[PATCH 5/5] NET : Reorder fields of struct dst_entry

[Eric Dumazet]

This last patch (but not least :) ) finally moves the next pointer at the end 
of struct dst_entry. This permits to perform route cache lookups with a 
minimal cost of one cache line per entry, instead of two.

Both 32bits and 64bits platforms benefit from this new layout.
Signed-off-by: Eric Dumazet <[EMAIL PROTECTED]>


--- linux-2.6.20/include/net/dst.h.inter        2007-02-08 21:43:21.000000000 
+0100
+++ linux-2.6.20-ed/include/net/dst.h   2007-02-08 21:43:21.000000000 +0100
@@ -37,14 +37,7 @@ struct sk_buff;
 
 struct dst_entry
 {
-       union {
-               struct dst_entry *next;
-               struct rtable    *rt_next;
-               struct rt6_info   *rt6_next;
-               struct dn_route  *dn_next;
-       };
-       atomic_t                __refcnt;       /* client references    */
-       int                     __use;
+       struct rcu_head         rcu_head;
        struct dst_entry        *child;
        struct net_device       *dev;
        short                   error;
@@ -55,7 +48,6 @@ struct dst_entry
 #define DST_NOPOLICY           4
 #define DST_NOHASH             8
 #define DST_BALANCED            0x10
-       unsigned long           lastuse;
        unsigned long           expires;
 
        unsigned short          header_len;     /* more space at head required 
*/
@@ -80,8 +72,16 @@ struct dst_entry
 #endif
 
        struct  dst_ops         *ops;
-       struct rcu_head         rcu_head;
                
+       unsigned long           lastuse;
+       atomic_t                __refcnt;       /* client references    */
+       int                     __use;
+       union {
+               struct dst_entry *next;
+               struct rtable    *rt_next;
+               struct rt6_info   *rt6_next;
+               struct dn_route  *dn_next;
+       };
        char                    info[0];
 };