tcp: add tcp_in_slow_start helper

Add a helper to test the slow start condition in various congestion
control modules and other places. This is to prepare a slight improvement
in policy as to exactly when to slow start.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Nandita Dukkipati <nanditad@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 950cfec..dba22fc 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -989,6 +989,11 @@ static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
 
 #define TCP_INFINITE_SSTHRESH  0x7fffffff
 
+static inline bool tcp_in_slow_start(const struct tcp_sock *tp)
+{
+       return tp->snd_cwnd <= tp->snd_ssthresh;
+}
+
 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
 {
        return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
@@ -1065,7 +1070,7 @@ static inline bool tcp_is_cwnd_limited(const struct sock *sk)
        const struct tcp_sock *tp = tcp_sk(sk);
 
        /* If in slow start, ensure cwnd grows to twice what was ACKed. */
-       if (tp->snd_cwnd <= tp->snd_ssthresh)
+       if (tcp_in_slow_start(tp))
                return tp->snd_cwnd < 2 * tp->max_packets_out;
 
        return tp->is_cwnd_limited;

diff --git a/net/ipv4/tcp_bic.c b/net/ipv4/tcp_bic.c
index c037644..fd1405d 100644 (file)
--- a/net/ipv4/tcp_bic.c
+++ b/net/ipv4/tcp_bic.c
@@ -146,7 +146,7 @@ static void bictcp_cong_avoid(struct sock *sk, u32 ack, u32 acked)
        if (!tcp_is_cwnd_limited(sk))
                return;
 
-       if (tp->snd_cwnd <= tp->snd_ssthresh)
+       if (tcp_in_slow_start(tp))
                tcp_slow_start(tp, acked);
        else {
                bictcp_update(ca, tp->snd_cwnd);

diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 84be008..654729a 100644 (file)
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -413,7 +413,7 @@ void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
                return;
 
        /* In "safe" area, increase. */
-       if (tp->snd_cwnd <= tp->snd_ssthresh) {
+       if (tcp_in_slow_start(tp)) {
                acked = tcp_slow_start(tp, acked);
                if (!acked)
                        return;

diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 06d3d66..28011fb 100644 (file)
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -320,7 +320,7 @@ static void bictcp_cong_avoid(struct sock *sk, u32 ack, u32 acked)
        if (!tcp_is_cwnd_limited(sk))
                return;
 
-       if (tp->snd_cwnd <= tp->snd_ssthresh) {
+       if (tcp_in_slow_start(tp)) {
                if (hystart && after(ack, ca->end_seq))
                        bictcp_hystart_reset(sk);
                acked = tcp_slow_start(tp, acked);
@@ -439,7 +439,7 @@ static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt_us)
                ca->delay_min = delay;
 
        /* hystart triggers when cwnd is larger than some threshold */
-       if (hystart && tp->snd_cwnd <= tp->snd_ssthresh &&
+       if (hystart && tcp_in_slow_start(tp) &&
            tp->snd_cwnd >= hystart_low_window)
                hystart_update(sk, delay);
 }

diff --git a/net/ipv4/tcp_highspeed.c b/net/ipv4/tcp_highspeed.c
index 882c08a..db78424 100644 (file)
--- a/net/ipv4/tcp_highspeed.c
+++ b/net/ipv4/tcp_highspeed.c
@@ -116,7 +116,7 @@ static void hstcp_cong_avoid(struct sock *sk, u32 ack, u32 acked)
        if (!tcp_is_cwnd_limited(sk))
                return;
 
-       if (tp->snd_cwnd <= tp->snd_ssthresh)
+       if (tcp_in_slow_start(tp))
                tcp_slow_start(tp, acked);
        else {
                /* Update AIMD parameters.

diff --git a/net/ipv4/tcp_htcp.c b/net/ipv4/tcp_htcp.c
index 58469ff..82f0d9e 100644 (file)
--- a/net/ipv4/tcp_htcp.c
+++ b/net/ipv4/tcp_htcp.c
@@ -236,7 +236,7 @@ static void htcp_cong_avoid(struct sock *sk, u32 ack, u32 acked)
        if (!tcp_is_cwnd_limited(sk))
                return;
 
