This NIC doesn't have hardware IRQ coalescing. Under high load,
interrupts can adversely affect performance. To mitigate this, enable
software IRQ coalescing by default. On my system this increases receive
throughput with iperf3 from 853 MBit/sec to 934 MBit/s, decreases
interrupts from 69489/sec to 2016/sec, and decreases CPU utilization
from 27% (4x Cortex-A53) to 14%. Latency is not affected (as far as I
can tell).

Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
---

 drivers/net/ethernet/cadence/macb_main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 127bb3208034..8e1e4b2b2386 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -4184,6 +4184,8 @@ static int macb_init(struct platform_device *pdev)
 		dev->ethtool_ops = &macb_ethtool_ops;
 	}
 
+	netdev_sw_irq_coalesce_default_on(dev);
+
 	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
 
 	/* Set features */
-- 
2.35.1.1320.gc452695387.dirty

On Tue, Sep 03, 2024 at 02:49:12PM -0400, Sean Anderson wrote:
> This NIC doesn't have hardware IRQ coalescing. Under high load,
> interrupts can adversely affect performance. To mitigate this, enable
> software IRQ coalescing by default. On my system this increases receive
> throughput with iperf3 from 853 MBit/sec to 934 MBit/s, decreases
> interrupts from 69489/sec to 2016/sec, and decreases CPU utilization
> from 27% (4x Cortex-A53) to 14%. Latency is not affected (as far as I
> can tell).
> 
> Signed-off-by: Sean Anderson <sean.anderson@linux.dev>

Nice performance improvement :)

Reviewed-by: Simon Horman <horms@kernel.org>