From a0ea700e4095e26a8e291374757dd29519900f18 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 26 Feb 2015 14:10:20 -0800 Subject: [PATCH] tcp: tso: allow CA_CWR state in tcp_tso_should_defer() Another TCP issue is triggered by ECN. Under pressure, receiver gets ECN marks, and send back ACK packets with ECE TCP flag. Senders enter CA_CWR state. In this state, tcp_tso_should_defer() is short cut : if (icsk->icsk_ca_state != TCP_CA_Open) goto send_now; This means that about all ACK packets we receive are triggering a partial send, and because cwnd is kept small, we can only send a small amount of data for each incoming ACK, which in return generate more ACK packets. Allowing CA_Open and CA_CWR states to enable TSO defer in tcp_tso_should_defer() brings performance back : TSO autodefer has more chance to defer under pressure. This patch increases TSO and LRO/GRO efficiency back to normal levels, and does not impact overall ECN behavior. Signed-off-by: Eric Dumazet Signed-off-by: Yuchung Cheng Signed-off-by: Neal Cardwell Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 5f4fb4d5bbd69..8bbd86cd81c82 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1762,7 +1762,7 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb, if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) goto send_now; - if (icsk->icsk_ca_state != TCP_CA_Open) + if (!((1 << icsk->icsk_ca_state) & (TCPF_CA_Open | TCPF_CA_CWR))) goto send_now; /* Avoid bursty behavior by allowing defer -- 2.50.1