Re: [PATCHv2 2/4] nvme: extend show-topology command to add support for multipath

[Hannes Reinecke <hare@suse.de>]

On 8/20/25 10:17, Daniel Wagner wrote:
> On Tue, Aug 19, 2025 at 08:15:09AM +0200, Hannes Reinecke wrote:
>>> Okay makes sense, so we'd print <numa-node> and exclude <queue-depth> if iopolicy
>>> is numa. For 'queue-depth' iopolicy, we'd print <queue-depth> and exclude <numa-node>.
>>> And for 'round-robin' iopolicy, we'd neither print <numa-node> nor <queue-depth>.
>>> I'll update this in the next patch.
>>>
>> Hmm. I'd rather have _some_ value for 'round-robin', too, as otherwise
>> the number of fields will be different (and making parsing harder).
> 
> What type of parser do you mean, a carbon based one or a computer? I
> strongly recommend to use the JSON output for the later.
> 
> I would really prefer that the default stdout is easy for a human to
> read not screen scrappers.
> 
That was my intention, too. And my prime objection was to have a
sequence of raw numbers, and requiring the user to figure out what
these numbers are for.

But really, I'm not sure if we should print out values from the various
I/O policies. For NUMA it probably makes sense, but for round-robin and
queue-depths the values are extremely volatile, so I wonder what benefit
for the user is here.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich