On Wed, Oct 30, 2019 at 12:07:17PM -0400, Wally Zhao wrote:
Unlike tcp_transmit_skb,
sctp_packet_transmit does not set ooo_okay explicitly,
causing unwanted Tx queue switching when multiqueue is in use;
It is initialized to 0 by __alloc_skb() via:
memset(skb, 0, offsetof(struct sk_buff, tail));
and never set to 1 by anyone for SCTP.
The patch description seems off. I don't see how the unwanted Tx queue
switching can happen. IOW, it's not fixing it OOO packets, but
improving it by allowing switching on the first packet. Am I missing
something?
quoted hunk ↗ jump to hunk
Tx queue switching may cause out-of-order packets.
Change sctp_packet_transmit to allow Tx queue switching only for
the first in flight packet, to avoid unwanted Tx queue switching.
Signed-off-by: Wally Zhao <redacted>
---
net/sctp/output.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/net/sctp/output.c b/net/sctp/output.c
index dbda7e7..5ff75cc 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -626,6 +626,10 @@ int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
/* neighbour should be confirmed on successful transmission or
* positive error
*/
+
+ /* allow switch tx queue only for the first in flight pkt */
+ head->ooo_okay = asoc->outqueue.outstanding_bytes == 0;
Considering we are talking about NIC queues here, we would have a
better result with tp->flight_size instead. As in, we can switch
queues if, for this transport, the queue is empty.
+
if (tp->af_specific->sctp_xmit(head, tp) >= 0 &&
tp->dst_pending_confirm)
tp->dst_pending_confirm = 0;
--
1.8.3.1