I run Ubuntu in VirtualBox. 18.04 is considerably less responsive than 16.04, with exactly the same VM settings (3D acceleration, 3 cores, 4 GB RAM, guest additions installed, host: macOS, VirtualBox 5.2.18).
18.04 is often slow to respond to clicks and even typing. It is borderline unusable. 16.04, on the other hand, works perfectly fine. The 18.04 is a fresh install.
Is this considerable performance drop an inevitable consequence of switching to Gnome 3? Are there any simple settings I can try to make it usable? I do not need animations or fancy visual effects—this in an OS in a VM so it gets only occasional use, and I mostly just need the terminal.
Right after boot, performance is satisfactory
After opening a Terminal, and maximizing it, performance becomes awful. It does not recover even after unmaximizing the Terminal window, or closing it.
Turning off 3D acceleration in VirtualBox makes is more sluggish after startup (e.g. moving window on the screen is choppy), but it never gets unusably slow after maximizing a window.