Can I reduce CPU use of conntrack/masq?

Can I reduce CPU use of conntrack/masq?

[Steve Snyder]

Hello.

I am working on what amounts to a Ethernet to Ultra-Wide Band (UWB) 
converter box.  Packets are simply routed from 1 interface to 
another.

This box is based on an ARM7TDMI CPU, running Linux 2.4.26, and the 
network throughput of the box is CPU-limited.  How limited?  The 
100Mbps/FD Ethernet can do no better than 35Mbps.

I've discovered that I can improve Ethernet throughput by about %20 by 
removing the the conntrack/masq support from the kernel.  The removal 
is good only as a test, though, since I need this functionality to 
move the packets between interfaces.  

This is the relevant config:

CONFIG_IP_NF_CONNTRACK=y
CONFIG_IP_NF_IPTABLES=y
CONFIG_IP_NF_NAT=y
CONFIG_IP_NF_NAT_NEEDED=y
CONFIG_IP_NF_TARGET_MASQUERADE=y

Enabled at boot time like this:

/sbin/iptables -t nat -A POSTROUTING -o uwb0 -j MASQUERADE
echo "1" > /proc/sys/net/ipv4/ip_forward

I wonder if I can improve conntrack/masq performance at the expense of 
flexibility.  This will be a closed system, with simple and static 
routing.  Are there any trade-offs I can make to sacrifice unneeded 
flexibility in routing for reduced CPU utilization in conntrack/masq?

Thanks.

Re: Can I reduce CPU use of conntrack/masq?

[Antonio Vargas]

On 11/2/05, Steve Snyder <R00020C@freescale.com> wrote:
> Hello.
>
> I am working on what amounts to a Ethernet to Ultra-Wide Band (UWB)
> converter box.  Packets are simply routed from 1 interface to
> another.
>
> This box is based on an ARM7TDMI CPU, running Linux 2.4.26, and the
> network throughput of the box is CPU-limited.  How limited?  The
> 100Mbps/FD Ethernet can do no better than 35Mbps.
>
> I've discovered that I can improve Ethernet throughput by about %20 by
> removing the the conntrack/masq support from the kernel.  The removal
> is good only as a test, though, since I need this functionality to
> move the packets between interfaces.
>
> This is the relevant config:
>
> CONFIG_IP_NF_CONNTRACK=y
> CONFIG_IP_NF_IPTABLES=y
> CONFIG_IP_NF_NAT=y
> CONFIG_IP_NF_NAT_NEEDED=y
> CONFIG_IP_NF_TARGET_MASQUERADE=y
>
> Enabled at boot time like this:
>
> /sbin/iptables -t nat -A POSTROUTING -o uwb0 -j MASQUERADE
> echo "1" > /proc/sys/net/ipv4/ip_forward
>
> I wonder if I can improve conntrack/masq performance at the expense of
> flexibility.  This will be a closed system, with simple and static
> routing.  Are there any trade-offs I can make to sacrifice unneeded
> flexibility in routing for reduced CPU utilization in conntrack/masq?

Hmmm... totally untested and don't know the details of UWB but...
can't you simply ether-bridge the interfaces instead of masquerading?
It should need less CPU


> Thanks.
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--
Greetz, Antonio Vargas aka winden of network

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thesameasabove@amigascne.org

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Re: Can I reduce CPU use of conntrack/masq?

[Steve Snyder]

On Wednesday 02 November 2005 15:23, Antonio Vargas wrote:
> On 11/2/05, Steve Snyder <R00020C@freescale.com> wrote:
[snip]
> > I wonder if I can improve conntrack/masq performance at the expense of
> > flexibility.  This will be a closed system, with simple and static
> > routing.  Are there any trade-offs I can make to sacrifice unneeded
> > flexibility in routing for reduced CPU utilization in conntrack/masq?
> 
> Hmmm... totally untested and don't know the details of UWB but...
> can't you simply ether-bridge the interfaces instead of masquerading?
> It should need less CPU

Hmm...  I'm not familiar with ether-bridge, and Google turns up only
commercial products and BSD references.

Pointer to info, please?

Thanks.

Re: Can I reduce CPU use of conntrack/masq?

[Stephen Hemminger]

On Wed, 2 Nov 2005 15:51:52 -0500
Steve Snyder <R00020C@freescale.com> wrote:

> On Wednesday 02 November 2005 15:23, Antonio Vargas wrote:
> > On 11/2/05, Steve Snyder <R00020C@freescale.com> wrote:
> [snip]
> > > I wonder if I can improve conntrack/masq performance at the expense of
> > > flexibility.  This will be a closed system, with simple and static
> > > routing.  Are there any trade-offs I can make to sacrifice unneeded
> > > flexibility in routing for reduced CPU utilization in conntrack/masq?
> > 
> > Hmmm... totally untested and don't know the details of UWB but...
> > can't you simply ether-bridge the interfaces instead of masquerading?
> > It should need less CPU
> 
> Hmm...  I'm not familiar with ether-bridge, and Google turns up only
> commercial products and BSD references.

It in the kernel already! Look at 
	http://linux-net.osdl.org/index.php/Bridge
For more info

-- 
Stephen Hemminger <shemminger@osdl.org>
OSDL http://developer.osdl.org/~shemminger