Red Hat build of MicroShift

Install the Red Hat Enterprise Linux for Real Time (real-time kernel) in a Red Hat Enterprise Linux for Edge (RHEL for Edge) image

To configure low latency for a MicroShift node, you can include the real-time kernel in a RHEL for Edge image deployment using image builder.

Prerequisites

You have a Red Hat subscription enabled on the host that includes Red Hat Enterprise Linux for Real Time (real-time kernel).
You are using the x86_64 architecture.
You configured osbuild to use the kernel-rt repository.

A subscription that includes the real-time kernel must be enabled on the host used to build the commit.

Procedure

Add the following example blueprint sections to your complete installation blueprint for installing the real-time kernel in a RHEL for Edge image:

Example blueprint snippet for the real-time kernel

[[packages]]
name = "microshift-low-latency"
version = "*"

# Kernel RT is supported only on the x86_64 architecture
[customizations.kernel]
name = "kernel-rt"

[customizations.services]
enabled = ["microshift", "microshift-tuned"]

[[customizations.files]]
path = "/etc/microshift/config.yaml"
data = """
kubelet:
  cpuManagerPolicy: static
  cpuManagerPolicyOptions:
    full-pcpus-only: "true"
  cpuManagerReconcilePeriod: 5s
  memoryManagerPolicy: Static
  topologyManagerPolicy: single-numa-node
  reservedSystemCPUs: 0-1
  reservedMemory:
  - limits:
      memory: 1100Mi
    numaNode: 0
  kubeReserved:
    memory: 500Mi
  systemReserved:
    memory: 500Mi
  evictionHard:
    imagefs.available: 15%
    memory.available: 100Mi
    nodefs.available: 10%
    nodefs.inodesFree: 5%
  evictionPressureTransitionPeriod: 5m
"""

[[customizations.files]]
path = "/etc/tuned/microshift-baseline-variables.conf"
data = """
# Isolated cores should be complementary to the kubelet configuration reserved CPUs.
# Isolated and reserved CPUs must contain all online CPUs.
# Core #3 is for testing offlining, therefore it is skipped.
isolated_cores=2,4-5
hugepages_size=2M
hugepages=10
additional_args=test1=on test2=true dummy
offline_cpu_set=3
"""

[[customizations.files]]
path = "/etc/microshift/tuned.yaml"
data = """
profile: microshift-baseline
reboot_after_apply: True
"""

Next steps

Complete the image building process.
If you have not completed the previous steps for enabling low latency for your MicroShift cluster, do so now. Update the blueprint with the information gathered in those steps.
If you have not configured workload partitioning, do so now.
Prepare your MicroShift workloads for low latency.