See using Linux getdents syscall and failing to use getdents system call on Linux for other futile attempts.

No, it is not futile. See Linux::NFS::BigDir.

It's harder to solve that way, but performance difference on the specific case I tested (large directories over NFS version 3) by using readdir and going down to the getdents can be measured in hours.

It might be a problem with the NFS server configuration? Yes, but I didn't have time to search for it or even root access to attempt.