Red Hat build of MicroShift

Configure the MicroShift TuneD profile

To use low latency with MicroShift workloads, configure a TuneD profile for your host by using the microshift-baseline-variables.conf file provided in the /etc/tuned/ directory.

Prerequisites

You have root access to the node.
You installed the microshift-low-latency RPM package.
Your RHEL host has TuneD installed. See Getting started with TuneD (RHEL documentation).

Procedure

You can use the default microshift-baseline-variables.conf TuneD profile in the /etc/tuned/ directory profile, or create your own to add more tunings.

Example microshift-baseline-variables.conf TuneD profile

# Isolate cores 2-7 for running application workloads
isolated_cores=2-7

# Size of the hugepages
hugepages_size=2M

# Number of hugepages
hugepages=0

# Additional kernel arguments
additional_args=

# CPU set to be offlined
offline_cpu_set=

isolated_cores

Controls which cores should be isolated. By default, 1 core per socket is reserved in MicroShift for housekeeping. The other cores are isolated. Valid values are a core list or range. You can isolate any range, for example: isolated_cores=2,4-7 or isolated_cores=2-23.

You must keep only one isolated_cores= variable.

The Kubernetes CPU manager can use any CPU to run the workload except the reserved CPUs defined in the kubelet configuration. For this reason it is best that:

The sum of the kubelet’s reserved CPUs and isolated cores include all online CPUs.
Isolated cores are complementary to the reserved CPUs defined in the kubelet configuration.

hugepages_size

Size of the hugepages. Valid values are 2M or 1G.

additional_args

Additional kernel arguments, for example, additional_args=console=tty0 console=ttyS0,115200.

offline_cpu_set

The CPU set to be offlined.

Must not overlap with isolated_cores.

Enable the profile or make changes active, by running the following command:
```
$ sudo tuned-adm profile microshift-baseline
```
Reboot the host to make kernel arguments active.

Verification

Optional: You can read the /proc/cmdline file that contains the arguments given to the currently running kernel on start.

$ cat /proc/cmdline

Example output

BOOT_IMAGE=(hd0,msdos2)/ostree/rhel-7f82ccd9595c3c70af16525470e32c6a81c9138c4eae6c79ab86d5a2d108d7fc/vmlinuz-5.14.0-427.31.1.el9_4.x86_64+rt crashkernel=1G-4G:192M,4G-64G:256M,64G-:512M rd.lvm.lv=rhel/root fips=0 console=ttyS0,115200n8 root=/dev/mapper/rhel-root rw ostree=/ostree/boot.1/rhel/7f82ccd9595c3c70af16525470e32c6a81c9138c4eae6c79ab86d5a2d108d7fc/0 skew_tick=1 tsc=reliable rcupdate.rcu_normal_after_boot=1 nohz=on nohz_full=2,4-5 rcu_nocbs=2,4-5 tuned.non_isolcpus=0000000b intel_pstate=disable nosoftlockup hugepagesz=2M hugepages=10

Next steps

Prepare your MicroShift workloads for low latency.
Optional: Configure automatic enablement of your TuneD profile.
Optional: If you are using the x86_64 architecture, you can install Red Hat Enterprise Linux for Real Time (real-time kernel).