sorry for my bad english.
I have a radeon rx 560 2gb card (radeon software 20.1.3)
I noticed this reproducible behavior:
right after installing the drivers (without reboot) doom 2016 (vulkan) performance is good: 60 fps mini on "foundry" level.
But after rebooting: 25fps.
I thought it was because of the graphics card, with only 2gb, but that's not the problem with this behavior.