net: add netdev_sw_irq_coalesce_default_on()

Bugzilla: https://bugzilla.redhat.com/2161921

commit d936070
Author: Heiner Kallweit <hkallweit1@gmail.com>
Date:   Wed Nov 30 23:28:26 2022 +0100

    net: add netdev_sw_irq_coalesce_default_on()

    Add a helper for drivers wanting to set SW IRQ coalescing
    by default. The related sysfs attributes can be used to
    override the default values.

    Follow Jakub's suggestion and put this functionality into
    net core so that drivers wanting to use software interrupt
    coalescing per default don't have to open-code it.

    Note that this function needs to be called before the
    netdevice is registered.

    Suggested-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Dan Campbell <dacampbe@redhat.com>

Author: Dan Campbell

include/linux/netdevice.h

@@ -77,6 +77,7 @@ struct xdp_buff;
 void synchronize_net(void);
 void netdev_set_default_ethtool_ops(struct net_device *dev,
 				    const struct ethtool_ops *ops);
+void netdev_sw_irq_coalesce_default_on(struct net_device *dev);
 
 /* Backlog congestion levels */
 #define NET_RX_SUCCESS		0	/* keep 'em coming, baby */

net/core/dev.c

@@ -10466,6 +10466,22 @@ void netdev_set_default_ethtool_ops(struct net_device *dev,
 }
 EXPORT_SYMBOL_GPL(netdev_set_default_ethtool_ops);
 
+/**
+ * netdev_sw_irq_coalesce_default_on() - enable SW IRQ coalescing by default
+ * @dev: netdev to enable the IRQ coalescing on
+ *
+ * Sets a conservative default for SW IRQ coalescing. Users can use
+ * sysfs attributes to override the default values.
+ */
+void netdev_sw_irq_coalesce_default_on(struct net_device *dev)
+{
+	WARN_ON(dev->reg_state == NETREG_REGISTERED);
+
+	dev->gro_flush_timeout = 20000;
+	dev->napi_defer_hard_irqs = 1;
+}
+EXPORT_SYMBOL_GPL(netdev_sw_irq_coalesce_default_on);
+
 void netdev_freemem(struct net_device *dev)
 {
 	char *addr = (char *)dev - dev->padded;