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[TCP]: add tcp_slow_start helper 

Move all the code that does linear TCP slowstart to one
inline function to ease later patch to add ABC support.

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 17:07:24 -08:00 committed by David S. Miller
parent 2d2abbab63
commit 7faffa1c7f
7 changed files with 43 additions and 59 deletions
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10
include/net/tcp.h
View File

@ -765,6 +765,16 @@ static inline __u32 tcp_current_ssthresh(const struct sock *sk)
(tp->snd_cwnd >> 2))); (tp->snd_cwnd >> 2)));
} }
/*
* Linear increase during slow start
*/
static inline void tcp_slow_start(struct tcp_sock *tp)
{
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
}
static inline void tcp_sync_left_out(struct tcp_sock *tp) static inline void tcp_sync_left_out(struct tcp_sock *tp)
{ {
if (tp->rx_opt.sack_ok && if (tp->rx_opt.sack_ok &&

10
net/ipv4/tcp_bic.c
View File

@ -220,14 +220,12 @@ static void bictcp_cong_avoid(struct sock *sk, u32 ack,
if (!tcp_is_cwnd_limited(sk, in_flight)) if (!tcp_is_cwnd_limited(sk, in_flight))
return; return;
if (tp->snd_cwnd <= tp->snd_ssthresh) { if (tp->snd_cwnd <= tp->snd_ssthresh)
/* In "safe" area, increase. */ tcp_slow_start(tp);
if (tp->snd_cwnd < tp->snd_cwnd_clamp) else {
tp->snd_cwnd++;
} else {
bictcp_update(ca, tp->snd_cwnd); bictcp_update(ca, tp->snd_cwnd);
/* In dangerous area, increase slowly. /* In dangerous area, increase slowly.
* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
*/ */
if (tp->snd_cwnd_cnt >= ca->cnt) { if (tp->snd_cwnd_cnt >= ca->cnt) {

11
net/ipv4/tcp_cong.c
View File

@ -189,12 +189,11 @@ void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 rtt, u32 in_flight,
if (!tcp_is_cwnd_limited(sk, in_flight)) if (!tcp_is_cwnd_limited(sk, in_flight))
return; return;
if (tp->snd_cwnd <= tp->snd_ssthresh) { /* In "safe" area, increase. */
/* In "safe" area, increase. */ if (tp->snd_cwnd <= tp->snd_ssthresh)
if (tp->snd_cwnd < tp->snd_cwnd_clamp) tcp_slow_start(tp);
tp->snd_cwnd++; else {
} else { /* In dangerous area, increase slowly.
/* In dangerous area, increase slowly.
* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
*/ */
if (tp->snd_cwnd_cnt >= tp->snd_cwnd) { if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {

7
net/ipv4/tcp_highspeed.c
View File

@ -119,10 +119,9 @@ static void hstcp_cong_avoid(struct sock *sk, u32 adk, u32 rtt,
if (!tcp_is_cwnd_limited(sk, in_flight)) if (!tcp_is_cwnd_limited(sk, in_flight))
return; return;
if (tp->snd_cwnd <= tp->snd_ssthresh) { if (tp->snd_cwnd <= tp->snd_ssthresh)
if (tp->snd_cwnd < tp->snd_cwnd_clamp) tcp_slow_start(tp);
tp->snd_cwnd++; else {
} else {
/* Update AIMD parameters */ /* Update AIMD parameters */
if (tp->snd_cwnd > hstcp_aimd_vals[ca->ai].cwnd) { if (tp->snd_cwnd > hstcp_aimd_vals[ca->ai].cwnd) {
while (tp->snd_cwnd > hstcp_aimd_vals[ca->ai].cwnd && while (tp->snd_cwnd > hstcp_aimd_vals[ca->ai].cwnd &&

11
net/ipv4/tcp_htcp.c
View File

@ -210,11 +210,10 @@ static void htcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
if (!tcp_is_cwnd_limited(sk, in_flight)) if (!tcp_is_cwnd_limited(sk, in_flight))
return; return;
if (tp->snd_cwnd <= tp->snd_ssthresh) { if (tp->snd_cwnd <= tp->snd_ssthresh)
/* In "safe" area, increase. */ tcp_slow_start(tp);
if (tp->snd_cwnd < tp->snd_cwnd_clamp) else {
tp->snd_cwnd++;
} else {
measure_rtt(sk); measure_rtt(sk);
/* keep track of number of round-trip times since last backoff event */ /* keep track of number of round-trip times since last backoff event */
@ -224,7 +223,7 @@ static void htcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
htcp_alpha_update(ca); htcp_alpha_update(ca);
} }
/* In dangerous area, increase slowly. /* In dangerous area, increase slowly.
* In theory this is tp->snd_cwnd += alpha / tp->snd_cwnd * In theory this is tp->snd_cwnd += alpha / tp->snd_cwnd
*/ */
if ((tp->snd_cwnd_cnt++ * ca->alpha)>>7 >= tp->snd_cwnd) { if ((tp->snd_cwnd_cnt++ * ca->alpha)>>7 >= tp->snd_cwnd) {

