diff options
| -rw-r--r-- | net/ipv4/tcp_cubic.c | 51 |
1 files changed, 28 insertions, 23 deletions
diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c index d02bb283c689..8f8eefd3a3ce 100644 --- a/net/ipv4/tcp_cubic.c +++ b/net/ipv4/tcp_cubic.c @@ -372,6 +372,26 @@ static void bictcp_state(struct sock *sk, u8 new_state) } } +/* Account for TSO/GRO delays. + * Otherwise short RTT flows could get too small ssthresh, since during + * slow start we begin with small TSO packets and ca->delay_min would + * not account for long aggregation delay when TSO packets get bigger. + * Ideally even with a very small RTT we would like to have at least one + * TSO packet being sent and received by GRO, and another one in qdisc layer. + * We apply another 100% factor because @rate is doubled at this point. + * We cap the cushion to 1ms. + */ +static u32 hystart_ack_delay(struct sock *sk) +{ + unsigned long rate; + + rate = READ_ONCE(sk->sk_pacing_rate); + if (!rate) + return 0; + return min_t(u64, USEC_PER_MSEC, + div64_ul((u64)GSO_MAX_SIZE * 4 * USEC_PER_SEC, rate)); +} + static void hystart_update(struct sock *sk, u32 delay) { struct tcp_sock *tp = tcp_sk(sk); @@ -385,7 +405,8 @@ static void hystart_update(struct sock *sk, u32 delay) if ((s32)(now - ca->last_ack) <= hystart_ack_delta_us) { ca->last_ack = now; - threshold = ca->delay_min; + threshold = ca->delay_min + hystart_ack_delay(sk); + /* Hystart ack train triggers if we get ack past * ca->delay_min/2. * Pacing might have delayed packets up to RTT/2 @@ -396,6 +417,9 @@ static void hystart_update(struct sock *sk, u32 delay) if ((s32)(now - ca->round_start) > threshold) { ca->found = 1; + pr_debug("hystart_ack_train (%u > %u) delay_min %u (+ ack_delay %u) cwnd %u\n", + now - ca->round_start, threshold, + ca->delay_min, hystart_ack_delay(sk), tp->snd_cwnd); NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHYSTARTTRAINDETECT); NET_ADD_STATS(sock_net(sk), @@ -447,30 +471,11 @@ static void bictcp_acked(struct sock *sk, const struct ack_sample *sample) delay = 1; /* first time call or link delay decreases */ - if (ca->delay_min == 0 || ca->delay_min > delay) { - unsigned long rate = READ_ONCE(sk->sk_pacing_rate); - - /* Account for TSO/GRO delays. - * Otherwise short RTT flows could get too small ssthresh, - * since during slow start we begin with small TSO packets - * and could lower ca->delay_min too much. - * Ideally even with a very small RTT we would like to have - * at least one TSO packet being sent and received by GRO, - * and another one in qdisc layer. - * We apply another 100% factor because @rate is doubled at - * this point. - * We cap the cushion to 1ms. - */ - if (rate) - delay += min_t(u64, USEC_PER_MSEC, - div64_ul((u64)GSO_MAX_SIZE * - 4 * USEC_PER_SEC, rate)); - if (ca->delay_min == 0 || ca->delay_min > delay) - ca->delay_min = delay; - } + if (ca->delay_min == 0 || ca->delay_min > delay) + ca->delay_min = delay; /* hystart triggers when cwnd is larger than some threshold */ - if (!ca->found && hystart && tcp_in_slow_start(tp) && + if (!ca->found && tcp_in_slow_start(tp) && hystart && tp->snd_cwnd >= hystart_low_window) hystart_update(sk, delay); } |