aboutsummaryrefslogtreecommitdiffstats
path: root/net/ipv4
diff options
context:
space:
mode:
authorYuchung Cheng <ycheng@google.com>2022-05-18 17:34:10 -0700
committerJakub Kicinski <kuba@kernel.org>2022-05-19 18:49:50 -0700
commit9ad084d666194c20a30e3589cbfaf971dae55c24 (patch)
tree59657475684dfced6cdf223b3eddbdea038396dd /net/ipv4
parentdocs: change the title of networking docs (diff)
downloadlinux-dev-9ad084d666194c20a30e3589cbfaf971dae55c24.tar.xz
linux-dev-9ad084d666194c20a30e3589cbfaf971dae55c24.zip
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.c10
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));