I am using Mellanox Technologies MT27800 Family [ConnectX-5] accelerated card for low latency network message transition.

However, when using the “Dummy Send” function provided by VMA, the dummy message that I passed to the function: send(fd, buf, len, VMA_SND_FLAGS_DUMMY) would be occasionally ( around 1 time per 1000 billion call ) sent out by this function. But the documentation shows that the dummy message would be dropped before it was sent.

This phenomenon happens rarely but every time it happens it brings us significant loss. The frequency that I call send(fd, buf, len, VMA_SND_FLAGS_DUMMY) is 20k/s to reduce the overhead of TCP Send.

I used vma_stats –p -v 3 to check whether the dummy send function works, the report shows that this function works properly but the phenomenon that the dummy message was send always happens once.

I cannot reproduce the problem because sometimes it works fine but sometimes it just sends out the dummy message.

May I know if anyone else encounter this problem? or there is any solution for this problem? or should I add VMA_TRIGGER_DUMMY_SEND_GETSOCKNAME when I use dummy send?

May we know if there is any one who could help me ?



The scenario you described requires a deeper investigation and reproduction (checking the code you are running). In this situation we recommend to open a support case in Nvidia portal, and it will be handled according to the entitlement.

Best Regards,


How do we open a support case for it ?

Thanks & Regards,

Michael from Alpha Quant