I just spent about 4h playing around with different driver versions to narrow down why this occurs.
Basically Deus Ex Mankind Divided performs significantly and measurably better on the old 375 branch than it does on the new 38X branch. I haven’t yet tried other games.
I’ve done a lot of testing and also played around with environment variables (__GL_THREADED_OPTIMIZATIONS has no effect, so it’s not that) as well as the Composition Pipeline, V-Sync and basically all driver versions that came after the last 375 one.
This likely matches a similar performance drop observed on another Feral game, Total War: WARHAMMER.
We’ve been tracking it internally as bug 1963500. There was a change, introduced in our r378 branch, to the logic of allocation of certain textures, but it apparently exposed a bug in our memory manager.
Our next release branch, r390, will carry a workaround, and we’re still working on finding and fixing the root cause.
There isn’t, in currently released drivers, a way to disable the new logic that is causing the problem.
Please downgrade to a driver version that isn’t affected, until we’ve released a driver with a fix or the new logic disabled by default.
I also can add Dawn of War 3 to the games with issues. Using Opengl the vram in my card shows 4GB which heavily cripples performance. Using the same graphical preset doing the benchmark in vulkan mode, i only see ~ 2.5gb vram usage and everything is working fine.