From 96b792d199d17545d6a53faf44b9c91d038f1ab3 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 21 May 2018 15:08:57 -0700 Subject: [PATCH] tcp: do not aggressively quick ack after ECN events [ Upstream commit 522040ea5fdd1c33bbf75e1d7c7c0422b96a94ef ] ECN signals currently forces TCP to enter quickack mode for up to 16 (TCP_MAX_QUICKACKS) following incoming packets. We believe this is not needed, and only sending one immediate ack for the current packet should be enough. This should reduce the extra load noticed in DCTCP environments, after congestion events. This is part 2 of our effort to reduce pure ACK packets. Signed-off-by: Eric Dumazet Acked-by: Soheil Hassas Yeganeh Acked-by: Yuchung Cheng Acked-by: Neal Cardwell Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp_input.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 5f0ef0b7ef37..3dc61a64022b 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -237,7 +237,7 @@ static void __tcp_ecn_check_ce(struct tcp_sock *tp, const struct sk_buff *skb) * it is probably a retransmit. */ if (tp->ecn_flags & TCP_ECN_SEEN) - tcp_enter_quickack_mode((struct sock *)tp, TCP_MAX_QUICKACKS); + tcp_enter_quickack_mode((struct sock *)tp, 1); break; case INET_ECN_CE: if (tcp_ca_needs_ecn((struct sock *)tp)) @@ -245,7 +245,7 @@ static void __tcp_ecn_check_ce(struct tcp_sock *tp, const struct sk_buff *skb) if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) { /* Better not delay acks, sender can have a very low cwnd */ - tcp_enter_quickack_mode((struct sock *)tp, TCP_MAX_QUICKACKS); + tcp_enter_quickack_mode((struct sock *)tp, 1); tp->ecn_flags |= TCP_ECN_DEMAND_CWR; } tp->ecn_flags |= TCP_ECN_SEEN;