diff --git a/src/Avalonia.Controls/AutoCompleteBox.cs b/src/Avalonia.Controls/AutoCompleteBox.cs
index bf177d64cd..9bc7ba9e2f 100644
--- a/src/Avalonia.Controls/AutoCompleteBox.cs
+++ b/src/Avalonia.Controls/AutoCompleteBox.cs
@@ -1630,7 +1630,7 @@ namespace Avalonia.Controls
         /// </summary>
         /// <param name="sender">The source object.</param>
         /// <param name="e">The event data.</param>
-        private void DropDownPopup_Closed(object sender, EventArgs e)
+        private void DropDownPopup_Closed(object sender, PopupClosedEventArgs e)
         {
             // Force the drop down dependency property to be false.
             if (IsDropDownOpen)
@@ -1638,6 +1638,11 @@ namespace Avalonia.Controls
                 IsDropDownOpen = false;
             }
 
+            if (e.CloseEvent is PointerEventArgs pointerEvent)
+            {
+                pointerEvent.Handled = true;
+            }
+
             // Fire the DropDownClosed event
             if (_popupHasOpened)
             {
diff --git a/src/Avalonia.Controls/Calendar/DatePicker.cs b/src/Avalonia.Controls/Calendar/DatePicker.cs
index 07e42c64e4..b4e4ad1452 100644
--- a/src/Avalonia.Controls/Calendar/DatePicker.cs
+++ b/src/Avalonia.Controls/Calendar/DatePicker.cs
@@ -895,12 +895,17 @@ namespace Avalonia.Controls
                 _ignoreButtonClick = false;
             }
         }
-        private void PopUp_Closed(object sender, EventArgs e)
+        private void PopUp_Closed(object sender, PopupClosedEventArgs e)
         {
             IsDropDownOpen = false;
 
             if(!_isPopupClosing)
             {
+                if (e.CloseEvent is PointerEventArgs pointerEvent)
+                {
+                    pointerEvent.Handled = true;
+                }
+
                 _isPopupClosing = true;
                 Threading.Dispatcher.UIThread.InvokeAsync(() => _isPopupClosing = false);
             }
diff --git a/src/Avalonia.Controls/ComboBox.cs b/src/Avalonia.Controls/ComboBox.cs
index 4b7d931d80..1daa6a5630 100644
--- a/src/Avalonia.Controls/ComboBox.cs
+++ b/src/Avalonia.Controls/ComboBox.cs
@@ -242,11 +242,16 @@ namespace Avalonia.Controls
             }
         }
 
-        private void PopupClosed(object sender, EventArgs e)
+        private void PopupClosed(object sender, PopupClosedEventArgs e)
         {
             _subscriptionsOnOpen?.Dispose();
             _subscriptionsOnOpen = null;
 
+            if (e.CloseEvent is PointerEventArgs pointerEvent)
+            {
+                pointerEvent.Handled = true;
+            }
+
             if (CanFocus(this))
             {
                 Focus();
diff --git a/src/Avalonia.Controls/Primitives/Popup.cs b/src/Avalonia.Controls/Primitives/Popup.cs
index f069903e05..66f2153b6c 100644
--- a/src/Avalonia.Controls/Primitives/Popup.cs
+++ b/src/Avalonia.Controls/Primitives/Popup.cs
@@ -95,7 +95,7 @@ namespace Avalonia.Controls.Primitives
         /// <summary>
         /// Raised when the popup closes.
         /// </summary>
-        public event EventHandler? Closed;
+        public event EventHandler<PopupClosedEventArgs>? Closed;
 
         /// <summary>
         /// Raised when the popup opens.
@@ -270,7 +270,7 @@ namespace Avalonia.Controls.Primitives
 
                 if (parentPopupRoot?.Parent is Popup popup)
                 {
-                    DeferCleanup(SubscribeToEventHandler<Popup, EventHandler>(popup, ParentClosed,
+                    DeferCleanup(SubscribeToEventHandler<Popup, EventHandler<PopupClosedEventArgs>>(popup, ParentClosed,
                         (x, handler) => x.Closed += handler,
                         (x, handler) => x.Closed -= handler));
                 }
@@ -306,28 +306,7 @@ namespace Avalonia.Controls.Primitives
         /// <summary>
         /// Closes the popup.
         /// </summary>
-        public void Close()
-        {
-            if (_openState is null)
-            {
-                using (BeginIgnoringIsOpen())
-                {
-                    IsOpen = false;
-                }
-
-                return;
-            }
-
-            _openState.Dispose();
-            _openState = null;
-
-            using (BeginIgnoringIsOpen())
-            {
-                IsOpen = false;
-            }
-
-            Closed?.Invoke(this, EventArgs.Empty);
-        }
+        public void Close() => CloseCore(null);
 
