diff --git a/Src/Newtonsoft.Json.Tests/Converters/XmlNodeConverterTest.cs b/Src/Newtonsoft.Json.Tests/Converters/XmlNodeConverterTest.cs
index 4c1c2c7b..59538f5c 100644
--- a/Src/Newtonsoft.Json.Tests/Converters/XmlNodeConverterTest.cs
+++ b/Src/Newtonsoft.Json.Tests/Converters/XmlNodeConverterTest.cs
@@ -2670,6 +2670,32 @@ namespace Newtonsoft.Json.Tests.Converters
 
             Assert.AreEqual("null", json);
         }
+
+        [Test]
+        public void SerializeExplicitAttributeNamespace()
+        {
+            var original = XElement.Parse("<MyElement xmlns=\"http://example.com\" />");
+            Assert.AreEqual(@"<MyElement xmlns=""http://example.com"" />", original.ToString());
+
+            var json = JsonConvert.SerializeObject(original);
+            Assert.AreEqual(@"{""MyElement"":{""@xmlns"":""http://example.com""}}", json);
+
+            var deserialized = JsonConvert.DeserializeObject<XElement>(json);
+            Assert.AreEqual(@"<MyElement xmlns=""http://example.com"" />", deserialized.ToString());
+        }
+
+        [Test]
+        public void SerializeImplicitAttributeNamespace()
+        {
+            var original = new XElement("{http://example.com}MyElement");
+            Assert.AreEqual(@"<MyElement xmlns=""http://example.com"" />", original.ToString());
+
+            var json = JsonConvert.SerializeObject(original);
+            Assert.AreEqual(@"{""MyElement"":{""@xmlns"":""http://example.com""}}", json);
+
+            var deserialized = JsonConvert.DeserializeObject<XElement>(json);
+            Assert.AreEqual(@"<MyElement xmlns=""http://example.com"" />", deserialized.ToString());
+        }
 #endif
     }
 }
diff --git a/Src/Newtonsoft.Json.Tests/Serialization/ExtensionDataTests.cs b/Src/Newtonsoft.Json.Tests/Serialization/ExtensionDataTests.cs
index 6acc24df..0a366552 100644
--- a/Src/Newtonsoft.Json.Tests/Serialization/ExtensionDataTests.cs
+++ b/Src/Newtonsoft.Json.Tests/Serialization/ExtensionDataTests.cs
@@ -374,6 +374,40 @@ namespace Newtonsoft.Json.Tests.Serialization
             Assert.AreEqual(7, c.ExtensionData.Count);
         }
 
+        [JsonObject(MemberSerialization.OptIn)]
+        public class MyClass
+        {
+            public int NotForJson { get; set; }
+
+            [JsonPropertyAttribute(Required = Required.Always)]
+            public int ForJson { get; set; }
+
+            [JsonExtensionData(ReadData = true, WriteData = true)]
+            public IDictionary<String, JToken> ExtraInfoJson { get; set; }
+
+            public MyClass(MyClass other = null)
+            {
+                if (other != null)
+                {
+                    // copy construct
+                }
+            }
+        }
+
+        [Test]
+        public void PopulateWithExtensionData()
+        {
+            string jsonStirng = @"{ ""ForJson"" : 33 , ""extra1"" : 11, ""extra2"" : 22 }";
+
+            MyClass c = new MyClass();
+
+            JsonConvert.PopulateObject(jsonStirng, c);
+
+            Assert.AreEqual(2, c.ExtraInfoJson.Count);
+            Assert.AreEqual(11, (int)c.ExtraInfoJson["extra1"]);
+            Assert.AreEqual(22, (int)c.ExtraInfoJson["extra2"]);
+        }
+
         public class MultipleExtensionDataAttributesTestClass
         {
             public string Name { get; set; }
diff --git a/Src/Newtonsoft.Json.Tests/Serialization/MetadataPropertyHandlingTests.cs b/Src/Newtonsoft.Json.Tests/Serialization/MetadataPropertyHandlingTests.cs
index f413e85f..44d195cc 100644
--- a/Src/Newtonsoft.Json.Tests/Serialization/MetadataPropertyHandlingTests.cs
+++ b/Src/Newtonsoft.Json.Tests/Serialization/MetadataPropertyHandlingTests.cs
@@ -528,6 +528,64 @@ namespace Newtonsoft.Json.Tests.Serialization
             JObject o = (JObject)actual.Payload;
             Assert.AreEqual("System.Byte[], mscorlib", (string)o["$type"]);
             Assert.AreEqual("AAECAwQFBgcICQ==", (string)o["$value"]);
+            Assert.AreEqual(null, o.Parent);
+        }
+
+        [Test]
+        public void ReadAhead_JObject_NoParent()
+        {
+            ItemWithUntypedPayload actual = JsonConvert.DeserializeObject<ItemWithUntypedPayload>(@"{
+  ""Payload"": {}
+}",
+                new JsonSerializerSettings
+                {
+                    MetadataPropertyHandling = MetadataPropertyHandling.ReadAhead
+                });
+
+            JObject o = (JObject)actual.Payload;
+            Assert.AreEqual(null, o.Parent);
+        }
+
+        public class ItemWithJTokens
+        {
+            public JValue Payload1 { get; set; }
+            public JObject Payload2 { get; set; }
+            public JArray Payload3 { get; set; }
+        }
+
+        [Test]
+        public void ReadAhead_TypedJValue_NoParent()
+        {
+            ItemWithJTokens actual = (ItemWithJTokens)JsonConvert.DeserializeObject(@"{
+  ""Payload1"": 1,
+  ""Payload2"": {},
+  ""Payload3"": [1],
+  ""$type"": ""Newtonsoft.Json.Tests.Serialization.MetadataPropertyHandlingTests+ItemWithJTokens, Newtonsoft.Json.Tests""
+}",
+                new JsonSerializerSettings
+                {
+                    MetadataPropertyHandling = MetadataPropertyHandling.ReadAhead,
+                    TypeNameHandling = TypeNameHandling.All
+                });
+
+            Assert.AreEqual(null, actual.Payload1.Parent);
+            Assert.AreEqual(null, actual.Payload2.Parent);
+            Assert.AreEqual(null, actual.Payload3.Parent);
+        }
+
+        [Test]
+        public void ReadAhead_JArray_NoParent()
+        {
+            ItemWithUntypedPayload actual = JsonConvert.DeserializeObject<ItemWithUntypedPayload>(@"{
+  ""Payload"": [1]
+}",
+                new JsonSerializerSettings
+                {
+                    MetadataPropertyHandling = MetadataPropertyHandling.ReadAhead
+                });
+
+            JArray o = (JArray)actual.Payload;
+            Assert.AreEqual(null, o.Parent);
         }
 
