[QUESTION] How to improve virtio-gpu performance

[Jun Piao]

Hi Gerd,

I'm using glmark2 to test virtio-gpu on AMDGPU, but the result is
unsatisfactory.

GPU: AMD Radeon Pro WX 5100
Host OS: CentOS Linux release 7.7.1908 (AltArch)
  --QEMU: 4.0.0
  --linux kernel 4.18
  --mesa 18.3
  --virglrenderer
  --spice server 0.14.2
  --spice-gtk3-0.35
  --libepoxy 1.5.2
Guest OS: CentOS Linux release 7.7.1908 (AltArch)
  --linux kernel 4.18
  --mesa 18.3
  --xorg server 1.20
TestSuit: glmark2

Host result:
glmark2 Score: 10043

Single Guest result:
glmark2 Score: 2209

Multi Guest result:
Guest1: glmark2 Score: 1136
Guest2: glmark2 Score: 1231
Guest3: glmark2 Score: 1282
Guest4: glmark2 Score: 1175
Guest5: glmark2 Score: 1398

It seems the whole performance of multi-guests is better than single
guest, but each one has lower performance. I change 'ctrl_vq' from 256
to 1024, but has little effect. I wonder the result is normal or
abnormal? And which is the bottleneck? I'm appreciated for you help.

thanks,
Jun