Re: Is SCTP throughput really this low compared to TCP?

[Vlad Yasevich <vyasevich@gmail.com>]

On 04/14/2014 12:47 PM, Butler, Peter wrote:
> Glad to be of help :o)
>

Hi Peter

Would you be able to run this test again with the following patch
on top of the problematic code.

Thanks
-vlad


commit c9888a220916284403c5115d6c6c7e33a00d0b55
Author: Vlad Yasevich <vyasevic@redhat.com>
Date:   Thu Apr 17 09:21:52 2014 -0400

    sctp: Trigger window update SACK after skb has been freed.

    Signed-off-by: Vlad Yasevich <vyasevic@redhat.com>

diff --git a/net/sctp/ulpevent.c b/net/sctp/ulpevent.c
index 8d198ae..b59a7c5 100644
--- a/net/sctp/ulpevent.c
+++ b/net/sctp/ulpevent.c
@@ -1011,7 +1011,6 @@ static void sctp_ulpevent_release_data(struct
sctp_ulpevent *event)
 {
 	struct sk_buff *skb, *frag;
 	unsigned int	len;
-	struct sctp_association *asoc;

 	/* Current stack structures assume that the rcv buffer is
 	 * per socket.   For UDP style sockets this is not true as
@@ -1036,11 +1035,7 @@ static void sctp_ulpevent_release_data(struct
sctp_ulpevent *event)
 	}

 done:
-	asoc = event->asoc;
-	sctp_association_hold(asoc);
 	sctp_ulpevent_release_owner(event);
-	sctp_assoc_rwnd_update(asoc, true);
-	sctp_association_put(asoc);
 }

 static void sctp_ulpevent_release_frag_data(struct sctp_ulpevent *event)
@@ -1071,12 +1066,21 @@ done:
  */
 void sctp_ulpevent_free(struct sctp_ulpevent *event)
 {
+	struct sctp_association *asoc = event->asoc;
+
 	if (sctp_ulpevent_is_notification(event))
 		sctp_ulpevent_release_owner(event);
 	else
 		sctp_ulpevent_release_data(event);

 	kfree_skb(sctp_event2skb(event));
+	/* The socket is locked and the assocaiton can't go anywhere
+	 * since we are walking the uplqueue.  No need to hold
+	 * another ref on the association.  Now that the skb has been
+	 * freed and accounted for everywhere, see if we need to send
+	 * a window update SACK.
+	 */
+	sctp_assoc_rwnd_update(asoc, true);
 }

 /* Purge the skb lists holding ulpevents. */