Possibly it would be useful for you to run command glmark2 (if it runs in Wayland; otherwise, try running it in Plasma X11, or in both Wayland and X11) and report your score(s) here. With 15.6 and Plasma 5 on my Oland with Intel Core2 6700 CPU (2 cores, 2 threads), the following were run both with and without kernel cmdline option rd.driver.blacklist=radeon, and with (separately) both amdgpu display driver, and modesetting display driver:
host fi965 running amdgpu module & amdgpu DDX on 15.6/Plasma5 X11
cmdline parameters radeon.si_support=0 amdgpu.si_support=1 rd.driver.blacklist=radeon:
# glmark2
=======================================================
glmark2 2021.12
=======================================================
OpenGL Information
GL_VENDOR: AMD
GL_RENDERER: AMD Radeon R7 200 Series (radeonsi, oland, LLVM 17.0.6, DRM 3.57, 6.4.0-150600.23.100-default)
GL_VERSION: 4.6 (Compatibility Profile) Mesa 23.3.4
Surface Config: buf=32 r=8 g=8 b=8 a=8 depth=24 stencil=0 samples=0
Surface Size: 800x600 windowed
...
=======================================================
glmark2 Score: 1411
=======================================================
#
host fi965 running amdgpu module & modesetting DIX on 15.6/Plasma5 X11
cmdline parameters radeon.si_support=0 amdgpu.si_support=1 rd.driver.blacklist=radeon:
# glmark2
=======================================================
glmark2 2021.12
=======================================================
OpenGL Information
GL_VENDOR: AMD
GL_RENDERER: AMD Radeon R7 200 Series (radeonsi, oland, LLVM 17.0.6, DRM 3.57, 6.4.0-150600.23.100-default)
GL_VERSION: 4.6 (Compatibility Profile) Mesa 23.3.4
Surface Config: buf=32 r=8 g=8 b=8 a=8 depth=24 stencil=0 samples=0
Surface Size: 800x600 windowed
...
=======================================================
glmark2 Score: 1413
=======================================================
#
host fi965 amdgpu module & modesetting DIX on 15.6/Plasma5 X11
cmdline parameters radeon.si_support=0 amdgpu.si_support=1:
# glmark2
=======================================================
glmark2 2021.12
=======================================================
OpenGL Information
GL_VENDOR: AMD
GL_RENDERER: AMD Radeon R7 200 Series (radeonsi, oland, LLVM 17.0.6, DRM 3.57, 6.4.0-150600.23.100-default)
GL_VERSION: 4.6 (Compatibility Profile) Mesa 23.3.4
Surface Config: buf=32 r=8 g=8 b=8 a=8 depth=24 stencil=0 samples=0
Surface Size: 800x600 windowed
...
=======================================================
glmark2 Score: 1414
=======================================================
#
host fi965 running amdgpu module & amdgpu DDX on 15.6/Plasma5 X11
cmdline parameters radeon.si_support=0 amdgpu.si_support=1:
# glmark2
=======================================================
glmark2 2021.12
=======================================================
OpenGL Information
GL_VENDOR: AMD
GL_RENDERER: AMD Radeon R7 200 Series (radeonsi, oland, LLVM 17.0.6, DRM 3.57, 6.4.0-150600.23.100-default)
GL_VERSION: 4.6 (Compatibility Profile) Mesa 23.3.4
Surface Config: buf=32 r=8 g=8 b=8 a=8 depth=24 stencil=0 samples=0
Surface Size: 800x600 windowed
...
=======================================================
glmark2 Score: 1413
=======================================================
#
Aside conclusions:
- cmdline parameter
rd.driver.blacklist=radeon does nothing more than bloat grub.cfg and logs; IOW, it’s unnecessary when radeon.si_support=0 amdgpu.si_support=1 are used.
- at best, glmark2 performance is the same whether running
amdgpu DDX or modesetting DIX display driver along with amdgpu kernel module. (last I tested, it was markedly worse using radeon kernel module, aka not including radeon.si_support=0 amdgpu.si_support=1 parameters).