504057 - Slow loading of relatively large pages

Status: RESOLVED DUPLICATE of bug 477564

(Firefox :: General, defect)

Description

[thomas_weiss]

User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1) Gecko/20090624 Firefox/3.5
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1) Gecko/20090624 Firefox/3.5

I noticed a performance problem with a page containing a custom select box composed of normal div and input tags. On my system (Intel Pentium D 2.8GHz) with a select box of around 400 entries Firefox loads the page and after about 3 seconds it consumes 100% CPU time for about 10 seconds. The more entries the select box has the longer it takes to render the page.

The problem does not exist in Firefox 3.0 (rendering there is much faster). I also tested with the current nightly build (firefox-3.5.1pre.en-US.linux-i686.tar.bz2, 2009-07-13). There the problem remains.

Reproducible: Always

Steps to Reproduce:
1. Build a page containing something like this:

<div>
	<div>
		<input type="checkbox">
		<span>Test</span>
		<input value="Test" type="hidden">
	</div>
</div>

2. Duplicate the inner div a few hundred times.
3. Load the resulting page.
Actual Results:  
Firefox consumes 100% CPU time for a few seconds while rendering the page.

Expected Results:  
Rendering should happen very much faster.

The problem also exists with Firefox on Windows and Mac.

Comment 1

[thomas_weiss]

Attachment: A test case demonstrating the problem

Comment 2

[John P Baker]

Changing browser.sessionstore.privacy_level improves situation.