php - Doctrine flush absolutely too long -

i have following situation: use symfony command list xml documents of given folder. parse each document , build document entity. want "import" new entities in mysql database using doctrine2.
php class looks this:

class importservice implements flushinterface {     private $entitymanager;     private $documentcache;     private $flushcounter;      public function __construct()     {         $this->documentcache = [];         $this->flushcounter = 0;     }      public function savedocument(documententity $doc)     {         $this->persistdocumententity($doc);         ...         $this->checkbulk();         return $this;     }      protected function persistdocumententity(documententity $doc)     {         $cachekey = hash('sha256', $doc->getsource() . ':' . $doc->getsourceid() . ':' . $doc->getclient());         $this->entitymanager->persist($doc);         $this->documentcache[$cachekey] = $doc;         return $this;     }      protected function checkbulk()     {         $this->flushcounter++;         if ($this->flushcounter > 20) {             $this->flushcounter = 0;             $this->flush(null, false);         }          return $this;     }      public function flush(flushinterface $flushinterface = null, $clearentitymanager = true)     {         // save database data         $em = $this->entitymanager;         $em->flush();          if ($clearentitymanager) {             $em->clear();         }         $this->documentcache = [];          // call flush interface         if ($flushinterface instanceof flushinterface) {             $flushinterface->flush();         }          return $this;     } } 

what happens? can execute app without problems on local system. folder contains 3,000 xml documents parse , import take 5 minutes. that's ok.
run same command (same application) on server , here import takes 5 days. that's absolutely long.
logged steps , made time measurements. found out problem line:

$em->flush(); 

it takes 12 seconds execute. looked log file , found out there 40 insert queries per flush execute. seems not much.
i've no idea why process executed fast locally , slow on server , i've no idea bottleneck comes from.

p.s. xdebug.profiling disabled in php.ini.