What tool would I use to measure the time taken for a page to load in ASP.NET that has multiple ajax requests along with synchronous execution on the server and client side logic.
I am interested in calculating the time taken to load the complete page (including the last ajax call). I understand I can use firebug only for XmlHttpRequest times, but I am not aware of a tool that calculates the synchronous time as well as accurately as possible.
YSlow by Yahoo is a pretty good developer tool for this kind of performance testing.
You can use HTML5 navigation timing and use this bookmarklet http://66.7percentangel.com/2011/12/breaking-down-onload-event-performance-bookmarklet/ This will be more accurate than any other tool like YSlow or Page Speed because here the latencies are recorded by browser on the completion of appropriate event (page load, DOM ready etc.) On the other hand tools like YSlow use Date function in JS to get the current time. It is not accurate because Javascript runtime has a single threaded execution and it gives you the time when the request got served not when the request was made.