The perfstat will provide information about volume names that are experiencing high latencies. If nothing else is wrong, moving the volume to a less loaded node will provide immediate relief. Other options such as adding load sharing mirrors can also be explored.
For more details you can refer KB article: https://kb.netapp.com/support/index?page=content&id=2017656 which talks about NFS resource not performing as quickly as expected (throughput or latency).
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