net: cadence: macb: Enable software IRQ coalescing by default

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>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20240903184912.4151926-1-sean.anderson@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 127bb32080340e0722f50c2d3d0ed39022633f21..8e1e4b2b23869291b3fbbc38ba4a57f92c78aed2 100644 (file)
--- 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 */