Re: [net-next PATCH v3 3/5] net: Enable Tx queue selection based on Rx queues

On Wed, Jun 6, 2018 at 3:08 PM, Samudrala, Sridhar
[off-list ref] wrote:

On 6/6/2018 11:56 AM, Willem de Bruijn wrote:

quoted

On Tue, Jun 5, 2018 at 4:38 AM, Amritha Nambiar
[off-list ref] wrote:

quoted

This patch adds support to pick Tx queue based on the Rx queue(s) map
configuration set by the admin through the sysfs attribute
for each Tx queue. If the user configuration for receive queue(s) map
does not apply, then the Tx queue selection falls back to CPU(s) map
based selection and finally to hashing.

Signed-off-by: Amritha Nambiar <redacted>
Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
---
  int sysctl_tcp_max_orphans __read_mostly = NR_FILE;

@@ -5574,6 +5575,7 @@ void tcp_finish_connect(struct sock *sk, struct

sk_buff *skb)
         if (skb) {
                 icsk->icsk_af_ops->sk_rx_dst_set(sk, skb);
                 security_inet_conn_established(sk, skb);
+               sk_mark_napi_id(sk, skb);
         }

This and the call below should be in a standalone patch, as the mark
changes are not rxq-xps specific. Is the additional earlier marking really
required?

The additional earlier marking in tcp_finish_connect() allows a client app
to do
SO_INCOMING_NAPI_ID after a a connect() call to get the right queue
association
for a socket.

The marking in tcp_conn_request() allows syn-ack to go on the right tx-queue
associated with the queue on which syn is received.

I understand the intent. My question really is whether it is needed.
Marking has been slightly lossy in this regard in the past, not
necessarily as an oversight. I don't mean to make that call here,
but it's worth discussion and its own patch.