core/lib/Drupal/Core/Config/Config.php             |  4 +++-
 .../Drupal/Core/Config/Entity/ConfigEntityBase.php | 22 ++++++++++++++++++++++
 core/lib/Drupal/Core/Entity/Entity.php             |  2 +-
 core/tests/Drupal/Tests/Core/Config/ConfigTest.php | 11 ++++++++---
 .../Core/Config/Entity/ConfigEntityStorageTest.php | 16 +++++++++-------
 5 files changed, 43 insertions(+), 12 deletions(-)

diff --git a/core/lib/Drupal/Core/Config/Config.php b/core/lib/Drupal/Core/Config/Config.php
index bc6ba29..ed9c28e 100644
--- a/core/lib/Drupal/Core/Config/Config.php
+++ b/core/lib/Drupal/Core/Config/Config.php
@@ -224,7 +224,9 @@ public function save() {
     }
 
     $this->storage->write($this->name, $this->data);
-    Cache::invalidateTags($this->getCacheTags());
+    if (!$this->isNew) {
+      Cache::invalidateTags($this->getCacheTags());
+    }
     $this->isNew = FALSE;
     $this->eventDispatcher->dispatch(ConfigEvents::SAVE, new ConfigCrudEvent($this));
     $this->originalData = $this->data;
diff --git a/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php b/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
index 8cca5bd..0304d09 100644
--- a/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
@@ -14,6 +14,7 @@
 use Drupal\Core\Entity\Entity;
 use Drupal\Core\Config\ConfigDuplicateUUIDException;
 use Drupal\Core\Entity\EntityStorageInterface;
+use Drupal\Core\Entity\EntityTypeInterface;
 use Drupal\Core\Entity\EntityWithPluginCollectionInterface;
 use Drupal\Core\Language\LanguageInterface;
 use Drupal\Core\Plugin\PluginDependencyTrait;
@@ -420,4 +421,25 @@ public function getConfigDependencyName() {
   public function onDependencyRemoval(array $dependencies) {
   }
 
+  /**
+   * {@inheritdoc}
+   *
+   * Override to never invalidate the entity's cache tag; the config system
+   * already invalidates it.
+   */
+  protected function invalidateTagsOnSave($update) {
+    Cache::invalidateTags($this->getEntityType()->getListCacheTags());
+  }
+
+  /**
+   * {@inheritdoc}
+   *
+   * Override to never invalidate the individual entities' cache tags; the
+   * config system already invalidates them.
+
+   */
+  protected static function invalidateTagsOnDelete(EntityTypeInterface $entity_type, array $entities) {
+    Cache::invalidateTags($entity_type->getListCacheTags());
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Entity/Entity.php b/core/lib/Drupal/Core/Entity/Entity.php
index c76dc40..d6b78be 100644
--- a/core/lib/Drupal/Core/Entity/Entity.php
+++ b/core/lib/Drupal/Core/Entity/Entity.php
@@ -406,7 +406,7 @@ public static function preDelete(EntityStorageInterface $storage, array $entitie
    * {@inheritdoc}
    */
   public static function postDelete(EntityStorageInterface $storage, array $entities) {
-    self::invalidateTagsOnDelete($storage->getEntityType(), $entities);
+    static::invalidateTagsOnDelete($storage->getEntityType(), $entities);
   }
 
   /**
diff --git a/core/tests/Drupal/Tests/Core/Config/ConfigTest.php b/core/tests/Drupal/Tests/Core/Config/ConfigTest.php
index 549e28a..fe3c819 100644
--- a/core/tests/Drupal/Tests/Core/Config/ConfigTest.php
+++ b/core/tests/Drupal/Tests/Core/Config/ConfigTest.php
@@ -151,6 +151,13 @@ public function testSave($data) {
 
     // Check that the original data it saved.
     $this->assertOriginalConfigDataEquals($data, TRUE);
+
+    // The above created a config object; now update it.
+    $new_data = $data;
+    $new_data['a']['d'] = 2;
+    $this->config->setData($new_data);
+    $this->config->save();
+    $this->assertOriginalConfigDataEquals($new_data, TRUE);
   }
 
   /**
@@ -293,9 +300,7 @@ public function testNestedClear($data) {
    * @dataProvider overrideDataProvider
    */
   public function testDelete($data, $module_data) {
-    // Verifying that invalidateTags() is invoked *twice*: once for saving, once
-    // for deleting.
-    $this->cacheTagsInvalidator->expects($this->exactly(2))
+    $this->cacheTagsInvalidator->expects($this->once())
       ->method('invalidateTags')
       ->with(['config:config.test']);
 
diff --git a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
index 4781dbe..f7eef52 100644
--- a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
+++ b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
@@ -302,8 +302,9 @@ public function testSaveUpdate(EntityInterface $entity) {
     $this->cacheTagsInvalidator->expects($this->once())
       ->method('invalidateTags')
       ->with(array(
-        'config:the_config_prefix.foo', // Own cache tag.
-        $this->entityTypeId . '_list', // List cache tag.
+        // List cache tag only; the own cache tag is invalidated by the config
+        // system.
+        $this->entityTypeId . '_list',
       ));
 
     $this->configFactory->expects($this->exactly(2))
@@ -362,8 +363,9 @@ public function testSaveRename(ConfigEntityInterface $entity) {
     $this->cacheTagsInvalidator->expects($this->once())
       ->method('invalidateTags')
       ->with(array(
-        'config:the_config_prefix.bar', // Own cache tag.
-        $this->entityTypeId . '_list', // List cache tag.
+        // List cache tag only; the own cache tag is invalidated by the config
+        // system.
+        $this->entityTypeId . '_list',
       ));
 
     $this->configFactory->expects($this->once())
@@ -728,9 +730,9 @@ public function testDelete() {
     $this->cacheTagsInvalidator->expects($this->once())
       ->method('invalidateTags')
       ->with(array(
-        'config:the_config_prefix.bar', // Own cache tag.
-        'config:the_config_prefix.foo', // Own cache tag.
-        $this->entityTypeId . '_list', // List cache tag.
+        // List cache tag only; the own cache tag is invalidated by the config
+        // system.
+        $this->entityTypeId . '_list',
       ));
 
     $this->configFactory->expects($this->exactly(2))