QEMU can allow guests to access more than one host core at a time.
Previously, this had to be done via ad-hoc arguments:
virtualisation.qemu.options = ["-smp 12"];
Now you can simply specify:
virtualisation.cores = 12;
*** NixOS *** NixOS is a Linux distribution based on the purely functional package management system Nix. More information can be found at http://nixos.org/nixos and in the manual in doc/manual.