net: Use a percpu_counter for sockets_allocated

Instead of using one atomic_t per protocol, use a percpu_counter
for "sockets_allocated", to reduce cache line contention on
heavy duty network servers. 

Note : We revert commit (248969ae31e1b3276fc4399d67ce29a5d81e6fd9
net: af_unix can make unix_nr_socks visbile in /proc),
since it is not anymore used after sock_prot_inuse_add() addition

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

3 files changed, 3 insertions, 2 deletions

diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
index 23797506f593..bbb7742195b0 100644
--- a/include/net/sctp/sctp.h
+++ b/include/net/sctp/sctp.h
@@ -138,6 +138,7 @@ void sctp_write_space(struct sock *sk);
 unsigned int sctp_poll(struct file *file, struct socket *sock,
                 poll_table *wait);
 void sctp_sock_rfree(struct sk_buff *skb);
+extern struct percpu_counter sctp_sockets_allocated;
 
 /*
  * sctp/primitive.c
diff --git a/include/net/sock.h b/include/net/sock.h
index 00cd486d362f..a2a3890959c4 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -649,7 +649,7 @@ struct proto {
         /* Memory pressure */
         void                    (*enter_memory_pressure)(struct sock *sk);
         atomic_t                *memory_allocated;      /* Current allocated memory. */
-        atomic_t                *sockets_allocated;     /* Current number of sockets. */
+        struct percpu_counter   *sockets_allocated;     /* Current number of sockets. */
         /*
          * Pressure flag: try to collapse.
          * Technical note: it is used by multiple contexts non atomically.
diff --git a/include/net/tcp.h b/include/net/tcp.h
index e8ae90a8c35e..cbca3b8a133d 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -238,7 +238,7 @@ extern int sysctl_tcp_slow_start_after_idle;
 extern int sysctl_tcp_max_ssthresh;
 
 extern atomic_t tcp_memory_allocated;
-extern atomic_t tcp_sockets_allocated;
+extern struct percpu_counter tcp_sockets_allocated;
 extern int tcp_memory_pressure;
 
 /*