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Subject[Patch net-next 02/12] net: hns3: avoid mult + div op in critical data path
Date
From: Yunsheng Lin <linyunsheng@huawei.com>

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

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.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
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