Persistent queue Issue on logstash

We have three logstash nodes to collect log in parallel. All three logstash have 6 output pipelines and 1 intake pipeline. After i try to enable persistent queue on one of the logstash, no matter how little the queue_max_event size is, the logstash event emitted rate for pipelines will drop to zero and only the most busy pipeline still running.
Is there anyone who know why it likes that?