From 5415e3c37a657f7b400ece28e73a6f6c6cc371c4 Mon Sep 17 00:00:00 2001 From: Pengcheng Yang Date: Mon, 16 Mar 2020 14:35:08 +0800 Subject: tcp: fix stretch ACK bugs in Scalable Change Scalable to properly handle stretch ACKs in additive increase mode by passing in the count of ACKed packets to tcp_cong_avoid_ai(). In addition, because we are now precisely accounting for stretch ACKs, including delayed ACKs, we can now change TCP_SCALABLE_AI_CNT to 100. Signed-off-by: Pengcheng Yang Acked-by: Neal Cardwell Signed-off-by: David S. Miller --- net/ipv4/tcp_scalable.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/net/ipv4/tcp_scalable.c b/net/ipv4/tcp_scalable.c index 471571e1ab26..6cebf412d590 100644 --- a/net/ipv4/tcp_scalable.c +++ b/net/ipv4/tcp_scalable.c @@ -10,10 +10,9 @@ #include /* These factors derived from the recommended values in the aer: - * .01 and and 7/8. We use 50 instead of 100 to account for - * delayed ack. + * .01 and and 7/8. */ -#define TCP_SCALABLE_AI_CNT 50U +#define TCP_SCALABLE_AI_CNT 100U #define TCP_SCALABLE_MD_SCALE 3 static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked) @@ -23,11 +22,13 @@ static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked) if (!tcp_is_cwnd_limited(sk)) return; - if (tcp_in_slow_start(tp)) - tcp_slow_start(tp, acked); - else - tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT), - 1); + if (tcp_in_slow_start(tp)) { + acked = tcp_slow_start(tp, acked); + if (!acked) + return; + } + tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT), + acked); } static u32 tcp_scalable_ssthresh(struct sock *sk) -- cgit v1.2.3-59-g8ed1b