Add benchmark for viewport creation/activation (#61)

Co-authored-by: Hugo Locurcio <hugo.locurcio@hugo.pro>

benchmarks/viewport/activation.gd

@@ -0,0 +1,45 @@
+extends Benchmark
+
+# In Godot, a lot of the cost of Viewport nodes comes during activation.
+# That is, when you create it, add it to the tree, set the size and allocate the viewport texture...
+# The point when the underlying render target is created is a huge weak point in some GPU drivers.
+const allocation = preload("./allocation.gd")
+
+
+class TestScene extends Node2D:
+	var viewports: Array[SubViewport] = []
+	var viewports_added := false
+
+	func _init(count: int):
+		viewports = allocation.create_viewports(count)
+
+	func _ready():
+		var cl := CanvasLayer.new()
+		add_child(cl)
+		var i := 0
+		for vp in viewports:
+			var vpc = SubViewportContainer.new()
+			vpc.add_child(vp)
+			vpc.size = Vector2.ONE * allocation.VIEWPORT_SIZE
+			cl.add_child(vpc)
+			vpc.position = Vector2.ONE * ((i * 10) % 1024)
+			i += 1
+
+
+func activate_viewports(count: int):
+	var node = TestScene.new(count)
+	Manager.get_tree().root.add_child(node)
+	await Manager.get_tree().process_frame
+	node.free()
+
+
+func benchmark_activate_64_viewports():
+	await activate_viewports(64)
+
+
+func benchmark_activate_256_viewports():
+	await activate_viewports(256)
+
+
+func benchmark_activate_1024_viewports():
+	await activate_viewports(1024)

benchmarks/viewport/allocation.gd

@@ -0,0 +1,32 @@
+extends Benchmark
+
+const VIEWPORT_SIZE = 512
+
+func _init() -> void:
+	pass
+
+
+static func create_viewports(count: int) -> Array[SubViewport]:
+	var viewports : Array[SubViewport] = []
+	for i in range(count):
+		var vp := SubViewport.new()
+		vp.size = Vector2.ONE * VIEWPORT_SIZE
+		viewports.append(vp)
+	return viewports
+
+
+static func free_items(items: Array):
+	for item in items:
+		item.free()
+
+
+func benchmark_create_64_viewports():
+	free_items(create_viewports(64))
+
+
+func benchmark_create_256_viewports():
+	free_items(create_viewports(256))
+
+
+func benchmark_create_1024_viewports():
+	free_items(create_viewports(1024))

manager.gd

@@ -152,7 +152,8 @@ func run_test(test_id: TestID) -> void:
 
 	# Call and time the function to be tested
 	var begin_time := Time.get_ticks_usec()
-	var bench_node = bench_script.call(languages[test_id.language]["test_prefix"] + test_id.name)
+	# Redundant awaits don't seem to cause a performance variation.
+	var bench_node = await bench_script.call(languages[test_id.language]["test_prefix"] + test_id.name)
 	results.time = (Time.get_ticks_usec() - begin_time) * 0.001
 
 	# Continue benchmarking if the function call has returned a node