llc: use a device based hash table to speed up multicast delivery

This patch adds a per SAP device based hash table to solve the
multicast delivery scalability issue when we have large number of
interfaces and a large number of sockets bound to the same SAP.

Signed-off-by: Octavian Purdila <opurdila@ixiacom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 27 insertions, 3 deletions

diff --git a/include/net/llc.h b/include/net/llc.h
index 1559cf10e874..dbef5917905b 100644
--- a/include/net/llc.h
+++ b/include/net/llc.h
@@ -32,6 +32,9 @@ struct llc_addr {
 #define LLC_SAP_STATE_INACTIVE  1
 #define LLC_SAP_STATE_ACTIVE    2
 
+#define LLC_SK_DEV_HASH_BITS 6
+#define LLC_SK_DEV_HASH_ENTRIES (1<<LLC_SK_DEV_HASH_BITS)
+
 /**
  * struct llc_sap - Defines the SAP component
  *
@@ -56,8 +59,16 @@ struct llc_sap {
         struct list_head node;
         spinlock_t sk_lock;
         struct hlist_nulls_head sk_list;
+        struct hlist_head sk_dev_hash[LLC_SK_DEV_HASH_ENTRIES];
 };
 
+static inline
+struct hlist_head *llc_sk_dev_hash(struct llc_sap *sap, int ifindex)
+{
+        return &sap->sk_dev_hash[ifindex % LLC_SK_DEV_HASH_ENTRIES];
+}
+
+
 #define LLC_DEST_INVALID         0      /* Invalid LLC PDU type */
 #define LLC_DEST_SAP             1      /* Type 1 goes here */
 #define LLC_DEST_CONN            2      /* Type 2 goes here */
diff --git a/include/net/llc_conn.h b/include/net/llc_conn.h
index fe982fd94c4a..2f97d8ddce92 100644
--- a/include/net/llc_conn.h
+++ b/include/net/llc_conn.h
@@ -77,6 +77,7 @@ struct llc_sock {
                                               received and caused sending FRMR.
                                               Used for resending FRMR */
         u32                 cmsg_flags;
+        struct hlist_node   dev_hash_node;
 };
 
 static inline struct llc_sock *llc_sk(const struct sock *sk)
diff --git a/net/llc/llc_conn.c b/net/llc/llc_conn.c
index 77bb3816655e..10cdfe2db830 100644
--- a/net/llc/llc_conn.c
+++ b/net/llc/llc_conn.c
@@ -682,10 +682,15 @@ static int llc_find_offset(int state, int ev_type)
  */
 void llc_sap_add_socket(struct llc_sap *sap, struct sock *sk)
 {
+        struct llc_sock *llc = llc_sk(sk);
+        struct hlist_head *dev_hb = llc_sk_dev_hash(sap, llc->dev->ifindex);
+
         llc_sap_hold(sap);
-        spin_lock_bh(&sap->sk_lock);
         llc_sk(sk)->sap = sap;
+
+        spin_lock_bh(&sap->sk_lock);
         sk_nulls_add_node_rcu(sk, &sap->sk_list);
+        hlist_add_head(&llc->dev_hash_node, dev_hb);
         spin_unlock_bh(&sap->sk_lock);
 }
 
@@ -699,8 +704,11 @@ void llc_sap_add_socket(struct llc_sap *sap, struct sock *sk)
  */
 void llc_sap_remove_socket(struct llc_sap *sap, struct sock *sk)
 {
+        struct llc_sock *llc = llc_sk(sk);
+
         spin_lock_bh(&sap->sk_lock);
         sk_nulls_del_node_init_rcu(sk);
+        hlist_del(&llc->dev_hash_node);
         spin_unlock_bh(&sap->sk_lock);
         llc_sap_put(sap);
 }
diff --git a/net/llc/llc_sap.c b/net/llc/llc_sap.c
index 94790e60d072..94cb706f6cc4 100644
--- a/net/llc/llc_sap.c
+++ b/net/llc/llc_sap.c
@@ -387,10 +387,14 @@ static void llc_sap_mcast(struct llc_sap *sap,
 {
         int i = 0, count = 256 / sizeof(struct sock *);
         struct sock *sk, *stack[count];
-        struct hlist_nulls_node *node;
+        struct hlist_node *node;
+        struct llc_sock *llc;
+        struct hlist_head *dev_hb = llc_sk_dev_hash(sap, skb->dev->ifindex);
 
         spin_lock_bh(&sap->sk_lock);
-        sk_nulls_for_each_rcu(sk, node, &sap->sk_list) {
+        hlist_for_each_entry(llc, node, dev_hb, dev_hash_node) {
+
+                sk = &llc->sk;
 
                 if (!llc_mcast_match(sap, laddr, skb, sk))
                         continue;