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Commit 92ee76b6 authored by Ilpo Järvinen's avatar Ilpo Järvinen Committed by David S. Miller
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tcp: Make shifting not clear the hints 



The earlier version was just very basic one which is "playing
safe" by always clearing the hints. However, clearing of a hint
is extremely costly operation with large windows, so it must be
avoided at all cost whenever possible, there is a way with
shifting too achieve not-clearing.

Signed-off-by: default avatarIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 832d11c5

net/ipv4/tcp_input.c

+14 −2
Original line number Diff line number Diff line
@@ -1379,6 +1379,11 @@ static int tcp_shifted_skb(struct sock *sk, struct sk_buff *prev, 


	BUG_ON(!pcount);



	/* Tweak before seqno plays */

	if (!tcp_is_fack(tp) && tcp_is_sack(tp) && tp->lost_skb_hint &&

	    !before(TCP_SKB_CB(tp->lost_skb_hint)->seq, TCP_SKB_CB(skb)->seq))

		tp->lost_cnt_hint += pcount;



	TCP_SKB_CB(prev)->end_seq += shifted;

	TCP_SKB_CB(skb)->seq += shifted;
@@ -1408,8 +1413,6 @@ static int tcp_shifted_skb(struct sock *sk, struct sk_buff *prev, 
	/* Difference in this won't matter, both ACKed by the same cumul. ACK */

	TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);



	tcp_clear_all_retrans_hints(tp);



	if (skb->len > 0) {

		BUG_ON(!tcp_skb_pcount(skb));

		return 0;
@@ -1417,6 +1420,15 @@ static int tcp_shifted_skb(struct sock *sk, struct sk_buff *prev, 


	/* Whole SKB was eaten :-) */



	if (skb == tp->retransmit_skb_hint)

		tp->retransmit_skb_hint = prev;

	if (skb == tp->scoreboard_skb_hint)

		tp->scoreboard_skb_hint = prev;

	if (skb == tp->lost_skb_hint) {

		tp->lost_skb_hint = prev;

		tp->lost_cnt_hint -= tcp_skb_pcount(prev);

	}



	TCP_SKB_CB(skb)->flags |= TCP_SKB_CB(prev)->flags;

	if (skb == tcp_highest_sack(sk))

		tcp_advance_highest_sack(sk, skb);