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From: Paul Barker <paul.barker.ct@bp.renesas.com>
To: Sergey Shtylyov <s.shtylyov@omp.ru>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>
Cc: Paul Barker <paul.barker.ct@bp.renesas.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
	Wolfram Sang <wsa+renesas@sang-engineering.com>,
	netdev@vger.kernel.org,
	linux-renesas-soc@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH net-next 8/8] net: ravb: Use NAPI threaded mode on 1-core CPUs with GbEth IP
Date: Wed, 31 Jan 2024 17:05:22 +0000
Message-Id: <20240131170523.30048-9-paul.barker.ct@bp.renesas.com>
In-Reply-To: <20240131170523.30048-1-paul.barker.ct@bp.renesas.com>
References: <20240131170523.30048-1-paul.barker.ct@bp.renesas.com>
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NAPI Threaded mode (along with the previously enabled SW IRQ Coalescing)
is required to improve network stack performance for single core SoCs
using the GbEth IP (currently the RZ/G2L SoC family and the RZ/G3S SoC).

For the RZ/G2UL, network throughput is increased by this change for all
test cases except UDP TX (results obtained with iperf3):
  * TCP TX: 30% more throughput
  * TCP RX: 9.8% more throughput
  * UDP TX: 9.7% less throughput
  * UDP RX: 89% more throughput

For the RZ/G3S we see improvements in network throughput similar to the
RZ/G2UL.

The improvement of UDP RX bandwidth for the single core SoCs (RZ/G2UL &
RZ/G3S) is particularly critical. NAPI Threaded mode can be disabled at
runtime via sysfs for applications where UDP TX performance is a
priority.

Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
---
 drivers/net/ethernet/renesas/ravb_main.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 483993ec25ba..202a3229d436 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -3029,8 +3029,11 @@ static int ravb_probe(struct platform_device *pdev)
 	if (info->nc_queues)
 		netif_napi_add(ndev, &priv->napi[RAVB_NC], info->poll);
 
-	if (info->needs_irq_coalesce)
+	if (info->needs_irq_coalesce) {
 		netdev_sw_irq_coalesce_default_on(ndev);
+		if (num_present_cpus() == 1)
+			dev_set_threaded(ndev, true);
+	}
 
 	/* Network device register */
 	error = register_netdev(ndev);
-- 
2.39.2