socket.7: Document SO_INCOMING_NAPI_ID

Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man7/socket.7 b/man7/socket.7
index 850d3162fbb97967c2f2576de3fd3d8edcce61cd..1f38273e9f261357ed92c39973635a51c2d1a93d 100644 (file)
--- a/man7/socket.7
+++ b/man7/socket.7
@@ -519,6 +519,18 @@ This provides optimal NUMA behavior and keeps CPU caches hot.
 .\" SO_REUSEPORT logic, selecting the socket to receive the packet, ignores
 .\" SO_INCOMING_CPU setting.
 .TP
+.BR SO_INCOMING_NAPI_ID " (gettable since Linux 4.12)"
+.\" getsockopt 6d4339028b350efbf87c61e6d9e113e5373545c9
+Returns a system level unique ID called NAPI ID that is associated with a RX
+queue on which the last packet associated with that socket is received.
+.IP
+This can be used by an application to split the incoming flows among worker
+threads based on the RX queue on which the packets associated with the flows
+are received. It allows each worker thread to be associated with a NIC HW
+receive queue and service all the connection requests received on that RX
+queue. This mapping between a app thread and a HW NIC queue streamlines the
+flow of data from the NIC to the application.
+.TP
 .B SO_KEEPALIVE
 Enable sending of keep-alive messages on connection-oriented sockets.
 Expects an integer boolean flag.