[PATCH net v2] r8152: avoid the driver drops a lot of packets

[Hayes Wang <hayeswang@realtek.com>]

Stop submitting rx, if the driver queue more than 256 packets.

If the hardware is more fast than the software, the driver would start
queuing the packets. And, the driver starts dropping the packets, if it
queues more than 1000 packets.

Increase the weight of NAPI could improve the situation. However, the
weight has been changed to 64, so we have to stop submitting rx when the
driver queues too many packets. Then, the device may send the pause frame
to slow down the receiving, when the FIFO of the device is full.

Fixes: cf74eb5a5bc8 ("eth: r8152: try to use a normal budget")
Signed-off-by: Hayes Wang <hayeswang@realtek.com>
---
v2:
Add WARN_ON_ONCE() and debug message for the skb_queue_len(&tp->rx_queue).

 drivers/net/usb/r8152.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 332c853ca99b..4a62e420a7be 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -2484,10 +2484,6 @@ static int rx_bottom(struct r8152 *tp, int budget)
 			unsigned int pkt_len, rx_frag_head_sz;
 			struct sk_buff *skb;
 
-			/* limit the skb numbers for rx_queue */
-			if (unlikely(skb_queue_len(&tp->rx_queue) >= 1000))
-				break;
-
 			pkt_len = le32_to_cpu(rx_desc->opts1) & RX_LEN_MASK;
 			if (pkt_len < ETH_ZLEN)
 				break;
@@ -2556,9 +2552,14 @@ static int rx_bottom(struct r8152 *tp, int budget)
 		}
 
 submit:
-		if (!ret) {
+		if (!ret && likely(skb_queue_len(&tp->rx_queue) < 256)) {
 			ret = r8152_submit_rx(tp, agg, GFP_ATOMIC);
 		} else {
+			WARN_ON_ONCE(skb_queue_len(&tp->rx_queue) >= 1000);
+			if (net_ratelimit())
+				netif_dbg(tp, rx_err, tp->netdev,
+					  "submit_rx=%d, rx_queue=%u\n",
+					  ret, skb_queue_len(&tp->rx_queue));
 			urb->actual_length = 0;
 			list_add_tail(&agg->list, next);
 		}
-- 
2.41.0