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Date: Fri, 08 Jun 2007 07:00:13 +0200
From: Eric Dumazet <dada1@cosmosbay.com>
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To: Eric Dumazet <dada1@cosmosbay.com>
CC: Davide Libenzi <davidel@xmailserver.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Ulrich Drepper <drepper@redhat.com>, Ingo Molnar <mingo@elte.hu>
Subject: Re: [patch 1/8] fdmap v2 - fdmap core
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Eric Dumazet a écrit :
> 
> struct fd_map {
>     /*
>      * read mostly part
>      */
>     unsigned int base;   /* 0x00 */
>     unsigned int size;   /* 0x04 */
>     struct list_head slist; /* 0x08 */
>     struct list_head *slots; /* 0x18 */
>     unsigned long *map; /* 0x28 */
>     void (*freecb)(void *, struct fd_map *); /* 0x30 */
>     void *freecb_priv; /* 0x38 */
> 
>     /*
>      * written part on a separate cache line in SMP
>      */
>     unsigned int fdnext ____cacheline_aligned_in_smp; /* 0x40 */
> 
>     struct fd_map *next;  /* 0x48 */
>     struct rcu_head rcu; /* 0x50 */
> };

Well, offsets are wrong but layout OK

struct fd_map {
     /*
      * read mostly part
      */
     unsigned int base;   /* 0x00 */
     unsigned int size;   /* 0x04 */
     struct list_head slist; /* 0x08 */
     struct list_head *slots; /* 0x18 */
     unsigned long *map; /* 0x20 */
     void (*freecb)(void *, struct fd_map *); /* 0x28 */
     void *freecb_priv; /* 0x30 */
	/* one 8 bytes hole */

     /*
      * written part on a separate cache line in SMP
      */
     unsigned int fdnext ____cacheline_aligned_in_smp; /* 0x40 */

     struct fd_map *next;  /* 0x48 */
     struct rcu_head rcu; /* 0x50 */
}; /* size 0x60 , aligned to 0x80 */