core/lib/Drupal/Core/Cache/CacheTagsChecksumInterface.php | 6 +++---
 core/lib/Drupal/Core/Cache/DatabaseBackend.php            | 4 ++--
 core/lib/Drupal/Core/Cache/DatabaseCacheTagsChecksum.php  | 5 ++++-
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/core/lib/Drupal/Core/Cache/CacheTagsChecksumInterface.php b/core/lib/Drupal/Core/Cache/CacheTagsChecksumInterface.php
index 7032eb7..f3ef62b 100644
--- a/core/lib/Drupal/Core/Cache/CacheTagsChecksumInterface.php
+++ b/core/lib/Drupal/Core/Cache/CacheTagsChecksumInterface.php
@@ -21,9 +21,9 @@
   /**
    * The checksum returned a database transaction is in progress.
    *
-   * Every cache backend SHOULD detect this and not write cache items with this
-   * checksum. Not detecting this would not yield incorrect cache reads, but
-   * would be a useless write.
+   * Every cache backend SHOULD detect this and not write cache items that have
+   * this checksum. Not detecting this would not yield incorrect cache reads,
+   * but would be a useless write.
    *
    * While a database transaction is progress, cache tag invalidations are
    * delayed to occur just before the commit, to allow:
diff --git a/core/lib/Drupal/Core/Cache/DatabaseBackend.php b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
index d5939da..793089e 100644
--- a/core/lib/Drupal/Core/Cache/DatabaseBackend.php
+++ b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
@@ -236,7 +236,7 @@ protected function doSetMultiple(array $items) {
         'checksum' => $this->checksumProvider->getCurrentChecksum($item['tags']),
       ];
 
-      // @see \Drupal\Core\Cache\CacheTagsChecksumInterface::CHECKSUM_WHILE_IN_TRANSACTION
+      // Avoid useless writes.
       if ($fields['checksum'] === CacheTagsChecksumInterface::CHECKSUM_WHILE_IN_TRANSACTION) {
         continue;
       }
@@ -252,7 +252,7 @@ protected function doSetMultiple(array $items) {
       $values[] = $fields;
     }
 
-    // @see \Drupal\Core\Cache\CacheTagsChecksumInterface::CHECKSUM_WHILE_IN_TRANSACTION
+    // If all $items were useless writes, we may end up with zero writes.
     if (empty($values)) {
       return;
     }
diff --git a/core/lib/Drupal/Core/Cache/DatabaseCacheTagsChecksum.php b/core/lib/Drupal/Core/Cache/DatabaseCacheTagsChecksum.php
index 7b6097c..f52782e 100644
--- a/core/lib/Drupal/Core/Cache/DatabaseCacheTagsChecksum.php
+++ b/core/lib/Drupal/Core/Cache/DatabaseCacheTagsChecksum.php
@@ -77,7 +77,10 @@ public function invalidateTags(array $tags) {
   }
 
   /**
-   * Helper method for ::invalidateTags().
+   * Marks cache items with any of the specified tags as invalid.
+   *
+   * @param string[] $tags
+   *   The list of tags for which to invalidate cache items.
    */
   protected function doInvalidateTags(array $tags) {
     try {