Explain --net=host option usage

Fixes docker#11630

Signed-off-by: Ankush Agarwal <[email protected]>

docs/sources/reference/run.md

@@ -279,6 +279,13 @@ container.  The container's hostname will match the hostname on the host
 system.  Publishing ports and linking to other containers will not work
 when sharing the host's network stack.
 
+Compared to the default `bridge` mode, the `host` mode gives *significantly*
+better networking performance since it uses the host's native networking stack
+wheras the bridge has to go through one level of virtualizaion through the
+docker daemon. It is recommended to run containers in this mode when their
+networking performance is critical, for example, a production Load Balancer
+or a High Performance Web Server.
+
 > **Note**: `--net="host"` gives the container full access to local system
 > services such as D-bus and is therefore considered insecure.