netdev - [PATCH net-next] r8169: enable GRO software interrupt coalescing per default

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Date:   Sat, 26 Nov 2022 15:07:07 +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] r8169: enable GRO software interrupt coalescing per
 default

There are reports about r8169 not reaching full line speed on certain
systems (e.g. SBC's) with a 2.5Gbps link.
There was a time when hardware interrupt coalescing was enabled per
default, but this was changed due to ASPM-related issues on few systems.

Meanwhile we have sysfs attributes for controlling kind of
"software interrupt coalescing" on the GRO level. However most distros
and users don't know about it. So lets set a conservative default for
both involved parameters. Users can still override the defaults via
sysfs. Don't enable these settings on the fast ethernet chip versions,
they are slow enough.

Even with these conservative setting interrupt load on my 1Gbps test
system reduced significantly.

Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
---
 drivers/net/ethernet/realtek/r8169_main.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
index 5bc1181f8..1cb51ec71 100644
--- a/drivers/net/ethernet/realtek/r8169_main.c
+++ b/drivers/net/ethernet/realtek/r8169_main.c
@@ -5282,6 +5282,12 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	dev->hw_features |= NETIF_F_RXALL;
 	dev->hw_features |= NETIF_F_RXFCS;

+	if (tp->supports_gmii) {
+		/* enable software interrupt coalescing per default */
+		dev->gro_flush_timeout = 20000;
+		dev->napi_defer_hard_irqs = 1;
+	}
+
 	/* configure chip for default features */
 	rtl8169_set_features(dev, dev->features);

-- 
2.38.1