I do need to express my deepest sincere thanks for your post! It save me.
Although i am not running processwire, I spent dayssss in solving my problem and finally read your post and my problem is solved. (you can imagine how desperated i am as i even have no idea of what processwire is)
My config: XAMPP, windows10, mysql, drupal
I tried numerous different settings (host file, various cache methods, ip4, turnoff firewall, etc), but it still takes more than 20secs for waiting server response.
Finally, after i followed your suggestion of fixing by " uncomment bind-address="127.0.0.1" in mysql\bin\my.ini", now server response down to 1.4 second!
Wish someone out there in the internet who encounters similar problem (slow drupal server response) can read this post.
Thanks very much again.
(P.S. i also have no idea where site\config.php and $config->dbHost are located in my system)