diff options
Diffstat (limited to 'net/ipv4/tcp_bbr.c')
| -rw-r--r-- | net/ipv4/tcp_bbr.c | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c index 56be7d27f208..32772d6ded4e 100644 --- a/net/ipv4/tcp_bbr.c +++ b/net/ipv4/tcp_bbr.c @@ -346,7 +346,7 @@ static void bbr_cwnd_event(struct sock *sk, enum tcp_ca_event event) /* Calculate bdp based on min RTT and the estimated bottleneck bandwidth: * - * bdp = bw * min_rtt * gain + * bdp = ceil(bw * min_rtt * gain) * * The key factor, gain, controls the amount of queue. While a small gain * builds a smaller queue, it becomes more vulnerable to noise in RTT @@ -370,7 +370,9 @@ static u32 bbr_bdp(struct sock *sk, u32 bw, int gain) w = (u64)bw * bbr->min_rtt_us; - /* Apply a gain to the given value, then remove the BW_SCALE shift. */ + /* Apply a gain to the given value, remove the BW_SCALE shift, and + * round the value up to avoid a negative feedback loop. + */ bdp = (((w * gain) >> BBR_SCALE) + BW_UNIT - 1) / BW_UNIT; return bdp; @@ -386,7 +388,7 @@ static u32 bbr_bdp(struct sock *sk, u32 bw, int gain) * which allows 2 outstanding 2-packet sequences, to try to keep pipe * full even with ACK-every-other-packet delayed ACKs. */ -static u32 bbr_quantization_budget(struct sock *sk, u32 cwnd, int gain) +static u32 bbr_quantization_budget(struct sock *sk, u32 cwnd) { struct bbr *bbr = inet_csk_ca(sk); @@ -397,7 +399,7 @@ static u32 bbr_quantization_budget(struct sock *sk, u32 cwnd, int gain) cwnd = (cwnd + 1) & ~1U; /* Ensure gain cycling gets inflight above BDP even for small BDPs. */ - if (bbr->mode == BBR_PROBE_BW && gain > BBR_UNIT) + if (bbr->mode == BBR_PROBE_BW && bbr->cycle_idx == 0) cwnd += 2; return cwnd; @@ -409,7 +411,7 @@ static u32 bbr_inflight(struct sock *sk, u32 bw, int gain) u32 inflight; inflight = bbr_bdp(sk, bw, gain); - inflight = bbr_quantization_budget(sk, inflight, gain); + inflight = bbr_quantization_budget(sk, inflight); return inflight; } @@ -529,7 +531,7 @@ static void bbr_set_cwnd(struct sock *sk, const struct rate_sample *rs, * due to aggregation (of data and/or ACKs) visible in the ACK stream. */ target_cwnd += bbr_ack_aggregation_cwnd(sk); - target_cwnd = bbr_quantization_budget(sk, target_cwnd, gain); + target_cwnd = bbr_quantization_budget(sk, target_cwnd); /* If we're below target cwnd, slow start cwnd toward target cwnd. */ if (bbr_full_bw_reached(sk)) /* only cut cwnd if we filled the pipe */ |