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 <francisyyan@gmail.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -2144,7 +2144,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
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unsigned int tso_segs, sent_pkts;
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int cwnd_quota;
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int result;
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bool is_cwnd_limited = false;
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bool is_cwnd_limited = false, is_rwnd_limited = false;
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u32 max_segs;
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sent_pkts = 0;
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@ -2181,8 +2181,10 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
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break;
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}
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if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
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if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
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is_rwnd_limited = true;
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break;
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}
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if (tso_segs == 1) {
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if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
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@ -2227,6 +2229,11 @@ repair:
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break;
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}
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if (is_rwnd_limited)
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tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
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else
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tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);
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if (likely(sent_pkts)) {
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if (tcp_in_cwnd_reduction(sk))
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tp->prr_out += sent_pkts;
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