[openwrt/openwrt] bcm53xx: disable GRO by default at kernel level

[LEDE Commits]

rmilecki pushed a commit to openwrt/openwrt.git, branch openwrt-21.02:
https://git.openwrt.org/c032ed3c267cae38be43991ce310883502c67f4b

commit c032ed3c267cae38be43991ce310883502c67f4b
Author: Rafał Miłecki <rafal at milecki.pl>
AuthorDate: Mon Jun 20 10:21:20 2022 +0200

    bcm53xx: disable GRO by default at kernel level
    
    This improves NAT masquarade network performance.
    
    An alternative to kernel change would be runtime setup but that requires
    ethtool and identifying relevant network interface and all related
    switch ports interfaces.
    
    Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
    (cherry picked from commit 82d0dd8f8aa11249944fe39cd0d75a1524ec22ec)
---
 .../600-net-disable-GRO-by-default.patch           | 32 ++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/target/linux/bcm53xx/patches-5.4/600-net-disable-GRO-by-default.patch b/target/linux/bcm53xx/patches-5.4/600-net-disable-GRO-by-default.patch
new file mode 100644
index 0000000000..a11054e718
--- /dev/null
+++ b/target/linux/bcm53xx/patches-5.4/600-net-disable-GRO-by-default.patch
@@ -0,0 +1,32 @@
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal at milecki.pl>
+Date: Mon, 20 Jun 2022 10:01:18 +0200
+Subject: [PATCH] net: disable GRO by default
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+In many cases GRO improves network performance however it comes at a
+cost of chacksums calculations. In case of slow CPU and missing hardware
+csum calculation support GRO can actually decrease network speed.
+
+On BCM4708 *disabling* GRO results in following NAT masquarade speed
+changes:
+1. 364 Mb/s → 396 Mb/s (packet steering disabled)
+2. 341 Mb/s → 566 Mb/s (packet steering enabled)
+
+Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
+---
+ include/linux/netdev_features.h | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+--- a/include/linux/netdev_features.h
++++ b/include/linux/netdev_features.h
+@@ -224,7 +224,7 @@ static inline int find_next_netdev_featu
+ #define NETIF_F_UPPER_DISABLES	NETIF_F_LRO
+ 
+ /* changeable features with no special hardware requirements */
+-#define NETIF_F_SOFT_FEATURES	(NETIF_F_GSO | NETIF_F_GRO)
++#define NETIF_F_SOFT_FEATURES	(NETIF_F_GSO)
+ 
+ #define NETIF_F_VLAN_FEATURES	(NETIF_F_HW_VLAN_CTAG_FILTER | \
+ 				 NETIF_F_HW_VLAN_CTAG_RX | \