netdev - Re: [PATCH net-next] netfilter: use jump_label for nf

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Date:	Mon, 21 Nov 2011 16:39:03 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
	kaber@...sh.net, pablo@...filter.org
Subject: Re: [PATCH net-next] netfilter: use jump_label for nf_hooks

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Sat, 19 Nov 2011 04:32:46 +0100

> On configs where CONFIG_JUMP_LABEL=y, we can replace in fast path a
> load/compare/conditional jump by a single jump with no dcache reference.
> 
> Jump target is modified as soon as nf_hooks[pf][hook] switches from
> empty state to non empty states. jump_label state is kept outside of
> nf_hooks array so has no cost on cpu caches.
> 
> This patch removes the test on CONFIG_NETFILTER_DEBUG : No need to call
> nf_hook_slow() at all if nf_hooks[pf][hook] is empty, this didnt give
> useful information, but slowed down things a lot.
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> CC: Patrick McHardy <kaber@...sh.net>
> CC: Pablo Neira Ayuso <pablo@...filter.org>
> ---
> This is obviously a netfilter patch, but since David committed two other
> jump_label patches lately, maybe its better he takes this patch as well
> directly ? Thanks !

I've applied this.

Originally I was at first concerned because you changed the logic that
forced nf_hook_slow() to be invoked when NETFILTER_DEBUG is enabled but
these days that has no real purpose so that part of the change is fine.

Someone might want to double-check this ;-)
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