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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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ilpo Järvinen 2008-11-24 21:26:56 -08:00 committed by David S. Miller
parent 832d11c5cd
commit 92ee76b6d9
1 changed files with 14 additions and 2 deletions
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16
net/ipv4/tcp_input.c
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@ -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);