11
net/ipv4/tcp_scalable.c
View File

@ -24,17 +24,16 @@ static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
if (!tcp_is_cwnd_limited(sk, in_flight)) if (!tcp_is_cwnd_limited(sk, in_flight))
return; return;
if (tp->snd_cwnd <= tp->snd_ssthresh) { if (tp->snd_cwnd <= tp->snd_ssthresh)
tp->snd_cwnd++; tcp_slow_start(tp);
} else { else {
tp->snd_cwnd_cnt++; tp->snd_cwnd_cnt++;
if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){ if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){
tp->snd_cwnd++; if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
tp->snd_cwnd_cnt = 0; tp->snd_cwnd_cnt = 0;
} }
} }
tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
tp->snd_cwnd_stamp = tcp_time_stamp;
} }
static u32 tcp_scalable_ssthresh(struct sock *sk) static u32 tcp_scalable_ssthresh(struct sock *sk)

42
net/ipv4/tcp_vegas.c
View File

@ -236,8 +236,7 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack,
/* We don't have enough RTT samples to do the Vegas /* We don't have enough RTT samples to do the Vegas
* calculation, so we'll behave like Reno. * calculation, so we'll behave like Reno.
*/ */
if (tp->snd_cwnd > tp->snd_ssthresh) tcp_reno_cong_avoid(sk, ack, seq_rtt, in_flight, cnt);
tp->snd_cwnd++;
} else { } else {
u32 rtt, target_cwnd, diff; u32 rtt, target_cwnd, diff;
@ -275,7 +274,7 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack,
*/ */
diff = (old_wnd << V_PARAM_SHIFT) - target_cwnd; diff = (old_wnd << V_PARAM_SHIFT) - target_cwnd;
if (tp->snd_cwnd < tp->snd_ssthresh) { if (tp->snd_cwnd <= tp->snd_ssthresh) {
/* Slow start. */ /* Slow start. */
if (diff > gamma) { if (diff > gamma) {
/* Going too fast. Time to slow down /* Going too fast. Time to slow down
@ -295,6 +294,7 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack,
V_PARAM_SHIFT)+1); V_PARAM_SHIFT)+1);
} }
tcp_slow_start(tp);
} else { } else {
/* Congestion avoidance. */ /* Congestion avoidance. */
u32 next_snd_cwnd; u32 next_snd_cwnd;
@ -327,37 +327,17 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack,
else if (next_snd_cwnd < tp->snd_cwnd) else if (next_snd_cwnd < tp->snd_cwnd)
tp->snd_cwnd--; tp->snd_cwnd--;
} }
}
/* Wipe the slate clean for the next RTT. */ if (tp->snd_cwnd < 2)
vegas->cntRTT = 0; tp->snd_cwnd = 2;
vegas->minRTT = 0x7fffffff; else if (tp->snd_cwnd > tp->snd_cwnd_clamp)
tp->snd_cwnd = tp->snd_cwnd_clamp;
}
} }
/* The following code is executed for every ack we receive, /* Wipe the slate clean for the next RTT. */
* except for conditions checked in should_advance_cwnd() vegas->cntRTT = 0;
* before the call to tcp_cong_avoid(). Mainly this means that vegas->minRTT = 0x7fffffff;
* we only execute this code if the ack actually acked some
* data.
*/
/* If we are in slow start, increase our cwnd in response to this ACK.
* (If we are not in slow start then we are in congestion avoidance,
* and adjust our congestion window only once per RTT. See the code
* above.)
*/
if (tp->snd_cwnd <= tp->snd_ssthresh)
tp->snd_cwnd++;
/* to keep cwnd from growing without bound */
tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
/* Make sure that we are never so timid as to reduce our cwnd below
* 2 MSS.
*
* Going below 2 MSS would risk huge delayed ACKs from our receiver.
*/
tp->snd_cwnd = max(tp->snd_cwnd, 2U);
} }
/* Extract info for Tcp socket info provided via netlink. */ /* Extract info for Tcp socket info provided via netlink. */