-       if (tp->snd_cwnd <= tp->snd_ssthresh)
+       if (tcp_in_slow_start(tp))
                tcp_slow_start(tp, acked);
        else {
                /* In dangerous area, increase slowly.

diff --git a/net/ipv4/tcp_illinois.c b/net/ipv4/tcp_illinois.c
index f71002e..2ab9bbb 100644 (file)
--- a/net/ipv4/tcp_illinois.c
+++ b/net/ipv4/tcp_illinois.c
@@ -268,7 +268,7 @@ static void tcp_illinois_cong_avoid(struct sock *sk, u32 ack, u32 acked)
                return;
 
        /* In slow start */
-       if (tp->snd_cwnd <= tp->snd_ssthresh)
+       if (tcp_in_slow_start(tp))
                tcp_slow_start(tp, acked);
 
        else {

diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index a51d63a..b3d64f6 100644 (file)
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -461,7 +461,7 @@ void tcp_update_metrics(struct sock *sk)
                                tcp_metric_set(tm, TCP_METRIC_CWND,
                                               tp->snd_cwnd);
                }
-       } else if (tp->snd_cwnd > tp->snd_ssthresh &&
+       } else if (!tcp_in_slow_start(tp) &&
                   icsk->icsk_ca_state == TCP_CA_Open) {
                /* Cong. avoidance phase, cwnd is reliable. */
                if (!tcp_metric_locked(tm, TCP_METRIC_SSTHRESH))

diff --git a/net/ipv4/tcp_scalable.c b/net/ipv4/tcp_scalable.c
index 333bcb2..bf5ea9e 100644 (file)
--- a/net/ipv4/tcp_scalable.c
+++ b/net/ipv4/tcp_scalable.c
@@ -22,7 +22,7 @@ static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
        if (!tcp_is_cwnd_limited(sk))
                return;
 
-       if (tp->snd_cwnd <= tp->snd_ssthresh)
+       if (tcp_in_slow_start(tp))
                tcp_slow_start(tp, acked);
        else
                tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),

diff --git a/net/ipv4/tcp_vegas.c b/net/ipv4/tcp_vegas.c
index a6cea1d..13951c4 100644 (file)
--- a/net/ipv4/tcp_vegas.c
+++ b/net/ipv4/tcp_vegas.c
@@ -225,7 +225,7 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 acked)
                         */
                        diff = tp->snd_cwnd * (rtt-vegas->baseRTT) / vegas->baseRTT;
 
-                       if (diff > gamma && tp->snd_cwnd <= tp->snd_ssthresh) {
+                       if (diff > gamma && tcp_in_slow_start(tp)) {
                                /* Going too fast. Time to slow down
                                 * and switch to congestion avoidance.
                                 */
@@ -240,7 +240,7 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 acked)
                                tp->snd_cwnd = min(tp->snd_cwnd, (u32)target_cwnd+1);
                                tp->snd_ssthresh = tcp_vegas_ssthresh(tp);
 
-                       } else if (tp->snd_cwnd <= tp->snd_ssthresh) {
+                       } else if (tcp_in_slow_start(tp)) {
                                /* Slow start.  */
                                tcp_slow_start(tp, acked);
                        } else {
@@ -281,7 +281,7 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 acked)
                vegas->minRTT = 0x7fffffff;
        }
        /* Use normal slow start */
-       else if (tp->snd_cwnd <= tp->snd_ssthresh)
+       else if (tcp_in_slow_start(tp))
                tcp_slow_start(tp, acked);
 }
 

diff --git a/net/ipv4/tcp_veno.c b/net/ipv4/tcp_veno.c
index 112151e..0d094b9 100644 (file)
--- a/net/ipv4/tcp_veno.c
+++ b/net/ipv4/tcp_veno.c
@@ -150,7 +150,7 @@ static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
 
                veno->diff = (tp->snd_cwnd << V_PARAM_SHIFT) - target_cwnd;
 
-               if (tp->snd_cwnd <= tp->snd_ssthresh) {
+               if (tcp_in_slow_start(tp)) {
                        /* Slow start.  */
                        tcp_slow_start(tp, acked);
                } else {