Latency in VR (with GSync) since 440.44

I’m playing in VR on Ubuntu, and realized a slighty but noticable lag/latency that was introduced with driver 440.44. It was fine with 440.36. I played on an GTX 1070 on Ubuntu 18.04 LTS with HTC Vive before and I’m now with a RTX 2080 on Ubuntu 19.10 and Valve Index. The notebook(s) I use have GSync monitors.
Ubuntu 19.10 installed driver 435 ootb which also doesn’t have this issue. Today I installed 440.82 and got this issue again.

A guess is, that it is related to this patch note entry (from driver 440.44):
“Fixed a bug that caused applications running directly on a display (such as VR HMDs) to tear when a G-SYNC or G-SYNC Compatible monitor is plugged in the system.”

I didn’t have any issues with tearing in VR though. The introduced latency is causing nausea, so a fix (or workaround) would be appreciated. I tried to disalbe GSync via nvidia-settings, but it didn’t change anything.

I tried to disable gsync via nvidia-settings:

nvidia-settings -q CurrentMetaMode  # get current mode, set again with AllowGSYNC=off

nvidia-settings -a CurrentMetaMode="DPY-3: 1920x1080_144 @1920x1080 +0+0 {ViewPortIn=1920x1080, ViewPortOut=1920:1080+0+0, AllowGSYNC=off}"

This does disable gsync, as it’s not shown in nvidia-settings anymore. But the lag in VR is still present.

Does using env variable
help with that?

I’ve set export __GL_MaxFramesAllowed=1 in my .profile, so it’s available to everything I start.

It seems not to get rid of the latency issue, but maybe it got mitigated. I have the impression, the lag almost vanishes, when the GPU is under heavier load. So when starting SteamVR, in the empty room (I’m not using SteamVR Home), the issue is very noticeable. As soon as I open the SteamVR dashboard, it seems already to get better.
When I play Beat Saber, in the song selection it is noticeable, when playing a song it seems mostly gone.
Also it seems to come back immediately, after the headset turned off after 5s of idling.
I need to test a bit more, as maybe the env variable doesn’t affect this, and the latency would also go away when playing games without it.

Nevertheless, the issues is still there, so the env var doesn’t get rid of it. Also I don’t know how to describe this properly, or even measure it. I can only describe my subjective experience.

This issue is still present. I upgraded my hardware and software, I’m running now a RTX 2080 on Ubuntu 20.04. No matter which driver after 440.36 I use, the issue comes up again and again.
Currently I’m on 440.100 drivers, Steam Client and Steam VR both on beta channels.

A workaround is though to open the Steam VR dashboard, then the issues is gone for a while. Comes back at random times and shortly opening the dashboard gets rid of it again.

I want to bring this topic up again, as a mate who wants to get into VR on Linux ran into the same issue (even without a G-Sync monitor), so it’s not my setup.