feat: sap_hana_preconfigure allow disabling modification of command line boot args

[GutiPerez]

Ansible Role

sap_hana_preconfigure

OS Family

All

Feature/Enhancement request

I believe after 1.7.0 release changes, specifically, the boot command line arguments checks added on #1083, there should a way to disable the modification of the arguments. I was expecting sap_hana_preconfigure_modify_grub_cmdline_linux variable to do so, but it is not.

Actually, I think it is counterproductive that all arguments are always set if not present. For instance, processor.max_cstate and intel_idle.max_cstat should not be set at all if we use sap-hana tuned profile (which the role does by default with sap_hana_preconfigure_use_tuned parameter). In our case, we have HPE hardware, and a mandatory HPE package for RHEL handles tsx and transparent_hugepages arguments.

Finally, a minor bug/unexpected situation. For the following task, included in v1.7.0, given that we need to run the playbook with become: true for the role to work, now I can not run the playbook from a user that can not become root, as this task is delegated to localhost. This could be easily fixed with a become: false on that specific task

Community participation

Unfortunately I am not in a position to help with the feature

Optional - Attempted solutions or manual steps

No response

[berndfinger]

@GutiPerez Many thanks for reporting this. I create a separate issue for supporting the new vars handling when running the role by a user who cannot become root.
The other topic - allow disabling modification of command line boot args is a regression after #1083, and will be handled in the current issue.

[GutiPerez]

Thanks, @berndfinger

If I may, an additional reflection on the topic.

For the (current) four boot arguments, the 'problematic' ones areprocessor.max_cstate=1 and intel_idle.max_cstate=1, as you may not want them to be added if sap-hana tuned profile is used. As for the other two, tsx=on and transparent_hugepages=madvise/never, given that it is first checked whether they are already in the cmdline, there is no issue on always setting them (I can not think of a situation where you should not set them).

An optimal and flexible way to handle this issue would be to add the cstate parameters (or not) depending on the sap_hana_preconfigure_use_tuned role parameter and always add the other two. Assuming sap_hana_preconfigure_modify_grub_cmdline_linux role parameter is set to true.

[berndfinger]

Thanks, @berndfinger

If I may, an additional reflection on the topic.

For the (current) four boot arguments, the 'problematic' ones areprocessor.max_cstate=1 and intel_idle.max_cstate=1, as you may not want them to be added if sap-hana tuned profile is used. As for the other two, tsx=on and transparent_hugepages=madvise/never, given that it is first checked whether they are already in the cmdline, there is no issue on always setting them (I can not think of a situation where you should not set them).

An optimal and flexible way to handle this issue would be to add the cstate parameters (or not) depending on the sap_hana_preconfigure_use_tuned role parameter and always add the other two. Assuming sap_hana_preconfigure_modify_grub_cmdline_linux role parameter is set to true.

Anyway, it's possible to:

• use the role variable sap_hana_preconfigure_modify_grub_cmdline_linux as before, meaning that the role can use the tuned profile or set the boot command line variables, or both, AND
• set your own list of boot command line arguments.

This should provide all the flexibility we can think of.

[berndfinger]

@GutiPerez Release 1.7.1 now has the fix for #1093, as well as the fix for #1095 (which is the second issue you reported in this issue). I omitted the ability to set your own list of boot command line arguments for this release because we first need to discuss how to validate such a list, and I wanted to quickly fix this issue.

With this, there are now the following options, just like before release 1.7.0:

• Activate the tuned profile sap-hana (or another one) and do not modify the boot command line as stated in the applicable SAP notes for RHEL.
• Activate the tuned profile sap-hana (or another one) and also modify the boot command line as stated in the applicable SAP notes for RHEL.
• Do not activate the tuned profile sap-hana (or another one) but modify the boot command line as stated in the applicable SAP notes for RHEL.

[GutiPerez]

Thanks a lot @berndfinger

Agreed, v1.7.1 solves my initial issues.

Nevertheless, for my use case, the most flexible solution would be the custom variable with the arguments I want to set. As now, it is set all or none of them.

Organizational wise, I would say to close this issue, but should I (or you) open a new one for that custom variable? If you are still convinced to implement it.

[marcelmamula]

@GutiPerez We agreed that custom args is good idea, but mentioned PR did not include enough validations so @berndfinger agreed to split it to ensure it is properly implemented.