Re: [PATCH] sched: cgroup SCHED_IDLE support

[Rik van Riel]

On Fri, 2021-06-25 at 10:08 +0200, Peter Zijlstra wrote:
> On Wed, Jun 16, 2021 at 11:42:05AM -0400, Tejun Heo wrote:
> > A high-level problem that I see with the proposal is that this
> > would bake
> > the current recursive implementation into the interface. The
> > semantics of
> > the currently exposed interface, at least the weight based part, is
> > abstract
> > and doesn't necessarily dictate how the scheduling is actually
> > performed.
> > Adding this would mean that we're now codifying the current
> > behavior of
> > fully nested scheduling into the interface.
> 
> It's a direct concequence of the hierarchical requirement. The
> approach
> is the only valid one. The other relative controllers that don't do
> this, are simply broken.
> 
> Absolute controllers have it easier, they can be trivially flattened.

I'm pretty sure CFS can be mostly flattened too, just not
trivially :)

Doing the delta_exectime to vruntime accounting in a somewhat
delayed fashion, with never more than one or two timeslices
worth of vruntime at a time being accounted, should make the
flat CFS runqueue model work.

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