Failed to write migration_cost_ns

Feedback
1

Started to receive this message during boot since last kernel update (could be the update before, but it’s max 4 days):

Nov 03 11:33:53 gaming systemd-tmpfiles[455]: Failed to write file "/sys/kernel/debug/sched/migration_cost_ns": Permission denied

❯ uname -a
Linux gaming 6.11.6-2-cachyos #1 SMP PREEMPT_DYNAMIC Fri, 01 Nov 2024 13:17:02 +0000 x86_64 GNU/Linux

My wild guess is that support for parameter migration_cost_ns have been dropped but some code still try to set it. (I’m a learning user here, so my guess is probably very wrong) (I hope my guess is not showing that I’m clueless and understand nothing! :joy:)

I do not consider this to be a bug, probably just require a code clean up somewhere if my guess is right.

2

Yes, BORE 5.7.0 introduced dynamic migration cost based on the number of cores you have. This will be reverted in 5.7.2 but the additional parameters will remain. Now, you set it through migration_cost_base_ns

1 Like
3

Thank you! Your answer made me realize that it was something I changed and not dead code! It cameback to me it was a recommandation in this guide from Arch:

https://wiki.archlinux.org/title/Gaming

That’s what happen when noobs copy/paste stuff arround! :sweat_smile:

I updated migration_cost_ns for migration_cost_base_ns and voilà!