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

Julian Elischer julian at
Mon Jul 7 22:17:23 UTC 2008

Peter Jeremy wrote:
> On 2008-Jul-07 13:25:13 -0700, Julian Elischer <julian at> wrote:
>> what you need is a speculative prefetch where you an tell teh 
>> processor "We will probably need the following address so start 
>> getting it while we go do other stuff".
> This looks like the PREFETCH instructions that exist in at least amd64
> and SPARC.  Unfortunately, their optimal use is very implementation-
> dependent and the AMD documentation suggests that incorrect use can
> degrade performance.

It might be worth looking to see if the network processing threads 
might be able to prefetch the IP header at least :-)

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