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, 10 insertions, 5 deletions

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 731789bb499f..4944b47ad628 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -55,7 +55,8 @@ static int sockstat_seq_show(struct seq_file *seq, void *v)
         seq_printf(seq, "TCP: inuse %d orphan %d tw %d alloc %d mem %d\n",
                    sock_prot_inuse_get(net, &tcp_prot),
                    atomic_read(&tcp_orphan_count),
-                   tcp_death_row.tw_count, atomic_read(&tcp_sockets_allocated),
+                   tcp_death_row.tw_count,
+                   (int)percpu_counter_sum_positive(&tcp_sockets_allocated),
                    atomic_read(&tcp_memory_allocated));
         seq_printf(seq, "UDP: inuse %d mem %d\n",
                    sock_prot_inuse_get(net, &udp_prot),
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 044224a341eb..e6fade9ebf62 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -290,9 +290,12 @@ EXPORT_SYMBOL(sysctl_tcp_rmem);
 EXPORT_SYMBOL(sysctl_tcp_wmem);
 
 atomic_t tcp_memory_allocated;  /* Current allocated memory. */
-atomic_t tcp_sockets_allocated; /* Current number of TCP sockets. */
-
 EXPORT_SYMBOL(tcp_memory_allocated);
+
+/*
+ * Current number of TCP sockets.
+ */
+struct percpu_counter tcp_sockets_allocated;
 EXPORT_SYMBOL(tcp_sockets_allocated);
 
 /*
@@ -2685,6 +2688,7 @@ void __init tcp_init(void)
 
         BUILD_BUG_ON(sizeof(struct tcp_skb_cb) > sizeof(skb->cb));
 
+        percpu_counter_init(&tcp_sockets_allocated, 0);
         tcp_hashinfo.bind_bucket_cachep =
                 kmem_cache_create("tcp_bind_bucket",
                                   sizeof(struct inet_bind_bucket), 0,
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index cab2458f86fd..26b9030747cc 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1797,7 +1797,7 @@ static int tcp_v4_init_sock(struct sock *sk)
         sk->sk_sndbuf = sysctl_tcp_wmem[1];
         sk->sk_rcvbuf = sysctl_tcp_rmem[1];
 
-        atomic_inc(&tcp_sockets_allocated);
+        percpu_counter_inc(&tcp_sockets_allocated);
 
         return 0;
 }
@@ -1845,7 +1845,7 @@ void tcp_v4_destroy_sock(struct sock *sk)
                 sk->sk_sndmsg_page = NULL;
         }
 
-        atomic_dec(&tcp_sockets_allocated);
+        percpu_counter_dec(&tcp_sockets_allocated);
 }
 
 EXPORT_SYMBOL(tcp_v4_destroy_sock);