[PATCH] tcp: splice as many packets as possible at once

[Willy Tarreau]

Currently, in non-blocking mode, tcp_splice_read() returns after
splicing one segment regardless of the len argument. This results
in low performance and very high overhead due to syscall rate when
splicing from interfaces which do not support LRO.

The fix simply consists in not breaking out of the loop after the
first read. That way, we can read up to the size requested by the
caller and still return when there is no data left.

Performance has significantly improved with this fix, with the
number of calls to splice() divided by about 20, and CPU usage
dropped from 100% to 75%.

Signed-off-by: Willy Tarreau <w@xxxxxx>
---
 net/ipv4/tcp.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 35bcddf..80261b4 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -615,7 +615,7 @@ ssize_t tcp_splice_read(struct socket *sock, loff_t *ppos,
 		lock_sock(sk);
 
 		if (sk->sk_err || sk->sk_state == TCP_CLOSE ||
-		    (sk->sk_shutdown & RCV_SHUTDOWN) || !timeo ||
+		    (sk->sk_shutdown & RCV_SHUTDOWN) ||
 		    signal_pending(current))
 			break;
 	}
-- 
1.6.0.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/