The PEP 471 announces a huge speed up of the os.walk() function, but os.walk() was not modified yet. I just merged the implementation of os.scandir() (issue #22524), it's now time to work on os.walk().

We need a patch and benchmarks on Linux and Windows.

On NFS shares (on Linux), d_type is not filled (set to DT_UNKNOWN, so a syscall is required to get the file type). Benchmarks of os.walk() on a NFS share is also required.