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[TCP]: Minimum congestion window consolidation.

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Many of the TCP congestion methods all just use ssthresh
as the minimum congestion window on decrease.  Rather than
duplicating the code, just have that be the default if that
handle in the ops structure is not set.

Minor behaviour change to TCP compound.  It probably wants
to use this (ssthresh) as lower bound, rather than ssthresh/2
because the latter causes undershoot on loss.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Stephen Hemminger
2006-06-05 17:30:08 -07:00
committed by David S. Miller
parent a4ed258495
commit 72dc5b9225
9 changed files with 23 additions and 48 deletions
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13
net/ipv4/tcp_input.c
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@@ -1689,17 +1689,26 @@ static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
tp->snd_cwnd_stamp = tcp_time_stamp;
}
/* Lower bound on congestion window is slow start threshold
* unless congestion avoidance choice decides to overide it.
*/
static inline u32 tcp_cwnd_min(const struct sock *sk)
{
const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh;
}
/* Decrease cwnd each second ack. */
static void tcp_cwnd_down(struct sock *sk)
{
const struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
int decr = tp->snd_cwnd_cnt + 1;
tp->snd_cwnd_cnt = decr&1;
decr >>= 1;
if (decr && tp->snd_cwnd > icsk->icsk_ca_ops->min_cwnd(sk))
if (decr && tp->snd_cwnd > tcp_cwnd_min(sk))
tp->snd_cwnd -= decr;
tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);