netdev - Re: [PATCH] ipv4: Avoid overhead when no custom FIB rules are installed.

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Date:	Fri, 06 Jul 2012 07:41:22 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] ipv4: Avoid overhead when no custom FIB rules are
 installed.

On Thu, 2012-07-05 at 22:31 -0700, David Miller wrote:
> If the user hasn't actually installed any custom rules, or fiddled
> with the default ones, don't go through the whole FIB rules layer.
> 
> It's just pure overhead.
> 
> Instead do what we do with CONFIG_IP_MULTIPLE_TABLES disabled, check
> the individual tables by hand, one by one.
> 
> Also, move fib_num_tclassid_users into the ipv4 network namespace.
> 
> Signed-off-by: David S. Miller <davem@...emloft.net>

> +static inline int fib_lookup(struct net *net, struct flowi4 *flp,
> +			     struct fib_result *res)
> +{
> +	if (!net->ipv4.fib_has_custom_rules) {
> +		if (net->ipv4.fib_local &&
> +		    !fib_table_lookup(net->ipv4.fib_local, flp, res,
> +				      FIB_LOOKUP_NOREF))
> +			return 0;
> +		if (net->ipv4.fib_main &&
> +		    !fib_table_lookup(net->ipv4.fib_main, flp, res,
> +				      FIB_LOOKUP_NOREF))
> +			return 0;
> +		if (net->ipv4.fib_default &&
> +		    !fib_table_lookup(net->ipv4.fib_default, flp, res,
> +				      FIB_LOOKUP_NOREF))
> +			return 0;
> +		return -ENETUNREACH;
> +	}
> +	return __fib_lookup(net, flp, res);
> +}
> +

Hmm, this seems quite big to be inlined ?


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