Re: [PATCH 3/3] tree: add attribute numa_nodes for NVMe path object

[Nilay Shroff <nilay@linux.ibm.com>]

On 4/7/25 1:14 PM, Daniel Wagner wrote:
> On Sat, Apr 05, 2025 at 06:32:49PM +0530, Nilay Shroff wrote:
>> Add a new attribute named "numa_nodes" under the NVMe path object. This
>> attribute is used by the iopolicy "numa". The numa_nodes value is stored
>> for each NVMe path and represents the NUMA node(s) associated with it.
>> When the iopolicy is set to "numa", I/O traffic originating from a given
>> NUMA node will be forwarded through the corresponding NVMe path.
>>
>> The numa_nodes attribute is useful for observing which NVMe path the
>> kernel would choose for I/O forwarding based on NUMA affinity. To support
>> this, export the attribute in libnvme.map so it can be accessed via
>> nvme-cli.
> 
> This one has the same limitation as the previous one. Given that libnvme
> currently caches everything, we could just accept this limitation for
> the time being. Any thoughts on this?

Yes agreed. So how about adding a new API, for instance, 
nvme_path_get_numa_nodes__no_cached which would not return 
the cached value but instead re-read the latest value from
sysfs attribute and return the latest value? We may similarly
extend other APIs where we don't want to retrieve cached 
value. 

Thanks,
--Nilay