Back port from 2.1.0-beta1:

emberjs#3641 Improve InternalModel (2x - 3x faster)
emberjs#3649 Empty object

packages/ember-data/lib/adapters/rest-adapter.js

@@ -12,14 +12,14 @@ import {
 import {
   MapWithDefault
 } from "ember-data/system/map";
+import EmptyObject from "ember-data/system/empty-object";
 import ArrayPolyfills  from 'ember-data/ext/ember/array';
 
 var get = Ember.get;
 var set = Ember.set;
 var forEach = ArrayPolyfills.forEach;
 
 import {
-  create,
   keysFunc
 } from 'ember-data/system/object-polyfills';
 
@@ -1042,7 +1042,7 @@ var RestAdapter = Adapter.extend(BuildURLMixin, {
 });
 
 function parseResponseHeaders(headerStr) {
-  var headers = create(null);
+  var headers = new EmptyObject();
   if (!headerStr) { return headers; }
 
   var headerPairs = headerStr.split('\u000d\u000a');

packages/ember-data/lib/system/clone-null.js

@@ -1,9 +1,7 @@
-import {
-  create
-} from 'ember-data/system/object-polyfills';
+import EmptyObject from "ember-data/system/empty-object";
 
 export default function cloneNull(source) {
-  var clone = create(null);
+  var clone = new EmptyObject();
   for (var key in source) {
     clone[key] = source[key];
   }

packages/ember-data/lib/system/empty-object.js

@@ -0,0 +1,17 @@
+// This exists because `Object.create(null)` is absurdly slow compared
+// to `new EmptyObject()`. In either case, you want a null prototype
+// when you're treating the object instances as arbitrary dictionaries
+// and don't want your keys colliding with build-in methods on the
+// default object prototype.
+var proto = Object.create(null, {
+  // without this, we will always still end up with (new
+  // EmptyObject()).constructor === Object
+  constructor: {
+    value: undefined,
+    enumerable: false,
+    writable: true
+  }
+});
+
+export default function EmptyObject() {}
+EmptyObject.prototype = proto;

packages/ember-data/lib/system/model/internal-model.js

@@ -2,6 +2,8 @@ import merge from "ember-data/system/merge";
 import RootState from "ember-data/system/model/states";
 import Relationships from "ember-data/system/relationships/state/create";
 import Snapshot from "ember-data/system/snapshot";
+import EmptyObject from "ember-data/system/empty-object";
+
 import ArrayPolyfills from 'ember-data/ext/ember/array';
 
 import {
@@ -16,8 +18,8 @@ var set = Ember.set;
 var forEach = ArrayPolyfills.forEach;
 var map = ArrayPolyfills.map;
 
-var _extractPivotNameCache = create(null);
-var _splitOnDotCache = create(null);
+var _extractPivotNameCache = new EmptyObject();
+var _splitOnDotCache = new EmptyObject();
 
 function splitOnDot(name) {
   return _splitOnDotCache[name] || (

packages/ember-data/lib/system/model/model.js

@@ -1,9 +1,9 @@
 import { PromiseObject } from "ember-data/system/promise-proxies";
 import Errors from "ember-data/system/model/errors";
+import EmptyObject from "ember-data/system/empty-object";
 import ArrayPolyfills from 'ember-data/ext/ember/array';
 
 import {
-  create,
   keysFunc
 } from 'ember-data/system/object-polyfills';
 
