Add soreceive_stream(), an optimized version of soreceive() for

stream (TCP) sockets.

It is functionally identical to generic soreceive() but has a
number stream specific optimizations:
o does only one sockbuf unlock/lock per receive independent of
  the length of data to be moved into the uio compared to
  soreceive() which unlocks/locks per *mbuf*.
o uses m_mbuftouio() instead of its own copy(out) variant.
o much more compact code flow as a large number of special
  cases is removed.
o much improved reability.

It offers significantly reduced CPU usage and lock contention
when receiving fast TCP streams.  Additional gains are obtained
when the receiving application is using SO_RCVLOWAT to batch up
some data before a read (and wakeup) is done.

This function was written by "reverse engineering" and is not
just a stripped down variant of soreceive().

It is not yet enabled by default on TCP sockets.  Instead it is
commented out in the protocol initialization in tcp_usrreq.c
until more widespread testing has been done.

Testers, especially with 10GigE gear, are welcome.

MFP4:	r164817 //depot/user/andre/soreceive_stream/

1 files changed, 6 insertions, 0 deletions

diff --git a/sys/netinet/tcp_usrreq.c b/sys/netinet/tcp_usrreq.c
index 1005d51e3988..f9217b5e906a 100644
--- a/sys/netinet/tcp_usrreq.c
+++ b/sys/netinet/tcp_usrreq.c
@@ -1032,6 +1032,9 @@ struct pr_usrreqs tcp_usrreqs = {
 	.pru_send =		tcp_usr_send,
 	.pru_shutdown =		tcp_usr_shutdown,
 	.pru_sockaddr =		in_getsockaddr,
+#if 0
+	.pru_soreceive =	soreceive_stream,
+#endif
 	.pru_sosetlabel =	in_pcbsosetlabel,
 	.pru_close =		tcp_usr_close,
 };
@@ -1053,6 +1056,9 @@ struct pr_usrreqs tcp6_usrreqs = {
 	.pru_send =		tcp_usr_send,
 	.pru_shutdown =		tcp_usr_shutdown,
 	.pru_sockaddr =		in6_mapped_sockaddr,
+#if 0
+	.pru_soreceive =	soreceive_stream,
+#endif
  	.pru_sosetlabel =	in_pcbsosetlabel,
 	.pru_close =		tcp_usr_close,
 };