BTW running warthunder under brand new 4.15 kernel + latest amd-staging-4.15 gives 25-30+ FPS and the same during the gameplay with performance set to 'auto' and fps spikes up to 50+ with 'high' performance on my R9 Fury. But it seems that 4.15 vanilla kernel doesn't have any patches from staging which improve performance so the results are nearly the same as it was with 4.14.