[PATCHv2 net-next] net: ucc_geth: Batch RX packets before stack handoff

[PATCHv2 net-next] net: ucc_geth: Batch RX packets before stack handoff

[Rosen Penev]

Collect received skbs on a local list during RX polling and pass the
completed batch to netif_receive_skb_list(). This lets the networking
stack process packets from a poll cycle in bulk instead of handing each
skb up individually.

Speedup tested with bidirectional iperf3 on a Watchguard Firebox T15-W.

Before:

[ ID][Role] Interval           Transfer     Bitrate         Retr
[  5][TX-C]   0.00-10.00  sec   490 MBytes   411 Mbits/sec                  sender
[  5][TX-C]   0.00-10.01  sec   488 MBytes   409 Mbits/sec                  receiver
[  7][RX-C]   0.00-10.00  sec   176 MBytes   147 Mbits/sec  167            sender
[  7][RX-C]   0.00-10.01  sec   175 MBytes   146 Mbits/sec                  receiver

After:

[ ID][Role] Interval           Transfer     Bitrate         Retr
[  5][TX-C]   0.00-10.00  sec   502 MBytes   421 Mbits/sec                  sender
[  5][TX-C]   0.00-10.01  sec   501 MBytes   420 Mbits/sec                  receiver
[  7][RX-C]   0.00-10.00  sec   212 MBytes   178 Mbits/sec  148            sender
[  7][RX-C]   0.00-10.01  sec   211 MBytes   177 Mbits/sec                  receiver

It would be nice to use napi_gro_receive, but the tradeoff is lower
routing performance. There is no support for hardware checksum offload,
which really hurts routing performance.

Assisted-by: Codex:GPT-5.5
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 v2: add extra info in description
 drivers/net/ethernet/freescale/ucc_geth.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/freescale/ucc_geth.c b/drivers/net/ethernet/freescale/ucc_geth.c
index 7af4b5e3f38e..bce1079fc06a 100644
--- a/drivers/net/ethernet/freescale/ucc_geth.c
+++ b/drivers/net/ethernet/freescale/ucc_geth.c
@@ -2894,6 +2894,7 @@ static int ucc_geth_rx(struct ucc_geth_private *ugeth, u8 rxQ, int rx_work_limit
 	u32 bd_status;
 	u8 *bdBuffer;
 	struct net_device *dev;
+	LIST_HEAD(rx_list);
 
 	ugeth_vdbg("%s: IN", __func__);
 
@@ -2934,7 +2935,7 @@ static int ucc_geth_rx(struct ucc_geth_private *ugeth, u8 rxQ, int rx_work_limit
 
 			dev->stats.rx_bytes += length;
 			/* Send the packet up the stack */
-			netif_receive_skb(skb);
+			list_add_tail(&skb->list, &rx_list);
 		}
 
 		skb = get_new_skb(ugeth, bd);
@@ -2960,6 +2961,8 @@ static int ucc_geth_rx(struct ucc_geth_private *ugeth, u8 rxQ, int rx_work_limit
 		bd_status = in_be32((u32 __iomem *)bd);
 	}
 
+	netif_receive_skb_list(&rx_list);
+
 	ugeth->rxBd[rxQ] = bd;
 	return howmany;
 }
-- 
2.54.0