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 itand 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)

Very slow running web application using Microsoft AJAX.NET Very slow running web application using Microsoft AJAX.NET Reviewed by Ran Davidovitz on 2:08 PM Rating: 5


Siderite said...

Thank you to linking to my blog entry. You might also be interested in this method of shrinking the updatepanel output from the second asynchronous postback on:

Anonymous said...

Thanks for this post. We had the same problem and it helped a bit :)

Ran Davidovitz said...

@Siderite: great post very pro, we used a product called ZumiPage that made what ASP.NET update panel is doing but approx 2 years before :), one of the later version it had support for htmlDiff (but we didn't use that because of memory foot print). how do you handle the back button(history of same page)
@"Anonymous": keep me posted on the progress maybe we can share some more knowledge

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