User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:58.0) Gecko/20100101 Firefox/58.0 Build ID: 20171108110838 Steps to reproduce: 1. Created new profile 2. Installed performance profiler 3. Restarted Firefox 4. Visited page _not_ visited before (in this case twitter.com) 5. Waited for 100% CPU usage to drop down to normal levels (~60s later) 6. Visited page _not_ visited before (in this case reddit.com) Actual results: The CPU usage of the Firefox process stayed at 100% for about 60s after twitter.com loaded. It then dropped down to about 1 to 5%. I then visited reddit.com and the same thing happened again. That kind of CPU usage is not normal on my machine. Profile: https://perfht.ml/2AmKdSH ~10s, opened twitter. CPU 100% ~60s, CPU returns to normal ~70s, opened reddit. CPU 100% Expected results: When a page is loading/rendering there's a spike in CPU usage. It then quickly drops down to normal. Currently with about 10 tabs open it's pedning between 5 to 15%. I don't have a supercomputer or anything, but 100% CPU for a single page for one min is beyond normal.

possible dupe of bug 1415387.