linux-kernel - Re: [PATCH 3/3] Minor improvement for smsc95xx netusb driver performance.

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Date:	Thu, 26 Nov 2015 00:26:06 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Ameen <ameenali023@...il.com>, teve.glendinning@...well.net
Cc:	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH 3/3] Minor improvement for smsc95xx netusb driver
 performance.

Hello.

On 11/25/2015 10:15 PM, Ameen wrote:

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

    CPU.

> Signed-off-by: Ameen Ali <AmeenAli023@...il.com>
> ---
>   drivers/net/usb/smsc95xx.c | 30 ++++++++++++++++--------------
>   1 file changed, 16 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
> index 66b3ab9..022d2f63 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;

    Need space after }.

>
>   	/* We do not advertise SG, so skbs should be already linearized */
>   	BUG_ON(skb_shinfo(skb)->nr_frags);
> @@ -1855,26 +1857,26 @@ static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev,
[...]
>
> -	skb_push(skb, 4);
> -	tx_cmd_b = (u32)(skb->len - 4);
> +	tx_cmds.cmd_a = (u32)(skb->len) | TX_CMD_A_FIRST_SEG_ |

    Parens around 'skb->len' not needed.

[...]

MBR, Sergei

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