tcp: optimize newreno cong ack handler

Type: improvement

Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: I196ee5f4630cec637245493f370b5f83a939fe44

diff --git a/src/vnet/tcp/tcp_newreno.c b/src/vnet/tcp/tcp_newreno.c
index 39035ba..8c7e77f 100644 (file)
--- a/src/vnet/tcp/tcp_newreno.c
+++ b/src/vnet/tcp/tcp_newreno.c
@@ -62,30 +62,31 @@ void
 newreno_rcv_cong_ack (tcp_connection_t * tc, tcp_cc_ack_t ack_type,
                      tcp_rate_sample_t * rs)
 {
+  /* With sacks prr controls the data in flight post congestion */
+  if (PREDICT_TRUE (tcp_opts_sack_permitted (tc)))
+    return;
+
   if (ack_type == TCP_CC_DUPACK)
     {
-      if (!tcp_opts_sack_permitted (tc))
-       tc->cwnd += tc->snd_mss;
+      tc->cwnd += tc->snd_mss;
     }
   else if (ack_type == TCP_CC_PARTIALACK)
     {
-      /* RFC 6582 Sec. 3.2 */
-      if (!tcp_opts_sack_permitted (&tc->rcv_opts))
-       {
-         /* Deflate the congestion window by the amount of new data
-          * acknowledged by the Cumulative Acknowledgment field.
-          * If the partial ACK acknowledges at least one SMSS of new data,
-          * then add back SMSS bytes to the congestion window. This
-          * artificially inflates the congestion window in order to reflect
-          * the additional segment that has left the network. This "partial
-          * window deflation" attempts to ensure that, when fast recovery
-          * eventually ends, approximately ssthresh amount of data will be
-          * outstanding in the network.*/
-         tc->cwnd = (tc->cwnd > tc->bytes_acked + tc->snd_mss) ?
-           tc->cwnd - tc->bytes_acked : tc->snd_mss;
-         if (tc->bytes_acked > tc->snd_mss)
-           tc->cwnd += tc->snd_mss;
-       }
+      /* RFC 6582 Sec. 3.2
+       * Deflate the congestion window by the amount of new data
+       * acknowledged by the Cumulative Acknowledgment field.
+       * If the partial ACK acknowledges at least one SMSS of new data,
+       * then add back SMSS bytes to the congestion window. This
+       * artificially inflates the congestion window in order to reflect
+       * the additional segment that has left the network. This "partial
+       * window deflation" attempts to ensure that, when fast recovery
+       * eventually ends, approximately ssthresh amount of data will be
+       * outstanding in the network. */
+      tc->cwnd = (tc->cwnd > tc->bytes_acked + tc->snd_mss) ?
+                  tc->cwnd - tc->bytes_acked :
+                  tc->snd_mss;
+      if (tc->bytes_acked > tc->snd_mss)
+       tc->cwnd += tc->snd_mss;
     }
 }