From 5615f88614a47d2b802e1d14d31b623696109276 Mon Sep 17 00:00:00 2001 From: Francis Yan Date: Sun, 27 Nov 2016 23:07:15 -0800 Subject: [PATCH] tcp: instrument how long TCP is limited by receive window This patch measures the total time when the TCP stops sending because the receiver's advertised window is not large enough. Note that once the limit is lifted we are likely in the busy status if we have data pending. Signed-off-by: Francis Yan Signed-off-by: Yuchung Cheng Signed-off-by: Soheil Hassas Yeganeh Acked-by: Neal Cardwell Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index e8ea584106e0..b74444cee24d 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2144,7 +2144,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, unsigned int tso_segs, sent_pkts; int cwnd_quota; int result; - bool is_cwnd_limited = false; + bool is_cwnd_limited = false, is_rwnd_limited = false; u32 max_segs; sent_pkts = 0; @@ -2181,8 +2181,10 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, break; } - if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) + if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) { + is_rwnd_limited = true; break; + } if (tso_segs == 1) { if (unlikely(!tcp_nagle_test(tp, skb, mss_now, @@ -2227,6 +2229,11 @@ repair: break; } + if (is_rwnd_limited) + tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED); + else + tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED); + if (likely(sent_pkts)) { if (tcp_in_cwnd_reduction(sk)) tp->prr_out += sent_pkts; -- 2.20.1