netdev - Re: [PATCH 1/2] ipv4: Add hash table of interface addresses.

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Date:	Fri, 18 Feb 2011 07:22:30 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH 1/2] ipv4: Add hash table of interface addresses.

Le jeudi 17 février 2011 à 20:46 -0800, David Miller a écrit :
> This will be used to optimize __ip_dev_find() and friends.
> 
> Signed-off-by: David S. Miller <davem@...emloft.net>
> ---
>  include/linux/inetdevice.h |    1 +
>  net/ipv4/devinet.c         |   44 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 45 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
> index ae8fdc5..5f81466 100644
> --- a/include/linux/inetdevice.h
> +++ b/include/linux/inetdevice.h
> @@ -144,6 +144,7 @@ static inline void ipv4_devconf_setall(struct in_device *in_dev)
>  #define IN_DEV_ARP_NOTIFY(in_dev)	IN_DEV_MAXCONF((in_dev), ARP_NOTIFY)
>  
>  struct in_ifaddr {
> +	struct hlist_node	hash;
>  	struct in_ifaddr	*ifa_next;
>  	struct in_device	*ifa_dev;
>  	struct rcu_head		rcu_head;
> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index 748cb5b..c1f2552 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -92,6 +92,38 @@ static const struct nla_policy ifa_ipv4_policy[IFA_MAX+1] = {
>  	[IFA_LABEL]     	= { .type = NLA_STRING, .len = IFNAMSIZ - 1 },
>  };
>  
> +/* inet_addr_hash's shifting is dependent upon this IN4_ADDR_HSIZE
> + * value.  So if you change this define, make appropriate changes to
> + * inet_addr_hash as well.
> + */
> +#define IN4_ADDR_HSIZE	256
> +static struct hlist_head inet_addr_lst[IN4_ADDR_HSIZE];
> +static DEFINE_SPINLOCK(inet_addr_hash_lock);
> +
> +static inline unsigned int inet_addr_hash(__be32 addr)
> +{
> +	u32 val = (__force u32) addr;
> +
> +	return ((val ^ (val >> 8) ^ (val >> 16) ^ (val >> 24)) &
> +		(IN4_ADDR_HSIZE - 1));
> +}

Maybe you should take into account net pointer here, or machines with
many net namespaces will hash collide for 127.0.0.1



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