On Sat, May 20, 2023, at 4:43 PM, Demi Marie Obenour wrote: Therefore, I am > asking if Fedora should use full kernel preemption by default.
https://pagure.io/fedora-workstation/issue/228 The outstanding questions: a. Do we need some tests that help decide this with metrics? If so what should those be? b. Should it be restricted to the desktop edition/spins? Or Fedora wide? c. How do we make the change? I have no ideas for a.) and I don't know what would be a sufficient sample of workloads across all of Fedora; or whether to separately test the different editions. I think if the answer to b.) is it should be Fedora-wide, means there's more pressure to answer yes to a.) Whereas if it's focused on desktops, perhaps less testing is needed? Still another strategy might be to just make preempt full the default Fedora wide in Rawhide with enough advance notice (like, nowish or soon after Fedora 39 branches). And once it starts causing issues, revert. That's a bit spaghetti on the wall test strategy but it's also cheap. (I am aware this is not a good strategy for testing doneness of spaghetti.) Regarding c.) gets tricky if it's not Fedora wide. The simplest case is, the change applies only to desktops, everything else remains on voluntary. The only way I'm aware of we can change it on the desktops is to set a kernel parameter. This means we need to have Anaconda set it as a boot parameter, but only for desktops. There is a debugfs facility for changing it during runtime, but this is not reliable due to debugfs being disabled when kernel lockdown is in place, which is tied to Secure Boot being enabled. Hence, the lkml thread referenced in the issue. But the lkml thread went no where (no responses). Possibly it wasn't provocative enough. Or simply there are no plans to expose this switch anywhere else. https://lkml.org/lkml/2023/4/11/1291 Conversely if even two other Fedora editions/spins/variants want some kind of opt out or opt in, it quickly gets tricky to do all that unique work setting a boot parameter, rather than just flipping the default across the board and not having a boot parameter. Anyway, it seems like it would be semi-straightforward to do it in Anaconda just for desktops using kickstart `bootloader --append=` command. https://pykickstart.readthedocs.io/en/latest/kickstart-docs.html#bootloader -- Chris Murphy _______________________________________________ devel mailing list -- [email protected] To unsubscribe send an email to [email protected] Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/[email protected] Do not reply to spam, report it: https://pagure.io/fedora-infrastructure/new_issue
