Can you confirm this happening still? osu! nowadays should only use OpenGL (not sure if there's a fallback to D3D) and CSMT (as-documented) only affects Direct3D.
dodorama wrote:...try installing wine staging, run winecfg and in the tab "staging" check "Enable_CSMT for better graphic performance" it will allow wine to multithread. it actually gave me a 300 fps boost, hope you will have the same :b