diff mbox

[net-next,v2,3/6] tcp: instrument how long TCP is limited by receive window

Message ID 1480316838-154141-4-git-send-email-ycheng@google.com
State Accepted, archived
Delegated to: David Miller
Headers show

Commit Message

Yuchung Cheng Nov. 28, 2016, 7:07 a.m. UTC 
From: Francis Yan <francisyyan@gmail.com>

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>
---
 net/ipv4/tcp_output.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

Comments

Neal Cardwell Nov. 28, 2016, 5:25 p.m. UTC | #1 
On Mon, Nov 28, 2016 at 2:07 AM, Yuchung Cheng <ycheng@google.com> wrote:
> From: Francis Yan <francisyyan@gmail.com>
>
> 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>

neal
diff mbox

Patch

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 @@  static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 			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;