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

[Artem Belevich]

Hi,

As was already mentioned, we can't avoid all cache misses as there's
data that's recently been updated in memory via DMA and therefor
kicked out of cache.

However, we may hide some of the latency penalty by prefetching
'interesting' data early. I.e. we know that we want to access some
ethernet headers, so we may start pulling relevant data into cache
early. Ideally, by the time we need to access the field, it will
already be in the cache. When we're counting nanoseconds per packet
this may bring some performance gain.

Just my $0.02.
--Artem