Table duplication on smp machine

[Thomas Heinz <creatix@hipac.org>]

Hi

Netfilter maintains different tables for each cpu which is especially
interesting for smp ;-)

This is done - according to the docs - to avoid write locking.
Now, what would be write locked in case we had only one set of
rules:

a) counters
b) match/target write operations to their match/target data

a) is clear. b) not really: if a target/match needs to store
data it would do it the way the limit match does it which
requires an in-module lock mechanism and an ugly pointer in the
private data of the match/target.

Hm, remains a). There must be another reason. Otherwise a lot
of space is wasted just to keep separate per-cpu counter values.

Is there another reason?


Regards

Thomas