linux-kernel - [Patch net-next 02/12] net: hns3: avoid mult + div op in critical data path

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Date:   Sat, 23 Feb 2019 17:22:09 +0800
From:   Huazhong Tan <tanhuazhong@...wei.com>
To:     <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <salil.mehta@...wei.com>, <yisen.zhuang@...wei.com>,
        <linuxarm@...wei.com>, Yunsheng Lin <linyunsheng@...wei.com>,
        Huazhong Tan <tanhuazhong@...wei.com>
Subject: [Patch net-next 02/12] net: hns3: avoid mult + div op in critical data path

From: Yunsheng Lin <linyunsheng@...wei.com>

This patch uses shift offset to avoid doing mult and div operation.

Signed-off-by: Yunsheng Lin <linyunsheng@...wei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@...wei.com>
---
 drivers/net/ethernet/hisilicon/hns3/hns3_enet.c | 15 ++++++++-------
 drivers/net/ethernet/hisilicon/hns3/hns3_enet.h |  3 +++
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
index d75977c..14c3aa7 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
@@ -658,7 +658,7 @@ static int hns3_set_tso(struct sk_buff *skb, u32 *paylen,
 
 	/* normal or tunnel packet*/
 	l4_offset = l4.hdr - skb->data;
-	hdr_len = (l4.tcp->doff * 4) + l4_offset;
+	hdr_len = (l4.tcp->doff << 2) + l4_offset;
 
 	/* remove payload length from inner pseudo checksum when tso*/
 	l4_paylen = skb->len - l4_offset;
@@ -1100,8 +1100,8 @@ static int hns3_fill_desc(struct hns3_enet_ring *ring, void *priv,
 
 	desc_cb->length = size;
 
-	frag_buf_num = (size + HNS3_MAX_BD_SIZE - 1) / HNS3_MAX_BD_SIZE;
-	sizeoflast = size % HNS3_MAX_BD_SIZE;
+	frag_buf_num = (size + HNS3_MAX_BD_SIZE - 1) >> HNS3_MAX_BD_SIZE_OFFSET;
+	sizeoflast = size & HNS3_TX_LAST_SIZE_M;
 	sizeoflast = sizeoflast ? sizeoflast : HNS3_MAX_BD_SIZE;
 
 	/* When frag size is bigger than hardware limit, split this frag */
@@ -1145,14 +1145,14 @@ static int hns3_nic_maybe_stop_tso(struct sk_buff **out_skb, int *bnum,
 	int i;
 
 	size = skb_headlen(skb);
-	buf_num = (size + HNS3_MAX_BD_SIZE - 1) / HNS3_MAX_BD_SIZE;
+	buf_num = (size + HNS3_MAX_BD_SIZE - 1) >> HNS3_MAX_BD_SIZE_OFFSET;
 
 	frag_num = skb_shinfo(skb)->nr_frags;
 	for (i = 0; i < frag_num; i++) {
 		frag = &skb_shinfo(skb)->frags[i];
 		size = skb_frag_size(frag);
-		bdnum_for_frag =
-			(size + HNS3_MAX_BD_SIZE - 1) / HNS3_MAX_BD_SIZE;
+		bdnum_for_frag = (size + HNS3_MAX_BD_SIZE - 1) >>
+				 HNS3_MAX_BD_SIZE_OFFSET;
 		if (bdnum_for_frag > HNS3_MAX_BD_PER_FRAG)
 			return -ENOMEM;
 
@@ -1160,7 +1160,8 @@ static int hns3_nic_maybe_stop_tso(struct sk_buff **out_skb, int *bnum,
 	}
 
 	if (unlikely(buf_num > HNS3_MAX_BD_PER_FRAG)) {
-		buf_num = (skb->len + HNS3_MAX_BD_SIZE - 1) / HNS3_MAX_BD_SIZE;
+		buf_num = (skb->len + HNS3_MAX_BD_SIZE - 1) >>
+			  HNS3_MAX_BD_SIZE_OFFSET;
 		if (ring_space(ring) < buf_num)
 			return -EBUSY;
 		/* manual split the send packet */
diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.h b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.h
index 71ff8f4..5c41465 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.h
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.h
@@ -184,6 +184,8 @@ enum hns3_nic_state {
 #define HNS3_TXD_MSS_S				0
 #define HNS3_TXD_MSS_M				(0x3fff << HNS3_TXD_MSS_S)
 
+#define HNS3_TX_LAST_SIZE_M                    0xffff
+
 #define HNS3_VECTOR_TX_IRQ			BIT_ULL(0)
 #define HNS3_VECTOR_RX_IRQ			BIT_ULL(1)
 
@@ -191,6 +193,7 @@ enum hns3_nic_state {
 #define HNS3_VECTOR_INITED			1
 
 #define HNS3_MAX_BD_SIZE			65535
+#define HNS3_MAX_BD_SIZE_OFFSET		16
 #define HNS3_MAX_BD_PER_FRAG			8
 #define HNS3_MAX_BD_PER_PKT			MAX_SKB_FRAGS
 
-- 
2.7.4