Re: Performance issue due to constant "modprobes"

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On Wednesday 2011-04-13 13:08, Ed W wrote:

>>> $ cat /tmp/modp.log
>>> ip_tables -q
>>> -q -- ipt_SET
>>> -q -- ipt_SET
>>> -q -- ipt_set
>>> -q -- ipt_set
>> 
>> The trailing -q is a hint towards the call from iptables, whereas the
>> leading -q is kernel-invoked calls. Specifically, it seems that
>> xt_set is indeed not built-in, but a module.
>
>Hmm, that's an interesting point.
>
>So ipt_SET of course not build in to the kernel (2.6.37/38).  Further I
>can't find any reference to it in a 2.6.38 kernel tree? I do however see
>something in the 2.6.39-rc3 tree (sanity check please - is this correct?)

Yes, ipset was first merged into the kernel for 2.6.39.

>This would seem to explain why the kernel autoloader was having a try to
>find some missing module? It's actually completely missing on this kernel?

On your 37/38, yes.

>However, I really don't understand the sequence of calls here that has
>caused apparently a "modprobe iptables" from xtables.c to trigger the
>kernel (?) to try and insert some module that it knows nothing about
>(only iptables seems to know about it)?

You mentioned your program _is_ actually compiled with --enable-static,
as such this applies:

Since libxt_SET and libxt_set are built into iptables-multi, their
revision will be checked unconditionally (previous to Maciej's patches).
Since the 37s and 38s kernel has no xt_SET/set, it will try probing.
All looks normal. Including that your modprobe count still is just 5
and not 20+.
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