netdev - Re: [PATCH iptables] extension: add xt

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Date:	Fri, 23 Jul 2010 16:13:08 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Jan Engelhardt <jengelh@...ozas.de>,
	Netfilter Development Mailinglist 
	<netfilter-devel@...r.kernel.org>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH iptables] extension: add xt_cpu match

On 23.07.2010 15:43, Eric Dumazet wrote:
> extension: add xt_cpu match
> 
> Kernel 2.6.36 supports xt_cpu match
> 
> In some situations a CPU match permits a better spreading of
> connections, or select targets only for a given cpu.
> 
> With Remote Packet Steering or multiqueue NIC and appropriate IRQ
> affinities, we can distribute trafic on available cpus, per session.
> (all RX packets for a given flow are handled by a given cpu)
> 
> Some legacy applications being not SMP friendly, one way to scale a
> server is to run multiple copies of them.
> 
> Instead of randomly choosing an instance, we can use the cpu number as a
> key so that softirq handler for a whole instance is running on a single
> cpu, maximizing cache effects in TCP/UDP stacks.
> 
> Using NAT for example, a four ways machine might run four copies of
> server application, using a separate listening port for each instance,
> but still presenting an unique external port :
> 
> iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 0 \
>         -j REDIRECT --to-port 8080
> 
> iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 1 \
>         -j REDIRECT --to-port 8081
> 
> iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 2 \
>         -j REDIRECT --to-port 8082
> 
> iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 3 \
>         -j REDIRECT --to-port 8083
> 

Applied to the iptables-next branch, thanks Eric.
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