netdev - Re: [PATCH net-next] ipv6: optimize ipv6 addresses compares

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Date:	Tue, 10 Jul 2012 21:14:50 -0700
From:	Joe Perches <joe@...ches.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] ipv6: optimize ipv6 addresses compares

On Wed, 2012-07-11 at 05:49 +0200, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> On 64 bit arches having efficient unaligned accesses (eg x86_64) we can
> use long words to reduce number of instructions for free.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Joe Perches <joe@...ches.com>
> ---
>  include/net/ipv6.h |   22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/include/net/ipv6.h b/include/net/ipv6.h
> index aecf884..9ac5ded 100644
> --- a/include/net/ipv6.h
> +++ b/include/net/ipv6.h
> @@ -302,10 +302,19 @@ static inline int
>  ipv6_masked_addr_cmp(const struct in6_addr *a1, const struct in6_addr *m,
>  		     const struct in6_addr *a2)
>  {
> +#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
> +	const unsigned long *ul1 = (const unsigned long *)a1;
> +	const unsigned long *ulm = (const unsigned long *)m;
> +	const unsigned long *ul2 = (const unsigned long *)a2;
> +
> +	return !!(((ul1[0] ^ ul2[0]) & ulm[0]) |
> +		  ((ul1[1] ^ ul2[1]) & ulm[1]));
> +#else
>  	return !!(((a1->s6_addr32[0] ^ a2->s6_addr32[0]) & m->s6_addr32[0]) |
>  		  ((a1->s6_addr32[1] ^ a2->s6_addr32[1]) & m->s6_addr32[1]) |
>  		  ((a1->s6_addr32[2] ^ a2->s6_addr32[2]) & m->s6_addr32[2]) |
>  		  ((a1->s6_addr32[3] ^ a2->s6_addr32[3]) & m->s6_addr32[3]));
> +#endif
>  }

Come to think of it, this should probably be bool to
avoid anyone possibly using this in a sorting function.


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