IE9 Javascript is slower than IE8 - it's weird!

Question

I find it hard to explain why the following code is slower in IE9 than IE8!

Here are some test codes that work smoothly after about half a second in the latest version of FF / Chrome / Safari on OS X, WinXP and Win7 plus IE7 and 8 on WinXP (for simplicity, I removed the setting that makes it work in IE6).

For some reason I cannot explain, this is terrible in IE9, slow and clumsy. Reducing the time for setTimeout makes it a little faster, but no less jerky.

I tried to remove and compare gasoline with the number of possible values ​​(for example, Math.min ... everything is unchanged.

I'm at a dead end ... can someone point me in the right direction? ... preferably one that doesn't require a sniff from the browser?

Here's the test code ...

<div id = 'panel' class='noShow' style='background-color: #aaa;'>
    <div id = 'wrapper' class='slideWrapper'>
        <p>xxxxxxxxxxx</p><p>xxxxxxxxxxx</p><p>xxxxxxxxxxx</p><p>xxxxxxxxxxx</p><p>xxxxxxxxxxx</p><p>xxxxxxxxxxx</p><p>xxxxxxxxxxx</p><p>xxxxxxxxxxx</p><p>xxxxxxxxxxx</p><p>xxxxxxxxxxx</p>
    </div>
</div>


<script type = 'text/javaScript'>

    var e = document.getElementById('panel');
    var w = document.getElementById('wrapper');

    w.style.overflow = 'hidden';                                                
    w.style.height = '1px'; 
    var sh = w.scrollHeight;
    show();
    function show()
    {
        setTimeout(function()
           {
                w.style.height = Math.min(sh, (w.offsetHeight + Math.ceil(sh/15))) + 'px';  
                if(
                     (w.offsetHeight < sh)
                ) 
                {
                    show(e);
                }
                else 
                {
                    w.style.height = 'auto'; 
                }                       
        }, 20); 
    }   
</script>

Answer 1

By default, IE9 for rendering software on VMware virtual machines (as of 7/8/2011) assumes that the patch will be released in the near future, but there will not be a timeline for this blog post .

Answer 2

Are you using 64-bit version of IE 9 or 32-bit version? The 64-bit version does not launch Chakra, which is an optimized JavaScript engine from the 32-bit version

Answer 3

When working in a virtualized environment, there are always odd variations in performance. Choosing drivers and how software offloads processing will have consequences. Have you tried updating drivers on your system?