dpm() does not display any results on screen I have the same problem as file_scan_directory() takes about 10 seconds to execute. I just tried the dpm(func_get_args()) suggestion, and unfortunately it doesn't show anything to me. 

I've cleared all the caches, and run the cron tasks. What am I missing?
Make sure you have print $messages; in your page.tpl.phptemplate file. By default, devel (dpm) is configured to print it's content in the message area of the site. So if your template for some reason does not render the contents of $messages, you won't see anything.