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tcp_bbr: introduce bbr_init_pacing_rate_from_rtt() helper

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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>
This commit is contained in:
Neal Cardwell 2017-07-14 17:49:23 -04:00 committed by David S. Miller
parent f19fd62daf
commit 79135b89b8
1 changed files with 18 additions and 5 deletions
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23
net/ipv4/tcp_bbr.c
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@ -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;