         /// <summary>
         /// Measures the control.
@@ -389,22 +368,44 @@ namespace Avalonia.Controls.Primitives
             }
         }
 
+        private void CloseCore(EventArgs? closeEvent)
+        {
+            if (_openState is null)
+            {
+                using (BeginIgnoringIsOpen())
+                {
+                    IsOpen = false;
+                }
+
+                return;
+            }
+
+            _openState.Dispose();
+            _openState = null;
+
+            using (BeginIgnoringIsOpen())
+            {
+                IsOpen = false;
+            }
+
+            Closed?.Invoke(this, new PopupClosedEventArgs(closeEvent));
+        }
+
         private void ListenForNonClientClick(RawInputEventArgs e)
         {
             var mouse = e as RawPointerEventArgs;
 
             if (!StaysOpen && mouse?.Type == RawPointerEventType.NonClientLeftButtonDown)
             {
-                Close();
+                CloseCore(e);
             }
         }
 
         private void PointerPressedOutside(object sender, PointerPressedEventArgs e)
         {
-            if (!StaysOpen && !IsChildOrThis((IVisual)e.Source))
+            if (!StaysOpen && e.Source is IVisual v && !IsChildOrThis(v))
             {
-                Close();
-                e.Handled = true;
+                CloseCore(e);
             }
         }
 
diff --git a/src/Avalonia.Controls/Primitives/PopupClosedEventArgs.cs b/src/Avalonia.Controls/Primitives/PopupClosedEventArgs.cs
new file mode 100644
index 0000000000..c51543438c
--- /dev/null
+++ b/src/Avalonia.Controls/Primitives/PopupClosedEventArgs.cs
@@ -0,0 +1,33 @@
+using System;
+using Avalonia.Interactivity;
+
+#nullable enable
+
+namespace Avalonia.Controls.Primitives
+{
+    /// <summary>
+    /// Holds data for the <see cref="Popup.Closed"/> event.
+    /// </summary>
+    public class PopupClosedEventArgs : EventArgs
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PopupClosedEventArgs"/> class.
+        /// </summary>
+        /// <param name="closeEvent"></param>
+        public PopupClosedEventArgs(EventArgs? closeEvent)
+        {
+            CloseEvent = closeEvent;
+        }
+
+        /// <summary>
+        /// Gets the event that closed the popup, if any.
+        /// </summary>
+        /// <remarks>
+        /// If <see cref="Popup.StaysOpen"/> is false, then this property will hold details of the
+        /// interaction that caused the popup to close if the close was caused by e.g. a pointer press
+        /// outside the popup. It can be used to mark the event as handled if the event should not
+        /// be propagated.
+        /// </remarks>
+        public EventArgs? CloseEvent { get; }
+    }
+}
diff --git a/src/Avalonia.Visuals/Rendering/SceneGraph/Scene.cs b/src/Avalonia.Visuals/Rendering/SceneGraph/Scene.cs
index b4bf4c799a..b2e827fa26 100644
--- a/src/Avalonia.Visuals/Rendering/SceneGraph/Scene.cs
+++ b/src/Avalonia.Visuals/Rendering/SceneGraph/Scene.cs
@@ -12,7 +12,7 @@ namespace Avalonia.Rendering.SceneGraph
     /// </summary>
     public class Scene : IDisposable
     {
-        private Dictionary<IVisual, IVisualNode> _index;
+        private readonly Dictionary<IVisual, IVisualNode> _index;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="Scene"/> class.
@@ -83,7 +83,7 @@ namespace Avalonia.Rendering.SceneGraph
         /// <returns>The cloned scene.</returns>
         public Scene CloneScene()
         {
-            var index = new Dictionary<IVisual, IVisualNode>();
+            var index = new Dictionary<IVisual, IVisualNode>(_index.Count);
             var root = Clone((VisualNode)Root, null, index);
 
             var result = new Scene(root, index, Layers.Clone(), Generation + 1)
@@ -162,9 +162,18 @@ namespace Avalonia.Rendering.SceneGraph
 
             index.Add(result.Visual, result);
 
