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

[Peter Zijlstra]

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.