I noticed that sometimes when browsing (with other processes in the background), I get very high CPU load for the browser process (over 100%) and the computer becomes really slow. I tried switching from Firefox (with just a few extensions) to Chromium, but same thing happens without me visiting graphics-intense sites, flash sites or anything like that. I also noticed python or node (when running "make") produce the same high CPU load from time to time so this is not necessarily browser-related.
When I only have a browser open, it doesn't seem to happen and everything is fine in Windows 7.
I switched from unity to gnome3 with no effect.
Specs: lenovo w510 (4gb RAM, i7 q820 @ 1.73) + up to date Ubuntu 14.04 64bit. Printscreen: http://imgur.com/8MZJNKC
Do you guys have any idea why this might happen? Please let me know if there's other info you need.