[openib-general] Multi-port HCA

[john t]

Hi,

I have two HCA cards, each having two ports and each connected to a separate
PCI-E x8 slot.

Using one HCA port I get end to end BW of 11.6 Gb/sec (uni-direction RDMA).
If I use two ports of the same HCA or different HCA, I get between 5
to 6.5Gb/sec point-to-point BW on each port. BW on each port further
reduces if I
use more ports. I am not able to understand this behaviour. Is there any
limitation on max. BW that a system can provide? Does the available BW get
divided among multiple HCA ports (which means having multiple ports will not
increase the BW)?


Regards,
John T
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