@@ -674,7 +674,7 @@ var Model = Ember.Object.extend(Ember.Evented, {
     var currentData = get(this._internalModel, '_attributes');
     var inFlightData = get(this._internalModel, '_inFlightAttributes');
     var newData = merge(copy(inFlightData), currentData);
-    var diffData = create(null);
+    var diffData = new EmptyObject();
 
     var newDataKeys = keysFunc(newData);
 

packages/ember-data/lib/system/model/states.js

@@ -1,3 +1,5 @@
+import EmptyObject from "ember-data/system/empty-object";
+
 import {
   create,
   keysFunc
@@ -360,7 +362,7 @@ var DirtyState = {
     },
 
     exit: function(internalModel) {
-      internalModel._inFlightAttributes = create(null);
+      internalModel._inFlightAttributes = new EmptyObject();
     }
   }
 };

packages/ember-data/lib/system/relationships/ext.js

@@ -7,12 +7,9 @@ import {
   Map,
   MapWithDefault
 } from "ember-data/system/map";
+import EmptyObject from "ember-data/system/empty-object";
 import ArrayPolyfills from 'ember-data/ext/ember/array';
 
-import {
-  create
-} from 'ember-data/system/object-polyfills';
-
 var get = Ember.get;
 var filter = ArrayPolyfills.filter;
 
@@ -191,7 +188,7 @@ Model.reopenClass({
   },
 
   inverseMap: Ember.computed(function() {
-    return create(null);
+    return new EmptyObject();
   }),
 
   /**

packages/ember-data/lib/system/relationships/state/create.js

@@ -1,9 +1,6 @@
 import ManyRelationship from "ember-data/system/relationships/state/has-many";
 import BelongsToRelationship from "ember-data/system/relationships/state/belongs-to";
-
-import {
-  create
-} from 'ember-data/system/object-polyfills';
+import EmptyObject from "ember-data/system/empty-object";
 
 var get = Ember.get;
 
@@ -24,7 +21,7 @@ var createRelationshipFor = function(record, relationshipMeta, store) {
 
 var Relationships = function(record) {
   this.record = record;
-  this.initializedRelationships = create(null);
+  this.initializedRelationships = new EmptyObject();
 };
 
 Relationships.prototype.has = function(key) {

packages/ember-data/lib/system/snapshot.js

@@ -4,10 +4,11 @@
 
 var get = Ember.get;
 import {
-  create,
   keysFunc
 } from 'ember-data/system/object-polyfills';
 
+import EmptyObject from "ember-data/system/empty-object";
+
 /**
   @class Snapshot
   @namespace DS
@@ -16,11 +17,11 @@ import {
   @param {DS.Model} internalModel The model to create a snapshot from
 */
 function Snapshot(internalModel) {
-  this._attributes = create(null);
-  this._belongsToRelationships = create(null);
-  this._belongsToIds = create(null);
-  this._hasManyRelationships = create(null);
-  this._hasManyIds = create(null);
+  this._attributes = new EmptyObject();
+  this._belongsToRelationships = new EmptyObject();
+  this._belongsToIds = new EmptyObject();
+  this._hasManyRelationships = new EmptyObject();
+  this._hasManyIds = new EmptyObject();
 
   var record = internalModel.getRecord();
   this.record = record;
@@ -172,7 +173,7 @@ Snapshot.prototype = {
     @return {Object} All changed attributes of the current snapshot
   */
   changedAttributes: function() {
-    let changedAttributes = create(null);
+    let changedAttributes = new EmptyObject();
     let changedAttributeKeys = keysFunc(this._changedAttributes);
 
     for (let i=0, length = changedAttributeKeys.length; i < length; i++) {

packages/ember-data/lib/system/store.js

@@ -53,10 +53,11 @@ import InternalModel from "ember-data/system/model/internal-model";
 import ArrayPolyfills from 'ember-data/ext/ember/array';
 
 import {
-  create,
   keysFunc
 } from 'ember-data/system/object-polyfills';
 
+import EmptyObject from "ember-data/system/empty-object";
+
 var Backburner = Ember._Backburner || Ember.Backburner || Ember.__loader.require('backburner')['default'] || Ember.__loader.require('backburner')['Backburner'];
 
 
@@ -329,7 +330,7 @@ Store = Service.extend({
   createRecord: function(modelName, inputProperties) {
     Ember.assert('Passing classes to store methods has been removed. Please pass a dasherized string instead of '+ Ember.inspect(modelName), typeof modelName === 'string');
     var typeClass = this.modelFor(modelName);
-    var properties = copy(inputProperties) || create(null);
+    var properties = copy(inputProperties) || new EmptyObject();
 
