2015-11-25 21:55:44

by Ameen

Subject: [PATCH 2/2] Minor improvement for smsc95xx netusb driver performance.

Reduce number of memcpy's by 1-2 improve transmit performance by 2-4%.
or reduce CPU usage on a comparable value.

Signed-off-by: Ameen Ali <[email protected]>
---
drivers/net/usb/smsc95xx.c | 28 ++++++++++++++--------------
1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index 66b3ab9..fff07cc 100644
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -1830,7 +1830,9 @@ static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev,
{
bool csum = skb->ip_summed == CHECKSUM_PARTIAL;
int overhead = csum ? SMSC95XX_TX_OVERHEAD_CSUM : SMSC95XX_TX_OVERHEAD;
- u32 tx_cmd_a, tx_cmd_b;
+ struct tx_commands_t {
+ u32 cmd_a, cmd_b, csum_preamble;
+ } tx_cmds;

/* We do not advertise SG, so skbs should be already linearized */
BUG_ON(skb_shinfo(skb)->nr_frags);
@@ -1855,26 +1857,24 @@ static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev,
+ skb->csum_offset)) = csum_fold(calc);

csum = false;
+ overhead = SMSC95XX_TX_OVERHEAD;
} else {
- u32 csum_preamble = smsc95xx_calc_csum_preamble(skb);
+ tx_cmds.csum_preamble = smsc95xx_calc_csum_preamble(skb);
skb_push(skb, 4);
- cpu_to_le32s(&csum_preamble);
- memcpy(skb->data, &csum_preamble, 4);
+ cpu_to_le32s(&tx_cmds.csum_preamble);
}
}

- skb_push(skb, 4);
- tx_cmd_b = (u32)(skb->len - 4);
+ tx_cmds.cmd_a = (u32)skb->len | TX_CMD_A_FIRST_SEG_ |
+ TX_CMD_A_LAST_SEG_;
+ cpu_to_le32s(&tx_cmds.cmd_a);
+ tx_cmds.cmd_b = (u32)skb->len;
if (csum)
- tx_cmd_b |= TX_CMD_B_CSUM_ENABLE;
- cpu_to_le32s(&tx_cmd_b);
- memcpy(skb->data, &tx_cmd_b, 4);
+ tx_cmds.cmd_b |= TX_CMD_B_CSUM_ENABLE;

- skb_push(skb, 4);
- tx_cmd_a = (u32)(skb->len - 8) | TX_CMD_A_FIRST_SEG_ |
- TX_CMD_A_LAST_SEG_;
- cpu_to_le32s(&tx_cmd_a);
- memcpy(skb->data, &tx_cmd_a, 4);
+ cpu_to_le32s(&tx_cmds.cmd_b);
+ skb_push(skb, 8);
+ memcpy(skb->data, &tx_cmds, overhead);

return skb;
}
--
2.5.0

2015-11-30 04:00:56

by David Miller

Subject: Re: [PATCH 2/2] Minor improvement for smsc95xx netusb driver performance.

From: Ameen <[email protected]>
Date: Wed, 25 Nov 2015 23:55:26 +0200

> if (csum)
> - tx_cmd_b |= TX_CMD_B_CSUM_ENABLE;
> - cpu_to_le32s(&tx_cmd_b);
> - memcpy(skb->data, &tx_cmd_b, 4);
> + tx_cmds.cmd_b |= TX_CMD_B_CSUM_ENABLE;

You've corrupted the indentation here.