Also, even when io_uring does copying in kernelspace, I wonder if it'd be more practical for it to use AVX instructions than from within a read syscall. As I u

Also, even when io_uring does copying in kernelspace, I wonder if it'd be more practical for it to use AVX instructions than from within a read syscall. As I understand it, userspace<->kernel transitions are lighter-weight than full context switches between processes. As discussed here: not saving/restoring the SIMD registers. (I think a bunch of other ways, too, like not replacing all the memory mappings.) There are also a bunch of pure-kernel processes (I don't know the terminology) shown on ps in square brackets, like [kthreadd], [rcu_gp], [rcu_par_gp], etc. I think a full context switch happens on entry/exit to one of these, just as between two different userspace processes. If the io_uring work always happens within one of these (does it?), the SIMD registers are already being saved/restored, and it'd be safe for it to use an avx_memcpy variant without paying any additional cost.