[gegl] gegl: make default tile cache size depend on system RAM

[Øyvind "pippin" Kolås <ok src gnome org>]

commit be8cd9eff3b82177123a39b545b9c6f36fdf6190
Author: Øyvind Kolås <pippin gimp org>
Date:   Sat Jan 26 01:42:34 2019 +0100

    gegl: make default tile cache size depend on system RAM
    
    Desire to use 50% of RAM, if this is not available settle for
    freeram+bufferram size, if this is less than 512mb, settle for
    512mb.  On other platforms the new default is 1GB.

 gegl/gegl-config.c | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 47 insertions(+), 1 deletion(-)
---
diff --git a/gegl/gegl-config.c b/gegl/gegl-config.c
index ef705b88e..fd243e51e 100644
--- a/gegl/gegl-config.c
+++ b/gegl/gegl-config.c
@@ -30,6 +30,10 @@
 
 #include "opencl/gegl-cl.h"
 
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
 G_DEFINE_TYPE (GeglConfig, gegl_config, G_TYPE_OBJECT)
 
 static GObjectClass * parent_class = NULL;
@@ -210,12 +214,54 @@ gegl_config_class_init (GeglConfigClass *klass)
                                                      0, G_MAXINT, 128,
                                                      G_PARAM_READWRITE));
 
+  {
+    long default_tile_cache_size = 1024l * 1024 * 1024;
+    long mem_total = default_tile_cache_size;
+    long mem_min = 512 << 20; // 512mb
+    long mem_available = mem_min;
+#ifdef G_OS_WIN32
+#ifdef G_OS_WIN32
+# if defined(_MSC_VER) && (_MSC_VER <= 1200)
+  MEMORYSTATUS memory_status;
+  memory_status.dwLength = sizeof (memory_status);
+
+  GlobalMemoryStatus (&memory_status);
+  mem_total = memory_status.dwTotalPhys;
+  mem_available = memory_status.dwAvailPhys;
+# else
+  /* requires w2k and newer SDK than provided with msvc6 */
+  MEMORYSTATUSEX memory_status;
+
+  memory_status.dwLength = sizeof (memory_status);
+
+  if (GlobalMemoryStatusEx (&memory_status))
+  {
+    mem_total = memory_status.ullTotalPhys;
+    mem_available = memory_status.ullAvailPhys;
+  }
+# endif
+#endif
+
+#else
+    mem_total = sysconf (_SC_PHYS_PAGES) * sysconf (_SC_PAGESIZE);
+    mem_available = sysconf (_SC_AVPHYS_PAGES) * sysconf (_SC_PAGESIZE);
+#endif
+
+    default_tile_cache_size = mem_total;
+    if (default_tile_cache_size > mem_available)
+    {
+      default_tile_cache_size = mem_available;
+    }
+    if (default_tile_cache_size < mem_min)
+      default_tile_cache_size = mem_min;
+
   g_object_class_install_property (gobject_class, PROP_TILE_CACHE_SIZE,
                                    g_param_spec_uint64 ("tile-cache-size",
                                                         "Tile Cache size",
                                                         "size of tile cache in bytes",
-                                                        0, G_MAXUINT64, 512 * 1024 * 1024,
+                                                        0, G_MAXUINT64, default_tile_cache_size,
                                                         G_PARAM_READWRITE));
+  }
 
   g_object_class_install_property (gobject_class, PROP_CHUNK_SIZE,
                                    g_param_spec_int ("chunk-size",