Performance loss on SLES 12 SP5 after updating to kernel 4.12.14-122.150 or higher

This document (000021233) is provided subject to the disclaimer at the end of this document.


SUSE Linux Enterprise Server 12 SP5


If a SCSI device is in use and SLES 12 SP5 is updated to kernel 4.12.14-122.150 or later, a significant performance drop may be noticed.

This issue is not expected to affect SLES 15 SPx.


A kernel update was released in October 2023, containing a fix.

For SLES 12 SP5 kernel-default 4.12.14-122.179
For kernel-azure:  4.12.14-16.152
For kernel-rt:  4.12.14-10.144


Kernel 4.12.14-122.150 received the following SCSI fix:

commit da5bd87e56640166a5a4d3053687c02b135bd5bd
Date:   Tue Feb 7 08:32:03 2023 -0800
    Revert "scsi: core: run queue if SCSI device queue isn't ready
    and queue is idle" (git-fixes).

However, the corresponding upstream commit b4fd63f4264 mentions this revert in scsi core should be done in tandem with 2 other commits in blk-mq, which were not present at that time:

ab3cee376 blk-mq: In blk_mq_dispatch_rq_list() "no budget" is a reason to kick
a0823421a blk-mq: Rerun dispatching in the case of budget contention

These have now been added and performance is back to normal.


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  • Document ID:000021233
  • Creation Date: 10-Oct-2023
  • Modified Date:10-Oct-2023
    • SUSE Linux Enterprise Server

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