Re: [RFC PATCH v5 18/29] sched/core: Cgroup v2 support

[Peter Zijlstra <peterz@infradead.org>]

On Wed, May 06, 2026 at 09:58:02PM +0200, luca abeni wrote:
> Hi Peter,
> 
> On Tue, 5 May 2026 16:59:22 +0200
> Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > On Thu, Apr 30, 2026 at 11:38:22PM +0200, Yuri Andriaccio wrote:
> > > From: luca abeni <luca.abeni@santannapisa.it>
> > > 
> > > Make rt_runtime_us and rt_period_us virtual files accessible also
> > > to the cgroup v2 controller, effectively enabling the
> > > RT_GROUP_SCHED mechanism to cgroups v2.  
> > 
> > Can we have a blub about why only strict periodic servers; eg. why no
> > sporadic? and such...
> 
> Maybe I am misunderstanding your question, anyway: the file is called
> "rt_runtime_us", but the scheduling algorithm used to schedule the
> cgroup is SCHED_DEADLINE.
> So, we do not use a strictly periodic server, but a CBS, that can also
> support sporadic / non-periodic activations.

The interface only exposes runtime and period, as such we can only
configure strict periodic servers (with implicit deadline). And I'm
thinking this makes sense, esp. to start off with, but I also think it
makes sense to explicitly call that out.

State that this does not allow configuring sporadic servers, and
hand-wave a reason for why not.

Or, if we struggle to justify it, perhaps add deadline, dunno.