Re: [PATCH 3/5] sched/deadline: Fix accounting after global limits change

[Juri Lelli <juri.lelli@redhat.com>]

On 14/07/25 10:59, Peter Zijlstra wrote:
> On Fri, Jun 27, 2025 at 01:51:16PM +0200, Juri Lelli wrote:
> 
> > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> > index 15d5855c542cb..be6e9bcbe82b6 100644
> > --- a/kernel/sched/rt.c
> > +++ b/kernel/sched/rt.c
> > @@ -2886,6 +2886,12 @@ static int sched_rt_handler(const struct ctl_table *table, int write, void *buff
> >  	sched_domains_mutex_unlock();
> >  	mutex_unlock(&mutex);
> >  
> > +	/*
> > +	 * After changing maximum available bandwidth for DEADLINE, we need to
> > +	 * recompute per root domain and per cpus variables accordingly.
> > +	 */
> > +	rebuild_sched_domains();
> > +
> >  	return ret;
> >  }
> 
> So I'll merge these patches since correctness first etc. But the above

Thanks!

> is quite terrible. It would be really good not to have to rebuild the
> sched domains for every rt change. Surely we can iterate the existing
> domains and update stuff?

Yeah, I agree. Tried doing an update at first, but then the involved
locking and the not so pleasant thing I could come up with made me
decide for the big hammer. Also because it should be a very infrequent
operation anyway.

But, I will try again somewhat soon.

Thanks,
Juri