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

[Waiman Long <longman@redhat.com>]

On 3/23/26 12:58 AM, sheviks wrote:
> Waiman Long <longman@redhat.com> 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
>