David S. Miller a écrit :
> From: Eric Dumazet <dada1@cosmosbay.com>
> Date: Fri, 08 Jul 2005 08:53:02 +0200
>
>
>>About making sk_buff smaller, I use this patch to declare 'struct
>>sec_path *sp' only ifdef CONFIG_XFRM, what do you think ?  I also
>>use a patch to declare nfcache, nfctinfo and nfct only if
>>CONFIG_NETFILTER_CONNTRACK or CONFIG_NETFILTER_CONNTRACK_MODULE are
>>defined, but thats more intrusive.  Also, tc_index is not used if
>>CONFIG_NET_SCHED only is declared but none of CONFIG_NET_SCH_* In my
>>case, I am using CONFIG_NET_SCHED only to be able to do : tc -s -d
>>qdisc
>
>
> Distributions enable all of the ifdefs, and that is thus the
> size and resultant performance most users see.

Well, I had this idea because I found another similar use in include/linux/ip.h

struct inet_sock {
     /* sk and pinet6 has to be the first two members of inet_sock */
     struct sock     sk;
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
     struct ipv6_pinfo   *pinet6;
#endif