How can I disable hud-service on Ubuntu?
The HUD is related to the Unity Launcher. For example it analyzes the files you are using and offers them when you press Super.
On my system (Ubuntu 15.10) the hud-service started using 100% of one CPU.
I solved this by installing Compiz Config Settings Manager (ccsm) and disabled all effects and set "Enable Low Graphics Mode" in "Ubuntu Unity Plugin":
sudo apt-get install compizconfig-settings-manager
ccsm