as far as i can tell there's nothing wrong in your code
(well except for a lacking "use strict"...)
(i tested it to search for /\.c$/ in /usr/src/linux and it took just less then 1 second for more than 4000 files on an average machine..)
try to compare it with the unix find command (if you are on unix)
also if you are using a slow terminal it could help to eliminate the print statement or redirecting it to a file.