Very slow running web application using Microsoft AJAX.NET

Last week we had a very serious issue of performance in our web application that is based on AJAX.NET (mainly under IE6).

few facts:

• our client response is quite large (between 70K – 250k)
• we are using AJAX.NET with partial update panels
• we have approx 4 update panels that return after post back
• we have lots of nodes (elements)

The average time it take for the response to be updated on the browser for most of our use cases is:

Browser	Time (seconds)
IE6 (SP3)	8
IE7	6
Fire Fox 3	5
Chrome	3.5

 

After intensive analysis that we have done that included:

• Checking entire user flow with fiddler
• code review (of some parts)
• Profiling of code
• Numerous running on many platforms

The root cause (or actually points) that effects the client side performance is:

• Apparently the debug=”TRUE” on the web.config which causes all AJAX.NET JS files to be rendered in debug mode (larger, more comments, larger names and LOTS of assertions) –> Dramatically effects performance (approx twice the time)
• Our response is too large (wider update panel) and contain number of update panels (reduction to 50% of the size reduced approx 1 seconds in release mode)
• Our update panel contains lots of node (DOM hierarchy) which affects the disposal of the DOM prior to the replacement of the innerHTML (did you know it – and to the point this)

My personal lesson learning for that scenario is “be cheap” and don't waste bytes. (Also always make sure that the basic weren't forgotten - debug)

At the end we cut approx 70% of the run time by doing the above

Hope this post will save other some time.

P.s. IE6 is the worst browser i have ever witnessed (Performance, compliance and memory handling)