diff --git a/include/os/freebsd/spl/sys/list.h b/include/os/freebsd/spl/sys/list.h
index 6c32402a7bd1..f15ec7a271e3 100644
--- a/include/os/freebsd/spl/sys/list.h
+++ b/include/os/freebsd/spl/sys/list.h
@@ -52,6 +52,7 @@ void *list_tail(list_t *);
 void *list_next(list_t *, void *);
 void *list_prev(list_t *, void *);
 int list_is_empty(list_t *);
+int list_length(list_t *);
 
 void list_link_init(list_node_t *);
 void list_link_replace(list_node_t *, list_node_t *);
diff --git a/include/os/linux/spl/sys/list.h b/include/os/linux/spl/sys/list.h
index 80300df15abe..e0b5091e8234 100644
--- a/include/os/linux/spl/sys/list.h
+++ b/include/os/linux/spl/sys/list.h
@@ -50,6 +50,7 @@ typedef struct list_head list_node_t;
 typedef struct list {
 	size_t list_size;
 	size_t list_offset;
+	uint32_t list_length;
 	list_node_t list_head;
 } list_t;
 
@@ -62,6 +63,12 @@ list_is_empty(list_t *list)
 	return (list_empty(&list->list_head));
 }
 
+static inline int
+list_length(list_t *list)
+{
+	return (list->list_length);
+}
+
 static inline void
 list_link_init(list_node_t *node)
 {
@@ -74,6 +81,7 @@ list_create(list_t *list, size_t size, size_t offset)
 {
 	list->list_size = size;
 	list->list_offset = offset;
+	list->list_length = 0;
 	INIT_LIST_HEAD(&list->list_head);
 }
 
@@ -86,12 +94,14 @@ list_destroy(list_t *list)
 static inline void
 list_insert_head(list_t *list, void *object)
 {
+	list->list_length++;
 	list_add(list_d2l(list, object), &list->list_head);
 }
 
 static inline void
 list_insert_tail(list_t *list, void *object)
 {
+	list->list_length++;
 	list_add_tail(list_d2l(list, object), &list->list_head);
 }
 
@@ -100,8 +110,10 @@ list_insert_after(list_t *list, void *object, void *nobject)
 {
 	if (object == NULL)
 		list_insert_head(list, nobject);
-	else
+	else {
+		list->list_length++;
 		list_add(list_d2l(list, nobject), list_d2l(list, object));
+	}
 }
 
 static inline void
@@ -109,19 +121,23 @@ list_insert_before(list_t *list, void *object, void *nobject)
 {
 	if (object == NULL)
 		list_insert_tail(list, nobject);
-	else
+	else {
+		list->list_length++;
 		list_add_tail(list_d2l(list, nobject), list_d2l(list, object));
+	}
 }
 
 static inline void
 list_remove(list_t *list, void *object)
 {
+	list->list_length--;
 	list_del(list_d2l(list, object));
 }
 
 static inline void *
 list_remove_head(list_t *list)
 {
+	list->list_length--;
 	list_node_t *head = list->list_head.next;
 	if (head == &list->list_head)
 		return (NULL);
@@ -133,6 +149,7 @@ list_remove_head(list_t *list)
 static inline void *
 list_remove_tail(list_t *list)
 {
+	list->list_length--;
 	list_node_t *tail = list->list_head.prev;
 	if (tail == &list->list_head)
 		return (NULL);
@@ -191,6 +208,8 @@ list_link_active(list_node_t *node)
 static inline void
 spl_list_move_tail(list_t *dst, list_t *src)
 {
+	dst->list_length += src->list_length;
+	src->list_length = 0;
 	list_splice_init(&src->list_head, dst->list_head.prev);
 }
 
diff --git a/lib/libspl/include/sys/list.h b/lib/libspl/include/sys/list.h
index 6c32402a7bd1..f15ec7a271e3 100644
--- a/lib/libspl/include/sys/list.h
+++ b/lib/libspl/include/sys/list.h
@@ -52,6 +52,7 @@ void *list_tail(list_t *);
 void *list_next(list_t *, void *);
 void *list_prev(list_t *, void *);
 int list_is_empty(list_t *);
+int list_length(list_t *);
 
