[NET]: use __read_mostly on kmem_cache_t , DEFINE_SNMP_STAT pointers

This patch puts mostly read only data in the right section
(read_mostly), to help sharing of these data between CPUS without
memory ping pongs.

On one of my production machine, tcp_statistics was sitting in a
heavily modified cache line, so *every* SNMP update had to force a
reload.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/xfrm/xfrm_input.c

@@ -12,7 +12,7 @@
 #include <net/ip.h>
 #include <net/xfrm.h>
 
-static kmem_cache_t *secpath_cachep;
+static kmem_cache_t *secpath_cachep __read_mostly;
 
 void __secpath_destroy(struct sec_path *sp)
 {

net/xfrm/xfrm_policy.c

@@ -37,7 +37,7 @@ EXPORT_SYMBOL(xfrm_policy_list);
 static DEFINE_RWLOCK(xfrm_policy_afinfo_lock);
 static struct xfrm_policy_afinfo *xfrm_policy_afinfo[NPROTO];
 
-static kmem_cache_t *xfrm_dst_cache;
+static kmem_cache_t *xfrm_dst_cache __read_mostly;
 
 static struct work_struct xfrm_policy_gc_work;
 static struct list_head xfrm_policy_gc_list =