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Commit 79135b89 authored by Neal Cardwell's avatar Neal Cardwell Committed by David S. Miller
Browse files

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: 0f8782ea ("tcp_bbr: add BBR congestion control")
Signed-off-by: default avatarNeal Cardwell <ncardwell@google.com>
Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
Signed-off-by: default avatarSoheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f19fd62d

net/ipv4/tcp_bbr.c

+18 −5
Original line number Diff line number Diff line
@@ -221,6 +221,23 @@ static u32 bbr_bw_to_pacing_rate(struct sock *sk, u32 bw, int gain) 
	return rate;

}



/* Initialize pacing rate to: high_gain * init_cwnd / RTT. */

static void bbr_init_pacing_rate_from_rtt(struct sock *sk)

{

	struct tcp_sock *tp = tcp_sk(sk);

	u64 bw;

	u32 rtt_us;



	if (tp->srtt_us) {		/* any RTT sample yet? */

		rtt_us = max(tp->srtt_us >> 3, 1U);

	} else {			 /* no RTT sample yet */

		rtt_us = USEC_PER_MSEC;	 /* use nominal default RTT */

	}

	bw = (u64)tp->snd_cwnd * BW_UNIT;

	do_div(bw, rtt_us);

	sk->sk_pacing_rate = bbr_bw_to_pacing_rate(sk, bw, bbr_high_gain);

}



/* Pace using current bw estimate and a gain factor. In order to help drive the

 * network toward lower queues while maintaining high utilization and low

 * latency, the average pacing rate aims to be slightly (~1%) lower than the
@@ -805,7 +822,6 @@ static void bbr_init(struct sock *sk) 
{

	struct tcp_sock *tp = tcp_sk(sk);

	struct bbr *bbr = inet_csk_ca(sk);

	u64 bw;



	bbr->prior_cwnd = 0;

	bbr->tso_segs_goal = 0;	 /* default segs per skb until first ACK */
@@ -821,11 +837,8 @@ static void bbr_init(struct sock *sk) 


	minmax_reset(&bbr->bw, bbr->rtt_cnt, 0);  /* init max bw to 0 */



	/* Initialize pacing rate to: high_gain * init_cwnd / RTT. */

	bw = (u64)tp->snd_cwnd * BW_UNIT;

	do_div(bw, (tp->srtt_us >> 3) ? : USEC_PER_MSEC);

	sk->sk_pacing_rate = 0;		/* force an update of sk_pacing_rate */

	bbr_set_pacing_rate(sk, bw, bbr_high_gain);

	bbr_init_pacing_rate_from_rtt(sk);



	bbr->restore_cwnd = 0;

	bbr->round_start = 0;