ike-sa-manager: Improve scalability of half-open IKE_SA checking

This patch is based on one by Christoph Gouault.

Currently, to count the total number of half_open IKE_SAs,
get_half_open_count sums up the count of each segment in the SA hash
table (acquiring a lock for each segment).  This procedure does not scale
well when the number of segments increases, as the method is called for
each new negotiation.

Instead, lets maintain a global atomic counter.

This optimization allows the use of big values for charon.ikesa_table_size
and charon.ikesa_table_segments.

1 files changed, 8 insertions, 7 deletions

diff --git a/src/libcharon/sa/ike_sa_manager.c b/src/libcharon/sa/ike_sa_manager.c
index f2f81cf33..525117f3b 100644
--- a/src/libcharon/sa/ike_sa_manager.c
+++ b/src/libcharon/sa/ike_sa_manager.c
@@ -354,6 +354,11 @@ struct private_ike_sa_manager_t {
 	shareable_segment_t *half_open_segments;
 
 	/**
+	 * Total number of half-open IKE_SAs.
+	 */
+	refcount_t half_open_count;
+
+	/**
 	 * Hash table with connected_peers_t objects.
 	 */
 	table_item_t **connected_peers_table;
@@ -764,6 +769,7 @@ static void put_half_open(private_ike_sa_manager_t *this, entry_t *entry)
 		this->half_open_table[row] = item;
 	}
 	this->half_open_segments[segment].count++;
+	ref_get(&this->half_open_count);
 	lock->unlock(lock);
 }
 
@@ -803,6 +809,7 @@ static void remove_half_open(private_ike_sa_manager_t *this, entry_t *entry)
 				free(item);
 			}
 			this->half_open_segments[segment].count--;
+			ignore_result(ref_put(&this->half_open_count));
 			break;
 		}
 		prev = item;
@@ -1962,13 +1969,7 @@ METHOD(ike_sa_manager_t, get_half_open_count, u_int,
 	}
 	else
 	{
-		for (segment = 0; segment < this->segment_count; segment++)
-		{
-			lock = this->half_open_segments[segment].lock;
-			lock->read_lock(lock);
-			count += this->half_open_segments[segment].count;
-			lock->unlock(lock);
-		}
+		count = (u_int)ref_cur(&this->half_open_count);
 	}
 	return count;
 }