Commit 85bdf7db authored Nov 27, 2018 by Eric Dumazet Committed by David S. Miller Nov 30, 2018

tcp: make tcp_space() aware of socket backlog



Jean-Louis Dupond reported poor iscsi TCP receive performance
that we tracked to backlog drops.

Apparently we fail to send window updates reflecting the
fact that we are under stress.

Note that we might lack a proper window increase when
backlog is fully processed, since __release_sock() clears
sk->sk_backlog.len _after_ all skbs have been processed.

This should not matter in practice. If we had a significant
load through socket backlog, we are in a dangerous
situation.

Reported-by: Jean-Louis Dupond <jean-louis@dupond.be>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Tested-by: Jean-Louis <Dupond&lt;jean-louis@dupond.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 19119f29

include/net/tcp.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -1368,7 +1368,7 @@ static inline int tcp_win_from_space(const struct sock *sk, int space)
		/* Note: caller must be prepared to deal with negative returns */
		static inline int tcp_space(const struct sock *sk)
		{
		return tcp_win_from_space(sk, sk->sk_rcvbuf -
		return tcp_win_from_space(sk, sk->sk_rcvbuf - sk->sk_backlog.len -
		atomic_read(&sk->sk_rmem_alloc));
		}

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