net: Add sendmmsg socket system call

This patch adds a multiple message send syscall and is the send
version of the existing recvmmsg syscall. This is heavily
based on the patch by Arnaldo that added recvmmsg.

I wrote a microbenchmark to test the performance gains of using
this new syscall:

http://ozlabs.org/~anton/junkcode/sendmmsg_test.c

The test was run on a ppc64 box with a 10 Gbit network card. The
benchmark can send both UDP and RAW ethernet packets.

64B UDP

batch   pkts/sec
1       804570
2       872800 (+ 8 %)
4       916556 (+14 %)
8       939712 (+17 %)
16      952688 (+18 %)
32      956448 (+19 %)
64      964800 (+20 %)

64B raw socket

batch   pkts/sec
1       1201449
2       1350028 (+12 %)
4       1461416 (+22 %)
8       1513080 (+26 %)
16      1541216 (+28 %)
32      1553440 (+29 %)
64      1557888 (+30 %)

We see a 20% improvement in throughput on UDP send and 30%
on raw socket send.

[ Add sparc syscall entries. -DaveM ]

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/net.h b/include/linux/net.h
index 94de83c0f877..1da55e9b6f01 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -42,6 +42,7 @@
 #define SYS_RECVMSG     17              /* sys_recvmsg(2)               */
 #define SYS_ACCEPT4     18              /* sys_accept4(2)               */
 #define SYS_RECVMMSG    19              /* sys_recvmmsg(2)              */
+#define SYS_SENDMMSG    20              /* sys_sendmmsg(2)              */
 
 typedef enum {
         SS_FREE = 0,                    /* not allocated                */