Freebsd IP Forwarding performance (question, and some info) [7-stable, current, em, smp]

Stefan Lambrev stefan.lambrev at
Mon Jun 30 11:32:23 UTC 2008

Paul wrote:
> The higher I set the buffer the worse it is.. 256 and 512 I get about 
> 50-60k more pps than i do with 2048 or 4096.. You
> would think it would be the other way around but obviously there is 
> some contention going on. :/
Looks like in bridge mode hw.em.rxd=512 and hw.em.txd=512 yields best 
results also. reducing or increasing those leads to worse performance.
btw is there any news with hwpmc for new CPUs ? last time I checked was 
real pain to get it working with core2 CPUs :(
> I'm sticking with 512 for now, as it seems to make it worse with 
> anything higher.
> Keep in mind, i'm using random source ips, random source and 
> destination ports.. Although that should have zero impact on the 
> amount of PPS it can route but for some reason it seems to.. ? Any 
> ideas on that one?   A single stream one source ip/port to one 
> destination ip/port seems to use less cpu, although I haven't 
> generated the same pps with that yet.. I am going to test it soon
> Ingo Flaschberger wrote:
>> Dear Paul,
>>> I tried this.. I put  6-STABLE (6.3), using default driver was 
>>> slower than FBSD7
>> have you set the rx/tx buffers?
>> /boot/loader.conf
>> hw.em.rxd=4096
>> hw.em.txd=4096
>> bye,
>>     Ingo
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Best Wishes,
Stefan Lambrev
ICQ# 24134177

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