[PATCHv7 RFC 2/3] nvme-multipath: Add visibility for numa io-policy

[Hannes Reinecke]

On 1/12/25 13:41, Nilay Shroff wrote:
> This patch helps add nvme native multipath visibility for numa io-policy.
> It adds a new attribute file named "numa_nodes" under namespace gendisk
> device path node which prints the list of numa nodes preferred by the
> given namespace path. The numa nodes value is comma delimited list of
> nodes or A-B range of nodes.
> 
> For instance, if we have a shared namespace accessible from two different
> controllers/paths then accessing head node of the shared namespace would
> show the following output:
> 
> $ ls -l /sys/block/nvme1n1/multipath/
> nvme1c1n1 -> ../../../../../pci052e:78/052e:78:00.0/nvme/nvme1/nvme1c1n1
> nvme1c3n1 -> ../../../../../pci058e:78/058e:78:00.0/nvme/nvme3/nvme1c3n1
> 
> In the above example, nvme1n1 is head gendisk node created for a shared
> namespace and this namespace is accessible from nvme1c1n1 and nvme1c3n1
> paths. For numa io-policy we can then refer the "numa_nodes" attribute
> file created under each namespace path:
> 
> $ cat /sys/block/nvme1n1/multipath/nvme1c1n1/numa_nodes
> 0-1
> 
> $ cat /sys/block/nvme1n1/multipath/nvme1c3n1/numa_nodes
> 2-3
> 
>>From the above output, we infer that I/O workload targeted at nvme1n1
> and running on numa nodes 0 and 1 would prefer using path nvme1c1n1.
> Similarly, I/O workload running on numa nodes 2 and 3 would prefer
> using path nvme1c3n1. Reading "numa_nodes" file when configured
> io-policy is anything but numa would show no output.
> 
> Reviewed-by: Sagi Grimberg <sagi at grimberg.me>
> Signed-off-by: Nilay Shroff <nilay at linux.ibm.com>
> ---
>   drivers/nvme/host/multipath.c | 27 +++++++++++++++++++++++++++
>   drivers/nvme/host/nvme.h      |  1 +
>   drivers/nvme/host/sysfs.c     |  5 +++++
>   3 files changed, 33 insertions(+)
> 
Reviewed-by: Hannes Reinecke <hare at suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare at suse.de                                +49 911 74053 688
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