Ray Tracing and VFIO. Any gotchas to keep in mind?

Operating Systems & Open Source Virtualization
1

Planning to get a RTX 2080 Ti to replace my GTX 1080 Ti because I want to play Control in 4K with ray tracing and DLSS, either through Lutris and the GOG DRM-free copy or through a Windows VM using my 10920X system.

Are there any gotchas to using DLSS or Ray Tracing in VFIO? Like performance differences between a VM and native and if Looking Glass affects performance with DXGI vs NVFBC.

I plan to use my 6900 XT I’m getting late this year for my 9900K system bare metal with Windows AME so that’s not an issue.

3

I know at least one of these options is good. If I could get Lutris working with DLSS and Ray Tracing, that would be great, but I ideally want to do it through VFIO.

And 6900 XT Bare Metal Windows AME is my backup case for playing Control if VFIO and the 2080 Ti has issues.

4

I have a Windows VM with a RTX A4000 and its been fine for RT although im not a super hardcore gamer, ive not noticed any real perfomance drops vs Windows apart from the little overhead VMs take

5

Good to hear. There were initial reports using the tensor cores for RT and DLSS reduces performance in a VM but if this is true it might not be as founded.

6

Im currently downloading Watch Dogs Legion again to do a playthrough and ill try it on a windows bare metal machine and VM and see what the results are with RTX on and off with the VM and baremetal.

and report back in 30mins / 1hr once its done

the machine is a TR 3945WX and RTX A4000 so its a pretty mid spec workstation that should handle it fine and should be near identical id hope, but ill report back with the findings

7

Also turn on/off DLSS. That’s likely to have a more important performance impact if system memory bandwidth is at issue for DLSS.

8

Did some quick testing of driving around the city and heres the results (hope this maybe helps a bit) :slight_smile:
Bare Metal
RTX ON | DLSS Quality 1440p Ultra = 42FPS Avg
RTX OFF | DLSS Quality 1440p Ultra = 48 FPS Avg
RTX ON | NO DLSS 1440p Ultra = 54Fps
RTF OFF No DLSS 1440p Ultra = 73fps avg

VM Win 11 (8 core 16t)
RTX ON | DLSS Quality 1440p Ultra = 40FPS Avg
RTX OFF | DLSS Quality 1440p Ultra = 45 FPS Avg
RTX ON | NO DLSS 1440p Ultra = 48Fps
RTF OFF No DLSS 1440p Ultra = 69fps avg

9

No DLSS seems outside of error margins, but with DLSS seems to bring results closer to each other.

Is VBS off?

10

VBS is on i think? this is a stock win 11 VM i just use for a few games havent tweaked anything apart from a wallpaper and removed icons on desktop so if VBS is on by default then yes its on.

11

Try to find a way to turn it off. VBS might be introducing nested virtualization.

12

sorry for late response, i turned VBS off and still getting the same performance give or take didnt notice any real performance gains

13

Very good to hear. Now I want to see if games that make heavy use of PCI-E Bandwidth copy are affected by VFIO.

This should be easy with the 3DMark PCI-E Bandwidth test. This also affects Looking Glass performance.