diff --git a/core/includes/config.inc b/core/includes/config.inc
index 4ce1b5a..0b01073 100644
--- a/core/includes/config.inc
+++ b/core/includes/config.inc
@@ -56,7 +56,7 @@ function config_get_storage_names_with_prefix($prefix = '') {
  * @code config(book.admin) @endcode will return a configuration object in which
  * the book module can store its administrative settings.
  *
- * @param $name
+ * @param string $name
  *   The name of the configuration object to retrieve. The name corresponds to
  *   a configuration file. For @code config(book.admin) @endcode, the config
  *   object returned will contain the contents of book.admin configuration file.
@@ -69,9 +69,11 @@ function config($name) {
 }
 
 /**
- * Retrieves a configuration object for administration. This means that it has a special
- * configuration context (admin = TRUE) and configuration plug-ins should mostly keep hands
- * off this object and don't override it.
+ * Retrieves a configuration object for administration.
+ *
+ * This configuration object has a special configuration context (admin = TRUE)
+ * and configuration plug-ins should mostly keep hands off this object and don't
+ * override it.
  *
  * @param $name
  *   The name of the configuration object to retrieve.
@@ -91,14 +93,21 @@ function config_admin($name) {
  * Retrieves a configuration factory object for a given context.
  *
  * @param array $context
- *   Array with contextual data to be used for the configuration factory.
+ *   (optional) Array with contextual data to be used for the configuration
+ *   factory. Defaults to an empty array.
  * @param Drupal\Core\Config\StorageInterface $storage
- *   The storage controller object to use for reading and writing
- *   configuration data.
+ *   (optional) The storage controller object to use for reading and writing
+ *   configuration data. Defaults to the storage controller object registered
+ *   in the Drupal Container.
  * @param Symfony\Component\EventDispatcher\EventDispatcher
- *   An event dispatcher instance to use for configuration events.
+ *   (optional) An event dispatcher instance to use for configuration events.
+ *   Defaults to the event dispatcher instance registered in the Drupal
+ *   Container.
+ *
+ * @return Drupal\Core\Config\ConfigFactory
+ *   Configuration factory object.
  */
-function config_factory($context = array(), StorageInterface $storage = NULL, EventDispatcher $event_dispatcher = NULL) {
+function config_factory(array $context = array(), StorageInterface $storage = NULL, EventDispatcher $event_dispatcher = NULL) {
   $storage = $storage ? $storage : drupal_container()->get('config.storage');
   $event_dispatcher = $event_dispatcher ? $event_dispatcher : drupal_container()->get('dispatcher');
   $factory = new ConfigFactory($storage, $event_dispatcher);
diff --git a/core/lib/Drupal/Core/Config/Config.php b/core/lib/Drupal/Core/Config/Config.php
index c594c4b..247af2d 100644
--- a/core/lib/Drupal/Core/Config/Config.php
+++ b/core/lib/Drupal/Core/Config/Config.php
@@ -74,7 +74,9 @@ class Config {
    *   A storage controller object to use for reading and writing the
    *   configuration data.
    * @param Drupal\Core\Config\ConfigFactory $factory
-   *   A configuration factory object that produces this config object.
+   *   (optional) A configuration factory object that produces this config
+   *   object. Defaults to the storage controller object registered in the
+   *   Drupal Container.
    */
   public function __construct($name, StorageInterface $storage, ConfigFactory $factory = NULL) {
     $this->name = $name;
@@ -372,14 +374,20 @@ class Config {
   }
 
   /**
-   * Retrieve the configuration factory used to create this configuration object.
+   * Retrieves the configuration factory that produces this configuration object.
+   *
+   * @return Drupal\Core\Config\ConfigFactory
+   *   A configuration factory that produces this configuration object.
    */
   public function getFactory() {
     return $this->factory;
   }
 
   /**
-   * Dispatch a config event.
+   * Dispatches a config event.
+   *
+   * @param $config_event_name
+   *   Event name.
    */
   protected function notify($config_event_name) {
     $this->factory->notify($config_event_name, $this);
diff --git a/core/lib/Drupal/Core/Config/ConfigEvent.php b/core/lib/Drupal/Core/Config/ConfigEvent.php
index 9449404..710f51f 100644
--- a/core/lib/Drupal/Core/Config/ConfigEvent.php
+++ b/core/lib/Drupal/Core/Config/ConfigEvent.php
@@ -14,7 +14,12 @@ class ConfigEvent extends Event {
   protected $config;
 
   /**
-   * Constructor.
+   * Constructs a configuration event object.
+   *
+   * @param Drupal\Core\Config\Config
+   *   Configuration object.
+   * @param Drupal\Core\Config\ConfigFactory
+   *   Configuration factory object.
    */
   public function __construct(Config $config, ConfigFactory $factory) {
     $this->config = $config;
@@ -30,6 +35,9 @@ class ConfigEvent extends Event {
 
