[PATCH net] Documentation: add description for net.core.gro_normal_batch

[Xin Long <lucien.xin@gmail.com>]

Describe it in admin-guide/sysctl/net.rst like other Network core options.
Users need to know gro_normal_batch for performance tuning.

Fixes: 323ebb61e32b ("net: use listified RX for handling GRO_NORMAL skbs")
Reported-by: Prijesh <prpatel@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 Documentation/admin-guide/sysctl/net.rst | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst
index f86b5e1623c6..d8a8506f31ad 100644
--- a/Documentation/admin-guide/sysctl/net.rst
+++ b/Documentation/admin-guide/sysctl/net.rst
@@ -374,6 +374,16 @@ option is set to SOCK_TXREHASH_DEFAULT (i. e. not overridden by setsockopt).
 If set to 1 (default), hash rethink is performed on listening socket.
 If set to 0, hash rethink is not performed.
 
+gro_normal_batch
+----------------
+
+Maximum number of GRO_NORMAL skbs to batch up for list-RX. When GRO decides
+not to coalesce a packet, instead of passing it to the stack immediately,
+place it on a list. Pass this list to the stack at flush time or whenever
+the number of skbs in this list exceeds gro_normal_batch.
+
+Default : 8
+
 2. /proc/sys/net/unix - Parameters for Unix domain sockets
 ----------------------------------------------------------
 
-- 
2.31.1