netdev - Re: [PATCH net-next] etherdevice: Optimize compare_ether_addr/ether_addr

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Message-ID: <522246FD.3080403@cogentembedded.com>
Date:	Sat, 31 Aug 2013 23:41:49 +0400
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Joe Perches <joe@...ches.com>
CC:	David Miller <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] etherdevice: Optimize compare_ether_addr/ether_addr_equal

Hello.

On 08/31/2013 12:54 PM, Joe Perches wrote:

> When CONFIG_HAS_EFFICIENT_UNALIGNED_ACCESS is set,
> optimize compare_ether_addr a little by removing an
> xor and or by using a u32 and u16 comparison
> instead of 3 separate u16 comparisons.

> Make the ether_addr_equal_64bits code a bit simpler
> by adding a test for CONFIG_64BIT and calling
> ether_addr_equal otherwise.

> This also slightly improves ether_addr_equal_64bits
> by removing the zap_last_2bytes shifts in the !64bit
> case.

> Signed-off-by: Joe Perches <joe@...ches.com>
> ---
>   include/linux/etherdevice.h | 17 ++++++++++-------
>   1 file changed, 10 insertions(+), 7 deletions(-)

> diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
> index c623861..2514d17 100644
> --- a/include/linux/etherdevice.h
> +++ b/include/linux/etherdevice.h
> @@ -208,11 +208,19 @@ static inline void eth_hw_addr_random(struct net_device *dev)
>    */
>   static inline unsigned compare_ether_addr(const u8 *addr1, const u8 *addr2)
>   {
> +#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
> +	u32 fold = ((*(const u32 *)addr1) ^ (*(const u32 *)addr2));

    Could you keep the same style as before and insert empty line after 
declaration?

> +	fold |= ((*(const u16 *)(addr1 + 4)) ^ (*(const u16 *)(addr2 + 4)));
> +
> +	BUILD_BUG_ON(ETH_ALEN != 6);
> +	return fold != 0;
> +#else
>   	const u16 *a = (const u16 *) addr1;
>   	const u16 *b = (const u16 *) addr2;
>
>   	BUILD_BUG_ON(ETH_ALEN != 6);
>   	return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | (a[2] ^ b[2])) != 0;
> +#endif
>   }
>
>   /**

WBR, Sergei

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