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):
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
cpu-partitioning profile is occasionally not applied and is rolled back leading to compute nodes without the appropriate tuning in place
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
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."
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
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
As mentioned in comment3 the ksm services are per default not part of the overcloud images in OSP14+ .  introduced a role parameter NovaComputeEnableKsm with which the ksm services can be enabled per compute role:
Closing this out as full support testing for OSP16 is tracked in https://bugzilla.redhat.com/show_bug.cgi?id=1782217