Re: [RFC PATCH V3 6/6] sched/fair: Implement starvation monitor

[Peter Zijlstra]

On Fri, Jun 16, 2023 at 02:05:07PM +0200, Peter Zijlstra wrote:
> On Tue, Jun 13, 2023 at 03:41:30PM +0200, Daniel Bristot de Oliveira wrote:
> 
> > In an 0-laxity scheduler, the server would run at 0-laxity, jumping in
> > front of DL tasks... that would break EDF. It would be mixing two
> > schedulers in one. It is not required and likely not a good idea either.
> 
> I did consider a hybrid 0-laxity and EDF scheduler for mixed
> criticality, as have others like Ted Baker IIRC. IIRC it can be done
> using an augmented tree, but none of that solves the problems 0-laxity
> has (like over preemption and the general problem of playing chicken by
> doing things at the *VERY* last possible moment).
> 
> I think I did a talk at OSPERT on this at some point many years ago.
> Luckily some bright fellow had this semi-partitioned stuff that would
> make live much simpler :-)

I must clarify; I was thinking Least-Laxity-First, which is ofcourse not
the same as a 0-laxity scheduler.