I’m on ubuntu 16.10 and i use unity 5.5.2f and it look like i always got one cores running at 100%… I was sure it was fixed ! My pc get very hot when i use Unity… Someone with the same problem ?
Do you have any web views visible? (Asset store, services window, …)
Same problem with Unity in Select Project window
Sorry im a bit late but you were right! It was the services window! Thank a lot!