Re: [B.A.T.M.A.N.] [RFC] batman-adv: Reorder structs to reduce padding

[Sven Eckelmann <sven@narfation.org>]

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On Monday 05 November 2012 19:58:54 Marek Lindner wrote:
> On Sunday, November 04, 2012 06:41:48 Sven Eckelmann wrote:
> > -       struct batadv_neigh_node __rcu *router; /* rcu protected pointer
> > */
> > 
> >  #ifdef CONFIG_BATMAN_ADV_DAT
> >  
> >         batadv_dat_addr_t dat_addr;
> >  
> >  #endif
> > 
> > +       uint8_t flags;
> > +       uint8_t gw_flags;
> > +       struct batadv_neigh_node __rcu *router; /* rcu protected pointer
> > */
> 
> Shouldn't we move batadv_dat_addr_t to the end of the struct to achieve the
> smallest possible struct regardless of whether DAT is compiled in or not ?
> Or does it have no effect ?

More or less. It is hard to optimize it for both situation. Just moving to the 
end will not fix the problem because it will create an 1 byte whole which has 
to filled using something else. And optimizing it for all architectures is 
even harder.

But this RFC is not really important. It was just a small fun test of pahole 
for me.

Kind regards,
	Sven

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