netdev - [PATCH net-next 1/2] net: add netdev_sw_irq_coalesce_default

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Message-ID: <783fca17-450f-c69f-46dc-8ed7394be03d@gmail.com>
Date:   Wed, 30 Nov 2022 23:28:26 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>,
        David Miller <davem@...emloft.net>,
        Realtek linux nic maintainers <nic_swsd@...ltek.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: [PATCH net-next 1/2] 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@...nel.org>
Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
---
 include/linux/netdevice.h |  1 +
 net/core/dev.c            | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 02a2318da..5be4b6a3b 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -78,6 +78,7 @@ 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 */
diff --git a/net/core/dev.c b/net/core/dev.c
index 117e830ca..cc6bbc0a3 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10537,6 +10537,22 @@ 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;
-- 
2.38.1