         public class ItemWithUntypedPayload
diff --git a/Src/Newtonsoft.Json/Converters/XmlNodeConverter.cs b/Src/Newtonsoft.Json/Converters/XmlNodeConverter.cs
index 051f6768..874c508b 100644
--- a/Src/Newtonsoft.Json/Converters/XmlNodeConverter.cs
+++ b/Src/Newtonsoft.Json/Converters/XmlNodeConverter.cs
@@ -46,7 +46,6 @@ using System.Linq;
 
 namespace Newtonsoft.Json.Converters
 {
-
     #region XmlNodeWrappers
 #if !DOTNET && !PORTABLE && !PORTABLE40
     internal class XmlDocumentWrapper : XmlNodeWrapper, IXmlDocument
@@ -235,6 +234,7 @@ namespace Newtonsoft.Json.Converters
     {
         private readonly XmlNode _node;
         private IList<IXmlNode> _childNodes;
+        private IList<IXmlNode> _attributes;
 
         public XmlNodeWrapper(XmlNode node)
         {
@@ -295,7 +295,14 @@ namespace Newtonsoft.Json.Converters
                     return null;
                 }
 
-                return _node.Attributes.Cast<XmlAttribute>().Select(WrapNode).ToList();
+                // attributes is read multiple times
+                // cache results to prevent multiple reads which kills perf in large documents
+                if (_attributes == null)
+                {
+                    _attributes = _node.Attributes.Cast<XmlAttribute>().Select(WrapNode).ToList();
+                }
+
+                return _attributes;
             }
         }
 
@@ -327,6 +334,7 @@ namespace Newtonsoft.Json.Converters
             XmlNodeWrapper xmlNodeWrapper = (XmlNodeWrapper)newChild;
             _node.AppendChild(xmlNodeWrapper._node);
             _childNodes = null;
+            _attributes = null;
 
             return newChild;
         }
@@ -861,6 +869,8 @@ namespace Newtonsoft.Json.Converters
 
     internal class XElementWrapper : XContainerWrapper, IXmlElement
     {
+        private IList<IXmlNode> _attributes;
+
         private XElement Element
         {
             get { return (XElement)WrappedNode; }
@@ -875,11 +885,52 @@ namespace Newtonsoft.Json.Converters
         {
             XObjectWrapper wrapper = (XObjectWrapper)attribute;
             Element.Add(wrapper.WrappedNode);
+            _attributes = null;
         }
 
         public override IList<IXmlNode> Attributes
         {
-            get { return Element.Attributes().Select(a => new XAttributeWrapper(a)).Cast<IXmlNode>().ToList(); }
+            get
+            {
+                // attributes is read multiple times
+                // cache results to prevent multiple reads which kills perf in large documents
+                if (_attributes == null)
+                {
+                    _attributes = Element.Attributes().Select(a => new XAttributeWrapper(a)).Cast<IXmlNode>().ToList();
+
+                    // ensure elements created with a namespace but no namespace attribute are converted correctly
+                    // e.g. new XElement("{http://example.com}MyElement");
+                    string namespaceUri = NamespaceUri;
+                    if (!string.IsNullOrEmpty(namespaceUri) && namespaceUri != ParentNode?.NamespaceUri)
+                    {
+                        if (string.IsNullOrEmpty(GetPrefixOfNamespace(namespaceUri)))
+                        {
+                            bool namespaceDeclared = false;
+                            foreach (IXmlNode attribute in _attributes)
+                            {
+                                if (attribute.LocalName == "xmlns" && string.IsNullOrEmpty(attribute.NamespaceUri) && attribute.Value == namespaceUri)
+                                {
+                                    namespaceDeclared = true;
+                                }
+                            }
+
+                            if (!namespaceDeclared)
+                            {
+                                _attributes.Insert(0, new XAttributeWrapper(new XAttribute("xmlns", namespaceUri)));
+                            }
+                        }
+                    }
+                }
+
+                return _attributes;
+            }
+        }
+
+        public override IXmlNode AppendChild(IXmlNode newChild)
+        {
+            IXmlNode result = base.AppendChild(newChild);
+            _attributes = null;
+            return result;
         }
 
         public override string Value