-            foreach (var child in source.Children)
+            int childCount = source.Children.Count;
+
+            if (childCount > 0)
             {
-                result.AddChild(Clone((VisualNode)child, result, index));
+                Span<IVisualNode> children = result.AddChildrenSpan(childCount);
+
+                for (var i = 0; i < childCount; i++)
+                {
+                    var child = source.Children[i];
+
+                    children[i] = Clone((VisualNode)child, result, index);
+                }
             }
 
             return result;
diff --git a/src/Avalonia.Visuals/Rendering/SceneGraph/SceneLayers.cs b/src/Avalonia.Visuals/Rendering/SceneGraph/SceneLayers.cs
index 5960b4f560..25f7383a1a 100644
--- a/src/Avalonia.Visuals/Rendering/SceneGraph/SceneLayers.cs
+++ b/src/Avalonia.Visuals/Rendering/SceneGraph/SceneLayers.cs
@@ -11,16 +11,28 @@ namespace Avalonia.Rendering.SceneGraph
     public class SceneLayers : IEnumerable<SceneLayer>
     {
         private readonly IVisual _root;
-        private readonly List<SceneLayer> _inner = new List<SceneLayer>();
-        private readonly Dictionary<IVisual, SceneLayer> _index = new Dictionary<IVisual, SceneLayer>();
+        private readonly List<SceneLayer> _inner;
+        private readonly Dictionary<IVisual, SceneLayer> _index;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="SceneLayers"/> class.
         /// </summary>
         /// <param name="root">The scene's root visual.</param>
-        public SceneLayers(IVisual root)
+        public SceneLayers(IVisual root) : this(root, 0)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="SceneLayers"/> class.
+        /// </summary>
+        /// <param name="root">The scene's root visual.</param>
+        /// <param name="capacity">Initial layer capacity.</param>
+        public SceneLayers(IVisual root, int capacity)
         {
             _root = root;
+
+            _inner = new List<SceneLayer>(capacity);
+            _index = new Dictionary<IVisual, SceneLayer>(capacity);
         }
 
         /// <summary>
@@ -84,7 +96,7 @@ namespace Avalonia.Rendering.SceneGraph
         /// <returns>The cloned layers.</returns>
         public SceneLayers Clone()
         {
-            var result = new SceneLayers(_root);
+            var result = new SceneLayers(_root, Count);
 
             foreach (var src in _inner)
             {
diff --git a/src/Avalonia.Visuals/Rendering/SceneGraph/VisualNode.cs b/src/Avalonia.Visuals/Rendering/SceneGraph/VisualNode.cs
index 82444a0c29..8cd1a47795 100644
--- a/src/Avalonia.Visuals/Rendering/SceneGraph/VisualNode.cs
+++ b/src/Avalonia.Visuals/Rendering/SceneGraph/VisualNode.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Reactive.Disposables;
+using Avalonia.Collections.Pooled;
 using Avalonia.Media;
 using Avalonia.Platform;
 using Avalonia.Utilities;
@@ -19,8 +20,8 @@ namespace Avalonia.Rendering.SceneGraph
 
         private Rect? _bounds;
         private double _opacity;
-        private List<IVisualNode> _children;
-        private List<IRef<IDrawOperation>> _drawOperations;
+        private PooledList<IVisualNode> _children;
+        private PooledList<IRef<IDrawOperation>> _drawOperations;
         private IRef<IDisposable> _drawOperationsRefCounter;
         private bool _drawOperationsCloned;
         private Matrix transformRestore;
@@ -349,6 +350,18 @@ namespace Avalonia.Rendering.SceneGraph
             context.Transform = transformRestore;
         }
 
+        /// <summary>
+        /// Inserts default constructed children into collection and returns a span for the newly created range.
+        /// </summary>
+        /// <param name="count">Count of children that will be added.</param>
+        /// <returns></returns>
+        internal Span<IVisualNode> AddChildrenSpan(int count)
+        {
+            EnsureChildrenCreated(count);
+
+            return _children.AddSpan(count);
+        }
+
         private Rect CalculateBounds()
         {
             var result = new Rect();
@@ -362,11 +375,11 @@ namespace Avalonia.Rendering.SceneGraph
             return result;
         }
 
-        private void EnsureChildrenCreated()
+        private void EnsureChildrenCreated(int capacity = 0)
         {
             if (_children == null)
             {
-                _children = new List<IVisualNode>();
+                _children = new PooledList<IVisualNode>(capacity);
             }
         }
 
