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authorFrancis Yan <francisyyan@gmail.com>2016-11-27 23:07:15 -0800
committerDavid S. Miller <davem@davemloft.net>2016-11-30 10:04:24 -0500
commit5615f88614a47d2b802e1d14d31b623696109276 (patch)
tree3e323a3aeb157cddf60f22d3581763c816d16897
parent0f87230d1a6c253681550c6064715d06a32be73d (diff)
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>
-rw-r--r--net/ipv4/tcp_output.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e8ea584..b74444c 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;