session tcp: support pacer idle timeouts

Type: feature

To avoid excessive bursts, pacer must be provided with an estimated rtt
for the connection. That's used to compute an idle timeout, i.e., time
after which the bucket is reset to 1 mtu due to inactivity. For now,
idle timeout is computed as 5% of the rtt.

Change-Id: Ia0b752fe7b4ad0ce97b477fb886b0133a2321541
Signed-off-by: Florin Coras <fcoras@cisco.com>

1 files changed, 19 insertions, 40 deletions

diff --git a/src/vnet/tcp/tcp_input.c b/src/vnet/tcp/tcp_input.c
index 172dcd2ee6f..c94e5babc50 100755
--- a/src/vnet/tcp/tcp_input.c
+++ b/src/vnet/tcp/tcp_input.c
@@ -575,21 +575,6 @@ tcp_estimate_initial_rtt (tcp_connection_t * tc)
   tcp_update_rto (tc);
 }
 
-always_inline u8
-tcp_recovery_no_snd_space (tcp_connection_t * tc)
-{
-  u32 space;
-
-  ASSERT (tcp_in_cong_recovery (tc));
-
-  if (tcp_in_recovery (tc))
-    space = tcp_available_output_snd_space (tc);
-  else
-    space = tcp_fastrecovery_prr_snd_space (tc);
-
-  return (space < tc->snd_mss + tc->burst_acked);
-}
-
 /**
  * Dequeue bytes for connections that have received acks in last burst
  */
@@ -610,33 +595,26 @@ tcp_handle_postponed_dequeues (tcp_worker_ctx_t * wrk)
       tc = tcp_connection_get (pending_deq_acked[i], thread_index);
       tc->flags &= ~TCP_CONN_DEQ_PENDING;
 
-      if (tc->burst_acked)
-	{
-	  /* Dequeue the newly ACKed bytes */
-	  session_tx_fifo_dequeue_drop (&tc->connection, tc->burst_acked);
-	  tcp_validate_txf_size (tc, tc->snd_una_max - tc->snd_una);
-
-	  if (PREDICT_FALSE (tc->flags & TCP_CONN_PSH_PENDING))
-	    {
-	      if (seq_leq (tc->psh_seq, tc->snd_una))
-		tc->flags &= ~TCP_CONN_PSH_PENDING;
-	    }
+      if (PREDICT_FALSE (!tc->burst_acked))
+	continue;
 
-	  /* If everything has been acked, stop retransmit timer
-	   * otherwise update. */
-	  tcp_retransmit_timer_update (tc);
+      /* Dequeue the newly ACKed bytes */
+      session_tx_fifo_dequeue_drop (&tc->connection, tc->burst_acked);
+      tcp_validate_txf_size (tc, tc->snd_una_max - tc->snd_una);
 
-	  /* Update pacer based on our new cwnd estimate */
-	  tcp_connection_tx_pacer_update (tc);
+      if (PREDICT_FALSE (tc->flags & TCP_CONN_PSH_PENDING))
+	{
+	  if (seq_leq (tc->psh_seq, tc->snd_una))
+	    tc->flags &= ~TCP_CONN_PSH_PENDING;
 	}
 
-      /* Reset the pacer if we've been idle, i.e., no data sent or if
-       * we're in recovery and snd space constrained */
-      if (tc->data_segs_out == tc->prev_dsegs_out
-	  || (tcp_in_cong_recovery (tc) && tcp_recovery_no_snd_space (tc)))
-	transport_connection_tx_pacer_reset_bucket (&tc->connection);
+      /* If everything has been acked, stop retransmit timer
+       * otherwise update. */
+      tcp_retransmit_timer_update (tc);
+
+      /* Update pacer based on our new cwnd estimate */
+      tcp_connection_tx_pacer_update (tc);
 
-      tc->prev_dsegs_out = tc->data_segs_out;
       tc->burst_acked = 0;
     }
   _vec_len (wrk->pending_deq_acked) = 0;
@@ -1623,10 +1601,11 @@ process_ack:
   if (tc->cfg_flags & TCP_CFG_F_RATE_SAMPLE)
     tcp_bt_sample_delivery_rate (tc, &rs);
 
-  tcp_program_dequeue (wrk, tc);
-
   if (tc->bytes_acked)
-    tcp_update_rtt (tc, &rs, vnet_buffer (b)->tcp.ack_number);
+    {
+      tcp_program_dequeue (wrk, tc);
+      tcp_update_rtt (tc, &rs, vnet_buffer (b)->tcp.ack_number);
+    }
 
   TCP_EVT (TCP_EVT_ACK_RCVD, tc);