ipv6 fib: Make rt6_info{} more cache-line aware.

The head element of rt6_info{} is dst_entry{}, and
IPv6 specific elements follow.

Because elements at the end of dst_entry{} are frequently
updated, it is not good to put frequently-used static
elements, such as rt6i_idev, rt6i_dst or rt6i_flags in the
same cache line.

On the other hand, fib6_table, rt6i_node or rt6i_gateway are
rarely used, so it is okay to stay in the same cache line.

Let's rearrange rt6_info{}.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 86f46c49e3183da8484d436a8aa2cf7dbe2418e7..4b1dc1161c37ca162eb3d69e82737192ebf8d220 100644 (file)
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -88,34 +88,37 @@ struct rt6_info {
                struct dst_entry        dst;
        } u;
 
-       struct inet6_dev                *rt6i_idev;
-
 #define rt6i_dev                       u.dst.dev
 #define rt6i_nexthop                   u.dst.neighbour
 #define rt6i_expires                   u.dst.expires
 
+       /*
+        * Tail elements of dst_entry (__refcnt etc.)
+        * and these elements (rarely used in hot path) are in
+        * the same cache line.
+        */
+       struct fib6_table               *rt6i_table;
        struct fib6_node                *rt6i_node;
 
        struct in6_addr                 rt6i_gateway;
-       
-       u32                             rt6i_flags;
-       u32                             rt6i_metric;
-       atomic_t                        rt6i_ref;
 
-       /* more non-fragment space at head required */
-       unsigned short                  rt6i_nfheader_len;
-
-       u8                              rt6i_protocol;
+       atomic_t                        rt6i_ref;
 
-       struct fib6_table               *rt6i_table;
+       /* These are in a separate cache line. */
+       struct rt6key                   rt6i_dst ____cacheline_aligned_in_smp;
+       u32                             rt6i_flags;
+       struct rt6key                   rt6i_src;
+       u32                             rt6i_metric;
 
-       struct rt6key                   rt6i_dst;
+       struct inet6_dev                *rt6i_idev;
 
 #ifdef CONFIG_XFRM
        u32                             rt6i_flow_cache_genid;
 #endif
+       /* more non-fragment space at head required */
+       unsigned short                  rt6i_nfheader_len;
 
-       struct rt6key                   rt6i_src;
+       u8                              rt6i_protocol;
 };
 
 static inline struct inet6_dev *ip6_dst_idev(struct dst_entry *dst)