[RFC PATCHv2 4/4] nvme-multipath: add debugfs attribute for adaptive I/O policy stat

[Hannes Reinecke]

On 10/9/25 12:05, Nilay Shroff wrote:
> This commit introduces a new debugfs attribute, "adaptive_stat", under
> both per-path and head debugfs directories (defined under /sys/kernel/
> debug/block/). This attribute provides visibility into the internal
> state of the adaptive I/O policy to aid in debugging and performance
> analysis.
> 
> For per-path entries, "adaptive_stat" reports the corresponding path
> statistics such as I/O weight, selection count, processed samples, and
> ignored samples.
> 
> For head entries, it reports per-CPU statistics for each reachable path,
> including I/O weight, path score, smoothed (EWMA) latency, selection
> count, processed samples, and ignored samples.
> 
> These additions enhance observability of the adaptive I/O path selection
> behavior and help diagnose imbalance or instability in multipath
> performance.
> 
> Signed-off-by: Nilay Shroff <nilay at linux.ibm.com>
> ---
>   drivers/nvme/host/core.c      |   3 +
>   drivers/nvme/host/debugfs.c   | 117 ++++++++++++++++++++++++++++++++++
>   drivers/nvme/host/multipath.c |   2 +
>   3 files changed, 122 insertions(+)
> 
Reviewed-by: Hannes Reinecke <hare at suse.de>

Might be an idea to have support for queue-depth in here, too.

Cheers,

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