net/mlx5: Add flow counters idr

Previous patch in series changed flow counter storage structure from
rb_tree to linked list in order to improve flow counter traversal
performance. The drawback of such solution is that flow counter lookup by
id becomes linear in complexity.

Store pointers to flow counters in idr in order to improve lookup
performance to logarithmic again. Idr is non-intrusive data structure and
doesn't require extending flow counter struct with new elements. This means
that idr can be used for lookup, while linked list from previous patch is
used for traversal, and struct mlx5_fc size is <= 2 cache lines.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Amir Vadai <amir@vadai.me>
Reviewed-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c

@@ -77,13 +77,18 @@ static struct list_head *mlx5_fc_counters_lookup_next(struct mlx5_core_dev *dev,
 						      u32 id)
 {
 	struct mlx5_fc_stats *fc_stats = &dev->priv.fc_stats;
+	unsigned long next_id = (unsigned long)id + 1;
 	struct mlx5_fc *counter;
 
-	list_for_each_entry(counter, &fc_stats->counters, list)
-		if (counter->id > id)
-			return &counter->list;
+	rcu_read_lock();
+	/* skip counters that are in idr, but not yet in counters list */
+	while ((counter = idr_get_next_ul(&fc_stats->counters_idr,
+					  &next_id)) != NULL &&
+	       list_empty(&counter->list))
+		next_id++;
+	rcu_read_unlock();
 
-	return &fc_stats->counters;
+	return counter ? &counter->list : &fc_stats->counters;
 }
 
 static void mlx5_fc_stats_insert(struct mlx5_core_dev *dev,
@@ -214,15 +219,29 @@ struct mlx5_fc *mlx5_fc_create(struct mlx5_core_dev *dev, bool aging)
 	counter = kzalloc(sizeof(*counter), GFP_KERNEL);
 	if (!counter)
 		return ERR_PTR(-ENOMEM);
+	INIT_LIST_HEAD(&counter->list);
 
 	err = mlx5_cmd_fc_alloc(dev, &counter->id);
 	if (err)
 		goto err_out;
 
 	if (aging) {
+		u32 id = counter->id;
+
 		counter->cache.lastuse = jiffies;
 		counter->aging = true;
 
+		idr_preload(GFP_KERNEL);
+		spin_lock(&fc_stats->counters_idr_lock);
+
+		err = idr_alloc_u32(&fc_stats->counters_idr, counter, &id, id,
+				    GFP_NOWAIT);
+
+		spin_unlock(&fc_stats->counters_idr_lock);
+		idr_preload_end();
+		if (err)
+			goto err_out_alloc;
+
 		llist_add(&counter->addlist, &fc_stats->addlist);
 
 		mod_delayed_work(fc_stats->wq, &fc_stats->work, 0);
@@ -230,6 +249,8 @@ struct mlx5_fc *mlx5_fc_create(struct mlx5_core_dev *dev, bool aging)
 
 	return counter;
 
+err_out_alloc:
+	mlx5_cmd_fc_free(dev, counter->id);
 err_out:
 	kfree(counter);
 
@@ -245,6 +266,10 @@ void mlx5_fc_destroy(struct mlx5_core_dev *dev, struct mlx5_fc *counter)
 		return;
 
 	if (counter->aging) {
+		spin_lock(&fc_stats->counters_idr_lock);
+		WARN_ON(!idr_remove(&fc_stats->counters_idr, counter->id));
+		spin_unlock(&fc_stats->counters_idr_lock);
+
 		llist_add(&counter->dellist, &fc_stats->dellist);
 		mod_delayed_work(fc_stats->wq, &fc_stats->work, 0);
 		return;
@@ -258,6 +283,8 @@ int mlx5_init_fc_stats(struct mlx5_core_dev *dev)
 {
 	struct mlx5_fc_stats *fc_stats = &dev->priv.fc_stats;
 
+	spin_lock_init(&fc_stats->counters_idr_lock);
+	idr_init(&fc_stats->counters_idr);
 	INIT_LIST_HEAD(&fc_stats->counters);
 	init_llist_head(&fc_stats->addlist);
 	init_llist_head(&fc_stats->dellist);
@@ -283,6 +310,8 @@ void mlx5_cleanup_fc_stats(struct mlx5_core_dev *dev)
 	destroy_workqueue(dev->priv.fc_stats.wq);
 	dev->priv.fc_stats.wq = NULL;
 
+	idr_destroy(&fc_stats->counters_idr);
+
 	tmplist = llist_del_all(&fc_stats->addlist);
 	llist_for_each_entry_safe(counter, tmp, tmplist, addlist)
 		mlx5_free_fc(dev, counter);

include/linux/mlx5/driver.h

@@ -583,6 +583,8 @@ struct mlx5_irq_info {
 };
 
 struct mlx5_fc_stats {
+	spinlock_t counters_idr_lock; /* protects counters_idr */
+	struct idr counters_idr;
 	struct list_head counters;
 	struct llist_head addlist;
 	struct llist_head dellist;