Re: [PATCHv5 RFC 0/3] Add visibility for native NVMe multipath using sysfs

Daniel Wagner
2024-12-10T09:37:59Z

On Tue, Dec 10, 2024 at 12:33:45PM +0530, Nilay Shroff wrote:
> >>> As we know, NVMe native multipath supports three different io policies
> >>> (numa, round-robin and queue-depth) for selecting I/O path, however, we
> >>> don't have any visibility about which path is being selected by multipath
> >>> code for forwarding I/O. This RFC helps add that visibility by adding new
> >>> sysfs attribute files named "numa_nodes" and "queue_depth" under each
> >>> namespace block device path /sys/block/nvmeXcYnZ/. We also create a
> >>> "multipath" sysfs directory under head disk node and then from this
> >>> directory add a link to each namespace path device this head disk node
> >>> points to.
> >>>
> >>> Please find below output generated with this proposed RFC patch applied on
> >>> a system with two multi-controller PCIe NVMe disks attached to it. This
> >>> system is also an NVMf-TCP host which is connected to an NVMf-TCP target
> >>> over two NIC cards. This system has four numa nodes online when the below
> >>> output was captured:

Looks good to me from libnvme's perspective. I just my question on the
lifetime of the new link, but I might just miss the point.