[webshit2]

  wxy[:,:,k] += mu*conj(err[i,k])*X

This should probably be

  wxy[:,:,k] .+= mu*conj(err[i,k]).*X

so allocations are avoided. This doubled the speed for me, although I don't what size inputs are realistic. The @benchmark and @profile macros are good for this stuff.

[crabbygrabby]

Why are you trying to optimize for performance if you don't have a goal in mind?