[vfio-users] Huge performance decrease in VM

[Marius Steffen]

Hi,
I'm running my VM on Arch for quite some time now, with varying success
on this hardware:

- NVIDIA GTX 1070
- 16 GB RAM (10 GB passed through to VM, tested with/without hugepages)
- i7 3770 (4 Cores, 4 Hyperthreads, various combinations tested)
- virtualized OS is Windows 10 Home x64

Arch is using my iGPU (unvirtualized), usally running KDE Plasma 5, but
I also tried without running any X-Session.

As I recently noticed when upgrading my GPU from a GTX 680 to my current
GTX 1070, there's an extremely huge performance impact compared to
running on native Windows.
When playing Just Cause 3, this was especially noteable: I've often got
only 40-50 FPS, compared to 75-120+ FPS in Windows 10, and my GPU being
used just about 20% or so in the VM.

Is there anything I can do to a) find the cause of this bad performance
b) make my VM perform better?

Greetings,

Marius