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>

2 files changed, 11 insertions, 7 deletions

diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 031ce350d3c1..33a1127270c1 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -49,7 +49,7 @@ extern int dccp_debug;
 
 extern struct inet_hashinfo dccp_hashinfo;
 
-extern atomic_t dccp_orphan_count;
+extern struct percpu_counter dccp_orphan_count;
 
 extern void dccp_time_wait(struct sock *sk, int state, int timeo);
 
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index ea85c423cdbd..db225f93cd5a 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -40,8 +40,7 @@ DEFINE_SNMP_STAT(struct dccp_mib, dccp_statistics) __read_mostly;
 
 EXPORT_SYMBOL_GPL(dccp_statistics);
 
-atomic_t dccp_orphan_count = ATOMIC_INIT(0);
-
+struct percpu_counter dccp_orphan_count;
 EXPORT_SYMBOL_GPL(dccp_orphan_count);
 
 struct inet_hashinfo dccp_hashinfo;
@@ -1000,7 +999,7 @@ 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.
@@ -1064,18 +1063,21 @@ static int __init dccp_init(void)
 {
         unsigned long goal;
         int ehash_order, bhash_order, i;
-        int rc = -ENOBUFS;
+        int rc;
 
         BUILD_BUG_ON(sizeof(struct dccp_skb_cb) >
                      FIELD_SIZEOF(struct sk_buff, cb));
-
+        rc = percpu_counter_init(&dccp_orphan_count, 0);
+        if (rc)
+                goto out;
+        rc = -ENOBUFS;
         inet_hashinfo_init(&dccp_hashinfo);
         dccp_hashinfo.bind_bucket_cachep =
                 kmem_cache_create("dccp_bind_bucket",
                                   sizeof(struct inet_bind_bucket), 0,
                                   SLAB_HWCACHE_ALIGN, NULL);
         if (!dccp_hashinfo.bind_bucket_cachep)
-                goto out;
+                goto out_free_percpu;
 
         /*
          * Size and allocate the main established and bind bucket
@@ -1168,6 +1170,8 @@ out_free_dccp_ehash:
 out_free_bind_bucket_cachep:
         kmem_cache_destroy(dccp_hashinfo.bind_bucket_cachep);
         dccp_hashinfo.bind_bucket_cachep = NULL;
+out_free_percpu:
+        percpu_counter_destroy(&dccp_orphan_count);
         goto out;
 }