On hibernate, it seems that nouveau pushes vram into physical ram instead of swap (possibly on the assumption that it is going to be swaped to disk on hibernation). In my case, I have 4GB physical ram and vram = 2GB. - Hibernate only works if amount of physical ram in use is less than 2G (4 - 2 = 2), otherwise I get an "error -12 creating hibernation image" "PM: Not enough free memory". - If hibernate works, on resume, vram is not freed from physical memory. rmmoding nouveau frees 500+ MB of physical ram. - So far, I have reproduced this on kernels 4.4 to 4.8rc6 (I have not attempted older kernels). - Cards tested are 630GT (fermi) and 730GT (kepler).