Thank you for posting your question on the Mellanox Community.
Packet Pacing is support on the ConnectX-5 from firmware version 16.20.1010 and higher. You can use the following Mellanox Community Document to configure 'Packet Pacing'-> https://community.mellanox.com/docs/DOC-2479
Even though the document mentions only ConnectX-4, the ConnectX-5 uses the same driver.
If you experiencing any new issues after enabling 'Packet Pacing', please open a Mellanox Support Case by sending an email to firstname.lastname@example.org
Thanks and regards,
~Mellanox Technical Support