   /**
    * Get configuration factory object.
+   *
+   * @return Drupal\Core\Config\ConfigFactory
+   *   Configuration factory object.
    */
   public function getFactory() {
     return $this->factory;
diff --git a/core/lib/Drupal/Core/Config/ConfigFactory.php b/core/lib/Drupal/Core/Config/ConfigFactory.php
index e09068e..a2b4b51 100644
--- a/core/lib/Drupal/Core/Config/ConfigFactory.php
+++ b/core/lib/Drupal/Core/Config/ConfigFactory.php
@@ -96,6 +96,9 @@ class ConfigFactory {
 
   /**
    * Get storage controller.
+   *
+   * @return Drupal\Core\Config\StorageInterface
+   *   A storage controller instance for reading and writing configuration data.
    */
   public function getStorage() {
     return $this->storage;
@@ -104,10 +107,11 @@ class ConfigFactory {
   /**
    * Gets data from this config context.
    *
-   * @param $key
-   *   A string that maps to a key within the context data or empty to get all data.
+   * @param string $key
+   *   (optional) A string that maps to a key within the context data or empty
+   *   to get all data.
    *
-   * @return
+   * @return array
    *   The data that was requested.
    */
   public function getContext($key = '') {
@@ -124,9 +128,11 @@ class ConfigFactory {
    *
    * @param $key
    *   A string that maps to a key within the configuration context.
-   *
    * @param $value
    *   Any value to be set for this key.
+   *
+   * @return Drupal\Core\Config\ConfigFactory
+   *   This ConfigFactory instance.
    */
   public function setContext($key, $value) {
     $this->context[$key] = $value;
@@ -134,9 +140,9 @@ class ConfigFactory {
   }
 
   /**
-   * Dispatch a config event.
+   * Dispatches a config event.
    *
-   * @param $config_event_name
+   * @param string $config_event_name
    *   Event name.
    * @param Drupal\Core\Config\Config
    *   Configuration object.
diff --git a/core/modules/config/config.api.php b/core/modules/config/config.api.php
index bd7212c..558ee08 100644
--- a/core/modules/config/config.api.php
+++ b/core/modules/config/config.api.php
@@ -125,15 +125,15 @@ function hook_config_import_delete($name, $new_config, $old_config) {
 }
 
 /**
- * Delete configuration upon synchronizing configuration changes.
+ * Deletes configuration upon synchronizing configuration changes.
  *
- * This callback is invoked when a new configuration factory is created
- * and allows a module to take over the synchronization of configuration data.
+ * This callback is invoked when a new configuration factory is created and
+ * allows a module to take over the synchronization of configuration data.
  *
  * Modules should implement this callback if they manage configuration data
- * (such as image styles, node types, or fields) which needs to be
- * prepared and passed through module API functions to properly handle a
- * configuration change.
+ * (such as image styles, node types, or fields) which needs to be prepared and
+ * passed through module API functions to properly handle a configuration
+ * change.
  *
  * @param Drupal\Core\Config\ConfigFactory $factory
  *   A configuration object containing the new configuration data.
@@ -145,4 +145,4 @@ function hook_config_factory($factory) {
       $factory->setContext('locale.language', user_preferred_language($account));
     }
   }
-}
\ No newline at end of file
+}
diff --git a/core/modules/locale/locale.module b/core/modules/locale/locale.module
index 093cd41..e6f55d7 100644
--- a/core/modules/locale/locale.module
+++ b/core/modules/locale/locale.module
@@ -11,6 +11,7 @@
  *   Gettext portable object files are supported.
  */
 
+use Drupal\Core\Config\ConfigFactory;
 use Drupal\locale\LocaleLookup;
 use Drupal\locale\LocaleConfigSubscriber;
 use Drupal\locale\TranslationsStream;
@@ -965,4 +966,4 @@ function locale_config_factory(ConfigFactory $factory) {
       $factory->setContext('locale.language', user_preferred_language($account));
     }
   }
-}
\ No newline at end of file
+}
diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index bcf2bb8..ff854a3 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -1595,7 +1595,7 @@ function system_logging_settings_submit($form, &$form_state) {
  */
 function system_performance_settings($form, &$form_state) {
   drupal_add_library('system', 'drupal.system');
-  $config = config('system.performance');
+  $config = config_admin('system.performance');
 
   $form['clear_cache'] = array(
     '#type' => 'fieldset',
@@ -1681,7 +1681,7 @@ function system_performance_settings($form, &$form_state) {
  * @ingroup forms
  */
 function system_performance_settings_submit($form, &$form_state) {
-  $config = config_admin('system.performance');
+  $config = config('system.performance');
   $config->set('cache.page.enabled', $form_state['values']['cache']);
   $config->set('cache.page.max_age', $form_state['values']['page_cache_maximum_age']);
   $config->set('response.gzip', $form_state['values']['page_compression']);