netdev - [RFC PATCH net-next v2 7/7] net: ravb: Use NAPI threaded mode on 1-core CPUs with GbEth IP

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Message-Id: <20240206091909.3191-8-paul.barker.ct@bp.renesas.com>
Date: Tue,  6 Feb 2024 09:19:09 +0000
From: Paul Barker <paul.barker.ct@...renesas.com>
To: Sergey Shtylyov <s.shtylyov@....ru>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Paul Barker <paul.barker.ct@...renesas.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	netdev@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH net-next v2 7/7] net: ravb: Use NAPI threaded mode on 1-core CPUs with GbEth IP

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 greatly increased by this change
(results obtained with iperf3) for all test cases except UDP TX:
  * 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@...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 7bb80608f260..522df82524ff 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -2984,8 +2984,11 @@ static int ravb_probe(struct platform_device *pdev)
 	if (info->nc_queues)
 		netif_napi_add(ndev, &priv->napi[RAVB_NC], ravb_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