net: Use a percpu_counter for orphan_count

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

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

1 files changed, 7 insertions, 5 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index e6fade9ebf62..019243408623 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -277,8 +277,7 @@
 
 int sysctl_tcp_fin_timeout __read_mostly = TCP_FIN_TIMEOUT;
 
-atomic_t tcp_orphan_count = ATOMIC_INIT(0);
-
+struct percpu_counter tcp_orphan_count;
 EXPORT_SYMBOL_GPL(tcp_orphan_count);
 
 int sysctl_tcp_mem[3] __read_mostly;
@@ -1837,7 +1836,7 @@ adjudge_to_death:
         state = sk->sk_state;
         sock_hold(sk);
         sock_orphan(sk);
-        atomic_inc(sk->sk_prot->orphan_count);
+        percpu_counter_inc(sk->sk_prot->orphan_count);
 
         /* It is the last release_sock in its life. It will remove backlog. */
         release_sock(sk);
@@ -1888,9 +1887,11 @@ adjudge_to_death:
                 }
         }
         if (sk->sk_state != TCP_CLOSE) {
+                int orphan_count = percpu_counter_read_positive(
+                                                sk->sk_prot->orphan_count);
+
                 sk_mem_reclaim(sk);
-                if (tcp_too_many_orphans(sk,
-                                atomic_read(sk->sk_prot->orphan_count))) {
+                if (tcp_too_many_orphans(sk, orphan_count)) {
                         if (net_ratelimit())
                                 printk(KERN_INFO "TCP: too many of orphaned "
                                        "sockets\n");
@@ -2689,6 +2690,7 @@ void __init tcp_init(void)
         BUILD_BUG_ON(sizeof(struct tcp_skb_cb) > sizeof(skb->cb));
 
         percpu_counter_init(&tcp_sockets_allocated, 0);
+        percpu_counter_init(&tcp_orphan_count, 0);
         tcp_hashinfo.bind_bucket_cachep =
                 kmem_cache_create("tcp_bind_bucket",
                                   sizeof(struct inet_bind_bucket), 0,