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Commit 90638a04 authored by Ilpo Järvinen's avatar Ilpo Järvinen Committed by David S. Miller
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tcp: don't clear lost_skb_hint when not necessary 



Most importantly avoid doing it with cumulative ACK. However,
since we have lost_cnt_hint in the picture as well needing
adjustments, it's not as trivial as dealing with
retransmit_skb_hint (and cannot be done in the all place we
could trivially leave retransmit_skb_hint untouched).

With the previous patch, this should mostly remove O(n^2)
behavior while cumulative ACKs start flowing once rexmit
after a lossy round-trip made it through.

Signed-off-by: default avatarIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ef9da47c

net/ipv4/tcp_input.c

+13 −1
Original line number Original line Diff line number Diff line
@@ -2844,6 +2844,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets) 
	int flag = 0;

	int flag = 0;

	u32 pkts_acked = 0;

	u32 pkts_acked = 0;

	u32 reord = tp->packets_out;

	u32 reord = tp->packets_out;

	u32 prior_sacked = tp->sacked_out;

	s32 seq_rtt = -1;

	s32 seq_rtt = -1;

	s32 ca_seq_rtt = -1;

	s32 ca_seq_rtt = -1;

	ktime_t last_ackt = net_invalid_timestamp();

	ktime_t last_ackt = net_invalid_timestamp();
@@ -2925,9 +2926,11 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets) 




		tcp_unlink_write_queue(skb, sk);

		tcp_unlink_write_queue(skb, sk);

		sk_wmem_free_skb(sk, skb);

		sk_wmem_free_skb(sk, skb);

		tcp_clear_retrans_hints_partial(tp);

		tp->scoreboard_skb_hint = NULL;

		if (skb == tp->retransmit_skb_hint)

		if (skb == tp->retransmit_skb_hint)

			tp->retransmit_skb_hint = NULL;

			tp->retransmit_skb_hint = NULL;

		if (skb == tp->lost_skb_hint)

			tp->lost_skb_hint = NULL;

	}

	}





	if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))

	if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
@@ -2946,6 +2949,15 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets) 
			/* Non-retransmitted hole got filled? That's reordering */

			/* Non-retransmitted hole got filled? That's reordering */

			if (reord < prior_fackets)

			if (reord < prior_fackets)

				tcp_update_reordering(sk, tp->fackets_out - reord, 0);

				tcp_update_reordering(sk, tp->fackets_out - reord, 0);



			/* No need to care for underflows here because

			 * the lost_skb_hint gets NULLed if we're past it

			 * (or something non-trivial happened)

			 */

			if (tcp_is_fack(tp))

				tp->lost_cnt_hint -= pkts_acked;

			else

				tp->lost_cnt_hint -= prior_sacked - tp->sacked_out;

		}

		}





		tp->fackets_out -= min(pkts_acked, tp->fackets_out);

		tp->fackets_out -= min(pkts_acked, tp->fackets_out);