[PATCH/RFC] NVMe: add support for doing offline/online of attached namespaces

[Christoph Hellwig]

On Fri, Jan 23, 2015 at 10:24:45AM -0700, Jens Axboe wrote:
> It'd be an interesting experiment in seeing how close scsi-mq is to raw
> performance, I'd be worried there's still quite a gap though. Maybe when
> we're further along it starts to become a more viable option, at least I
> would not rule it out.

I'd love to try it.  On the submission side SCSI for some drivers
actually is more efficient than nvme in terms of memory allocations
as we don't require any allocation for common I/O. (Your patch closes
that gap for the smallest possible IO), altough the per-host and
per-device shost_busy/sdev_busy counters will show some issues with
enough sockets.  On the completion side SCSI might still be a bit
worse as we haven't really haven't started any optimizations yet.

> At the same time, this is a feature we use/need now. So I don't think a
> potential switch in future direction should preclude that from being done
> now.

Sure, I was just answering your question for potential alternatives.