This is a note to let you know that I've just added the patch titled
tcp_bbr: introduce bbr_init_pacing_rate_from_rtt() helper
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tcp_bbr-introduce-bbr_init_pacing_rate_from_rtt-helper.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Tue Aug 8 16:27:53 PDT 2017
From: Neal Cardwell <ncardwell@xxxxxxxxxx>
Date: Fri, 14 Jul 2017 17:49:23 -0400
Subject: tcp_bbr: introduce bbr_init_pacing_rate_from_rtt() helper
From: Neal Cardwell <ncardwell@xxxxxxxxxx>
[ Upstream commit 79135b89b8af304456bd67916b80116ddf03d7b6 ]
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: 0f8782ea1497 ("tcp_bbr: add BBR congestion control")
Signed-off-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
Signed-off-by: Yuchung Cheng <ycheng@xxxxxxxxxx>
Signed-off-by: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ipv4/tcp_bbr.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)
--- a/net/ipv4/tcp_bbr.c
+++ b/net/ipv4/tcp_bbr.c
@@ -192,6 +192,23 @@ static u32 bbr_bw_to_pacing_rate(struct
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
@@ -776,7 +793,6 @@ 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 */
@@ -792,11 +808,8 @@ 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;
Patches currently in stable-queue which might be from ncardwell@xxxxxxxxxx are
queue-4.9/tcp_bbr-remove-sk_pacing_rate-0-transient-during-init.patch
queue-4.9/tcp_bbr-introduce-bbr_bw_to_pacing_rate-helper.patch
queue-4.9/tcp_bbr-introduce-bbr_init_pacing_rate_from_rtt-helper.patch
queue-4.9/tcp_bbr-init-pacing-rate-on-first-rtt-sample.patch
queue-4.9/tcp_bbr-cut-pacing-rate-only-if-filled-pipe.patch