATA or RLIMIT_AS are not exceeded, but
+with a lower bound of 4096 (four megabytes) and an upper bound of
+131072 (128 megabytes).  If GCC is not able to calculate RAM on a
+particular platform, the lower bound is used.  Setting this parameter
+very large effectively disables garbage collection.  Setting this
+parameter and @option{ggc-min-expand} to zero causes a full collection
+to occur at every opportunity.
 
 @item max-reload-search-insns
 The maximum number of instruction reload should look backward for equivalent

gcc/ggc-common.c

@@ -669,30 +669,34 @@ mmap_gt_pch_use_address (void *base, size_t size, int fd, size_t offset)
 }
 #endif /* HAVE_MMAP_FILE */
 
-/* Modify the bound based on rlimits.  Keep the smallest number found.  */
+/* Modify the bound based on rlimits.  */
 static double
 ggc_rlimit_bound (double limit)
 {
 #if defined(HAVE_GETRLIMIT)
   struct rlimit rlim;
-# ifdef RLIMIT_RSS
-  if (getrlimit (RLIMIT_RSS, &rlim) == 0
+# if defined (RLIMIT_AS)
+  /* RLIMIT_AS is what POSIX says is the limit on mmap.  Presumably
+     any OS which has RLIMIT_AS also has a working mmap that GCC will use.  */
+  if (getrlimit (RLIMIT_AS, &rlim) == 0
       && rlim.rlim_cur != (rlim_t) RLIM_INFINITY
       && rlim.rlim_cur < limit)
     limit = rlim.rlim_cur;
-# endif
-# ifdef RLIMIT_DATA
+# elif defined (RLIMIT_DATA)
+  /* ... but some older OSs bound mmap based on RLIMIT_DATA, or we
+     might be on an OS that has a broken mmap.  (Others don't bound
+     mmap at all, apparently.)  */
   if (getrlimit (RLIMIT_DATA, &rlim) == 0
       && rlim.rlim_cur != (rlim_t) RLIM_INFINITY
-      && rlim.rlim_cur < limit)
-    limit = rlim.rlim_cur;
-# endif
-# ifdef RLIMIT_AS
-  if (getrlimit (RLIMIT_AS, &rlim) == 0
-      && rlim.rlim_cur != (rlim_t) RLIM_INFINITY
-      && rlim.rlim_cur < limit)
+      && rlim.rlim_cur < limit
+      /* Darwin has this horribly bogus default setting of
+	 RLIMIT_DATA, to 6144Kb.  No-one notices because RLIMIT_DATA
+	 appears to be ignored.  Ignore such silliness.  If a limit
+	 this small was actually effective for mmap, GCC wouldn't even
+	 start up.  */
+      && rlim.rlim_cur >= 8 * 1024 * 1024)
     limit = rlim.rlim_cur;
-# endif
+# endif /* RLIMIT_AS or RLIMIT_DATA */
 #endif /* HAVE_GETRLIMIT */
 
   return limit;
@@ -721,20 +725,39 @@ ggc_min_expand_heuristic (void)
 int
 ggc_min_heapsize_heuristic (void)
 {
-  double min_heap_kbytes = physmem_total();
-
-  /* Adjust for rlimits.  */
-  min_heap_kbytes = ggc_rlimit_bound (min_heap_kbytes);
+  double phys_kbytes = physmem_total();
+  double limit_kbytes = ggc_rlimit_bound (phys_kbytes * 2);
 
-  min_heap_kbytes /= 1024; /* Convert to Kbytes.  */
+  phys_kbytes /= 1024; /* Convert to Kbytes.  */
+  limit_kbytes /= 1024;
 
   /* The heuristic is RAM/8, with a lower bound of 4M and an upper
      bound of 128M (when RAM >= 1GB).  */
-  min_heap_kbytes /= 8;
-  min_heap_kbytes = MAX (min_heap_kbytes, 4 * 1024);
-  min_heap_kbytes = MIN (min_heap_kbytes, 128 * 1024);
+  phys_kbytes /= 8;
+
+#if defined(HAVE_GETRLIMIT) && defined (RLIMIT_RSS)
+  /* Try not to overrun the RSS limit while doing garbage collection.  
+     The RSS limit is only advisory, so no margin is subtracted.  */
+ {
+   struct rlimit rlim;
+   if (getrlimit (RLIMIT_RSS, &rlim) == 0
+       && rlim.rlim_cur != (rlim_t) RLIM_INFINITY)
+     phys_kbytes = MIN (phys_kbytes, rlim.rlim_cur / 1024);
+ }
+# endif
+
+  /* Don't blindly run over our data limit; do GC at least when the
+     *next* GC would be within 16Mb of the limit.  If GCC does hit the
+     data limit, compilation will fail, so this tries to be
+     conservative.  */
+  limit_kbytes = MAX (0, limit_kbytes - 16 * 1024);
+  limit_kbytes = (limit_kbytes * 100) / (110 + ggc_min_expand_heuristic());
+  phys_kbytes = MIN (phys_kbytes, limit_kbytes);
+
+  phys_kbytes = MAX (phys_kbytes, 4 * 1024);
+  phys_kbytes = MIN (phys_kbytes, 128 * 1024);
 
-  return min_heap_kbytes;
+  return phys_kbytes;
 }
 
 void