ZTS: zpool_iostat_interval_all

[behlendorf]

System information

Type	Version/Name
Distribution Name	all
Distribution Version	all
Kernel Version	all
Architecture	all
OpenZFS Version	2.4.1

Describe the problem you're observing

Occasional failure of test case zpool_iostat_interval_all.

Describe how to reproduce the problem

Observed in the CI environment.

https://github.com/openzfs/zfs/actions/runs/22460178332/job/65052174887?pr=18148

Include any warning/errors/backtraces from the system logs

 Debuginfo of failed tests:
cli_root/zpool_iostat/zpool_iostat_interval_all (1 KiB)
  [2026-02-26T21:27:13.922470] Test: /usr/local/share/zfs/zfs-tests/tests/functional/cli_root/zpool_iostat/zpool_iostat_interval_all (run as root) [00:03] [FAIL]
  21:27:11.04 SUCCESS: mkfile 268435456 /var/tmp/tmp.8o9qH8SNfk /var/tmp/tmp.8TRp0wix4u
  21:27:11.39 SUCCESS: zpool create pool1 /var/tmp/tmp.8o9qH8SNfk
  21:27:11.74 SUCCESS: zpool create pool2 /var/tmp/tmp.8TRp0wix4u
  21:27:12.08 SUCCESS: zpool export -a
  21:27:12.51 SUCCESS: zpool import -d /var/tmp/tmp.8TRp0wix4u pool2
  21:27:12.94 SUCCESS: zpool import -d /var/tmp/tmp.8o9qH8SNfk pool1
  21:27:13.27 SUCCESS: zpool destroy pool1
  21:27:13.60 SUCCESS: zpool destroy pool2
  21:27:13.90 /usr/local/share/zfs/zfs-tests/tests/functional/cli_root/zpool_iostat/zpool_iostat_interval_all.ksh[86]: stop_iostat[74]: wait: 32490: Terminated
  21:27:13.90 NOTE: expected: NOPOOL HEADER POOL1 HEADER POOLBOTH NOPOOL HEADER POOL2 HEADER POOLBOTH HEADER POOL2 NOPOOL
  21:27:13.90 NOTE:      got: NOPOOL HEADER POOL1 HEADER POOLBOTH HEADER POOL1 NOPOOL HEADER POOL2 HEADER POOLBOTH HEADER POOL2 NOPOOL
  21:27:13.90 zpool iostat did not produce expected output
  21:27:13.90 NOTE: Performing test-fail callback (/usr/local/share/zfs/zfs-tests/callbacks/zfs_dmesg.ksh)