linux-kernel - [PATCH] net: hisilicon: Fix ping latency when deal with high throughput

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Date:   Sat, 26 Oct 2019 16:49:39 +0800
From:   Jiangfeng Xiao <xiaojiangfeng@...wei.com>
To:     <davem@...emloft.net>, <yisen.zhuang@...wei.com>,
        <salil.mehta@...wei.com>, <xiaojiangfeng@...wei.com>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <leeyou.li@...wei.com>, <zhanghan23@...wei.com>,
        <nixiaoming@...wei.com>, <zhangqiang.cn@...ilicon.com>,
        <dingjingcheng@...ilicon.com>
Subject: [PATCH] net: hisilicon: Fix ping latency when deal with high throughput

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@...wei.com>
---
 drivers/net/ethernet/hisilicon/hip04_eth.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hip04_eth.c b/drivers/net/ethernet/hisilicon/hip04_eth.c
index ad6d912..78f338a 100644
--- a/drivers/net/ethernet/hisilicon/hip04_eth.c
+++ b/drivers/net/ethernet/hisilicon/hip04_eth.c
@@ -575,7 +575,7 @@ 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);
+	static unsigned int cnt_remaining;
 	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) {
+	cnt_remaining += hip04_recv_cnt(priv);
+	while (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) {
+			--cnt_remaining;
 			goto done;
+		}
 
-		if (--cnt == 0)
-			cnt = hip04_recv_cnt(priv);
+		if (--cnt_remaining == 0)
+			cnt_remaining += hip04_recv_cnt(priv);
 	}
 
 	if (!(priv->reg_inten & RCV_INT)) {
-- 
1.8.5.6