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Experimental Firefox DNS Issue - LeptienM - 09-05-2011 07:41 PM

Hi Pat!

I just tried the new Firefox Experimental Feature. While testing I saw that it seems, that pending DNS Queries are pushing CPU load to 100%. Look at objects No. 61 & 62 and the corresponding CPU load graph at the bottom. Is this just due to the experimental implementation? Or is this real world behaviour / bug of Firefox 6?

http://www.webpagetest.org/result/110905_S7_1GJRZ/1/details/

Kind regards,
Markus


RE: Experimental Firefox DNS Issue - LeptienM - 09-06-2011 06:04 AM

While thniking about it... Probably it is the other way around. Due to the CPU spike, it takes so long to process the DNS Query response...


RE: Experimental Firefox DNS Issue - pmeenan - 09-06-2011 10:46 PM

Just got to look at it. Yes, Just like with IE, since the browsers are all generally single threaded, if the main browser thread gets really busy doing something then it can make the network requests look like they take longer.

"something" is usually Javascript.

It looks like the CPU spike lines up pretty well with the end of main.js downloading (which should be the point where it actually gets parsed and executed). The content blocking isn't implemented for firefox yet (coming soon) so your best bet might be to use DynaTrace Ajax Edition and manually profile the page to see if anything jumps out.