tcp: dequeue acked only once per burst

Avoid dequeuing acked bytes more than once per burst for a connection.
Although the fifos do not use locks, size decrements are atomic, so they
rely on locked instructions.

Change-Id: Id65f4ea40b2c10057461402dfd0393034e6472d5
Signed-off-by: Florin Coras <fcoras@cisco.com>
diff --git a/src/vnet/tcp/tcp.h b/src/vnet/tcp/tcp.h
index bd5e4f7..480b924 100644
--- a/src/vnet/tcp/tcp.h
+++ b/src/vnet/tcp/tcp.h
@@ -122,6 +122,7 @@
   _(FINPNDG, "FIN pending")			\
   _(FRXT_PENDING, "Fast-retransmit pending")	\
   _(FRXT_FIRST, "Fast-retransmit first again")	\
+  _(DEQ_PENDING, "Pending dequeue acked")	\
 
 typedef enum _tcp_connection_flag_bits
 {
@@ -308,6 +309,7 @@
   u32 prev_ssthresh;	/**< ssthresh before congestion */
   u32 prev_cwnd;	/**< ssthresh before congestion */
   u32 bytes_acked;	/**< Bytes acknowledged by current segment */
+  u32 burst_acked;	/**< Bytes acknowledged in current burst */
   u32 snd_rxt_bytes;	/**< Retransmitted bytes */
   u32 snd_rxt_ts;	/**< Timestamp when first packet is retransmitted */
   u32 tsecr_last_ack;	/**< Timestamp echoed to us in last healthy ACK */
@@ -392,6 +394,7 @@
 						     now doing fast rxt */
   u32 *postponed_fast_rxt;			/**< vector of connections
 						     that will do fast rxt */
+  u32 *pending_deq_acked;
   vlib_main_t *vm;				/**< pointer to vm */
 
     CLIB_CACHE_LINE_ALIGN_MARK (cacheline1);