Re: [PATCH] sched/fair: Force idle aware load balancing

[Peter Zijlstra <peterz@infradead.org>]

On Fri, Nov 28, 2025 at 02:55:36PM +0100, Vincent Guittot wrote:
> On Thu, 27 Nov 2025 at 21:28, Fernand Sieber <sieberf@amazon.com> wrote:

> > @@ -10135,15 +10136,15 @@ static inline int sg_imbalanced(struct sched_group *group)
> >  static inline bool
> >  group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
> >  {
> > -       if (sgs->sum_nr_running < sgs->group_weight)
> > +       if (sgs->sum_nr_running < (sgs->group_weight - sgs->forceidle_weight))
> >                 return true;
> >
> > -       if ((sgs->group_capacity * imbalance_pct) <
> > -                       (sgs->group_runnable * 100))
> > +       if ((sgs->group_capacity * imbalance_pct * (sgs->group_weight - sgs->forceidle_weight)) <
> > +                       (sgs->group_runnable * 100 * sgs->group_weight))
> 
> so you apply a ratio on group capacity based on the number of forced
> idle but what if you have heterogeneous systems ?

Ah, good point. I suppose tracking force_idle_capacity in
update_sg_lb_stats() should be possible, and then subtract that from
group_capacity or so.