Re: [PATCH 1/3] netfilter : 3 patches to boost ip_tables performance

[Harald Welte <laforge@netfilter.org>]

On Wed, Sep 21, 2005 at 11:29:13PM +0200, Eric Dumazet wrote:
> Patch 1/3
> 
> 1) No more one rwlock_t protecting the 'curtain'

I have no problem with this change "per se", but with the
implementation.

As of now, we live without any ugly #ifdef CONFIG_SMP / #endif sections
in the code - and if possible, I would continue this good tradition.

For example the get_counters() function.  Wouldn't all the smp specific
code (for_each_cpu(), ...)  be #defined to nothing anyway?

And if we really need the #ifdef's, I would appreciate if those
sectionas are as small as possible.  in get_counters() the section can
definitely be smaller, rather than basically having the whole function
body separate for smp and non-smp cases.

Also, how much would we loose in runtime performance if we were using a
"rwlock_t *" even in the UP case?.  I mean, it's just one more pointer
dereference of something that is expected to be in cache anyway, isn't
it?  This gets rid of another huge set of #ifdefs that make the code
unreadable and prone to errors being introduced later on.

-- 
- Harald Welte <laforge@netfilter.org>                 http://netfilter.org/
============================================================================
  "Fragmentation is like classful addressing -- an interesting early
   architectural error that shows how much experimentation was going
   on while IP was being designed."                    -- Paul Vixie

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