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

Artem Belevich fbsdlist at
Tue Jul 8 16:34:50 UTC 2008

On 7/8/08, Robert Watson <rwatson at> wrote:
>  There were some patches floating around for if_em to do a prefetch of the
> first bit of packet data on packets before handing them up the stack.  My

I found Andre Oppermann's optimization patch mentioned in july 2005
status report:

Is that the patch you had in mind?

In the report Andre says: "Use [of prefetch] in both of these places
show a very significant performance gain but not yet fully

"very significant" bit looks promising. Unfortunately, it does not
look like prefetch changes in the patch made it into official kernel.
I wonder why.

It should be easy enough to apply prefetch-related changes and see
if/how it affects forwarding performance.


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