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tcp: don't clear lost_skb_hint when not necessary

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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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ilpo Järvinen 2008-09-20 21:25:52 -07:00 committed by David S. Miller
parent ef9da47c7c
commit 90638a04ad
1 changed files with 13 additions and 1 deletions
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14
net/ipv4/tcp_input.c
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@ -2844,6 +2844,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
int flag = 0;
u32 pkts_acked = 0;
u32 reord = tp->packets_out;
u32 prior_sacked = tp->sacked_out;
s32 seq_rtt = -1;
s32 ca_seq_rtt = -1;
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);
sk_wmem_free_skb(sk, skb);
tcp_clear_retrans_hints_partial(tp);
tp->scoreboard_skb_hint = NULL;
if (skb == tp->retransmit_skb_hint)
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))
@ -2946,6 +2949,15 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
/* Non-retransmitted hole got filled? That's reordering */
if (reord < prior_fackets)
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);