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).
This patch gives the following improvements during testing with iperf3.
* RZ/G2UL:
* TCP TX: +32% bandwidth (638Mbps -> 841Mbps)
* TXP RX: +8.8% bandwidth (667Mbps -> 726Mbps)
* UDP RX: +104% bandwidth (53Mbps -> 108Mbps)
* RZ/G3S:
* TCP TX: 29% bandwidth (529Mbps -> 681Mbps)
* UDP RX: +1290% bandwidth (6.46Mbps -> 90Mbps)
* RZ/Five:
* UDP RX: Test no longer crashes (0 -> 20 Mbps)
This patch gives the following reductions in performance in the same
testing:
* RZ/G2UL:
* UDP TX: -7.5% bandwidth (594Mbps -> 549Mbps)
* RZ/G3S:
* UDP TX: -5% bandwidth (625Mbps -> 594Mbps)
These losses are considered acceptable given the benefits shown above.
If UDP TX bandwidth must be maximised for a particular use case, NAPI
threaded mode can be disabled at runtime via sysfs writes.
The improvement of UDP RX bandwidth for the single core SoCs (RZ/G2UL &
RZ/G3S) is particularly critical.
Signed-off-by: Paul Barker <paul.barker.ct@xxxxxxxxxxxxxx>
Reviewed-by: Sergey Shtylyov <s.shtylyov@xxxxxx>
---
Changes v3->v4:
* Added Sergey's Reviewed-by tag.
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 e95e0b6e1fe6..dd92f074881a 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -2944,8 +2944,11 @@ static int ravb_probe(struct platform_device *pdev)
if (info->nc_queues)
netif_napi_add(ndev, &priv->napi[RAVB_NC], ravb_poll);
- if (info->coalesce_irqs)
+ if (info->coalesce_irqs) {
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
