COS-2508: docs: explain how to enable swap

[jbtrystram]

swap support is now beta2 in kubernetes (as 1.28) and should be stable in 1.30.
Document how to enable the feature on OCP.

Follow #1479

[openshift-ci-robot]

@jbtrystram: This pull request references COS-2507 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the story to target the "4.16.0" version, but no target version was set.

In response to this:

swap support is now beta2 in kubernetes (as 1.28) and should be stable in 1.30.
Document how to enable the feature on OCP.

Follow #1479

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[openshift-ci-robot]

@jbtrystram: This pull request references COS-2508 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the story to target the "4.16.0" version, but no target version was set.

In response to this:

swap support is now beta2 in kubernetes (as 1.28) and should be stable in 1.30.
Document how to enable the feature on OCP.

Follow #1479

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the openshift-eng/jira-lifecycle-plugin repository.

[jlebon]

It's tempting to add more in-depth docs here, but I would suggest not going too deep into that. That level of depth I think belongs better in the OCP docs. Otherwise we end up with competing docs that need to be maintained in parallel. We have the FAQ, but that's meant to be more shorter answers that ideally link to more comprehensive docs (OCP/RHEL/upstream).

Specifically for this, e.g. we could reformulate it as a FAQ question like:

Q: Does RHCOS support swap?

It's supported as Tech Preview in 4.16. To enable it, first enable the tech preview feature gate, then enable the swapBehavior: LimitedSwap option in a KubeletConfig. swap can be a separate partition (via Ignition), or you can use swap on zram.

Once we have more in-depth docs in the official docs, we can link to that.

[jbtrystram]

It's tempting to add more in-depth docs here, but I would suggest not going too deep into that. That level of depth I think belongs better in the OCP docs.

100% agree. My idea was to have a draft so someone from the docs could take over.
Now i realize I should have opened this in the docs repo...

[aaradhak]

minor : may be we can remove these extra lines at the eof?
The remaining content lgtm otherwise

[jlebon]

It's tempting to add more in-depth docs here, but I would suggest not going too deep into that. That level of depth I think belongs better in the OCP docs.

100% agree. My idea was to have a draft so someone from the docs could take over. Now i realize I should have opened this in the docs repo...

Normally the docs team adds those and might already be working on it (cc @jldohmann). But yeah, definitely useful to have this written out even just here in PR form as something to start with for the official docs.

[travier]

LGTM overall. Agree with Jonathan. Let's make this proper OCP docs.
/hold

[jbtrystram]

@jldohmann was this added to the OCP docs ? I see a couple of PRs but nothing related to ZRAM swap

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