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

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Date:	Fri, 6 Jul 2012 18:19:31 +0100
From:	Ben Hutchings <bhutchings@...arflare.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.
[...]
> --- a/net/ipv4/fib_rules.c
> +++ b/net/ipv4/fib_rules.c
[...]
> @@ -189,12 +190,14 @@ errout:
>  
>  static void fib4_rule_delete(struct fib_rule *rule)
>  {
> +	struct net *net = rule->fr_net;
>  #ifdef CONFIG_IP_ROUTE_CLASSID
>  	struct fib4_rule *rule4 = (struct fib4_rule *) rule;
>  
>  	if (rule4->tclassid)
> -		fib_num_tclassid_users--;
> +		net->ipv4.fib_num_tclassid_users--;
>  #endif
> +	net->ipv4.fib_has_custom_rules = true;
>  }
[...]

Do you really mean to set fib_has_custom_rules = true on deletion?
Shouldn't it conditionally be set false?  (Though the condition may be
too expensive to evaluate here without maintaining a separate counter.)

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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