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[TCP]: Appropriate Byte Count support

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This is an updated version of the RFC3465 ABC patch originally
for Linux 2.6.11-rc4 by Yee-Ting Li. ABC is a way of counting
bytes ack'd rather than packets when updating congestion control.

The orignal ABC described in the RFC applied to a Reno style
algorithm. For advanced congestion control there is little
change after leaving slow start.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Stephen Hemminger
2005-11-10 17:09:53 -08:00
committed by David S. Miller
parent 7faffa1c7f
commit 9772efb970
9 changed files with 63 additions and 11 deletions
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19
include/net/tcp.h
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@@ -218,6 +218,7 @@ extern int sysctl_tcp_low_latency;
extern int sysctl_tcp_nometrics_save;
extern int sysctl_tcp_moderate_rcvbuf;
extern int sysctl_tcp_tso_win_divisor;
extern int sysctl_tcp_abc;
extern atomic_t tcp_memory_allocated;
extern atomic_t tcp_sockets_allocated;
@@ -770,6 +771,23 @@ static inline __u32 tcp_current_ssthresh(const struct sock *sk)
*/
static inline void tcp_slow_start(struct tcp_sock *tp)
{
if (sysctl_tcp_abc) {
/* RFC3465: Slow Start
* TCP sender SHOULD increase cwnd by the number of
* previously unacknowledged bytes ACKed by each incoming
* acknowledgment, provided the increase is not more than L
*/
if (tp->bytes_acked < tp->mss_cache)
return;
/* We MAY increase by 2 if discovered delayed ack */
if (sysctl_tcp_abc > 1 && tp->bytes_acked > 2*tp->mss_cache) {
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
}
}
tp->bytes_acked = 0;
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
}
@@ -804,6 +822,7 @@ static inline void tcp_enter_cwr(struct sock *sk)
struct tcp_sock *tp = tcp_sk(sk);
tp->prior_ssthresh = 0;
tp->bytes_acked = 0;
if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
__tcp_enter_cwr(sk);
tcp_set_ca_state(sk, TCP_CA_CWR);