Re: [QUESTION/REGRESSION] Unbound kthreads scheduled on nohz_full CPUs after commit 041ee6f3727a

[Waiman Long]

On 3/23/26 12:58 AM, sheviks wrote:
> Waiman Long <longman@xxxxxxxxxx> 於 2026年3月23日 週一 05:18 寫道：
> > The plan is to make nohz_full also dynamically changeable at run time in
> > the future. We are not there yet. Now HK_TYPE_KTHREAD is equivalent to
> > HK_TYPE_DOMAIN.
> >
> > A CPU cannot be considered fully isolated if it is in either
> > HK_TYPE_DOMAIN or HK_TYPE_KERNEL_NOISE. Currently, the nohz_full kernel
> > parameter can be used to put a set of partially isolated CPUs in the
> > nohz_full reservoir. To fully isolate them, some or all of them will be
> > need to be put in an isolated cpuset partition. BTW, HK_TYPE_MANAGED_IRQ
> > will be made to be dynamic too.
> >
> > That is my current view.
> That sounds like a great roadmap. I am very much looking forward to
> seeing the final implementation, as making nohz_full and managed IRQs
> dynamic would be a significant improvement for runtime isolation
> flexibility.
>
> However, regarding the current state in 7.0rc4, I observed that
> HK_TYPE_KTHREAD still appears to be initialized as
> HK_TYPE_KERNEL_NOISE rather than HK_TYPE_DOMAIN in the initialization
> path.
> Perhaps this part of the alignment hasn't been merged into the mainline yet?

Yes, I notice that too. I am working on a patch to alias  it to 
HK_TYPE_DOMAIN instead.

Cheers,
Longman

> Thanks for the clarification and for your work on this!
> Best regards,
> Sheviks