tcp_bbr: introduce bbr_init_pacing_rate_from_rtt() helper
Introduce a helper to initialize the BBR pacing rate unconditionally,
based on the current cwnd and RTT estimate. This is a pure refactor,
but is needed for two following fixes.
Fixes: 0f8782ea14
("tcp_bbr: add BBR congestion control")
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -221,6 +221,23 @@ static u32 bbr_bw_to_pacing_rate(struct sock *sk, u32 bw, int gain)
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return rate;
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}
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/* Initialize pacing rate to: high_gain * init_cwnd / RTT. */
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static void bbr_init_pacing_rate_from_rtt(struct sock *sk)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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u64 bw;
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u32 rtt_us;
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if (tp->srtt_us) { /* any RTT sample yet? */
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rtt_us = max(tp->srtt_us >> 3, 1U);
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} else { /* no RTT sample yet */
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rtt_us = USEC_PER_MSEC; /* use nominal default RTT */
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}
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bw = (u64)tp->snd_cwnd * BW_UNIT;
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do_div(bw, rtt_us);
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sk->sk_pacing_rate = bbr_bw_to_pacing_rate(sk, bw, bbr_high_gain);
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}
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/* Pace using current bw estimate and a gain factor. In order to help drive the
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* network toward lower queues while maintaining high utilization and low
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* latency, the average pacing rate aims to be slightly (~1%) lower than the
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@ -805,7 +822,6 @@ static void bbr_init(struct sock *sk)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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struct bbr *bbr = inet_csk_ca(sk);
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u64 bw;
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bbr->prior_cwnd = 0;
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bbr->tso_segs_goal = 0; /* default segs per skb until first ACK */
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@ -821,11 +837,8 @@ static void bbr_init(struct sock *sk)
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minmax_reset(&bbr->bw, bbr->rtt_cnt, 0); /* init max bw to 0 */
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/* Initialize pacing rate to: high_gain * init_cwnd / RTT. */
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bw = (u64)tp->snd_cwnd * BW_UNIT;
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do_div(bw, (tp->srtt_us >> 3) ? : USEC_PER_MSEC);
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sk->sk_pacing_rate = 0; /* force an update of sk_pacing_rate */
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bbr_set_pacing_rate(sk, bw, bbr_high_gain);
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bbr_init_pacing_rate_from_rtt(sk);
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bbr->restore_cwnd = 0;
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bbr->round_start = 0;
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