 void list_link_init(list_node_t *);
 void list_link_replace(list_node_t *, list_node_t *);
diff --git a/lib/libspl/include/sys/list_impl.h b/lib/libspl/include/sys/list_impl.h
index 24c1ceb2a9fa..cc6b54168a70 100644
--- a/lib/libspl/include/sys/list_impl.h
+++ b/lib/libspl/include/sys/list_impl.h
@@ -41,6 +41,7 @@ struct list_node {
 struct list {
 	size_t	list_size;
 	size_t	list_offset;
+	uint32_t list_length;
 	struct list_node list_head;
 };
 
diff --git a/lib/libspl/list.c b/lib/libspl/list.c
index 24403698627c..e2c2d718dde4 100644
--- a/lib/libspl/list.c
+++ b/lib/libspl/list.c
@@ -67,6 +67,7 @@ list_create(list_t *list, size_t size, size_t offset)
 
 	list->list_size = size;
 	list->list_offset = offset;
+	list->list_length = 0;
 	list->list_head.next = list->list_head.prev = &list->list_head;
 }
 
@@ -88,6 +89,7 @@ list_insert_after(list_t *list, void *object, void *nobject)
 	if (object == NULL) {
 		list_insert_head(list, nobject);
 	} else {
+		list->list_length++;
 		list_node_t *lold = list_d2l(list, object);
 		list_insert_after_node(list, lold, nobject);
 	}
@@ -99,6 +101,7 @@ list_insert_before(list_t *list, void *object, void *nobject)
 	if (object == NULL) {
 		list_insert_tail(list, nobject);
 	} else {
+		list->list_length++;
 		list_node_t *lold = list_d2l(list, object);
 		list_insert_before_node(list, lold, nobject);
 	}
@@ -107,6 +110,7 @@ list_insert_before(list_t *list, void *object, void *nobject)
 void
 list_insert_head(list_t *list, void *object)
 {
+	list->list_length++;
 	list_node_t *lold = &list->list_head;
 	list_insert_after_node(list, lold, object);
 }
@@ -114,6 +118,7 @@ list_insert_head(list_t *list, void *object)
 void
 list_insert_tail(list_t *list, void *object)
 {
+	list->list_length++;
 	list_node_t *lold = &list->list_head;
 	list_insert_before_node(list, lold, object);
 }
@@ -121,6 +126,7 @@ list_insert_tail(list_t *list, void *object)
 void
 list_remove(list_t *list, void *object)
 {
+	list->list_length--;
 	list_node_t *lold = list_d2l(list, object);
 	ASSERT(!list_empty(list));
 	ASSERT(lold->next != NULL);
@@ -130,6 +136,7 @@ list_remove(list_t *list, void *object)
 void *
 list_remove_head(list_t *list)
 {
+	list->list_length--;
 	list_node_t *head = list->list_head.next;
 	if (head == &list->list_head)
 		return (NULL);
@@ -140,6 +147,7 @@ list_remove_head(list_t *list)
 void *
 list_remove_tail(list_t *list)
 {
+	list->list_length--;
 	list_node_t *tail = list->list_head.prev;
 	if (tail == &list->list_head)
 		return (NULL);
@@ -200,6 +208,8 @@ list_move_tail(list_t *dst, list_t *src)
 	if (list_empty(src))
 		return;
 
+	dst->list_length += src->list_length;
+
 	dstnode->prev->next = srcnode->next;
 	srcnode->next->prev = dstnode->prev;
 	dstnode->prev = srcnode->prev;
@@ -207,6 +217,8 @@ list_move_tail(list_t *dst, list_t *src)
 
 	/* empty src list */
 	srcnode->next = srcnode->prev = srcnode;
+
+	src->list_length = 0;
 }
 
 void
@@ -241,3 +253,9 @@ list_is_empty(list_t *list)
 {
 	return (list_empty(list));
 }
+
+int
+list_length(list_t *list)
+{
+	return (list->list_length);
+}
diff --git a/module/zfs/vdev_queue.c b/module/zfs/vdev_queue.c
index 08d918467d03..cf727404346d 100644
--- a/module/zfs/vdev_queue.c
+++ b/module/zfs/vdev_queue.c
@@ -1069,7 +1069,7 @@ vdev_queue_class_length(vdev_t *vd, zio_priority_t p)
 {
 	vdev_queue_t *vq = &vd->vdev_queue;
 	if (vdev_queue_class_fifo(p))
-		return (list_is_empty(&vq->vq_class[p].vqc_list) == 0);
+		return (list_length(&vq->vq_class[p].vqc_list));
 	else
 		return (avl_numnodes(&vq->vq_class[p].vqc_tree));
 }