diff -u b/core/modules/node/src/Tests/NodeAccessPagerTest.php b/core/modules/node/src/Tests/NodeAccessPagerTest.php
--- b/core/modules/node/src/Tests/NodeAccessPagerTest.php
+++ b/core/modules/node/src/Tests/NodeAccessPagerTest.php
@@ -80,8 +80,9 @@
     // Look up the general discussion term.
     $tree = \Drupal::entityManager()->getStorage('taxonomy_term')->loadTree($vid, 0, 1);
     $tid = reset($tree)->tid;
-    unset($tree); // Save memory.
     $this->assertTrue($tid, 'General discussion term is found in the forum vocabulary.');
+    // Unset $tree to save memory as it is not used anymore.
+    unset($tree);
 
     // Create 30 nodes.
     for ($i = 0; $i < 30; $i++) {
diff -u b/core/modules/taxonomy/src/Form/OverviewTerms.php b/core/modules/taxonomy/src/Form/OverviewTerms.php
--- b/core/modules/taxonomy/src/Form/OverviewTerms.php
+++ b/core/modules/taxonomy/src/Form/OverviewTerms.php
@@ -173,7 +173,7 @@
       $current_page[$key] = $term;
     } while (isset($tree[++$tree_index]));
 
-    // Free memory now we don't need $tree anymore.
+    // Unset $tree to save memory as it is not used anymore.
     $tree_count = count($tree);
     unset($tree);
 
diff -u b/core/modules/taxonomy/src/Tests/TermTest.php b/core/modules/taxonomy/src/Tests/TermTest.php
--- b/core/modules/taxonomy/src/Tests/TermTest.php
+++ b/core/modules/taxonomy/src/Tests/TermTest.php
@@ -239,7 +239,8 @@
     }
     $tree = $this->container->get('entity.manager')->getStorage('taxonomy_term')->loadTree($this->vocabulary->id());
     $this->assertTrue(empty($tree), 'The terms are not created on preview.');
-    unset($tree); // Save memory.
+    // Unset $tree to save memory as it is not used anymore.
+    unset($tree);
 
     // taxonomy.module does not maintain its static caches.
     taxonomy_terms_static_reset();
@@ -421,6 +422,8 @@
     $this->assertEqual($terms[1]->id(), $term2->id(), 'Term 2 was moved to back below term 1.');
     $this->assertEqual($terms[2]->id(), $term3->id(), 'Term 3 is still below term 2.');
     $this->assertEqual($terms[2]->parents, array($term2->id()), 'Term 3 is still a child of term 2.');
+    // Unset $terms to save memory as it is not used anymore.
+    unset($terms);
   }
 
   /**
only in patch2:
unchanged:
--- a/core/modules/forum/src/ForumManager.php
+++ b/core/modules/forum/src/ForumManager.php
@@ -421,6 +421,8 @@ public function getChildren($vid, $tid) {
       $forum->last_post = $this->getLastPost($forum->id());
       $forums[$forum->id()] = $forum;
     }
+    // Unset $_forums to save memory as it is not used anymore.
+    unset($_forums);
 
     $this->forumChildren[$tid] = $forums;
     return $forums;
only in patch2:
unchanged:
--- a/core/modules/taxonomy/src/Plugin/EntityReferenceSelection/TermSelection.php
+++ b/core/modules/taxonomy/src/Plugin/EntityReferenceSelection/TermSelection.php
@@ -75,6 +75,8 @@ public function getReferenceableEntities($match = NULL, $match_operator = 'CONTA
           foreach ($terms as $term) {
             $options[$vocabulary->id()][$term->id()] = str_repeat('-', $term->depth) . SafeMarkup::checkPlain($term->getName());
           }
+          // Unset $terms to save memory as it is not used anymore.
+          unset($terms);
         }
       }
     }
only in patch2:
unchanged:
--- a/core/modules/taxonomy/src/Tests/TermKernelTest.php
+++ b/core/modules/taxonomy/src/Tests/TermKernelTest.php
@@ -118,6 +118,8 @@ public function testTaxonomyVocabularyTree() {
     // Count $term[1] parents with $max_depth = 1.
     $tree = $taxonomy_storage->loadTree($vocabulary->id(), $term[1]->id(), 1);
     $this->assertEqual(1, count($tree), 'We have one parent with depth 1.');
+    // Unset $tree to save memory as it is not used anymore.
+    unset($tree);
 
     // Count all vocabulary tree elements.
     $tree = $taxonomy_storage->loadTree($vocabulary->id());
@@ -130,6 +132,8 @@ public function testTaxonomyVocabularyTree() {
       }
       $depth_count[$element->depth]++;
     }
+    // Unset $tree to save memory as it is not used anymore.
+    unset($tree);
     $this->assertEqual(3, $depth_count[0], 'Three elements in taxonomy tree depth 0.');
     $this->assertEqual(2, $depth_count[1], 'Two elements in taxonomy tree depth 1.');
     $this->assertEqual(2, $depth_count[2], 'Two elements in taxonomy tree depth 2.');
only in patch2:
unchanged:
--- a/core/modules/taxonomy/taxonomy.module
+++ b/core/modules/taxonomy/taxonomy.module
@@ -165,6 +165,9 @@ function taxonomy_check_vocabulary_hierarchy(VocabularyInterface $vocabulary, $c
       $hierarchy = TAXONOMY_HIERARCHY_SINGLE;
     }
   }
+  // Unset $tree to save memory as it is not used anymore.
+  unset($tree);
+
   if ($hierarchy != $vocabulary->getHierarchy()) {
     $vocabulary->setHierarchy($hierarchy);
     $vocabulary->save();