You typically don't want to do this anyway in games. You're probably doing something wrong if you're reading textures/meshes on both the CPU and GPU.
> Don't forget about how much more RAM a general purpose OS like Steam OS can consume versus a gaming specific OS too.
SteamOS is meant to be a gaming specific OS first. It has a desktop environment but none of that loads unless you switch to desktop mode. That's just taking up some disk space while you play games.