Re: iptables very slow after commit 784544739a25c30637397ace5489eeb6e15d7d49

Jeff Chua
2009-04-11T16:05:50Z

On Sat, Apr 11, 2009 at 11:07 PM, Stephen Hemminger
<shemminger@vyatta.com> wrote:
>> iptables works in whole tables. Userspace submits a table, checkentry is
>> called for all rules in the new table, things are swapped, then destroy
>> is called for all rules in the old table. By that logic (which existed
>> since dawn I think), only the swap operation needs to be locked.
> Part of the overhead is the API choice to take counter values from user
> space during the replace.  If the rule replacement just always started with
> zero counters it could be done with less overhead.

It's always good practice to start from zero with these ...

# iptables -F
# iptables -t nat -F
# iptables -X

And most of the time, rules should be put into a file so that it can
rerun easily after reboot. So if it can be speed up for just this
case, it'll help many out there.

Thanks,
Jeff.