net: snmp: inline snmp_get_cpu_field()

This trivial function is called ~90,000 times on 256 cpus hosts,
when reading /proc/net/netstat. And this number keeps inflating.

Inlining it saves many cycles.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/ip.h

@@ -291,7 +291,11 @@ void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
 #define NET_ADD_STATS(net, field, adnd)	SNMP_ADD_STATS((net)->mib.net_statistics, field, adnd)
 #define __NET_ADD_STATS(net, field, adnd) __SNMP_ADD_STATS((net)->mib.net_statistics, field, adnd)
 
-u64 snmp_get_cpu_field(void __percpu *mib, int cpu, int offct);
+static inline u64 snmp_get_cpu_field(void __percpu *mib, int cpu, int offt)
+{
+	return  *(((unsigned long *)per_cpu_ptr(mib, cpu)) + offt);
+}
+
 unsigned long snmp_fold_field(void __percpu *mib, int offt);
 #if BITS_PER_LONG==32
 u64 snmp_get_cpu_field64(void __percpu *mib, int cpu, int offct,

net/ipv4/af_inet.c

@@ -1662,12 +1662,6 @@ int inet_ctl_sock_create(struct sock **sk, unsigned short family,
 }
 EXPORT_SYMBOL_GPL(inet_ctl_sock_create);
 
-u64 snmp_get_cpu_field(void __percpu *mib, int cpu, int offt)
-{
-	return  *(((unsigned long *)per_cpu_ptr(mib, cpu)) + offt);
-}
-EXPORT_SYMBOL_GPL(snmp_get_cpu_field);
-
 unsigned long snmp_fold_field(void __percpu *mib, int offt)
 {
 	unsigned long res = 0;