diff options
| author | Neal Cardwell <ncardwell@google.com> | 2018-01-31 15:43:05 -0500 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-02-01 09:43:38 -0500 |
| commit | 3aff3b4b986e51bcf4ab249e5d48d39596e0df6a (patch) | |
| tree | 578224f45d5d80e61ccfd2fa008bc65145b16c8e | |
| parent | 2e85283dabc22f4715b136e8a7426bd9bef4ce69 (diff) | |
| download | linux-3aff3b4b986e51bcf4ab249e5d48d39596e0df6a.tar.bz2 | |
tcp_bbr: fix pacing_gain to always be unity when using lt_bw
This commit fixes the pacing_gain to remain at BBR_UNIT (1.0) when
using lt_bw and returning from the PROBE_RTT state to PROBE_BW.
Previously, when using lt_bw, upon exiting PROBE_RTT and entering
PROBE_BW the bbr_reset_probe_bw_mode() code could sometimes randomly
end up with a cycle_idx of 0 and hence have bbr_advance_cycle_phase()
set a pacing gain above 1.0. In such cases this would result in a
pacing rate that is 1.25x higher than intended, potentially resulting
in a high loss rate for a little while until we stop using the lt_bw a
bit later.
This commit is a stable candidate for kernels back as far as 4.9.
Fixes: 0f8782ea1497 ("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>
Reported-by: Beyers Cronje <bcronje@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | net/ipv4/tcp_bbr.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c index 785712be5b0d..a471f696e13c 100644 --- a/net/ipv4/tcp_bbr.c +++ b/net/ipv4/tcp_bbr.c @@ -481,7 +481,8 @@ static void bbr_advance_cycle_phase(struct sock *sk) bbr->cycle_idx = (bbr->cycle_idx + 1) & (CYCLE_LEN - 1); bbr->cycle_mstamp = tp->delivered_mstamp; - bbr->pacing_gain = bbr_pacing_gain[bbr->cycle_idx]; + bbr->pacing_gain = bbr->lt_use_bw ? BBR_UNIT : + bbr_pacing_gain[bbr->cycle_idx]; } /* Gain cycling: cycle pacing gain to converge to fair share of available bw. */ @@ -490,8 +491,7 @@ static void bbr_update_cycle_phase(struct sock *sk, { struct bbr *bbr = inet_csk_ca(sk); - if ((bbr->mode == BBR_PROBE_BW) && !bbr->lt_use_bw && - bbr_is_next_cycle_phase(sk, rs)) + if (bbr->mode == BBR_PROBE_BW && bbr_is_next_cycle_phase(sk, rs)) bbr_advance_cycle_phase(sk); } |