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>

1 files changed, 16 insertions, 13 deletions

diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 86f46c49e318..4b1dc1161c37 100644
--- 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)