Wednesday, September 13th, 2006

Dramatically improved IE7 JavaScript performance

Category: IE, JavaScript

Sebastian Werner has posted some good news over on the QooXdoo blog today – that the Javascript performance of the upcoming Internet Explorer 7 has been greatly increased.

Really good news. My vocabulary may to be too limited to tell you how great the latest changes in IE7 RC1 are. Microsoft announced that they have “recently made some great fixes to our engine to improve the garbage collection routine and to reduce unbounded memory growth.” and that one “should see noticeable improvements on AJAX sites in the Release Candidate we shipped last week”. Yes indeed, we do see tremendeous improvements.

He gives the example of the qooxdoo framework running “much faster” in the new update (at times, even faster than Firefox 1.5). You can check out the demos and compare them if you’d like to see the result.

The reason behind this dramatic improvement? Microsoft decided to fix something that’s been causing problems in Javascript for years now – the more objects in the same scope you have, the slower things get. He also includes a test case to help illustrate this point specifically.

Posted by Chris Cornutt at 8:37 am

4 rating from 34 votes


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I believe this issue was known as “The Wall,” we hit it when working on Yahoo! Photos and had to throw away some objects to prevent IE from bogging down. (Firefox et al, naturally, didn’t show any problems here.)

To give an idea of what a performance hit this was, simple operations like looping through a collection of nodes were made incredibly slow after a large number of objects had been created.

I don’t know if “much faster” is necessarily accurate as I suspect a small number of sites may have been hitting this issue (plus it’s something that shouldn’t have been a problem to begin with) – “the new version doesn’t slow down” might be what I’d call it! ;) – but I am glad to hear they’ve been looking into it. (Memory leaks are the other biggie which I hear there’s been progess on as well.)

Comment by Scott Schiller — September 13, 2006

A big congratulations to MS and the IE team. You guys are now only 2 years behind everyone else. Keep up the good work.

Comment by Richard White — September 13, 2006

Hmmm now microsoft’s javascript heavy can load well hehhe ;)

Comment by Bert — September 13, 2006

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