I/O Scheduler changes for NVMe devices after patching

This document (000019772) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server 15

Situation

After patching and reboot, the i/o scheduler changes on NVMe devices.

For example, a server before being patched shows the scheduler set as none:
lsblk -o NAME,FSTYPE,ROTA,SCHED
NAME        FSTYPE ROTA SCHED
nvme0n1               0 none
└─nvme0n1p1 xfs       0 none
After patching and rebooting, the scheduler has changed to mq-deadline:
lsblk -o NAME,FSTYPE,ROTA,SCHED
NAME        FSTYPE ROTA SCHED
nvme0n1               0 mq-deadline
└─nvme0n1p1 xfs       0 mq-deadline

Resolution

To change back to the previous I/O scheduler immediately, but not persistently after reboot, run the following command:
echo SCHEDULER > /sys/block/DEVICE/queue/scheduler

For example, to change from mq-deadline back to none, run the following command:

echo none > /sys/block/nvme0n1/queue/scheduler

To make these changes persistent after reboot, edit the file, /usr/lib/udev/rules.d/60-io-scheduler.rules and remove the following lines:

# MQ: deadline scheduler for SSD
ENV{.IS_MQ}=="1", ATTR{queue/rotational}=="0", ATTR{queue/scheduler}="mq-deadline"

Cause

There was a regression in a udev patch which erroneously added the change to mq-deadline scheduler for multi-queue SSD devices.

Additional Information

A maintenance release is scheduled to automatically fix this issue.

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.

  • Document ID:000019772
  • Creation Date: 02-Nov-2020
  • Modified Date:03-Nov-2020
    • SUSE Linux Enterprise Server
    • SUSE Linux Enterprise Server for SAP Applications

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