[PATCH v2] net: hisilicon: Fix ping latency when deal with high throughput

[PATCH v2] net: hisilicon: Fix ping latency when deal with high throughput

[Jiangfeng Xiao]

This is due to error in over budget processing.
When dealing with high throughput, the used buffers
that exceeds the budget is not cleaned up. In addition,
it takes a lot of cycles to clean up the used buffer,
and then the buffer where the valid data is located can take effect.

Signed-off-by: Jiangfeng Xiao <xiaojiangfeng@huawei.com>
---
ChangeLog v1->v2:
- Make rx_cnt_remaining part of struct hip04_priv.
---
 drivers/net/ethernet/hisilicon/hip04_eth.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hip04_eth.c b/drivers/net/ethernet/hisilicon/hip04_eth.c
index c841674..f51bc02 100644
--- a/drivers/net/ethernet/hisilicon/hip04_eth.c
+++ b/drivers/net/ethernet/hisilicon/hip04_eth.c
@@ -237,6 +237,7 @@ struct hip04_priv {
 	dma_addr_t rx_phys[RX_DESC_NUM];
 	unsigned int rx_head;
 	unsigned int rx_buf_size;
+	unsigned int rx_cnt_remaining;
 
 	struct device_node *phy_node;
 	struct phy_device *phy;
@@ -575,7 +576,6 @@ static int hip04_rx_poll(struct napi_struct *napi, int budget)
 	struct hip04_priv *priv = container_of(napi, struct hip04_priv, napi);
 	struct net_device *ndev = priv->ndev;
 	struct net_device_stats *stats = &ndev->stats;
-	unsigned int cnt = hip04_recv_cnt(priv);
 	struct rx_desc *desc;
 	struct sk_buff *skb;
 	unsigned char *buf;
@@ -588,8 +588,8 @@ static int hip04_rx_poll(struct napi_struct *napi, int budget)
 
 	/* clean up tx descriptors */
 	tx_remaining = hip04_tx_reclaim(ndev, false);
-
-	while (cnt && !last) {
+	priv->rx_cnt_remaining += hip04_recv_cnt(priv);
+	while (priv->rx_cnt_remaining && !last) {
 		buf = priv->rx_buf[priv->rx_head];
 		skb = build_skb(buf, priv->rx_buf_size);
 		if (unlikely(!skb)) {
@@ -635,11 +635,13 @@ static int hip04_rx_poll(struct napi_struct *napi, int budget)
 		hip04_set_recv_desc(priv, phys);
 
 		priv->rx_head = RX_NEXT(priv->rx_head);
-		if (rx >= budget)
+		if (rx >= budget) {
+			--priv->rx_cnt_remaining;
 			goto done;
+		}
 
-		if (--cnt == 0)
-			cnt = hip04_recv_cnt(priv);
+		if (--priv->rx_cnt_remaining == 0)
+			priv->rx_cnt_remaining += hip04_recv_cnt(priv);
 	}
 
 	if (!(priv->reg_inten & RCV_INT)) {
@@ -724,6 +726,7 @@ static int hip04_mac_open(struct net_device *ndev)
 	int i;
 
 	priv->rx_head = 0;
+	priv->rx_cnt_remaining = 0;
 	priv->tx_head = 0;
 	priv->tx_tail = 0;
 	hip04_reset_ppe(priv);
-- 
1.8.5.6

Re: [PATCH v2] net: hisilicon: Fix ping latency when deal with high throughput

[David Miller]

From: Jiangfeng Xiao <xiaojiangfeng@huawei.com>
Date: Mon, 28 Oct 2019 13:09:46 +0800

> This is due to error in over budget processing.
> When dealing with high throughput, the used buffers
> that exceeds the budget is not cleaned up. In addition,
> it takes a lot of cycles to clean up the used buffer,
> and then the buffer where the valid data is located can take effect.
> 
> Signed-off-by: Jiangfeng Xiao <xiaojiangfeng@huawei.com>

Applied and queued up for -stable, thanks.