enhancements: support real-time kernels #166

miabbott · 2019-12-19T17:05:53Z

This proposal covers adding support for real-time kernels to RHCOS and
the ability to select those kernels with the MCO.

miabbott · 2019-12-19T17:06:42Z

cc: @cgwalters @ashcrow @runcom @sinnykumari @imcleod @darkmuggle @mrguitar

darkmuggle

A few questions, but otherwise it looks good to me. The prose is clear and concise.

darkmuggle · 2019-12-19T17:14:12Z

enhancements/support-for-realtime-kernel.md

+If there are additional changes required across the OCP product to properly support
+real-time kernel (i.e. container runtime, etc) which cannot be delivered at the
+same time, the real-time kernel packages can still be included as part of the
+`machine-os-content` image.  Additionally, exposing the tunable in the MachineConfig


Mind clarifying this? The part about lacking full support pivots to removing the tunable.

My logic was:

we prep RT kernel support in RHCOS + MCO

we discover there are other components that are not ready

mitigation: keep the RT kernel in the machine-os-content and backout the MCO change, effectively hiding the knob from users

Does that help?

darkmuggle · 2019-12-19T17:20:29Z

enhancements/support-for-realtime-kernel.md

+
+1.  Include the `kernel-rt` packages in the `machine-os-content` image
+2.  Provide tunable in MachineConfig that selects the type of kernel to use
+3.  Do initial tuning of RHCOS node after real-time kernel is applied


I think we need to clarify what "tuning" is affected. For example, FIPS and encryption?

I believe this falls into the bucket of tuned profiles. @cgwalters can you provide some details?

sinnykumari

Overall it looks good to me. One inline comment

sinnykumari · 2019-12-19T17:59:40Z

enhancements/support-for-realtime-kernel.md

+- Test removal of `kernel-rt` packages on single RHCOS node
+- Test `kernelType: realtime` on OCP cluster with RHCOS nodes using default kernel
+- Test `kernelType: default` on OCP cluster with RHCOS nodes using default kernel
+- Test `kernelType: default` on OCP cluster with RHCOS nodes already using real-time kernel


Specifying one MC with setting kerneType to realtime and another one to default can lead to uncertain behavior because rendered MC will pick one of them. Instead of creating another MC with kernelType: default, We might want to test here deleting MC which adds kernelType: realtime .

Got it; will update that test case.

ashcrow · 2019-12-19T19:42:54Z

enhancements/support-for-realtime-kernel.md

+
+### Providing the Packages
+
+The proposal is to include the `kernel-rt` packages in the `machine-os-content`


nit: In the standard machine-os-content. Basically denote it's not a special or different one.

ashcrow · 2019-12-19T19:44:09Z

enhancements/support-for-realtime-kernel.md

+
+When the MCO parses a MachineConfig with `kernelType: default`, it shall instruct `rpm-ostree`
+on the RHCOS node to remove any `kernel-rt` packages and use the default kernel.  If the
+`kernel-rt` packages are not present, it should be a no-op.


Any logging/warning?

I wasn't going to get into those details, but no harm in calling it out explicitly.

ashcrow

Added a couple minor items but it looks quite good!

ericavonb · 2019-12-19T23:22:59Z

enhancements/support-for-realtime-kernel.md

+for things like nVidia GPUs will need to rebuild the kernel modules
+to support the real-time kernel.
+
+- Customers requiring FIPS support **SHOULD NOT** use the real-time kernel.


Can we handle this situation explicitly in the MCO? Like, the MCO can refuse to enable it (e.g. by setting the kerneltype=default on the rendered MC when fips=true)?

Seems feasible. @sinnykumari WDYT?

yes should be possible. MCO can print some message saying Not supported when FIPS is already enabled.

enhancements/support-for-realtime-kernel.md

This proposal covers adding support for real-time kernels to RHCOS and the ability to select those kernels with the MCO.

miabbott · 2020-01-27T18:05:33Z

Finally got around to making the updates ⬆️

ashcrow

LGTM with the latest updates

ashcrow · 2020-01-30T14:59:28Z

Anyone object to merging?

miabbott · 2020-02-18T20:58:19Z

Can someone give a /lgtm here?

It's just a formality at this point; the machine-os-content already contains the RT kernel as described and the MCO has the functionality to switch kernels

sdodson · 2020-02-18T20:59:48Z

/lgtm

openshift-ci-robot · 2020-02-18T21:01:27Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ashcrow, cgwalters, miabbott, mike-nguyen, sdodson

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openshift-ci-robot added the size/L Denotes a PR that changes 100-499 lines, ignoring generated files. label Dec 19, 2019

openshift-ci-robot requested review from jwforres and sdodson December 19, 2019 17:06

miabbott force-pushed the realtime branch from c1d89ac to 47fcf73 Compare December 19, 2019 17:23

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sinnykumari mentioned this pull request Jan 24, 2020

Bump RHCOS to 44.81.202001240222.0 openshift/installer#2974

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enhancements: support real-time kernels

98cb9d8

This proposal covers adding support for real-time kernels to RHCOS and the ability to select those kernels with the MCO.

miabbott force-pushed the realtime branch from 47fcf73 to 98cb9d8 Compare January 27, 2020 18:04

ashcrow approved these changes Jan 29, 2020

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openshift-ci-robot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Jan 29, 2020

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cgwalters approved these changes Jan 30, 2020

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slintes mentioned this pull request Feb 13, 2020

Add periodic job for OCP with realtime workers openshift/release#7154

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openshift-ci-robot assigned sdodson Feb 18, 2020

openshift-ci-robot added the lgtm Indicates that a PR is ready to be merged. label Feb 18, 2020

openshift-merge-robot merged commit 6d25129 into openshift:master Feb 18, 2020


		### Providing the Packages

		The proposal is to include the `kernel-rt` packages in the `machine-os-content`

enhancements: support real-time kernels #166

enhancements: support real-time kernels #166

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