     // If the passed properties do not include a primary key,
     // give the adapter an opportunity to generate one. Typically,
@@ -1338,7 +1339,7 @@ Store = Service.extend({
         record.destroy(); // maybe within unloadRecord
       }
 
-      typeMap.metadata = create(null);
+      typeMap.metadata = new EmptyObject();
     }
 
     function byType(entry) {
@@ -1689,9 +1690,9 @@ Store = Service.extend({
     if (typeMap) { return typeMap; }
 
     typeMap = {
-      idToRecord: create(null),
+      idToRecord: new EmptyObject(),
       records: [],
-      metadata: create(null),
+      metadata: new EmptyObject(),
       type: typeClass
     };
 

packages/ember-data/lib/system/store/container-instance-cache.js

@@ -1,10 +1,11 @@
 import Ember from 'ember';
 
 import {
-  create,
   keysFunc
 } from 'ember-data/system/object-polyfills';
 
+import EmptyObject from "ember-data/system/empty-object";
+
 /**
  * The `ContainerInstanceCache` serves as a lazy cache for looking up
  * instances of serializers and adapters. It has some additional logic for
@@ -25,10 +26,10 @@ import {
 */
 function ContainerInstanceCache(container) {
   this._container  = container;
-  this._cache      = create(null);
+  this._cache      = new EmptyObject();
 }
 
-ContainerInstanceCache.prototype = create(null);
+ContainerInstanceCache.prototype = new EmptyObject();
 
 Ember.merge(ContainerInstanceCache.prototype, {
   get: function(type, preferredKey, fallbacks) {

packages/ember-data/tests/integration/store-test.js

@@ -149,8 +149,8 @@ test("destroying the store correctly cleans everything up", function() {
     filterdPeople = store.filter('person', function() { return true; });
   });
 
-  var filterdPeopleWillDestroy =  tap(filterdPeople.content, 'willDestroy');
-  var adapterPopulatedPeopleWillDestroy = tap(adapterPopulatedPeople.content, 'willDestroy');
+  var filterdPeopleWillDestroy = tap(filterdPeople.get('content'), 'willDestroy');
+  var adapterPopulatedPeopleWillDestroy = tap(adapterPopulatedPeople.get('content'), 'willDestroy');
 
   run(function() {
     store.findRecord('person', 2);

packages/ember-data/tests/unit/model-test.js

@@ -227,12 +227,23 @@ test("changedAttributes() return correct values", function() {
   equal(keysFunc(mascot.changedAttributes()).length, 0, 'after rollback attributes there are no changes');
 });
 
+function toObj(obj) {
+  // https://github.com/jquery/qunit/issues/851
+  var result = Object.create(null);
+  for (var key in obj) {
+    result[key] = obj[key];
+  }
+  return result;
+}
+
 test("changedAttributes() works while the record is being saved", function() {
   expect(1);
   var cat;
   var adapter = DS.Adapter.extend({
     createRecord(store, model, snapshot) {
-      deepEqual(cat.changedAttributes(), { name: [undefined, 'Argon'], likes: [undefined, 'Cheese'] });
+      deepEqual(toObj(cat.changedAttributes()), {
+        name: [undefined, 'Argon'],
+        likes: [undefined, 'Cheese'] });
       return {};
     }
   });
@@ -259,7 +270,7 @@ test("changedAttributes() works while the record is being updated", function() {
   var cat;
   var adapter = DS.Adapter.extend({
     updateRecord(store, model, snapshot) {
-      deepEqual(cat.changedAttributes(), { name: ['Argon', 'Helia'], likes: ['Cheese', 'Mussels'] });
+      deepEqual(toObj(cat.changedAttributes()), { name: ['Argon', 'Helia'], likes: ['Cheese', 'Mussels'] });
       return { id: '1', type: 'mascot' };
     }
   });