net: use indirect call wrappers for skb_copy_datagram_iter()
TCP recvmsg() calls skb_copy_datagram_iter(), which
calls an indirect function (cb pointing to simple_copy_to_iter())
for every MSS (fragment) present in the skb.
CONFIG_RETPOLINE=y forces a very expensive operation
that we can avoid thanks to indirect call wrappers.
This patch gives a 13% increase of performance on
a single flow, if the bottleneck is the thread reading
the TCP socket.
Fixes: 8dc3f0dbe4ca ("datagram: consolidate datagram copy to iter helpers") Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Paolo Abeni <pabeni@redhat.com> Acked-by: Willem de Bruijn <willemb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>