llc: replace the socket list with a local address based hash

For the cases where a lot of interfaces are used in conjunction with a
lot of LLC sockets bound to the same SAP, the iteration of the socket
list becomes prohibitively expensive.

Replacing the list with a a local address based hash significantly
improves the bind and listener lookup operations as well as the
datagram delivery.

Connected sockets delivery is also improved, but this patch does not
address the case where we have lots of sockets with the same local
address connected to different remote addresses.

In order to keep the socket sanity checks alive and fast a socket
counter was added to the SAP structure.

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

1 files changed, 30 insertions, 14 deletions

diff --git a/net/llc/llc_proc.c b/net/llc/llc_proc.c
index 6b3d033..09dec63 100644
--- a/net/llc/llc_proc.c
+++ b/net/llc/llc_proc.c
@@ -34,17 +34,22 @@ static struct sock *llc_get_sk_idx(loff_t pos)
 {
 	struct list_head *sap_entry;
 	struct llc_sap *sap;
-	struct hlist_nulls_node *node;
 	struct sock *sk = NULL;
+	int i;
 
 	list_for_each(sap_entry, &llc_sap_list) {
 		sap = list_entry(sap_entry, struct llc_sap, node);
 
 		spin_lock_bh(&sap->sk_lock);
-		sk_nulls_for_each(sk, node, &sap->sk_list) {
-			if (!pos)
-				goto found;
-			--pos;
+		for (i = 0; i < LLC_SK_LADDR_HASH_ENTRIES; i++) {
+			struct hlist_nulls_head *head = &sap->sk_laddr_hash[i];
+			struct hlist_nulls_node *node;
+
+			sk_nulls_for_each(sk, node, head) {
+				if (!pos)
+					goto found; /* keep the lock */
+				--pos;
+			}
 		}
 		spin_unlock_bh(&sap->sk_lock);
 	}
@@ -61,6 +66,19 @@ static void *llc_seq_start(struct seq_file *seq, loff_t *pos)
 	return l ? llc_get_sk_idx(--l) : SEQ_START_TOKEN;
 }
 
+static struct sock *laddr_hash_next(struct llc_sap *sap, int bucket)
+{
+	struct hlist_nulls_node *node;
+	struct sock *sk = NULL;
+
+	while (++bucket < LLC_SK_LADDR_HASH_ENTRIES)
+		sk_nulls_for_each(sk, node, &sap->sk_laddr_hash[bucket])
+			goto out;
+
+out:
+	return sk;
+}
+
 static void *llc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
 	struct sock* sk, *next;
@@ -80,17 +98,15 @@ static void *llc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 	}
 	llc = llc_sk(sk);
 	sap = llc->sap;
+	sk = laddr_hash_next(sap, llc_sk_laddr_hashfn(sap, &llc->laddr));
+	if (sk)
+		goto out;
 	spin_unlock_bh(&sap->sk_lock);
-	sk = NULL;
-	for (;;) {
-		if (sap->node.next == &llc_sap_list)
-			break;
-		sap = list_entry(sap->node.next, struct llc_sap, node);
+	list_for_each_entry_continue(sap, &llc_sap_list, node) {
 		spin_lock_bh(&sap->sk_lock);
-		if (!hlist_nulls_empty(&sap->sk_list)) {
-			sk = sk_nulls_head(&sap->sk_list);
-			break;
-		}
+		sk = laddr_hash_next(sap, -1);
+		if (sk)
+			break; /* keep the lock */
 		spin_unlock_bh(&sap->sk_lock);
 	}
 out: