[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/ipv4/af_inet.c

@@ -113,7 +113,7 @@
 #include <linux/mroute.h>
 #endif
 
-DEFINE_SNMP_STAT(struct linux_mib, net_statistics);
+DEFINE_SNMP_STAT(struct linux_mib, net_statistics) __read_mostly;
 
 extern void ip_mc_drop_socket(struct sock *sk);
 

net/ipv4/fib_hash.c

@@ -45,8 +45,8 @@
 
 #include "fib_lookup.h"
 
-static kmem_cache_t *fn_hash_kmem;
-static kmem_cache_t *fn_alias_kmem;
+static kmem_cache_t *fn_hash_kmem __read_mostly;
+static kmem_cache_t *fn_alias_kmem __read_mostly;
 
 struct fib_node {
 	struct hlist_node	fn_hash;

net/ipv4/fib_trie.c

@@ -166,7 +166,7 @@ static struct tnode *halve(struct trie *t, struct tnode *tn);
 static void tnode_free(struct tnode *tn);
 static void trie_dump_seq(struct seq_file *seq, struct trie *t);
 
-static kmem_cache_t *fn_alias_kmem;
+static kmem_cache_t *fn_alias_kmem __read_mostly;
 static struct trie *trie_local = NULL, *trie_main = NULL;
 
 

net/ipv4/icmp.c

@@ -114,7 +114,7 @@ struct icmp_bxm {
 /*
  *	Statistics
  */
-DEFINE_SNMP_STAT(struct icmp_mib, icmp_statistics);
+DEFINE_SNMP_STAT(struct icmp_mib, icmp_statistics) __read_mostly;
 
 /* An array of errno for error messages from dest unreach. */
 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */

net/ipv4/inetpeer.c

@@ -73,7 +73,7 @@
 /* Exported for inet_getid inline function.  */
 DEFINE_SPINLOCK(inet_peer_idlock);
 
-static kmem_cache_t *peer_cachep;
+static kmem_cache_t *peer_cachep __read_mostly;
 
 #define node_height(x) x->avl_height
 static struct inet_peer peer_fake_node = {

net/ipv4/ip_input.c

@@ -150,7 +150,7 @@
  *	SNMP management statistics
  */
 
-DEFINE_SNMP_STAT(struct ipstats_mib, ip_statistics);
+DEFINE_SNMP_STAT(struct ipstats_mib, ip_statistics) __read_mostly;
 
 /*
  *	Process Router Attention IP option

net/ipv4/ipmr.c

@@ -103,7 +103,7 @@ static DEFINE_SPINLOCK(mfc_unres_lock);
    In this case data path is free of exclusive locks at all.
  */
 
-static kmem_cache_t *mrt_cachep;
+static kmem_cache_t *mrt_cachep __read_mostly;
 
 static int ip_mr_forward(struct sk_buff *skb, struct mfc_cache *cache, int local);
 static int ipmr_cache_report(struct sk_buff *pkt, vifi_t vifi, int assert);

net/ipv4/ipvs/ip_vs_conn.c

@@ -40,7 +40,7 @@
 static struct list_head *ip_vs_conn_tab;
 
 /*  SLAB cache for IPVS connections */
-static kmem_cache_t *ip_vs_conn_cachep;
+static kmem_cache_t *ip_vs_conn_cachep __read_mostly;
 
 /*  counter for current IPVS connections */
 static atomic_t ip_vs_conn_count = ATOMIC_INIT(0);

net/ipv4/netfilter/ip_conntrack_core.c

@@ -70,8 +70,8 @@ static LIST_HEAD(helpers);
 unsigned int ip_conntrack_htable_size = 0;
 int ip_conntrack_max;
 struct list_head *ip_conntrack_hash;
-static kmem_cache_t *ip_conntrack_cachep;
-static kmem_cache_t *ip_conntrack_expect_cachep;
+static kmem_cache_t *ip_conntrack_cachep __read_mostly;
+static kmem_cache_t *ip_conntrack_expect_cachep __read_mostly;
 struct ip_conntrack ip_conntrack_untracked;
 unsigned int ip_ct_log_invalid;
 static LIST_HEAD(unconfirmed);

net/ipv4/netfilter/ipt_hashlimit.c

@@ -94,7 +94,7 @@ struct ipt_hashlimit_htable {
 static DEFINE_SPINLOCK(hashlimit_lock);	/* protects htables list */
 static DECLARE_MUTEX(hlimit_mutex);	/* additional checkentry protection */
 static HLIST_HEAD(hashlimit_htables);
-static kmem_cache_t *hashlimit_cachep;
+static kmem_cache_t *hashlimit_cachep __read_mostly;
 
 static inline int dst_cmp(const struct dsthash_ent *ent, struct dsthash_dst *b)
 {

net/ipv4/tcp.c

@@ -269,7 +269,7 @@
 
 int sysctl_tcp_fin_timeout = TCP_FIN_TIMEOUT;
 
-DEFINE_SNMP_STAT(struct tcp_mib, tcp_statistics);
+DEFINE_SNMP_STAT(struct tcp_mib, tcp_statistics) __read_mostly;
 
 atomic_t tcp_orphan_count = ATOMIC_INIT(0);
 

net/ipv4/udp.c

@@ -113,7 +113,7 @@
  *	Snmp MIB for the UDP layer
  */
 
-DEFINE_SNMP_STAT(struct udp_mib, udp_statistics);
+DEFINE_SNMP_STAT(struct udp_mib, udp_statistics) __read_mostly;
 
 struct hlist_head udp_hash[UDP_HTABLE_SIZE];
 DEFINE_RWLOCK(udp_hash_lock);