socket.7: Enhance the description of SO_INCOMING_CPU

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man7/socket.7 b/man7/socket.7
index 15bff45b1ac6693766266ad25ed2afe73593d3cd..81e15b663babba0e8b3d868d8bcb1c9d2cb2defc 100644 (file)
--- a/man7/socket.7
+++ b/man7/socket.7
@@ -504,8 +504,12 @@ setsockopt(fd, SOL_SOCKET, SO_INCOMING_CPU, &cpu, &len);
 .fi
 .in
 
-The typical use case is one listener per RX queue, as the associated listener
-should accept only flows handled in softirq by the same CPU.
+Because all of the packets for a single stream
+(i.e., all packets for the same 4-tuple)
+arrive on the single RX queue that is associated with a particular CPU,
+the typical use case is to employ one listening process per RX queue,
+with the incoming flow being handled by a listener
+on the same CPU that is handling the RX queue.
 This provides optimal NUMA behavior and keeps CPU caches hot.
 .TP
 .B SO_KEEPALIVE