Comment 59 for bug 20765

Actually, I figured out that my problem (huge slow down on a mega-powerful PC) is actually, because of this bug: https://bugzilla.mozilla.org/show_bug.cgi?id=235853
Firefox is unresponsive when processing (or retrieving) the automatic proxy configuration file.

I wonder if most of people who noticed this bug (266627) are actually suffering from the slow automatic proxy configuration processing. It is very easy to verify: just manually read your configuration file, figure out which proxy you are supposed to use and tell Firefox to use this proxy. If everything is fast, then you are suffering from 235853.

P.S.
This bug did not happen on my work laptop, because: 1) when using VPN all the pictures on the web page are fetched from 1-2 servers - quick PAC file processing; 2) when browsing normal internet, I disable the automatic proxy confuguration