iostat does not show statistics for multipath capable NVMe devices

This document (000021184) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4

Situation

iostat does not show I/O statistics for multipath capable NVMe devices, the output doesn't show any values for device utilization:

iostat -tkx 1 /dev/nvme0n1
Linux 5.14.21-150500.53-default (localhost)     06/07/23        _x86_64_        (64 CPU)

06/07/23 15:01:06
avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.10    0.00    0.11    0.04    0.00   99.74

Device            r/s     w/s     rkB/s     wkB/s   rrqm/s   wrqm/s  %rrqm  %wrqm r_await w_await aqu-sz rareq-sz wareq-sz  svctm  %util
nvme0n1          0.00    0.00      0.00      0.00     0.00     0.00   0.00   0.00    0.00    0.00   0.00     0.00     0.00   0.00   0.00

06/07/23 15:01:07
avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.02    0.00    0.09    1.44    0.00   98.45

Device            r/s     w/s     rkB/s     wkB/s   rrqm/s   wrqm/s  %rrqm  %wrqm r_await w_await aqu-sz rareq-sz wareq-sz  svctm  %util
nvme0n1          0.00    0.00      0.00      0.00     0.00     0.00   0.00   0.00    0.00    0.00   0.00     0.00     0.00   0.00   0.00

Resolution

The following SLES15 SP4 and SP5 kernel updates include the patch to support I/O statistics on the mpath device:

SLES15 SP5 kernel version 5.14.21-150500.55.7.1 (released July/2023)
SLES15 SP4 kernel version 5.14.21-150400.24.74.1 (released August/2023)

Cause

The nvme driver didn't collect I/O statistics on mpath devices.

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.