Recently upgraded a 16.04 Ubuntu guest (Windows 10 host) to to 18.04 and saw a massive drop in performance. The lag in the desktop environment was unbearable. This was even with the guest additions properly installed. These settings finally fixed it:
- System
- Motherboard
- Chipset: ICH9
- Extended Features: Enable I/O APIC, Hardware Clock in UTC Time.
- Processor
- Extended Features: Enable PAE/NX
- Acceleration
- Paravirtualization Interface: KVM.
- Hardware Virtualization: Enable VT-x/AMD-V, Enable Nested Paging.
- Motherboard
- Display
- Disable 3D Acceleration
- Storage
- Controller: SATA
- Use Host I/O Cache enabled[1]
- Controller: SATA
- Network
- Adapter 1
- Advanced – Adapter Type: virtio
- Adapter 1
[1] This can lead to wasted memory via double-caching since the guest and host have their own I/O cache, among other tradeoffs.