summaryrefslogtreecommitdiffstats
path: root/net/ipv4/tcp_bbr.c
diff options
context:
space:
mode:
Diffstat (limited to 'net/ipv4/tcp_bbr.c')
-rw-r--r--net/ipv4/tcp_bbr.c49
1 files changed, 38 insertions, 11 deletions
diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c
index dbcc935..69ee877 100644
--- a/net/ipv4/tcp_bbr.c
+++ b/net/ipv4/tcp_bbr.c
@@ -112,7 +112,8 @@ struct bbr {
cwnd_gain:10, /* current gain for setting cwnd */
full_bw_cnt:3, /* number of rounds without large bw gains */
cycle_idx:3, /* current index in pacing_gain cycle array */
- unused_b:6;
+ has_seen_rtt:1, /* have we seen an RTT sample yet? */
+ unused_b:5;
u32 prior_cwnd; /* prior cwnd upon entering loss recovery */
u32 full_bw; /* recent bw, to estimate if pipe is full */
};
@@ -211,6 +212,35 @@ static u64 bbr_rate_bytes_per_sec(struct sock *sk, u64 rate, int gain)
return rate >> BW_SCALE;
}
+/* Convert a BBR bw and gain factor to a pacing rate in bytes per second. */
+static u32 bbr_bw_to_pacing_rate(struct sock *sk, u32 bw, int gain)
+{
+ u64 rate = bw;
+
+ rate = bbr_rate_bytes_per_sec(sk, rate, gain);
+ rate = min_t(u64, rate, sk->sk_max_pacing_rate);
+ 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);
+ struct bbr *bbr = inet_csk_ca(sk);
+ u64 bw;
+ u32 rtt_us;
+
+ if (tp->srtt_us) { /* any RTT sample yet? */
+ rtt_us = max(tp->srtt_us >> 3, 1U);
+ bbr->has_seen_rtt = 1;
+ } 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
@@ -220,12 +250,13 @@ static u64 bbr_rate_bytes_per_sec(struct sock *sk, u64 rate, int gain)
*/
static void bbr_set_pacing_rate(struct sock *sk, u32 bw, int gain)
{
+ struct tcp_sock *tp = tcp_sk(sk);
struct bbr *bbr = inet_csk_ca(sk);
- u64 rate = bw;
+ u32 rate = bbr_bw_to_pacing_rate(sk, bw, gain);
- rate = bbr_rate_bytes_per_sec(sk, rate, gain);
- rate = min_t(u64, rate, sk->sk_max_pacing_rate);
- if (bbr->mode != BBR_STARTUP || rate > sk->sk_pacing_rate)
+ if (unlikely(!bbr->has_seen_rtt && tp->srtt_us))
+ bbr_init_pacing_rate_from_rtt(sk);
+ if (bbr_full_bw_reached(sk) || rate > sk->sk_pacing_rate)
sk->sk_pacing_rate = rate;
}
@@ -798,7 +829,6 @@ 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 */
@@ -814,11 +844,8 @@ 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->has_seen_rtt = 0;
+ bbr_init_pacing_rate_from_rtt(sk);
bbr->restore_cwnd = 0;
bbr->round_start = 0;
OpenPOWER on IntegriCloud