GreatBlakes

This is a WordPress plugin that adds advanced load timing to each page. Know exactly what is causing slow (or fast) page loading on every page. It’s like doing a lightweight and fast speed test on every page! It does not require any settings and is displayed at the bottom-left of the page. The overall load time is shown initially, and when clicked, the advanced load times appear.
The processes being timed are: 
Redirection (and quantity) 
App Cache 
DNS Lookup 
TCP Connection 
Server Request 
Server Response 
DOM Processing 
Page Load
This timing only display to site admins, and can also be triggered by adding “?debug” at the end of the URL. Considerably slow or fast times are dictated with coloring.

Simple Site Speed

Add page load times for admins on the front-end.

Scott Grant

Hook Timer attaches to the start and end of each action and filter, stores the timestamp, and when the hook finishes, logs the total time spent. If you want to examine why a page is slow or aren’t sure where the majority of your page load time is spent, this plugin will show you the most costly hooks in your installation.
Hook Timer appears as a menu option in your admin dashboard, and displays the total time spent in each hook on the previous page load. This allows you to load a particular page that’s slow, then to view the results in the admin dashboard immediately after.

Hook Timer

Track the time used between the start and end of each hook (action or filter).

Simple Site Speed vs Hook Timer