After receiving updates to gnome-shell (now 3.26.2, was 3.26.1) and reboot issue not observed anymore. So I close bug.
** Changed in: gnome-shell (Ubuntu) Status: Triaged => Invalid -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to gnome-shell in Ubuntu. https://bugs.launchpad.net/bugs/1735389 Title: gnome-shell under gdm user eats more CPU than other processes Status in gnome-shell package in Ubuntu: Invalid Bug description: gnome-shell under 'gdm' user most of time eats more CPU than any other real user process. 'top' screenshot attached, see first line, most CPU eating and time consuming process. ProblemType: Bug DistroRelease: Ubuntu 17.10 Package: gnome-shell 3.26.1-0ubuntu5 ProcVersionSignature: Ubuntu 4.13.0-16.19-generic 4.13.4 Uname: Linux 4.13.0-16-generic x86_64 ApportVersion: 2.20.7-0ubuntu3.5 Architecture: amd64 CurrentDesktop: ubuntu:GNOME Date: Thu Nov 30 12:27:46 2017 DisplayManager: gdm3 SourcePackage: gnome-shell UpgradeStatus: Upgraded to artful on 2017-10-24 (36 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/1735389/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp