netdev - Re: [resend] Passive OS fingerprint xtables match.

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Message-ID: <4A27CD94.9040604@trash.net>
Date:	Thu, 04 Jun 2009 15:35:16 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	Jan Engelhardt <jengelh@...ozas.de>
CC:	Evgeniy Polyakov <zbr@...emap.net>, netdev@...r.kernel.org,
	David Miller <davem@...emloft.net>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Netfilter Development Mailinglist 
	<netfilter-devel@...r.kernel.org>
Subject: Re: [resend] Passive OS fingerprint xtables match.

Jan Engelhardt wrote:
> On Thursday 2009-06-04 15:16, Patrick McHardy wrote:
>> Evgeniy Polyakov wrote:
>>> On Thu, Jun 04, 2009 at 02:11:24PM +0200, Patrick McHardy (kaber@...sh.net)
>>> wrote:
>>>> Thats not what I meant. struct xt_match_param is passed to the
>>>> ->match() callbacks from *t_do_table(). This is where you can
>>>> add the real hook number to have it available in ->match().
>>>>
>>>> (Forgot to mention earlier: please in a seperate patch and adjusting
>>>> all *tables copies)
>>> Kind of this (for ipv4 only so far, also reorderd a field to fill the
>>> gap):
>> Exactly. But please verify that by reordering, you're not moving
>> the more commonly used members out of the first cacheline.
>>
> I am not sure the struct was ordered for optimized cacheline performance
> beforehand either.
> 
> * par->in, par->out is only rarely used (think of xt_physdev, besides
>   ipt_do_table itself);
> * par->match similarly (xt_hashlimit)
> * par->matchinfo, though showing more grep results, is usually copied to
>   the stack by means of struct foo_target_info *info = par->matchinfo;
> etc.

Probably not (you ought to know :)). Just want to make sure if
it by accident had a good layout to not make it worse for this.
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