If you own an NVIDIA based video card and you are experiencing a performance drop when you are playing Total War: WARHAMMER on Linux, you should probably read this.
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.
