Subject: Re: [PATCH 0/3] netfilter : 3 patches to boost ip_tables performance

From: Andi Kleen <[email-masked]>
Date: Tue, 27 Sep 2005 18:23:18 +0200

On Friday 23 September 2005 19:09, Harald Welte wrote:
> On Thu, Sep 22, 2005 at 03:03:21PM +0200, Andi Kleen wrote:
> > > 1) No more central rwlock protecting each table (filter, nat, mangle,
> > > raw), but one lock per CPU. It avoids cache line ping pongs for each
> > > packet.
> >
> > Another useful change would be to not take the lock when there are no
> > rules. Currently just loading iptables has a large overhead.
>
> This is partially due to the netfilter hooks that are registered (so we
> always take nf_hook_slow() in the NF_HOOK() macro).

Not sure it's that. nf_hook_slow uses RCU, so it should be quite
fast.

> The default policies inside an iptables chain are internally implemented
> as a rule.  Thus, policies as built-in rules have packet/byte counters.

That could be special cased and done lockless, with the counting
done per CPU.

-Andi