$use_sub_dirs

Smarty will create subdirectories under the templates_c and cache directories if $use_sub_dirs is set to true. 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. The default is false (disabled). 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.

See also $compile_dir, and $cache_dir.