[PATCHv3 0/4] nvme-cli: enhance the visibility of multipath using show-topology command

[Nilay Shroff]

Hi Daniel,

A gentle ping on this patchset. Please let me know, in case, if you've
any further query/comment/suggestion for this patchset. 

Thanks,
--Nilay

On 9/4/25 11:26 PM, Nilay Shroff wrote:
> Hi,
> 
> There has been recent work to improve the visibility of NVMe multipath
> configurations. The native NVMe multipath kernel driver supports three
> I/O path selection policies: numa, round-robin, and queue-depth. However,
> until now, users have had no insight into which path is selected by the
> multipath logic for forwarding I/O.
> 
> To address this, an RFC was proposed [1] and has since been merged into
> the Linux kernel as of v6.15. Following that, libnvme was extended to
> discover multiple paths to a shared NVMe namespace [2]. This patchset
> builds on those efforts to improve userspace observability of multipath
> configurations via nvme-cli.
> 
> This patchset contains four patches:
> The first patch in the series fixes a <device> filter option using which
> we could be able to filter the output of nvme show-topology command.
> 
> The second patch in the series enhances the nvme show-topology command to
> display multipath configuration, including all discovered paths to a
> namespace, along with details such as ANA state, NUMA nodes, and queue
> depth. The show-topology "--ranking" option is extended with a new sub-
> option: multipath.
> 
> The third patch in the series adds common table APIs for printing nvme cli
> command output in tabular format.  With these APIs, developers no longer
> need to pre-calculate column or row widths. The output is consistently
> aligned and easy to read.
> 
> The fourth patch adds support for printing show-topology in tabular form
> leveraging the introduced table APIs to produce well-aligned, easy-to-read
> output.
> 
> As usual, any feedback/sugegstion is most welcome!
> 
> Thanks!
> 
> Changes from v2:
>   - For iopolicy=numa, print NUMA nodes and exclude queue-depth.
>     Similarly, for iopolicy=queue-depth, print queue-depth but exclude
>     NUMA nodes. And for iopolicy=round-robin, exclude printing
>     both NUMA nodes and queue-depth. (Hannes Reinecke, Daniel
>     Wagner)
> Link to v2: https://lore.kernel.org/all/20250812125614.164445-1-nilay@linux.ibm.com/
> 
> Changes from v1:
>   - Added the third patch in the series that implements the common table
>     APIs for printing nvme cli command output in tabular format
>     (Daniel Wagner)
>   - Added the fourth patch in the series which adds the support for
>     printing show-topology in tabular form (Daniel Wagner)
> Link to v1: https://lore.kernel.org/all/20250704135001.292763-1-nilay@linux.ibm.com/
> 
> Nilay Shroff (4):
>   nvme: support <device> option in show-topology command
>   nvme: extend show-topology command to add support for multipath
>   nvme: add common APIs for printing tabular format output
>   nvme: add support for printing show-topology in tabular form
> 
>  nvme-print-binary.c |   1 +
>  nvme-print-json.c   |  36 ++++-
>  nvme-print-stdout.c | 312 +++++++++++++++++++++++++++++++++++++++++-
>  nvme-print.c        |   9 +-
>  nvme-print.h        |   3 +
>  nvme.c              |  29 +++-
>  nvme.h              |   2 +
>  util/meson.build    |   3 +-
>  util/table.c        | 320 ++++++++++++++++++++++++++++++++++++++++++++
>  util/table.h        | 149 +++++++++++++++++++++
>  10 files changed, 849 insertions(+), 15 deletions(-)
>  create mode 100644 util/table.c
>  create mode 100644 util/table.h
>