[CI:DOCS] Add notes to flags not supported on cgroups V2

[hshiina]

Clarify what flags are not supported on cgroups V2 in documentation.
The following flags of create and run commands are not supported:

• --cpu-rt-period
• --cpu-rt-runtime
• --kernel-memory
• --memory-swappiness

Signed-off-by: Hironori Shiina [email protected]

[mheon]

Can you add "systems" to the end - so "not supported on cgroups v2 systems."

[mheon]

@TomSweeneyRedHat PTAL

[mheon]

/approve

[openshift-ci]

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[rhatdan]

LGTM
Would love a head nod from @giuseppe to confirm the lack of support of these options.

[rhatdan]

BTW Do we give a decent error when a user attempts one of these flags? Something like this option is not supported on cgroup v2 systems, as opposed to some random file object does not exist in the cgroup file system?

[mheon]

Podman itself won't give any error - we rely on the OCI runtime. Which probably means it's the latter.

[rhatdan]

Well Podman could check if it is running in cgroupv2 and then report errors on the unsupported options. Although this would not work as easily on the --remote.

[ashley-cui]

/lgtm