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This patch helps add nvme native multipath visibility for queue-depth io-policy. It adds a new attribute file named "queue_depth" under namespace device path node which would print the number of active/ in-flight I/O requests currently queued for the given path. For instance, if we have a shared namespace accessible from two different controllers/paths then accessing head block 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 the namespace is accessible from nvme1c1n1 and nvme1c3n1 paths. For queue-depth io-policy we can then refer the "queue_depth" attribute file created under each namespace path: $ cat /sys/block/nvme1n1/multipath/nvme1c1n1/queue_depth 518 $cat /sys/block/nvme1n1/multipath/nvme1c3n1/queue_depth 504 >From the above output, we can infer that I/O workload targeted at nvme1n1 uses two paths nvme1c1n1 and nvme1c3n1 and the current queue depth of each path is 518 and 504 respectively. Reading "queue_depth" file when configured io-policy is anything but queue-depth would show no output. Reviewed-by: Sagi Grimberg <sagi@grimberg.me> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Nilay Shroff <nilay@linux.ibm.com> Signed-off-by: Keith Busch <kbusch@kernel.org>
Linux kernel
============
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