diff options
| author | Yuchung Cheng <ycheng@google.com> | 2022-05-18 17:34:10 -0700 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2022-05-19 18:49:50 -0700 |
| commit | 9ad084d666194c20a30e3589cbfaf971dae55c24 (patch) | |
| tree | 59657475684dfced6cdf223b3eddbdea038396dd /net/ipv4 | |
| parent | 7ebe52f555de21a1f239b963aa49972a6916a49a (diff) | |
| download | linux-9ad084d666194c20a30e3589cbfaf971dae55c24.tar.bz2 | |
tcp: improve PRR loss recovery
This patch improves TCP PRR loss recovery behavior for a corner
case. Previously during PRR conservation-bound mode, it strictly
sends the amount equals to the amount newly acked or s/acked.
The patch changes s.t. PRR may send additional amount that was banked
previously (e.g. application-limited) in the conservation-bound
mode, similar to the slow-start mode. This unifies and simplifies the
algorithm further and may improve the recovery latency. This change
still follow the general packet conservation design principle and
always keep inflight/cwnd below the slow start threshold set
by the congestion control module.
PRR is described in RFC 6937. We'll include this change in the
latest revision rfc6937-bis as well.
Reported-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20220519003410.2531936-1-ycheng@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/tcp_input.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 97cfcd85f84e..3231af73e430 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2620,12 +2620,12 @@ void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int newly_lost, u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered + tp->prior_cwnd - 1; sndcnt = div_u64(dividend, tp->prior_cwnd) - tp->prr_out; - } else if (flag & FLAG_SND_UNA_ADVANCED && !newly_lost) { - sndcnt = min_t(int, delta, - max_t(int, tp->prr_delivered - tp->prr_out, - newly_acked_sacked) + 1); } else { - sndcnt = min(delta, newly_acked_sacked); + sndcnt = max_t(int, tp->prr_delivered - tp->prr_out, + newly_acked_sacked); + if (flag & FLAG_SND_UNA_ADVANCED && !newly_lost) + sndcnt++; + sndcnt = min(delta, sndcnt); } /* Force a fast retransmit upon entering fast recovery */ sndcnt = max(sndcnt, (tp->prr_out ? 0 : 1)); |