ConfigEntityStorage::doLoadMultiple

protected ConfigEntityStorage::doLoadMultiple(array $ids = NULL)

protected function doLoadMultiple(array $ids = NULL) {
  $prefix = $this->getPrefix();

  // Get the names of the configuration entities we are going to load.
  if ($ids === NULL) {
    $names = $this->configFactory->listAll($prefix);
  }
  else {
    $names = array();
    foreach ($ids as $id) {
      // Add the prefix to the ID to serve as the configuration object name.
      $names[] = $prefix . $id;
    }
  }

  // Load all of the configuration entities.
  /** @var \Drupal\Core\Config\Config[] $configs */
  $configs = [];
  $records = [];
  foreach ($this->configFactory->loadMultiple($names) as $config) {
    $id = $config->get($this->idKey);
    $records[$id] = $this->overrideFree ? $config->getOriginal(NULL, FALSE) : $config->get();
    $configs[$id] = $config;
  }
  $entities = $this->mapFromStorageRecords($records, $configs);

  // Config entities wrap config objects, and therefore they need to inherit
  // the cacheability metadata of config objects (to ensure e.g. additional
  // cacheability metadata added by config overrides is not lost).
  foreach ($entities as $id => $entity) {
    // But rather than simply inheriting all cacheability metadata of config
    // objects, we need to make sure the self-referring cache tag that is
    // present on Config objects is not added to the Config entity. It must be
    // removed for 3 reasons:
    // 1. When renaming/duplicating a Config entity, the cache tag of the
    //    original config object would remain present, which would be wrong.
    // 2. Some Config entities choose to not use the cache tag that the under-
    //    lying Config object provides by default (For performance and
    //    cacheability reasons it may not make sense to have a unique cache
    //    tag for every Config entity. The DateFormat Config entity specifies
    //    the 'rendered' cache tag for example, because A) date formats are
    //    changed extremely rarely, so invalidating all render cache items is
    //    fine, B) it means fewer cache tags per page.).
    // 3. Fewer cache tags is better for performance.
    $self_referring_cache_tag = ['config:' . $configs[$id]->getName()];
    $config_cacheability = CacheableMetadata::createFromObject($configs[$id]);
    $config_cacheability->setCacheTags(array_diff($config_cacheability->getCacheTags(), $self_referring_cache_tag));
    $entity->addCacheableDependency($config_cacheability);
  }

  return $entities;
}