[PATCH v8 00/10] nvme-multipath: introduce latency I/O policy

[Sagi Grimberg]

> I think Nilay has done some great work with the latency scheduler, and
> we have it in our queue for evaluation.  But we have not done so yet,
> so I would appreciate if queue-depth would continue to be available
> until the latency scheduler has been more fully established as the
> prime choice.
>
> As to round-robin, I agree it would be great to see it disappear from
> all of our customers installations, but I have found it useful in
> evaluating multipath failover behavior because it is easier to reason
> about and construct the test cases.  So, I would appreciate if it
> would remain for debugging only.  I would certainly be open to a
> mechanism that made it a little bit hard to set round-robin as the
> queue policy, though.

Randy, would it be possible for you folks to evaluate it as well? I will ask
some folks on our side as well. I'm concerned that Nilay is the only one who
has evaluated it in his lab.

Overall, I am perfectly fine with the approach this path selector is 
taking, but I worry
that we are growing path-selectors that are slightly different in subtle 
ways...
TBH, I still don't understand what use-cases this path selector is more
appropriate than queue-depth, or vice-versa.