Subject: Re: [PATCH] reduce netfilte sk_buff enlargement

From: Harald Welte <[email-masked]>
Date: Wed, 20 Jul 2005 09:23:05 -0400

On Mon, Jul 18, 2005 at 08:31:45PM -0700, David S. Miller wrote:
> From: Harald Welte <[email-masked]>
> Date: Mon, 18 Jul 2005 00:04:51 +0200
> 
> > The only real in-tree user of nfcache was IPVS, who only needs a single
> > bit.  Unfortunately I couldn't find some other free bit in sk_buff to
> > stuff that bit into, so I introduced a separate field for them.  Maybe
> > the IPVS guys can resolve that to further save space.
> 
> I think we must resolve this one before 2.6.14 goes out, which
> gives us a lot of time, but for now I'll eat that one-bit member.

Well, I hope IPVS people will take care of this.  I don't really know
that code too well...

> > Initially I wanted to shrink pkt_type to three bits (PACKET_HOST and
> > alike are only 6 values defined), but unfortunately the bluetooth code
> > overloads pkt_type :(
> 
> This also must be cured somehow, that really isn't a clean nor nice
> usage of this field.

I just ran into Marcel Holtmann earlier today.  He thinks moving that
data into the cb is fine, though he has to double-check that.

He also said that he really only needs 5 bits, so even if the current
pkt_type overloading would persist, we could probably shrink it to make
space for the IPVS bit.

-- 
- Harald Welte <[email-masked]>                 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