MAGETWO-85983: [Backport for 2.1.x] Admin login always takes >30 sec when using Redis on 2.2.1 #12385

Author: Bohdan Korablov

lib/internal/Magento/Framework/Session/SessionManager.php

@@ -503,18 +503,9 @@ public function regenerateId()
         if (headers_sent()) {
             return $this;
         }
-        //@see http://php.net/manual/en/function.session-regenerate-id.php#53480 workaround
+
         if ($this->isSessionExists()) {
-            $oldSessionId = session_id();
-            session_regenerate_id();
-            $newSessionId = session_id();
-            session_id($oldSessionId);
-            session_destroy();
-
-            $oldSession = $_SESSION;
-            session_id($newSessionId);
-            session_start();
-            $_SESSION = $oldSession;
+            session_regenerate_id(true);
         } else {
             session_start();
         }