Re: [RFC PATCH 01/23] sched/task_struct: Introduce classes of tasks

Ricardo Neri
2022-10-02T22:26:17Z

On Tue, Sep 27, 2022 at 03:01:07PM +0200, Peter Zijlstra wrote:
> On Fri, Sep 16, 2022 at 07:41:13AM -0700, Ricardo Neri wrote:
>
> > At least on Intel processors, class 0 is a valid class. The scheduler needs to
> > have a notion of unclassified tasks and decide how to handle them, IMO.
> >
> > Intel processors currently support 8-bit, unsigned classes. I doubt other
> > architectures will ever support more than 256 classes. Short can handle all the
> > possible classification values and also the unclassified case.
> >
> > On the other hand, class 0 could be the default classification unless hardware
> > classifies differently. 0 would be special and need to be documented clearly.
> > This would work for Intel processors.
>
> You can always do: class = hw_class + 1; that makes 0 'special' and the
> hardware class can be trivially reconstructed by subtracting 1.

This makes sense to me. I will implement as you suggest.

Thanks and BR,
Ricardo