tcp_cubic: optimize hystart_update()

We do not care which bit in ca->found is set.

We avoid accessing hystart and hystart_detect unless really needed,
possibly avoiding one cache line miss.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 1b3d032..2979360 100644 (file)
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -381,9 +381,6 @@ static void hystart_update(struct sock *sk, u32 delay)
        struct tcp_sock *tp = tcp_sk(sk);
        struct bictcp *ca = inet_csk_ca(sk);
 
-       if (ca->found & hystart_detect)
-               return;
-
        if (hystart_detect & HYSTART_ACK_TRAIN) {
                u32 now = bictcp_clock();
 
@@ -391,7 +388,7 @@ static void hystart_update(struct sock *sk, u32 delay)
                if ((s32)(now - ca->last_ack) <= hystart_ack_delta) {
                        ca->last_ack = now;
                        if ((s32)(now - ca->round_start) > ca->delay_min >> 4) {
-                               ca->found |= HYSTART_ACK_TRAIN;
+                               ca->found = 1;
                                NET_INC_STATS(sock_net(sk),
                                              LINUX_MIB_TCPHYSTARTTRAINDETECT);
                                NET_ADD_STATS(sock_net(sk),
@@ -412,7 +409,7 @@ static void hystart_update(struct sock *sk, u32 delay)
                } else {
                        if (ca->curr_rtt > ca->delay_min +
                            HYSTART_DELAY_THRESH(ca->delay_min >> 3)) {
-                               ca->found |= HYSTART_DELAY;
+                               ca->found = 1;
                                NET_INC_STATS(sock_net(sk),
                                              LINUX_MIB_TCPHYSTARTDELAYDETECT);
                                NET_ADD_STATS(sock_net(sk),
@@ -450,7 +447,7 @@ static void bictcp_acked(struct sock *sk, const struct ack_sample *sample)
                ca->delay_min = delay;
 
        /* hystart triggers when cwnd is larger than some threshold */
-       if (hystart && tcp_in_slow_start(tp) &&
+       if (!ca->found && hystart && tcp_in_slow_start(tp) &&
            tp->snd_cwnd >= hystart_low_window)
                hystart_update(sk, delay);
 }