@@ -377,13 +390,21 @@ namespace Avalonia.Rendering.SceneGraph
         {
             if (_drawOperations == null)
             {
-                _drawOperations = new List<IRef<IDrawOperation>>();
+                _drawOperations = new PooledList<IRef<IDrawOperation>>();
                 _drawOperationsRefCounter = RefCountable.Create(CreateDisposeDrawOperations(_drawOperations));
                 _drawOperationsCloned = false;
             }
             else if (_drawOperationsCloned)
             {
-                _drawOperations = new List<IRef<IDrawOperation>>(_drawOperations.Select(op => op.Clone()));
+                var oldDrawOperations = _drawOperations;
+
+                _drawOperations = new PooledList<IRef<IDrawOperation>>(oldDrawOperations.Count);
+
+                foreach (var drawOperation in oldDrawOperations)
+                {
+                    _drawOperations.Add(drawOperation.Clone());
+                }
+
                 _drawOperationsRefCounter.Dispose();
                 _drawOperationsRefCounter = RefCountable.Create(CreateDisposeDrawOperations(_drawOperations));
                 _drawOperationsCloned = false;
@@ -397,14 +418,16 @@ namespace Avalonia.Rendering.SceneGraph
         /// </summary>
         /// <param name="drawOperations">Draw operations that need to be disposed.</param>
         /// <returns>Disposable for given draw operations.</returns>
-        private static IDisposable CreateDisposeDrawOperations(List<IRef<IDrawOperation>> drawOperations)
+        private static IDisposable CreateDisposeDrawOperations(PooledList<IRef<IDrawOperation>> drawOperations)
         {
-            return Disposable.Create(() =>
+            return Disposable.Create(drawOperations, operations =>
             {
-                foreach (var operation in drawOperations)
+                foreach (var operation in operations)
                 {
                     operation.Dispose();
                 }
+
+                operations.Dispose();
             });
         }
 
@@ -414,6 +437,8 @@ namespace Avalonia.Rendering.SceneGraph
         {
             _drawOperationsRefCounter?.Dispose();
 
+            _children?.Dispose();
+
             Disposed = true;
         }
     }
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
index 1a2c93ac22..0b9c94f850 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
@@ -298,13 +298,6 @@ namespace Avalonia.Controls.UnitTests.Primitives
             }
         }
 
-        Window PreparedWindow(object content = null)
-        {
-            var w = new Window {Content = content};
-            w.ApplyTemplate();
-            return w;
-        }
-
         [Fact]
         public void DataContextBeginUpdate_Should_Not_Be_Called_For_Controls_That_Dont_Inherit()
         {
@@ -351,6 +344,56 @@ namespace Avalonia.Controls.UnitTests.Primitives
             }
         }
 
+        [Fact]
+        public void StaysOpen_False_Should_Not_Handle_Closing_Click()
+        {
+            using (CreateServices())
+            {
+                var window = PreparedWindow();
+                var target = new Popup() 
+                { 
+                    PlacementTarget = window ,
+                    StaysOpen = false,
+                };
+
+                target.Open();
+
+                var e = CreatePointerPressedEventArgs(window);
+                window.RaiseEvent(e);
+
+                Assert.False(e.Handled);
+            }
+        }
+
+        [Fact]
+        public void Should_Pass_Closing_Click_To_Closed_Event()
+        {
+            using (CreateServices())
+            {
+                var window = PreparedWindow();
+                var target = new Popup()
+                {
+                    PlacementTarget = window,
+                    StaysOpen = false,
+                };
+
+                target.Open();
+
+                var press = CreatePointerPressedEventArgs(window);
+                var raised = 0;
+
+                target.Closed += (s, e) =>
+                {
+                    Assert.Same(press, e.CloseEvent);
+                    ++raised;
+                };
+
+                window.RaiseEvent(press);
+
+                Assert.Equal(1, raised);
+            }
+        }
+
         private IDisposable CreateServices()
         {
             return UnitTestApplication.Start(TestServices.StyledWindow.With(windowingPlatform:
@@ -363,6 +406,26 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     })));
         }
 
+        private PointerPressedEventArgs CreatePointerPressedEventArgs(Window source)
+        {
+            var pointer = new Pointer(Pointer.GetNextFreeId(), PointerType.Mouse, true);
+            return new PointerPressedEventArgs(
+                source,
+                pointer,
+                source,
+                default,
+                0,
+                new PointerPointProperties(RawInputModifiers.None, PointerUpdateKind.LeftButtonPressed),
+                KeyModifiers.None);
+        }
+
+        private Window PreparedWindow(object content = null)
+        {
+            var w = new Window { Content = content };
+            w.ApplyTemplate();
+            return w;
+        }
+
         private static IControl PopupContentControlTemplate(PopupContentControl control, INameScope scope)
         {
             return new Popup