I'm having a similar problem with Mint 18.2. It's triggered by launching freeciv-client-gtk.
When I boot it's fine. Open a terminal window, fine. Open Chrome, fine. Open Freeciv, the initial screens are OK, but once the full screen game starts, XORG pegs to 100% of a single core, even when nothing is happening. Closing Freeciv returns XORG to normal. Screen shots of atop output during all of these test cases are here: https://drive.google.com/open?id=1e15ZaYrxgWcFNRaquUHcTMxZ99_pZDf0 apt-cache policy freeciv-client-gtk freeciv-client-gtk: Installed: 2.5.10-1 Candidate: 2.5.10-1 Version table: *** 2.5.10-1 500 500 http://mirror.genesisadaptive.com/ubuntu bionic/universe amd64 Packages 100 /var/lib/dpkg/statusapt-cache policy xorg apt-cache policy xorg xorg: Installed: 1:7.7+19ubuntu7.1 Candidate: 1:7.7+19ubuntu7.1 Version table: *** 1:7.7+19ubuntu7.1 500 500 http://mirror.genesisadaptive.com/ubuntu bionic-updates/main amd64 Packages 100 /var/lib/dpkg/status 1:7.7+19ubuntu7 500 500 http://mirror.genesisadaptive.com/ubuntu bionic/main amd64 Packages Please let me know if you need more info. Thanks - Pete