Description of problem:
The Realtime (RT) variant of the RHEL kernel shipped in downstream RHCOS appears to not be synchronized with the standard kernel.
For example, the latest currently shipping stable version as of the BZ authoring is version 4.6.9. That corresponds to 46.82.202012151054-0, which has kernel version 4.18.0-193.37.1.el8_2.x86_64.
When switching to the RT variant of the kernel via the Performance AddOn Operator, one gets booted into RT kernel version
4.18.0-193.28.1.rt13.77.el8_2.x86_64. This should be a more recent kernel.
Additional info:
The 28.1 kernel is from October and should be on a later release, such as 37.1, which is from December.
In looking at nightly builds for 4.6, it still has the kernel version from October. (4.6.0-0.nightly-2021-01-08-200800) mounting the machine-os-content and looking in the extensions folder.
./extensions/kernel-rt/kernel-headers-4.18.0-193.28.1.el8_2.x86_64.rpm
./extensions/kernel-rt/kernel-rt-core-4.18.0-193.28.1.rt13.77.el8_2.x86_64.rpm
./extensions/kernel-rt/kernel-rt-devel-4.18.0-193.28.1.rt13.77.el8_2.x86_64.rpm
./extensions/kernel-rt/kernel-rt-kvm-4.18.0-193.28.1.rt13.77.el8_2.x86_64.rpm
./extensions/kernel-rt/kernel-rt-modules-4.18.0-193.28.1.rt13.77.el8_2.x86_64.rpm
./extensions/kernel-rt/kernel-rt-modules-extra-4.18.0-193.28.1.rt13.77.el8_2.x86_64.rpm
There are numerous fixes in more recent RT kernel versions that are absolutely critical for low latency applications running on OpenShift 4.6.
RHCOS 4.6 is billed as an EUS release and uses the RHEL 8.2 EUS sources. The kernel-rt package does not have an EUS release, rather it uses the moniker "Telecommunications Update Service". See the most recent advisory for `kernel-rt` - https://access.redhat.com/errata/RHSA-2020:5428
The RHCOS build process is incorrectly using the wrong location for TUS updates on `kernel-rt`, so we'll have to update our build process/configuration to use the proper location.
The RHCOS build configuration for 4.7 is tracking the standard RHEL 8 repos, so this problem does not need to be addressed in 4.7 directly. Will close this as NOTABUG for 4.7.
The fix applies to 4.6.z, so I've created the clone here - https://bugzilla.redhat.com/show_bug.cgi?id=1914988
Please see the 4.6.z BZ to follow the fixes.