Re: [PATCH] [NET] reduce sizeof(struct flow)

[Steven Whitehouse <steve@chygwyn.com>]

Hi,

On Tue, Oct 17, 2006 at 11:53:36PM -0700, David Miller wrote:
> From: Eric Dumazet <dada1@cosmosbay.com>
> Date: Wed, 18 Oct 2006 07:42:17 +0200
> 
> > How many people are using DECNET and want to pay the price of this
> > 20 bytes dnports structure ?
> 
Point taken :-) Eric, you also need to add a || defined(CONFIG_DECNET_MODULE)
I think in your patch, if you want to make this optional.

> I bet you could make that cost get hidden by careful rearrangement
> of the struct flow, or adjustment of the implementation.
> 
> BTW, I see assignments to these fields, and as a specific example
> uli_u.dnports.objnamel but no use of it.  Perhaps much of dnports can
> even be deleted outright. :-)
> -

Its not used at the moment[*], but would be required for any kind of flow
tracking. The objnum field, could be folded into the objname field I
guess on the basis that objnamel == 0 means objname[0] represents the objnum,
but that doesn't really buy much.

Looking at the rearrangement option, and the relative lengths of
ipv6 and DECnet node addresses, dn_u is a lot smaller than ip6_u and thus
the obj[num|name|namel] fields could be moved into that structure.
Even after doing this, dn_u would still be shorter than ip6_u, although
12 bytes longer than ip4_u (if my counting is correct). Is that an
acceptable solution?

[*] By which I mean, as you've already alluded to, that its set up correctly
but not currently read/tested by anything yet.

Steve.