User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1b2pre) Gecko/20081118 Minefield/3.1b2pre Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1b2pre) Gecko/20081118 Minefield/3.1b2pre When loading http://www-cs-students.stanford.edu/~amitp/gameprog.html in minefield, the browser becomes unresponsive. Upon loading the task manager, Firefox is revealed to be using up all of a processor core. Reproducible: Always Steps to Reproduce: 1. Go to http://www-cs-students.stanford.edu/~amitp/gameprog.html 2. let page load 3.Laaaaaaaaaaaaaaaaaaaaaaaaaaaaaag Actual Results: Browser becomes very slow until tab containing page is closed Expected Results: Browser is responsive and allows me to read the page

Confirmed on Windows XP, latest trunk.

Regression range: http://hg.mozilla.org/mozilla-central/pushloghtml?startdate=2008-07-07+01%3A00%3A00&enddate=2008-07-08+11%3A00%3A00

Maybe caused by Bug 212633 ? On my Vista computer I see no hang, but vertical scrolling is nearly impossible. I see also a superfluous horizontal scrollbar, but I think this is a different bug.

Vertical scrolling was very slow for me, as was changing tabs.

Since entering this: javascript:void(document.getElementsByTagName("head")[0].innerHTML += "<style type='text/css'>*{-moz-box-shadow: none!important}</style>") in the URL bar makes things faster for me, blaming -moz-box-shadow seems reasonable. And the page does use -moz-box-shadow. Does that make things faster for you as well?

The problem is almost certainly just that we create a temporary surface for blurring the whole box irrespective of the dirty area. We should optimize box-shadow drawing so that blur computation is restricted to the dirty area. It's a little tricky but not all that hard.

Yup, that made it nice and zippy.

The work in 458031 should fix this.

Fixed by checkin for bug 458031.

This was also an issue on OS X. Now I can verify that the fix on bug 458031 solves the hang. Tested with Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.2a1pre) Gecko/20081203 Minefield/3.2a1pre For now setting the TM to 1.9.2a1. We should adjust when the patch has been landed on 1.9.1 branch.

Bug 458031 has been checked in to 1.9.1 branch already. marking fixed1.9.1 here too and adjusting TM.

Sorry for my last comment. We shouldn't change TM. Branch 1.9.1 and trunk are different nowadays. Setting the keyword is enough.

Verified on 1.9.1 with Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1b3pre) Gecko/20081221 Shiretoko/3.1b3pre ID:20081221020430