600M ram were employed to run after run Unity takes all 8 gigabytes ram and 2 gigabytes swap. Further application closes with an error after save attempt. In 4 of 5 cases closed Сompiz and Gnome (+ dependence). Ubuntu 15.10
The problem was solved by adding another section under the swap, and it turned out that my project unity eat 11Gb (ram + swap)
Well Unity can use quite a lot of memory, if I can remember correctly developer of Rust ( game ) said that it took 32GB of memory at some point. So if You can & You are really into game making I would say buy additional memory. I have 16GB & I'm looking to get more.
The project - an illegal port, commercial but a dying game. Income from it is not assumed (just for fun). So I will not put money into it.