related to #1693 changed smarty version to 4.1.0

include/smarty/docs/programmers/api-variables/variable-use-sub-dirs.md

@@ -0,0 +1,31 @@
+\$use\_sub\_dirs {#variable.use.sub.dirs}
+================
+
+Smarty will create subdirectories under the [compiled
+templates](#variable.compile.dir) and [cache](#variable.cache.dir)
+directories if `$use_sub_dirs` is set to TRUE, default is FALSE. In an
+environment where there are potentially tens of thousands of files
+created, this may help the filesystem speed. On the other hand, some
+environments do not allow PHP processes to create directories, so this
+must be disabled which is the default.
+
+Sub directories are more efficient, so use them if you can.
+Theoretically you get much better perfomance on a filesystem with 10
+directories each having 100 files, than with 1 directory having 1000
+files. This was certainly the case with Solaris 7 (UFS)\... with newer
+filesystems such as ext3 and especially reiserfs, the difference is
+almost nothing.
+
+> **Note**
+>
+> -   `$use_sub_dirs=true` doesn\'t work with
+>     [safe\_mode=On](&url.php-manual;features.safe-mode), that\'s why
+>     it\'s switchable and why it\'s off by default.
+>
+> -   `$use_sub_dirs=true` on Windows can cause problems.
+>
+> -   Safe\_mode is being deprecated in PHP6.
+>
+See also [`$compile_id`](#variable.compile.id),
+[`$cache_dir`](#variable.cache.dir), and
+[`$compile_dir`](#variable.compile.dir).