Is it possible to disable "Coalesced Acknowledge Messages" for RDMA Write?

Hello everyone,

According to the IB specification, “Coalesced Acknowledge Messages” means “It is not required that there be a unique, discrete response for each request packet. Instead, the responder may acknowledge several outstanding request packets with a single acknowledge packet.”

And in my own tests, I’ve comfirmed that the number of RDMA write request packets exceeds the number of acknowledge packets, indicating that the requests and acknowledgements are not strictly one-to-one.

For my specific needs, I would like each RDMA write request to trigger a unique acknowledge from the responding NIC, rather than using a single acknowledge to respond to multiple requests. Is there a way to achieve this?

Previously, I used a script with mstmcra to disable ICRC checking, and I wonder if there might be a similar method to disable “Coalesced Acknowledge Messages” for RDMA write? I’m using ConnectX-5.

Thank you in advance for any insights or advice you can offer!

Hi zhmayusi,

Thank you posting your query on NVIDIA Community.

Unfortunately, the addressed behavior will need to validated behavior with Engineering Team and requires debug.

This will require an active support entitlement. If there an active entitlement/support contract in place, please do not hesitate to open a support ticket by emailing

For contracts, please reach out to


I understand, thanks.