Bug 1653834 - [OSP16][RFE][Deployment][TechPreview] Ability to manage KSM service and have it disabled per default
Summary: [OSP16][RFE][Deployment][TechPreview] Ability to manage KSM service and have ...
Alias: None
Product: Red Hat OpenStack
Classification: Red Hat
Component: openstack-tripleo-heat-templates
Version: 15.0 (Stein)
Hardware: All
OS: All
Target Milestone: z2
: 16.0 (Train on RHEL 8.1)
Assignee: Martin Schuppert
QA Contact: Gurenko Alex
Depends On:
Blocks: 1665520 1782217
TreeView+ depends on / blocked
Reported: 2018-11-27 17:41 UTC by Chris Fields
Modified: 2020-05-12 14:47 UTC (History)
16 users (show)

Fixed In Version: openstack-tripleo-heat-templates-11.3.2-0.20200219061444.a1824a3.el8ost
Doc Type: Enhancement
Doc Text:
This enhancement adds the Boolean parameter `NovaComputeEnableKsm`. The parameter enables the ksm and ksmtuned service on compute nodes. You can set `NovaComputeEnableKsm` for each Compute role. The default value is`False`.
Clone Of:
: 1665520 1782217 (view as bug list)
Last Closed: 2020-02-19 09:22:45 UTC
Target Upstream Version:

Attachments (Terms of Use)

System ID Private Priority Status Summary Last Updated
Launchpad 1862921 0 None None None 2020-02-12 11:04:54 UTC
OpenStack gerrit 631021 0 'None' MERGED Add functionality to manage KSM on compute nodes per role 2020-10-19 15:32:24 UTC
OpenStack gerrit 707351 0 None MERGED Add dependency for enable KSM for RHEL/CentOS8 2020-10-19 15:32:24 UTC

Description Chris Fields 2018-11-27 17:41:58 UTC
Description of problem:
KSM enabled on overcloud images conflicts with the tuned cpu-partitioning profile for NFV configurations.  See https://bugzilla.redhat.com/show_bug.cgi?id=1622252.  This issue was discussed in the 11/27 NFV DFG Status meeting where it was agreed that ksm has little benefit in overcloud nodes and should be masked off in OSP 15 and onward.  Proposed solution is that overcloud images should have the 'ksm' and 'ksmtuned' service masked as in: systemctl mask ksm ksmtuned

Version-Release number of selected component (if applicable):
OSP 15

How reproducible:

The issue is not reproducible consistently but occurs roughly one time in four on the customer's system.

Steps to Reproduce:
1. Boot the compute node repeatedly until the issue occurs

Actual results:

cpu-partitioning profile is occasionally not applied and is rolled back leading to compute nodes without the appropriate tuning in place

Expected results:

cpu-partitioning applied

Additional info:

This issue was discovered during testing for an upgrade to OSP10z8 with OVS 2.9 where RHEL was also upgraded from RHEL 7.4 to RHEL 7.5

Additional info:
Need to add to release notes:

"In previous overcloud images the ksm and ksmtuned services were enabled by default.  In OSP 15 and onward these services will be disabled by default."

Comment 2 Kashyap Chamarthy 2019-01-11 15:17:25 UTC
Based on tihs description, this request sounds to me to disable KSM (Kernel Same-page Merging) on the OverCloud images on OSP 15.


More useful context in the 'tuned' bug here: https://bugzilla.redhat.com/show_bug.cgi?id=1622239

And the commit in the 'tuned' profile: https://github.com/redhat-performance/tuned/commit/1b80d4eac24eca5aefb0926d8f2696caa2257c22


Comment 3 Martin Schuppert 2019-01-23 14:17:13 UTC
Just a note, /usr/lib/systemd/system/ksm.service and /usr/lib/systemd/system/ksmtuned.service are part of qemu-kvm-common-rhev, which is not part of the overcloud image in OSP14+ (at least at the moment)

We have it in OSP10 and 13:
[root@compute-0 ~]# ps -ef |grep ksm
root          37       2  0 Jan18 ?        00:00:00 [ksmd]
root        3103       1  0 Jan18 ?        00:00:04 /bin/bash /usr/sbin/ksmtuned
root      658868   29430  0 09:16 pts/0    00:00:00 grep --color=auto ksm

Comment 4 Martin Schuppert 2019-02-28 07:46:55 UTC
As mentioned in comment3 the ksm services are per default not part of the overcloud images in OSP14+ . [1] introduced a role parameter NovaComputeEnableKsm with which the ksm services can be enabled per compute role:

        NovaComputeEnableKsm: True
        NovaComputeEnableKsm: False

[1] https://review.openstack.org/631021

Comment 11 Martin Schuppert 2020-02-19 09:22:45 UTC
Closing this out as full support testing for OSP16 is tracked in https://bugzilla.redhat.com/show_bug.cgi?id=1782217

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