Re: [PATCH v2 3/2] sched/deadline: Check bandwidth overflow earlier for hotplug

Juri Lelli
2025-02-13T14:51:52Z

On 13/02/25 13:38, Christian Loehle wrote:
> On 2/13/25 13:33, Juri Lelli wrote:

...

> > Not sure I get what your worry is, sorry. In my understanding when the
> > last cpu of a policy/cluster gets offlined the corresponding sugov
> > kthread gets stopped as well (sugov_exit)?
> >
>
> The other way round.
> We may have sugov kthread of cluster [6,7] affined to CPU1. Is it
> guaranteed that we cannot offline CPU1 (while CPU6 or CPU7 are still
> online)?

Uhu, is this a sane/desired setup? Anyway, I would say that if CPU1 is
offlined sugov[6,7] will need to be migrated someplace else.

> Or without the affinity:
> cluster [6,7] with isolcpu=6 (i.e. sugov kthread of that cluster can
> only run on CPU7). Is offlining of CPU6 then prevented (as long as
> CPU7 is online)?
> I don't see how.
> Anyway we probably want to change isolcpu and affinity to merely be
> a suggestion for the sugov DL case. Fundamentally it belongs to what
> is run on that CPU anyway.

I would tend to agree.