From: Eric Dumazet edumazet@google.com
[ Upstream commit 85bdf7db5b53cdcc7a901db12bcb3d0063e3866d ]
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 Dupondjean-louis@dupond.be Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/tcp.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h index abcf53a6db045..3f4223a550d92 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1353,7 +1353,7 @@ 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)); }