[SPDK] The parameter max_qpairs_per_ctrlr is misleading

[SPDK] The parameter max_qpairs_per_ctrlr is misleading

[Wenhua Liu]

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When creating nvmf transport using command “rpc.py nvmf_create_transport”, there is a parameter max_qpairs_per_ctrlr. It means number of IO queues plus admin queue per controller. But when people talk about number of queues, usually it means number of IO queues. When someone creates nvmf transport, if he/she knows what max_qpairs_per_ctrlr mean and wants to have 8 IO queues, he/she will set this parameter to 9. If given 8, he/she will get only 7 IO queues.

In the worst case, if someone gives one to this parameter, he won’t get any IO queue !!!

I would suggest SPDK NVMF target changes the definition of this parameter and treat it as number of IO queues. Internally, SPDK should allow one extra qpair be created for admin queue.

Thanks,
-Wenhua Liu