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Commit 119768c9 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'tcp-ECN-quickack' 



Eric Dumazet says:

====================
tcp: reduce quickack pressure for ECN

Small patch series changing TCP behavior vs quickack and ECN

First patch is a refactoring, adding parameter to tcp_incr_quickack()
and tcp_enter_quickack_mode() helpers.

Second patch implements the change, lowering number of ACK packets
sent after an ECN event.
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents 290aa0ad 522040ea

net/ipv4/tcp_input.c

+13 −11
Original line number Original line Diff line number Diff line
@@ -203,21 +203,23 @@ static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb) 
	}

	}

}

}





static void tcp_incr_quickack(struct sock *sk)

static void tcp_incr_quickack(struct sock *sk, unsigned int max_quickacks)

{

{

	struct inet_connection_sock *icsk = inet_csk(sk);

	struct inet_connection_sock *icsk = inet_csk(sk);

	unsigned int quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);

	unsigned int quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);





	if (quickacks == 0)

	if (quickacks == 0)

		quickacks = 2;

		quickacks = 2;

	quickacks = min(quickacks, max_quickacks);

	if (quickacks > icsk->icsk_ack.quick)

	if (quickacks > icsk->icsk_ack.quick)

		icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);

		icsk->icsk_ack.quick = quickacks;

}

}





static void tcp_enter_quickack_mode(struct sock *sk)

static void tcp_enter_quickack_mode(struct sock *sk, unsigned int max_quickacks)

{

{

	struct inet_connection_sock *icsk = inet_csk(sk);

	struct inet_connection_sock *icsk = inet_csk(sk);

	tcp_incr_quickack(sk);



	tcp_incr_quickack(sk, max_quickacks);

	icsk->icsk_ack.pingpong = 0;

	icsk->icsk_ack.pingpong = 0;

	icsk->icsk_ack.ato = TCP_ATO_MIN;

	icsk->icsk_ack.ato = TCP_ATO_MIN;

}

}
@@ -261,7 +263,7 @@ static void __tcp_ecn_check_ce(struct tcp_sock *tp, const struct sk_buff *skb) 
		 * it is probably a retransmit.

		 * it is probably a retransmit.

		 */

		 */

		if (tp->ecn_flags & TCP_ECN_SEEN)

		if (tp->ecn_flags & TCP_ECN_SEEN)

			tcp_enter_quickack_mode((struct sock *)tp);

			tcp_enter_quickack_mode((struct sock *)tp, 1);

		break;

		break;

	case INET_ECN_CE:

	case INET_ECN_CE:

		if (tcp_ca_needs_ecn((struct sock *)tp))

		if (tcp_ca_needs_ecn((struct sock *)tp))
@@ -269,7 +271,7 @@ static void __tcp_ecn_check_ce(struct tcp_sock *tp, const struct sk_buff *skb) 




		if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) {

		if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) {

			/* Better not delay acks, sender can have a very low cwnd */

			/* Better not delay acks, sender can have a very low cwnd */

			tcp_enter_quickack_mode((struct sock *)tp);

			tcp_enter_quickack_mode((struct sock *)tp, 1);

			tp->ecn_flags |= TCP_ECN_DEMAND_CWR;

			tp->ecn_flags |= TCP_ECN_DEMAND_CWR;

		}

		}

		tp->ecn_flags |= TCP_ECN_SEEN;

		tp->ecn_flags |= TCP_ECN_SEEN;
@@ -686,7 +688,7 @@ static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) 
		/* The _first_ data packet received, initialize

		/* The _first_ data packet received, initialize

		 * delayed ACK engine.

		 * delayed ACK engine.

		 */

		 */

		tcp_incr_quickack(sk);

		tcp_incr_quickack(sk, TCP_MAX_QUICKACKS);

		icsk->icsk_ack.ato = TCP_ATO_MIN;

		icsk->icsk_ack.ato = TCP_ATO_MIN;

	} else {

	} else {

		int m = now - icsk->icsk_ack.lrcvtime;

		int m = now - icsk->icsk_ack.lrcvtime;
@@ -702,7 +704,7 @@ static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) 
			/* Too long gap. Apparently sender failed to

			/* Too long gap. Apparently sender failed to

			 * restart window, so that we send ACKs quickly.

			 * restart window, so that we send ACKs quickly.

			 */

			 */

			tcp_incr_quickack(sk);

			tcp_incr_quickack(sk, TCP_MAX_QUICKACKS);

			sk_mem_reclaim(sk);

			sk_mem_reclaim(sk);

		}

		}

	}

	}
@@ -4179,7 +4181,7 @@ static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb) 
	if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&

	if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&

	    before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {

	    before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {

		NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);

		NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);

		tcp_enter_quickack_mode(sk);

		tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS);





		if (tcp_is_sack(tp) && sock_net(sk)->ipv4.sysctl_tcp_dsack) {

		if (tcp_is_sack(tp) && sock_net(sk)->ipv4.sysctl_tcp_dsack) {

			u32 end_seq = TCP_SKB_CB(skb)->end_seq;

			u32 end_seq = TCP_SKB_CB(skb)->end_seq;
@@ -4706,7 +4708,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) 
		tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);

		tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);





out_of_window:

out_of_window:

		tcp_enter_quickack_mode(sk);

		tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS);

		inet_csk_schedule_ack(sk);

		inet_csk_schedule_ack(sk);

drop:

drop:

		tcp_drop(sk, skb);

		tcp_drop(sk, skb);
@@ -5790,7 +5792,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, 
			 * to stand against the temptation 8)     --ANK

			 * to stand against the temptation 8)     --ANK

			 */

			 */

			inet_csk_schedule_ack(sk);

			inet_csk_schedule_ack(sk);

			tcp_enter_quickack_mode(sk);

			tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS);

			inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,

			inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,

						  TCP_DELACK_MAX, TCP_RTO_MAX);

						  TCP_DELACK_MAX, TCP_RTO_MAX);