Known performance issues regarding FPS, Frame Times and Vsyncs

[ruineka]

I'm opening up this issue here so that others can share there experiences.

Some known issues you might run into are the following:

• Steam capped at 15, 30, or any other refresh rate that you wouldn't expect
• Games run fine, but when the overlay is opened the FPS is capped to 15,20,30 etc.
• Sudden frame time spikes that toggling between a random target back to off resolves
• Frame times remain high no matter what until you reboot the system
• Enabling/Disabling VRR can cause consistent frame time issues until you reboot
• The FPS limiter doesn't do anything when vsync isn't enabled in game like it does on the Steam Deck

Some or all of these issues are known to have issues on actual deck hardware when it's not running on SteamOS. When testing the neptune 6.1 kernel the issues go away.

[elmar-ops]

Using RX 6400. When opening Overlay FPS drops from e.g. 50 to 7. Need to restart game to fix it.

[ruineka]

Using RX 6400. When opening Overlay FPS drops from e.g. 50 to 7. Need to restart game to fix it.

Thanks for sharing. This is actively being worked on. We have it working under specific conditions with a few unknowns. Once we sort that out we'll get the fix into our testing branch.

[emkultra64]

I've noticed a persistent issue where certain refresh rates do not work well with VRR and it brings down the framerate/frametimes. E.g. on my RX 6800, if I set a frame limit of 90 fps, the game will be fine without VRR; then when I turn it on, the framerate drops dramatically or becomes highly erratic. I might get drops back and forth between 75 and the low 80s, or it might tank all the way down to exactly half the target frame rate, so 45 fps in this case.

My current workaround is to turn the refresh up to my monitor's maximum (170 Hz), set the target framerate to half of the refresh (85 fps) and turn on VRR, so it will get around 92 fps because VRR causes it to slightly break the frame limit.