[PATCH 4.19 014/142] tcp: Do not underestimate rwnd_limited

Greg Kroah-Hartman
2018-12-14T12:44:20Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 41727549de3e7281feb174d568c6e46823db8684 ]

If available rwnd is too small, tcp_tso_should_defer()
can decide it is worth waiting before splitting a TSO packet.

This really means we are rwnd limited.

Fixes: 5615f88614a4 ("tcp: instrument how long TCP is limited by receive window")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/tcp_output.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2338,8 +2338,11 @@ static bool tcp_write_xmit(struct sock *
} else {
if (!push_one &&
tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
- max_segs))
+ max_segs)) {
+ if (!is_cwnd_limited)
+ is_rwnd_limited = true;
break;
+ }
}

limit = mss_now;