There is no reason why one needs to have a lo(4) MTU that is arch specific.

There is no reason why one needs to have a lo(4) MTU that is arch specific.
Also making the size 32k + some extra is not very helpful since we don't
do something like zerocopy or sendfile. Just go back to 32768 and we can
bikeshed over the right value later on once we have features that benefit
from it. OK mpi@