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>

2 files changed, 8 insertions, 4 deletions

diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index a8ca743241ee..d5ea232c9126 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -102,6 +102,8 @@ struct sock *sctp_get_ctl_sock(void)
 /* Set up the proc fs entry for the SCTP protocol. */
 static __init int sctp_proc_init(void)
 {
+        if (percpu_counter_init(&sctp_sockets_allocated, 0))
+                goto out_nomem;
 #ifdef CONFIG_PROC_FS
         if (!proc_net_sctp) {
                 struct proc_dir_entry *ent;
@@ -110,7 +112,7 @@ static __init int sctp_proc_init(void)
                         ent->owner = THIS_MODULE;
                         proc_net_sctp = ent;
                 } else
-                        goto out_nomem;
+                        goto out_free_percpu;
         }
 
         if (sctp_snmp_proc_init())
@@ -135,6 +137,8 @@ out_snmp_proc_init:
                 proc_net_sctp = NULL;
                 remove_proc_entry("sctp", init_net.proc_net);
         }
+out_free_percpu:
+        percpu_counter_destroy(&sctp_sockets_allocated);
 out_nomem:
         return -ENOMEM;
 #else
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index ba81fe3ccab8..a2de585888d0 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -114,7 +114,7 @@ extern int sysctl_sctp_wmem[3];
 
 static int sctp_memory_pressure;
 static atomic_t sctp_memory_allocated;
-static atomic_t sctp_sockets_allocated;
+struct percpu_counter sctp_sockets_allocated;
 
 static void sctp_enter_memory_pressure(struct sock *sk)
 {
@@ -3613,7 +3613,7 @@ SCTP_STATIC int sctp_init_sock(struct sock *sk)
         sp->hmac = NULL;
 
         SCTP_DBG_OBJCNT_INC(sock);
-        atomic_inc(&sctp_sockets_allocated);
+        percpu_counter_inc(&sctp_sockets_allocated);
 
         local_bh_disable();
         sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
@@ -3632,7 +3632,7 @@ SCTP_STATIC void sctp_destroy_sock(struct sock *sk)
         /* Release our hold on the endpoint. */
         ep = sctp_sk(sk)->ep;
         sctp_endpoint_free(ep);
-        atomic_dec(&sctp_sockets_allocated);
+        percpu_counter_dec(&sctp_sockets_allocated);
         local_bh_disable();
         sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
         local_bh_enable();